BIO 121 Lecture Notes PDF

BIO 12I: Introduction to Medical Parasitology Lecture 1 Introduction - A run through the course outline - Definition of some terms 1. What is a Parasite? 2. What is Parasitism? 3. What is medical parasitology? 4. Of what impo...

BIO 12I: Introduction to Medical Parasitology Lecture 1 Introduction - A run through the course outline - Definition of some terms 1. What is a Parasite? 2. What is Parasitism? 3. What is medical parasitology? 4. Of what importance is proper knowledge of these organisms to students in the medical disciplines? Definitions 1. A Parasite is an organism that lives in or on another organism called a host. It depends on its host for survival, and it might cause disease or other negative effects on the host. Parasites exist in all living organisms, in diverse habitats, in cells, tissues and organs, each adapting differently to its environment. 2. What is Parasitism? Parasitism is defined as a non-mutual symbiotic relationship in which one of the symbionts (the parasite), benefits at the expense of the host, while the host is harmed. The parasite lives on or in the body of the host. 3. What is Parasitology? Parasitology is the study of parasites and parasitism, which is the dependence of organisms on one another for sustenance and survival. 4. What Is Medical Parasitology? Medical Parasitology is the study of parasites which live on humans, and most especially those which affect man in one way or the other. 5. Relevance of the course to medical students. Parasites live in man and animals, adversely affecting their lives. They course harm to our animals which serve as very important sources of protein and adorable pets. As such, we need to understand their biology and how they function, in order to combat them. Page 1 of 1 Categories or Types of Parasites. Parasites have been classified based on their varied forms, habitats, and level of dependency on their hosts. The different categories of parasites include: 1. Ectoparasites: Also called external parasites, live on the external surfaces of their hosts. Examples; ticks, louse (head, pubic and body), mites. 2. Endoparasites: These are also known as internal parasites. They live inside their hosts bodies. Examples are tapeworms, roundworms or ascaris, plasmodium. 3. Extracellular parasites: These are parasites which live outside the cells of their hosts. Good examples are the ectoparasites. But we also have internal parasites such as ascaris which live in the vacuum of the intestines. 4. Intracellular parasites: They are parasites which live in or are resident inside the cells of their host. Examples are tapeworm cyst in the meat of cow and pork; the guinea worm in the foot muscles, the malaria parasite in blood cells. 5. Hyperparasites: They are parasites which live on other parasites 6. Accidental parasites: These are occasional parasites, which parasitize animals because of prevailing circumstances. A good example is the maggot causing myiasis, which gets three because poor treatment of wounds, such as bed sores. 7. Obligatory parasites: These are parasites which absolutely depend on their host for total survival. They start and complete part of or their entire life cycles on the host. Good examples are the malaria parasite, tapeworms, head and body lice. 8. Facultative parasites: They are called opportunistic parasites. For example, Leeches. They can live their lives in water, sucking blood from fishes and other sea animals, Page 2 of 2  but when they are opportune to come inContact with man, they inflict pains, wounds and suck his blood. 9. Micro-parasites: These are simply those parasites which cannot be seen with our naked eyes. They must be viewed with a microscope. The malaria and typhus parasites are excellent examples. The disease-causing viruses such as the HIV, hepatitis, corona virus, and ebola virus 10.Macro-parasites: These are parasites that can be seen with the naked eye. They are large and multicellular. Some examples are worms, leeches, ticks, louse, flees, bed bugs, and some birds. Take Home Assignment! - Use any Five facts and explain the importance of the study of parasites to students of the medical fields. (8 marks) - List and define any five categories of parasites. (5 marks)  Lecture attendance = 2marks. Submit your assignment, through the course delegate at the start of our next lecture. Note: Evidence of any copied word or downloaded material will earn a zero score!!! BIO 12I: Introduction to Medical Parasitology Lecture 2 TOPIC: HOSTS OF PARASITES!  Let us review our last lecture  Let us also look at our assignment!  What is the meaning of the word ‘host”? A host is any organism that provides accommodation/residence to another organism, be it temporal or permanent. Examples: - When you visit somebody, that person is your host. - When you move to live with somebody, that person is your host. - When you organize a party, a sporting competition, you become a host to the invitees / the other teams that will come to compete. - When you travel to stay in another country, that country becomes your host. - As you have come to study in Veritas University, she is now your host. Page 3 of 3  - List more! IF we examine all the examples listed above, two things immediately come to mind! What are these? 1. The host should be able /or willing to accommodate the visitor. 2. The visitor should be able /or willing to live under the conditions of the host. In our context, the visitor is the parasite, and MUST BE ABLE to live under the enabling conditions of the host! In this situation there is no willingness or not, by the host.  What is a Parasite’s Host? It is a living organism which harbors the parasite and provides nourishment and shelter to it, and gets nothing in return but harm, damage or death.  The host is always larger than the parasite. For example: Ascaris worm dwelling in the human intestines.  The host can be humans, animals or plants.  The host provides temporal or permanent residence / habitat to the parasite. And in medical parasitology, focus is on those parasitic relationships which directly or indirectly affect human health. For example, if your dog or cat, cow or pig harbours parasites, should that be of concern to you or not? (This is the bases of veterinary medicine--- producing healthy animals for human consumption) Brainstorming!!! Is there any difference between “Parasites Hosts” and “Parasitic Hosts”? Types of Parasites’ Hosts Categorization of parasites’ hosts is dependent upon their role in the life cycle of the parasites or the type of residency on the host---whether permanent or temporal. 1. Definitive Hosts 2. Intermediate Hosts 3. Reservoir Hosts 4. Transport / Paratenic Hosts 5. Dead-end Hosts Page 4 of 4 1. Definitive Hosts The definitive hosts, also known as the primary hosts, are the ones which harbor the adult parasite and it is where the parasite reproduces sexually. A primary host or definitive host is a host in which the parasite reaches maturity i.e., its life cycle is completed in the host and, if applicable, reproduces sexually. The definitive host can be a mammalian host or other living hosts. Examples include sheep for Fasciola gigantica, a dog for Echinococcus granulosus, and a female anopheles mosquito for Plasmodium spp. In the majority of human parasitic infections, man is definitive host; in malaria and hydatid disease, however, man acts as the intermediate host. Examples: 2. Intermediate Hosts The intermediate hosts, also called the secondary hosts, are hosts which harbor the larval stage or the asexual forms of the parasite. Usually when there is an obligatory passage of that stage of its lifecycle to go through the host. These hosts harbor the parasite only for a short transition period, during which, some developmental stage is completed. For example, humans are the intermediate hosts for Plasmodium (malarial parasites). Intermediate hosts are mandatory for the completion of the life cycle for some parasites. Some parasites require two intermediate hosts to complete their different larval stages. These are known as the first and second intermediate hosts respectively. Examples: 3. Reservoir Hosts Are hosts, which harbor the parasites, it grows and multiply, and serves as an important source of infection to other susceptible hosts. Reservoir hosts do not get the disease carried by the pathogen or it is asymptomatic and non-lethal. Examples: 4. Paratenic Hosts Paratenic or Storage Hosts, serves as temporary refuge and vehicle for reaching an obligatory host, Page 5 of 5 usually the definitive host. A paratenic host harbors the sexually immature parasite, but it cannot develop further in this host. When a suitable definitive host ingests the paratenic host or a part of it containing the infective stage, the parasite can grow to maturity otherwise it remains stored in the host itself. Examples: 5. Dead-end Hosts Also known as Incidental or Accidental Hosts, are hosts that shelter parasitic organisms but are unable to transmit them to different hosts. This happens because the life cycle of the parasite can no longer progress, and everything stops there. And so it is a dead-end for the parasite. For example, humans are dead-end hosts for the Japanese encephalitis virus (JEV), whose life cycle is normally between culicine mosquitoes and birds. People can become infected, but the level of virus in their blood does not become high enough to pass on the infection to mosquitoes that bite them. Examples: Our Take home Assignment: QUESTION Do intensive research and give three examples each, for the five categories of parasites hosts discussed in our lecture. SCORE = 8 marks Attendance = 2 marks. Keep putting-in little efforts, God will magnify them. Our next Topic: Host-Parasite Relationships---Interactions between the two! BIO 12I: Introduction to Medical Parasitology Lecture 3 10/05/2022 TOPIC: HOSTS and PARASITES INTERACTIONS!  Let us review our last lecture!  Let us also go through our assignment! Page 6 of 6 Types of Interactions between Living Organisms. Because different species often inhabit the same spaces and share the same resources, they interact in a variety of ways, known collectively as symbiosis. Hence, any form of interaction between 2 or more species of living organisms, be them plants or animals, is referred to as SYMBIOSIS. What is a symbiotic relationship then?  It is a close ecological relationship between the individuals of two (or more) different species, in which at least one specie benefits. For the other species, the relationship may be positive, negative, or neutral.  A symbiotic relationship may benefit both species, at times one species benefits at the other's expense, and in other cases neither species benefits. This has given rise to five main types of symbiotic relationships vis; mutualism, commensalism, predation, competition, and parasitism. 1. Mutualism What is mutualism?  Mutualism is a type of symbiotic relationship where all species involved benefit from their interactions.  A mutualistic relationship is where two organisms of different species "work together," each benefiting from the relationship.  Mutualism describes the ecological interaction between two or more species where each species has a net benefit. Some examples of mutualistic relationships.  Aphids and ants....  Woolly bats and pitcher plants  Bees and flowers  Butterfly and the hibiscus flower.  Nitrogen-fixing bacteria and leguminous plants  Cows and their rumen bacteria. The later gets shelter and nutients from the cow and helps in digesting the tough uncooked plants the cow consumes. Page 7 of 7 2. Commensalism What is commensalism? Commensalism is a Latin word that means ‘to eat at the same table’.  In biology, commensalism is a kind of symbiotic relationship between two species wherein one species obtains food, shelter, or transport from the other without harming it.  The time they spend together varies from short to long.  The partner that draws the benefit is known as a commensal while the other is known as the host species. The simplest example of commensalism is a bird making a nest in a tree. The tree provides shelter and protection to the bird without getting significantly harmed or affected by the bird. Examples of commensalism? Page 8 of 8 More Examples of Commensalism  Orchids Growing on Branches. Orchids are a family of flowering plants that grow on trunks and branches of other trees.  Sharks and Remora Fish. The remora or suckerfish is a small fish that grows to about three feet....  Milkweed and Monarch Butterfly.  Cow and cattle eaglet  Barnacle larvae and whales. Barnacles are immobile/sessile Crustaceans. However, the larvae of these crustaceans latch themselves to the whales or shells where these larvae grow and flourish. In addition, barnacles feed upon the planktons while whales are moving around. Thus, barnacles grow and thrive on whales’ surfaces and move from one place to another without affecting the host whale or shell. 3. Predation i. Predation is a biological interaction, a symbiotic relationship where one organism, the predator, kills and eats another organism, its prey. It includes parasitism, micropredation and parasitoidism. ii. Predation is an interaction in which one organism, the predator, eats all or part of the body of another organism, the prey. Herbivory is a form of predation in which the prey organism is a plant. Predator and prey populations affect each other's dynamics. Examples of predation! a. A pride of lions attacking a larger animal, such as an elephant or wildebeest. b. Dolphins chasing and eating fish. c. Orca whales hunting seals, sharks, and penguins. d. House cats killing mice, birds, and other small animals. Page 9 of 9  e. An owl catching and devouring rats. In a community, predation reduces the number of individuals in the prey population. The best-known examples of predation involve carnivorous interactions, in which one animal consumes another.  Types of Predations There are four known types of predations, based on whether or not it results in the death of the prey. (1) Carnivory, (2) Herbivory, (3) Parasitism, (4) Mutualism. - Carnivory/Carnivorous Predation. Carnivorous predators kill and eat their prey.... - Herbivory/ Herbivorous Predation. Herbivorous predation involves the consumption of autotrophs, such as plants or photosynthetic algae.... - Parasitism/ Parasitic Predation. - Mutualistic Predation... How do prey and predators manage their cycles for sustainability? Predator and prey populations alternate through cycles with time! - When predators’ number decrease, numbers of prey increases. - When prey population turn to decrease, predators’ number also decreases. This reduces predation pressure and allows prey populations to rebuild up. 4. Competitive Interactions == Intra-species and Inter-species  Competition is a symbiotic relationship or interaction where individuals struggle for a common resource that is in limited supply.  It can also be defined as, the direct or indirect interaction of organisms that leads to a change in fitness when the organisms share the same resource. (Survival of the fittest syndrome)!  The outcome usually has negative effects on the weaker competitors.  There are three major forms of competition; interference competition, exploitation Page 10 of 10  competition, (considered as real competition), and apparent competition.  Interference competition occurs directly between individuals, while exploitation competition and apparent competition occur indirectly.  Interference competition occurs when an individual directly alters the resources or stops other individuals from having access to them. For example, when a male gorilla prohibits other males from accessing a mate by using physical aggression or displays of aggression, the dominant male is directly altering the mating chances of other males. This is a typical example of an intra-specific interaction or competition. Give examples among human beings!  Exploitation competition occurs when individuals interact indirectly as they compete for common resources, such as space, prey or food. In simply understanding, the use of the resource by one individual will decrease the amount available for other individuals. Be it interference or exploitation competition, over time a superior competitor can eliminate an inferior one from the area. This is termed Competitive Exclusion. This simply implies that; each species will inhibit their own population growth before they inhibit that of the competitor. Give some very practical examples in human life!!!  Apparent competition occurs when two individuals that do not directly compete for resources affect each other indirectly by being prey for the same predator. Consider a hawk (predator), that preys both on squirrels and mice, if the squirrel population increases, the mouse population may be positively affected since more squirrels will be available as prey for the hawks. However, an increased squirrel population may eventually lead to a higher population of hawks requiring more prey, thus, negatively affecting the mice through increased predation pressure as the squirrel population declines. The opposite effect could also occur through a decrease in food resources for the predator. If the squirrel population decreases, it can indirectly lead to a reduction in the mouse population since they will be the more abundant food source for the hawks. Apparent competition can be difficult to identify in nature, often because of the complexity of indirect interactions that involve multiple species and changing environmental conditions. 5. Parasitism What is parasitism?  Parasitism is a type of symbiosis in which one organism, the parasite, causes harm to another called the host, which the parasite utilizes as its habitat and depends on for resource acquisition.  Parasitism, a relationship between two species of plants or animals in which one benefits at the expense of the other, sometimes without killing the host organism.  It is a parasitic relationship in which one organism, the parasite, lives on another organism, the host, harming it and possibly causing death. The parasite lives on or in the body of the host. A few examples of parasites are tapeworms, fleas, and barnacles (sessile crustaceans, with free Page 11 of 11  swimming larvae). Table 1: Differences between different types of symbiotic relationships: Commensalism; Mutualism; Parasitism Commensalism Mutualismalism ParParasitism 11 Interspecies relationship Interspecies relationship Interspecies relationship 1 wherein one is benefited wherein both the wherein one is benefited while the other remains organisms benefit from while the association unaffected their association harms the other It is non-obligatory It is an obligatory It can be obligatory as 2 interspecies symbiosis interspecies association well as non-obligatory commensalism wherein both partners are interspecies association in mutual symbiosis Only one species draws Both species depend on Only one species draws 3 benefit for its survival, while each other for their benefit for its survival, others remain unaffected survival and benefit while the other is harmed with the association 4 It is a positive association It is a positive It is a negative 4 association association between different types of symbiotic relationship, i.e., commensalism, mutualism, parasitism In Summary  Species interactions (symbiosis) within the ecosystem include the following main types of interactions: mutualism, commensalism, predation and herbivory, competition, and parasitism.  Because of linkages among species within a food web, changes to one species usually have far-reaching effects on the ecosystem. Examples? If a parasite kills your Father or Mother, what will be the far-reaching effects or consequences?  The interactions above are only some of the known interactions that occur in nature and can be difficult to identify because they can directly or indirectly influence other intra-specific and inter-specific interactions.  Species interactions form the bases of the complexity of ecological communities. The interactions are extremely important in shaping community dynamism and development. How, discuss??? Page 12 of 12  Some ecologists had earlier thought that competition was the driving force of community structure, but it is now understood that all of the interactions, along with their indirect effects and the variation of responses within and between species, define communities and ecosystems. STOP! Our quiz of the day! Questions. 1. What is symbiosis? 2marks 2. List the five main or common types of symbiotic interactions between living organisms. 5marks 3. Give two examples of mutualistic interactions. 2marks 4. What is the difference between Predation and Parasitism? 2marks 5. List the three types of competitive interactions among living organisms. 3marks 6. In a maximum of four lines explain “competitive exclusion” and its negative consequences on human communities. 4 marks Score = 18 marks Attendance = 2 marks TOTAL SCORE = 20 marks’ Our Next Lecture will be on, Interactions between Parasites and their Hosts. Thanks for being present, to listen to my little stories!!! Keep up with your little efforts, Jesus will turn them into giant results. AMEN! Page 13 of 13 Parasitic Vectors Page 14 of 14 Parasitism - Types and Examples Parasitism: Examples Can microorganisms assist the survival and parasitism of plant-parasitic nematodes? Page 15 of 15 Page 16 of 16 Parasitic Plant Page 17 of 17 Parasites: The little bugs are everywhere, and they are our enemies. Parasitism of the Tomato Hornworm Parasitism - Page 18 of 18 Common Parasitic Animal Relationships - Parasites: Types, in humans, worms, ectoparasites Symbiosis: Commensalism, Mutualism, Parasitism, Neutralism Page 19 of 19  BIO 12I: Introduction to Medical Parasitology Lecture 3 10/05/2022 TOPIC: HOSTS and PARASITES INTERACTIONS!  Let us review our last lecture!  Let us also go through our assignment! Types of Interactions between Living Organisms. Because different species often inhabit the same spaces and share the same resources, they interact in a variety of ways, known collectively as symbiosis. Hence, any form of interaction between 2 or more species of living organisms, be them plants or animals, is referred to as SYMBIOSIS. What is a symbiotic relationship then?  It is a close ecological relationship between the individuals of two (or more) different species, in which at least one specie benefits. For the other species, the relationship may be positive, negative, or neutral. Page 20 of 20   A symbiotic relationship may benefit both species, at times one species benefits at the other's expense, and in other cases neither species benefits. This has given rise to five main types of symbiotic relationships vis; mutualism, commensalism, predation, competition, and parasitism. 6. Mutualism What is mutualism?  Mutualism is a type of symbiotic relationship where all species involved benefit from their interactions.  A mutualistic relationship is where two organisms of different species "work together," each benefiting from the relationship.  Mutualism describes the ecological interaction between two or more species where each species has a net benefit. Some examples of mutualistic relationships.  Aphids and ants....  Woolly bats and pitcher plants  Bees and flowers  Butterfly and the hibiscus flower.  Nitrogen-fixing bacteria and leguminous plants  Cows and their rumen bacteria. The later gets shelter and nutients from the cow and helps in digesting the tough uncooked plants the cow consumes. 7. Commensalism What is commensalism? Commensalism is a Latin word that means ‘to eat at the same table’.  In biology, commensalism is a kind of symbiotic relationship between two species wherein one species obtains food, shelter, or transport from the other without harming it.  The time they spend together varies from short to long.  The partner that draws the benefit is known as a commensal while the other is known as the host species. The simplest example of commensalism is a bird making a nest in a tree. The tree provides shelter and protection to the bird without getting significantly harmed or affected by the bird. Page 21 of 21 Examples of commensalism? More Examples of Commensalism  Orchids Growing on Branches. Orchids are a family of flowering plants that grow on trunks and branches of other trees.  Sharks and Remora Fish. The remora or suckerfish is a small fish that grows to about three feet....  Milkweed and Monarch Butterfly.  Cow and cattle eaglet  Barnacle larvae and whales. Barnacles are immobile/sessile Crustaceans. However, the larvae of these crustaceans latch themselves to the whales or shells where these larvae grow and flourish. In addition, barnacles feed upon the planktons while whales are moving around. Thus, barnacles grow and thrive on whales’ surfaces and move from one place to another without affecting the host whale or shell. 8. Predation iii. Predation is a biological interaction, a symbiotic relationship where one organism, the predator, kills and eats another organism, its prey. It includes parasitism, micropredation and parasitoidism. iv. Predation is an interaction in which one organism, the predator, eats all or part of the Page 22 of 22  body of another organism, the prey. Herbivory is a form of predation in which the prey organism is a plant. Predator and prey populations affect each other's dynamics. Examples of predation! f. A pride of lions attacking a larger animal, such as an elephant or wildebeest. g. Dolphins chasing and eating fish. h. Orca whales hunting seals, sharks, and penguins. i. House cats killing mice, birds, and other small animals. j. An owl catching and devouring rats. In a community, predation reduces the number of individuals in the prey population. The best-known examples of predation involve carnivorous interactions, in which one animal consumes another.  Types of Predations There are four known types of predations, based on whether or not it results in the death of the prey. (1) Carnivory, (2) Herbivory, (3) Parasitism, (4) Mutualism. - Carnivory/Carnivorous Predation. Carnivorous predators kill and eat their prey.... - Herbivory/ Herbivorous Predation. Herbivorous predation involves the consumption of autotrophs, such as plants or photosynthetic algae.... - Parasitism/ Parasitic Predation. - Mutualistic Predation... Page 23 of 23 How do prey and predators manage their cycles for sustainability? Predator and prey populations alternate through cycles with time! - When predators’ number decrease, numbers of prey increases. - When prey population turn to decrease, predators’ number also decreases. This reduces predation pressure and allows prey populations to rebuild up. 9. Competitive Interactions == Intra-species and Inter-species  Competition is a symbiotic relationship or interaction where individuals struggle for a common resource that is in limited supply.  It can also be defined as, the direct or indirect interaction of organisms that leads to a change in fitness when the organisms share the same resource. (Survival of the fittest syndrome)!  The outcome usually has negative effects on the weaker competitors.  There are three major forms of competition; interference competition, exploitation competition, (considered as real competition), and apparent competition.  Interference competition occurs directly between individuals, while exploitation competition and apparent competition occur indirectly.  Interference competition occurs when an individual directly alters the resources or stops other individuals from having access to them. For example, when a male gorilla prohibits other males from accessing a mate by using physical aggression or displays of aggression, the dominant male is directly altering the mating chances of other males. This is a typical example of an intra-specific interaction or competition. Give examples among human beings!  Exploitation competition occurs when individuals interact indirectly as they compete for common resources, such as space, prey or food. In simply understanding, the use of the resource by one individual will decrease the amount available for other individuals. Be it interference or exploitation competition, over time a superior competitor can eliminate an inferior one from the area. This is termed Competitive Exclusion. This simply implies that; Page 24 of 24  each species will inhibit their own population growth before they inhibit that of the competitor. Give some very practical examples in human life!!!  Apparent competition occurs when two individuals that do not directly compete for resources affect each other indirectly by being prey for the same predator. Consider a hawk (predator), that preys both on squirrels and mice, if the squirrel population increases, the mouse population may be positively affected since more squirrels will be available as prey for the hawks. However, an increased squirrel population may eventually lead to a higher population of hawks requiring more prey, thus, negatively affecting the mice through increased predation pressure as the squirrel population declines. The opposite effect could also occur through a decrease in food resources for the predator. If the squirrel population decreases, it can indirectly lead to a reduction in the mouse population since they will be the more abundant food source for the hawks. Apparent competition can be difficult to identify in nature, often because of the complexity of indirect interactions that involve multiple species and changing environmental conditions. 10.Parasitism What is parasitism?  Parasitism is a type of symbiosis in which one organism, the parasite, causes harm to another called the host, which the parasite utilizes as its habitat and depends on for resource acquisition.  Parasitism, a relationship between two species of plants or animals in which one benefits at the expense of the other, sometimes without killing the host organism.  It is a parasitic relationship in which one organism, the parasite, lives on another organism, the host, harming it and possibly causing death. The parasite lives on or in the body of the host. A few examples of parasites are tapeworms, fleas, and barnacles (sessile crustaceans, with free swimming larvae). Table 1: Differences between different types of symbiotic relationships: Commensalism; Mutualism; Parasitism Commensalism Mutualismalism ParParasitism 11 Interspecies relationship Interspecies relationship Interspecies relationship 1 wherein one is benefited wherein both the wherein one is benefited while the other remains organisms benefit from while the association unaffected their association harms the other Page 25 of 25  It is non-obligatory It is an obligatory It can be obligatory as 2 interspecies symbiosis interspecies association well as non-obligatory commensalism wherein both partners are interspecies association in mutual symbiosis Only one species draws Both species depend on Only one species draws 3 benefit for its survival, while each other for their benefit for its survival, others remain unaffected survival and benefit while the other is harmed with the association 4 It is a positive association It is a positive It is a negative 4 association association between different types of symbiotic relationship, i.e., commensalism, mutualism, parasitism In Summary  Species interactions (symbiosis) within the ecosystem include the following main types of interactions: mutualism, commensalism, predation and herbivory, competition, and parasitism.  Because of linkages among species within a food web, changes to one species usually have far-reaching effects on the ecosystem. Examples? If a parasite kills your Father or Mother, what will be the far-reaching effects or consequences?  The interactions above are only some of the known interactions that occur in nature and can be difficult to identify because they can directly or indirectly influence other intra-specific and inter-specific interactions.  Species interactions form the bases of the complexity of ecological communities. The interactions are extremely important in shaping community dynamism and development. How, discuss???  Some ecologists had earlier thought that competition was the driving force of community structure, but it is now understood that all of the interactions, along with their indirect effects and the variation of responses within and between species, define communities and ecosystems. STOP! Our quiz of the day! Questions. 7. What is symbiosis? 2marks Page 26 of 26 8. List the five main or common types of symbiotic interactions between living organisms. 5marks 9. Give two examples of mutualistic interactions. 2marks 10. What is the difference between Predation and Parasitism? 2marks 11.List the three types of competitive interactions among living organisms. 3marks 12. In a maximum of four lines explain “competitive exclusion” and its negative consequences on human communities. 4 marks Score = 18 marks Attendance = 2 marks TOTAL SCORE = 20 marks’ Our Next Lecture will be on, Interactions between Parasites and their Hosts. Thanks for being present, to listen to my little stories!!! Keep up with your little efforts, Jesus will turn them into giant results. AMEN! Page 27 of 27 Parasitic Vectors Page 28 of 28 Parasitism - Types and Examples Parasitism: Examples Can microorganisms assist the survival and parasitism of plant-parasitic nematodes? Page 29 of 29 Page 30 of 30 Parasitic Plant Page 31 of 31 Parasites: The little bugs are everywhere, and they are our enemies. Parasitism of the Tomato Hornworm Parasitism - Page 32 of 32 Common Parasitic Animal Relationships - Parasites: Types, in humans, worms, ectoparasites Symbiosis: Commensalism, Mutualism, Parasitism, Neutralism Page 33 of 33 Page 34 of 34  Tapeworm Page 35 of 35 BIO12I: Introduction to Medical Parasitology LECTURE 4 TOPIC: Host and Parasite Relationships/Interactions. Introduction The study of parasites and their hosts has been focused on the physiological, morphological, and immunological adaptations to parasitism. These are adaptations which the parasite employs to survive and reproduce in the host, and those used by the host in self-defense. The Relationship - Parasitism is a one-sided partnership in which the host receives no benefits but instead some degree of harm, and/or death. - An ‘ideal’ or true parasite must not dare to kill its host, because the death of the host means its own death. - However, an “ideal” parasite does not exist, because the slightest effects of all parasites are detrimental to their hosts. - Parasitism is a case of balance of power. The parasites and the host form a functional balance system which is opposed to the external environment. - The host reacts to keep the parasite away or to a minimum, while the parasite attempts to live as un-undisturbed as possible, despite all the host’s reactions which threatens its existence. The INTERACTIONS: The interaction, like many other types, is characterized by specific problems or challenges. Challenges faced by Parasites: All parasites face three major problems. 1. The first is dispersal of propagules, i.e., the developmental stages fitted for spreading the parasite to new hosts, as per different species. Parasitic groups with free-living stages can accomplish this relatively easily; examples are the parasitoids, in which the free-living stage typically locates and infects new hosts. Parasitic species with no free-living stages must use other methods, such as passing through other hosts, or environmental signals. 2. The second problem faced by parasites is, obtaining sufficient energy for growth, maintenance, and reproduction at the expense of the host.  The parasite can alter the host's energy budget (total energy build up as it grows), to increase Page 36 of 36  the amount of the host's energy potentially available to itself. How will this affect the host? 3. Thirdly, the host must survive until the parasite has matured and is able to reproduce.  Physiologically, parasites will show selective tissue destruction and avoid ingestion of the host's vital organs too soon, such that the host will not die.  Behaviorally, parasites will try to reduce the frequency of behaviors on the part of the host which will entail exposure to predation or increased risk of accidental death. Challenges faced by Hosts: 1. Reduction in individual fitness: A host infected with a parasite will show a reduction in individual fitness, ranging from; - Complete loss of reproductive success or small decrease in reproductive success. The reproductive fitness of the host is dependent on its parasitic load. - Hampered growth, and health complications; and - Death Faced with parasitic attack, the host—or potential host—can attempt to increase its reproductive fitness in two ways. 1. It can protect itself or it can protect its kin. Certain actions on the part of the host can prevent infection by a parasite or kill the parasite once it has entered the host's body. Physiological and morphological mechanisms such as the host's immunological system, phagocytic cells, and encapsulation of parasites are commonly employed by the parasite. 2. It can prevent its kin from the parasitic infection. How? Find out.  What do Parasites derive from their hosts? Parasites’ metabolism is dependent on their hosts in many ways. It can be for; a) Nutrition. As in Flukes and tapeworms and most ectoparasites. b) Development. As in P. intergerrinum and Opalina ranarum, (parasites of frog) c) Need of digestive enzymes. As in tapeworms such as Taenia species and Echinococcus sp. d) Shelter. As in endoparasites such as Plasmodium sp, Entamoeba sp and Ascaris sp e) Movement. As in ectoparasites such as lice, fleas, ticks and mites f) Control of maturation. As in P. intergerrinum and Opalina ranarum g) Some form of combined needs from the list above. Page 37 of 37   There are four (4) major ways or methods of interactions between parasites and their hosts. Each is determined by the group to which the parasite belongs. What are these groups? Group 1 Parasites, are parasitoids Group 2 Parasites, are parasitic castrators Group 3 Parasites, are single-host true parasites Group 4 Parasites; are multi-host true parasites a. Parasitoid-host interactions. —Parasitoids (group 1 parasites) in general do not depend upon their hosts for dispersal. In nearly all cases there is a free-living stage which accomplishes this. For example, the adult females of the majority of parasitic hymenopteran species actively locate and oviposit on the progeny of their host. b. Parasitic castrator- host interactions. - Parasitic castration has been defined as "destruction or alteration of gonad tissue, reproductive behavior, hormonal balance, or other modification of host reproductive effort. - Many parasitic castrators have a free-living stage and so do not necessarily depend upon the activities of the host for dispersal. Any behavioral and physiological modifications performed are expected to increase the amount of energy available to the parasite and reduce the risk of accidental death of the host. - One advantage of castration is that the parasite can obtain energy from host tissues without increasing host mortality, but reproductive behaviour such as nest building, courtship, and male-male competition may be affected. - Castration is usually permanent, resulting in total sterility. In some cases, it may be temporary, resulting in sterility during the period of infection, or relative, resulting in reduced reproductive output c. Interactions between single - host true parasites. —True parasites with a single host (group 3) may or may not have a free-living stage. If a free-living stage is present the group 3 parasite, like parasitoids and castrators, need not depend upon the host for dispersal. If the group 3 parasite has no free-living stage, survival of the propagules depends upon their contact with a member of the host species. Modification of the host's behavior, whether to promote dispersal of parasite propagules or to alter the host's energy budget, is expected to be rare among group 3 parasites. First, a single host usually harbors a large number of group 3 parasites. Any parasite with the ability to modify the host's behavior would share the benefits with all the other parasites present, while incurring all the expense itself. its fitness relative to that of parasites in other hosts, the beneficent trait can be selected for even if other unrelated parasites in the same host receive a greater increase in fitness than the benefactor. Page 38 of 38 d. Interactions between hosts and multiple-host true parasites. —The multi-host, true parasite (group 4) matures and reproduces in association with a definitive host. Immature stages pass through one, two, or three intermediate hosts. The intermediate hosts may be facultative or obligatory. The addition of intermediate hosts adds a new level of complexity to the host parasite interactions. A single group 4 parasite may employ different strategies of energy budget modification and different strategies for dispersal of propagules in each of its hosts, and in some cases may employ the strategies of parasitoids and castrators.  Last, any behavior on the part of the host which entails exposure to predation or accidental death should be prevented lest the host be killed before the parasitoid has a chance to mature. How does this work??? - The parasitoid causes the insect host to pupate prematurely. In some of these cases this may be a mechanism to keep the host inactive and inconspicuous to predators after it has built up food reserves sufficient to maintain the parasitoid. - The host almost invariably dies as a result of a parasitoid infection: Its individual fitness is reduced to zero. The host's inclusive fitness, however, includes both its individual fitness and the sum of the fitness of each of its relatives. - An infected individual may behave in such a manner as to become more conspicuous to predators or easier to capture. As a result, the host may be killed before the parasitoid is able to mature. The host's kin are now protected against infection by this particular parasitoid individual. Natural selection can act to reinforce this "suicidal" behavior. IN SUMMARY  Parasites and their hosts show behavioral as well as physiological interactions. Parasites are able to alter the behavior of their hosts, and hosts in turn may employ behavioral retaliation in response to parasitic infection.  There are four types of endoparasites, the parasitoids (group 1), parasitic castrators (group 2), single-host true parasites (group 3) and multi-host true parasites (group 4), which largely determine the kind of interactions in a parasite/host relationship.  For these four types of endo-parasites, their induced modifications of host behavior are with respect to: i. dispersal of the parasite propagules to new hosts, ii. modification of the host's energy budget to provide energy for the parasite's growth and maturation; and iii. keeping the host alive until the parasite has completed its life cycle. Page 39 of 39   This interaction between parasites and their hosts, has given rise to varied forms of adaptive behaviors and life patterns.  The consequences of prolonged hosts/ parasites relationships/interactions. 1. Parasites have mechanisms for locating their host like chemotaxis and active penetration, such as Schistosome cercariae and hookworm larvae 2. Transmission of parasites to the new host may be associated with daily or circadian rhythms such as cell division and migrating patterns. 3. Parasites have to survive in their host using several mechanisms, such as encystations, transformation or tail loss, as in Schistosome cercariae 4. Parasites have surfaces that play important roles in nutrition. There is usually a major nutritional interface with the host such as the digestive-absorptive epithelium in Platyhelminthes which has enormous increase in surface area by development of folds and microvilli such as tubercules, spines and pores of flukes and tapeworms. 5. Damage to host can be as a result of immune response (immuno-pathology). This can be more damaging than the infection itself. 6. Parasites exhibit host specificity and are adapted to infect specific species but cannot invade certain species or strains of host, for example, the malaria parasite Plasmodium yoelli can alone, affect mice while Plasmodium falciparium and P. malariae are human specific. Have a beautiful day! Page 40 of 40  LECTURE 5 Topic: EFFECTS OF PRARASITES ON THEIR HOSTS, AND EFFECTS OF HOSTS ON PARASITES. A. Effects of Parasites on their Hosts: Their effects and harmful or injurious. Parasites May Injure their Host in a Number of Ways 1. Toxins: Apart from disease and death, parasites can produce poisonous substances in the form of secretions, excretions or other products such as proteolytic enzymes and pigments. These can harm or sensitize the host, for example, Schistosome cercariae, Entamoeba histolytica and Malaria parasites. 2. Mechanical Effects: Mechanical damage due to big size or number of parasites occurs such as the cysts of Echinococcus species. Intestinal obstruction, blockage Page 41 of 41 and entangling of worms also occur such as in Ascaris lumbricoides. Parasites can perforate vital organs when migrating as in hookworms and Ascaris. Adhesive structures of parasites also cause mechanical damage as in Taenids. 3. Absorption of Food: Parasites can deplete the host nutritional level to reach disease level for the host. For example, Diphyllobothrium latum, the broad fish tapeworm absorbs a great quantity of vitamin B12 reaching to megaloblastic anaemia. Hook worm absorbs iron daily leading to iron deficiency anaemia. 4. Destruction of Host Tissues: Skin penetrating parasites cause skin destruction such as the larvae of hookworm and Schistosomes which causes swimmer’s itch and the larvae of myasis producing flies. Microfilariae of Onchocerca volvulus causes skin onchodermatitis, nodules, leopard skin and lizard skin. The skin lesions become the site of secondary bacterial infection. 5. Ingestion of Host’s Body Constituent: Some parasites such as hookworms and microfilariae of filarial worms feed on the body fluids (blood and lymph), and epithelia cells causing blood and fluid loss. 6. Gigantism: Some parasites such as larval stages of trematodes enhance growth of their snail intermediate host. 7. Parasitic Castration: Sex reversal and parasitic castration occurs when gonadal tissues of intermediate hosts such as in crabs and snails are destroyed. B. Effects of Hosts on their Parasites (Host Reactions/ Retaliations) These effects are not as apparent as parasites effects. Some of them include: 1. Tissue Reaction: These are host defense mechanisms. The tissue reactions are localized in the vicinity of the parasite’s invasion. They usually disappear after the invading organism has been eliminated, for example, inflammatory reactions, nodules, induction of abnormal growth, hyperplasia, metaplasia and neoplasia (tumors) and hypertrophy such as in Trichinella spiralis and Onchocerca volvulus infections. 2. Immunity: This is a generalized effect on the body. It can originate in organs or Page 42 of 42 systems remote from the vicinity of the infection. It persists for a long time even after elimination. This is a physiological response directed against the survival of the parasite. Anti-bodies are produced to destroy parasites in some cases. Cell mediated immunity by complement activation occurs such as in helminths infections. 3. Host Specification: Hosts have their own specific parasites. Some parasites are naturally adapted to certain species of hosts. For example, Trypanosoma brucei brucei infects only cattle but Trypanosoma brucei gambiense and Trypanosoma brucei rhodesiense infects humans. 4. Adaptations: Certain parasites develop certain morphological and drastic modifications to enable them fit to the host. For, example blood flagellates have torpedo shape to enhance swimming. Giardia lamblia has adhesive discs and Taenia solium have hooks to hold fast to the intestinal wall of host 5. Host Resistance: Host insusceptibility is the unsuitability of a host as physiology, behavior, and structure Host parasite interactions may also influence host resistance. For example, Plasmodium vivax is not popular among West African because of the Duffy factor in their red blood cells In Conclusion In Concluding, we can confidently say that; i. Parasites have undermined the health status of individuals and jeopardized the economic development of nations in tropical Africa leading to poverty. ii. Parasitism is also the major cause of low productivity of livestock and poultry in the tropics. iii. Parasites are ‘unwelcomed strangers’ because the body of an infected host reacts and builds a resistance against them. The immune system of hosts fights back against parasites, but unfortunately parasites fight back using several mechanisms of evading their hosts immune systems. iv. Only the host with the most vibrant immune systems can fight back successfully. Notwithstanding, the battle continues. Where and how, by whom? LECTURE 6. ZOONOSIS What is ZOONOSIS ??? Definition BIO 12I: Introduction to Medical Parasitology Lecture 6 Page 43 of 43  TOPIC: ZOONOSIS What is Zoonosis? DEFINITION OF ZOONOSIS.  Zoonosis is a disease that can be transmitted to humans from animals. Transmission occurs when an animal infected with bacteria, viruses, and fungi comes into contact with humans.  A zoonosis (zoonoses -plural) or zoonotic disease, is an infectious disease that is transmitted between species, from animals to humans or from humans to animals.  Is zoonosis therefore a condition or a disease? Classification of Zoonoses. As explained by many parasitologists, the gravity of zoonotic problems and the complexity of their epidemiological patterns, have necessitate their classification into suiting groups. This is to facilitate their diagnosis and management. Zoonotic diseases have been classified in four major categories; A. According to the Type of Causative Agents. i. Viral zoonoses, caused by virus e.g. rabies ii. Bacterial zoonoses, caused by bacteria e.g. anthrax, brucellosis, tuberculosis and diarrhea. iii. Rickettsial zoonoses, caused by rickettsia e.g. Q-fever iv. Chlamydial zoonoses, caused by Chlamydia e.g. Chlamydiosis v. Mycotic zoonoses, caused by fungi e.g. Aspergillosis, ringworm vi. Protozoan zoonoses, caused by protozoa e.g. Amoebiasis, toxoplasmosis vii. Helminthic zoonoses, caused by helminth parasites e.g. Taeniasis,/ Ascariasis schistosomiasis viii. Ectoparasitic zoonoses, caused by ectoparasites e.g. Scabies, Myiasis, B. According to the Direction of Transmission i. Anthropo-zoonosis: are diseases transmitted from animals (lower vertebrates) to man e.g., anthrax, brucellosis, tuberculosis, rabies. ii. Zoo-anthroponosis: are human diseases shared naturally by animals or transmitted to lower Page 44 of 44 vertebrate animals, e.g., diphtheria, human type tuberculosis, infectious hepatitis, measles. iii. Amphixenosis: this is a situation whereby infection is maintained in both man and lower vertebrate animals and may be transmitted in either direction, e.g., staphylococcosis, salmonellosis, E. coli infection C. According to Maintenance of the Life Cycle of the Agent in Nature - This classification is of immense epidemiological importance. It is very useful in developing appropriate strategies for the management of zoonotic diseases. 1. Direct Zoonoses: These are zoonoses that can be perpetuated in nature by a single vertebrate species. They are transmitted from an infected vertebrate host to a susceptible host by contact, vehicle or mechanical vector. The agent itself undergoes little or no propagative change during transmission, e.g., chlamydiosis, glanders, leptospirosis, ringworm, rabies, brucellosis, staphylococcus and syphilis. The direct zoonoses may be of the following types; a) Direct anthropozoonosis; in which the lower vertebrates (various species of domestic and wild vertebrate animals) are the reservoir host of the infectious agents and human involvement often occurs only through accidental exposures. These infections can exist in nature independently of man. b) Direct zoo-anthroponosis: This includes those diseases which normally are transmitted from man to man but which may occasionally infect lower vertebrates, e.g., tuberculosis, diphtheria. c) Direct amphixenosis: Some zoonotic infections may be maintained in nature either by lower vertebrate animals or by man. Transmission may occur in either or both directions. Man, and lower vertebrates are equally suitable reservoir hosts and infection can occur in the absence of one or the other, e.g., staphylococcosis 2. Cyclo-zoonoses: Here, more than one vertebrate host, but no invertebrate host is required for completion of the agent’s developmental cycle, e.g., tapeworm infection, hydatidosis. It may be obligatory or non-obligatory. a) Obligatory cyclo-zoonoses: Man must be one of the vertebrate hosts e.g., Taenia saginata infection b) Non-obligatory cyclo-zoonoses: Human involvement may not be involved, e.g. hydatidosis 3. Meta-zoonoses: Here, cycle required both vertebrates and invertebrates, and are transmitted biologically by invertebrate vectors. The invertebrate host may or may not serve as a reservoir of infection. 4. Sapro-zoonoses, require a non-animal site to serve either as a true reservoir of infection or as site for an essential phase of development, besides vertebrate host. The inanimate site may be organic matter, water, food, soil or plants. The agent may propagate in the non-animate site, e.g., histoplasmosis, or may undergo essential development without propagation (developmental stage) e.g. Ancylostoma braziliensis a) Sapro-anthropozoonosis: here infection is normally transmitted between a lower vertebrate and a Page 45 of 45 non-animate site and human involvement is only accidental. b) Sapro-amphixenosis: man, and lower vertebrates are equally susceptible host and infection can occur in the absence of one or another, e.g., histoplasmosis c) Sapro-meta-anthropozoonosis: this requires both an invertebrate host as well as a non-animate site in their transmission cycle, e.g., fascioliasis D. According to Mode of Transmission Zoonoses can be transmitted in different ways, which comprise; 1. Contact-borne, e.g., brucellosis 2. Food and water-borne, e.g., E. coli infection, Vibrio cholerae 3. Air-borne, e.g., anthrax, covid 4. Vector-borne, e.g., - - - - - - - - - a) Mechanical; carry the infectious agent on their body parts to susceptible host, e.g. anthrax, colibacillosis b) Biological; in which the infectious agent undergoes some biological transformation before infecting the host. This can be propagative or Cyclo-propagative. c) Trans-ovarian; the infection may be transmitted in vectors vertically from one generation to the next, e.g., Rift valley fever, sickle cell anemia( not parasitic). d) Trans-stadial; the infection may be transmitted in vectors from stage to stage. Zoonoses such as “those diseases and infections that are naturally transmitted between vertebrate animals and man”. Impacts of Zoonotic Diseases on Man. Their impacts on human life vary from mild effects to lethal. The following are just some common effects of zoonotic diseases on any given human population. 1. Acute or chronic debilitating illness 2. Impairment of productivity-reduced human output 3. Mortality 4. Reduced reproductivity 5. Loss of man-hours 6. Monetary/financial loss (for diagnosis, treatment, surveillance and control) 7. Adverse effect on morale of individuals. ( Our story in class of the Driver who had myiasis) ! Page 46 of 46  8. Unfavourable publicity – Fake news of a disease outbreak or resurgence in a country or locality, just to discourage tourists and other visitors, or destroy a market potential. Give examples! 9. Loss of export and foreign exchange. EXAMPLES OF ZOONOTIC DISEASES More than 200 diseases are currently classified as zoonoses. Common examples include tick-borne illnesses such as Lyme disease, wildlife-transmitted illnesses such as rabies, farm animal- transmitted diseases such as bovine tuberculosis from cattle, and mosquito-transmitted diseases such as the West Nile virus, malaria, and yellow fever. Other few well studied examples common to us include: 1. Tuberculosis: This is a chronic bacterial disease of cattle, swine, sheep, goats and human caused by mycobacterium spp. Horses, dogs and poultry are also susceptible, while wild animals which live in the wild are less susceptible to tuberculosis. However, animals in captivity suffer from the infection, since it is mainly a disease of overcrowding. Humans acquire the infection by inhalation, ingestion, and it could be also due to occupational hazards. The initial infection usually goes unnoticed. Tuberculosis sensitivity appears within a few weeks. Serious outcome of the initial infection is more frequent in infants, very old and immune- compromised adults. Infectious agents in humans are Mycobacterium tuberculosis and Mycobacterium africanum, M. bovis for cattle, and M. avium for poultry. Mortality and Morbidity rates increase with age, and in older persons, they are higher in males than females. It is much higher among the poor than the rich. Avian Tuberculosis: This is due primarily to Mycobacterium avium. Poultry TB has been reported in Nigeria and more likely to occur in old birds, especially old layers. Turkey is also susceptible to M. avium infection though not commonly reported. Clinically, there is initial fatigue, fever & weight loss with localizing symptoms of cough, chest pain, hemoptysis, and hoarseness, which becomes prominent in advanced stages. 2. Anthrax: This is a gram positive bacterial zoonoses primarily of ruminants but infective to man. Caused by Bacillus anthracis in humans, it causes a hyper acute infectious disease characterized by fever, septicemia, and rapid death. It may also assume Acute Meningitis Syndrome, following either cutaneous or respiratory infection. Intestinal form of anthrax may be from consumption of contaminated meat. 3. Glanders: This is a highly communicable disease of horse, mules or donkeys. Human infection can occur, but rarely and if it occurs, it is usually fatal. 4. Travelers’ diarrhea: Escherichia coli. This is a major cause of travelers’ diarrhea, and the diarrhea causing E. Coli are of 5 major categories: Enterotoxigenic, Enteropathogenic, Enteroinvasive, Enterohaemorrhagic and Enteroaggregative. Each has a different pathogenicity, possesses distinct Page 47 of 47 virulence, properties and comprises a separate serotype, differing clinical syndromes and epidemiologic patterns. 5. Tetanus/ Lockjaw. Caused by Clostridium tetani. Found in the soil and in animals and human faeces. It is more common in the tropics than in the cold climate. Horses are the most affected, although sheep, goat and cattle can develop the disease. All herbivores are primarily susceptible to infection. The disease in man is characterized by tonic spasm of masseter muscles and other muscles. The reflexes are exaggerated and convulsion may occur. The disease in animals is similar in signs and symptoms as in humans. The major source of infection is through wounds and during routine procedures like dehorning, shaving and tail docking. Iatrogenic tetanus can also occur during routine procedures like castration. Both animals and man may contribute to the contaminated environment, since the organism is a normal inhabitant of the soil. Prevention & Control: Immunization plays an important role in prevention. 6. Human Sleeping Sickness caused by Trypanosoma brucei rhodesiense is an important example in which mass treatment of cattle significantly reduces the risk of disease in humans. 7. Human Epilepsy. Another example is in which neuro- cysticercosis caused by the intermediate host of the pork tapeworm (Taenia solium). 8. AIDS, EBOLA, ……... and COVID. Who knows the next??? Human Health Implications of Zoonoses i. Zoonoses are among the most frequent and dreaded risks to which mankind is exposed. ii. Domestication of animals has come along with more opportunities for the passage of pathogens from animals to man, and vice versa. This is because numerous species of animals are sources of viral, bacterial and parasitic diseases transmitted in many ways, including direct contact with them or water contaminated by them. iii. Infections which pose challenges to human health and welfare, originate either from animals directly, or through their products and by-products. Hence human health is unavoidably directly connected to animal health and production. This could be the bases of the YOGISTS’ philosophy!!! iv. In both developing and industrialized nations, this has led to a serious risk to public health, with severe economic consequences. About 75% of the new diseases (emerging zoonosis) that have affected humans over the past 10 years, have been caused by pathogens originating from animals. Many of these diseases have the potential to spread through various means, over long distances and have become global problems. E.G., the Covid 19? AND OTHERS? The reasons for some compulsory Page 48 of 48  international vaccines, such as the Yellow Fever Vaccine. v. Approximately 80% of all described human diseases are from animals. For many diseases only circumstantial evidences for natural transmission is there so known as “suspected zoonosis” and epidemiology of many diseases is not sufficiently understood hence are called “masked zoonosis”. vi. Some humans are more at risk to zoonotic diseases than others e.g. infants and children (immature immune systems, poor hygiene) , pregnant women(immune systems are more susceptible and there are additional fetal hazards), elderly persons(immune systems may be impaired), immune-compromised people (undergoing cancer therapy, AIDS/HIV patients), people who have received organ or bone marrow transplant , people born with congenital immune deficiencies, veterinarians ,farm families and other animal health care workers. vii. All major zoonotic diseases prevent the efficient production of food of animal origin, particularly of much needed protein and creation of international trade in animals and animal by- products Socio-Economic Impacts of Zoonosis. 1. Zoonosis is a social and economic burden. For many years and in many countries these diseases, with their reservoirs in domestic and wild animals, have imposed and are still imposing a very heavy burden, especially among the vast number of people living and working in rural areas. 2. The significance of zoonotic and parasitic diseases and related food-borne diseases, is growing continuously and their health and socio-economic impacts are increasingly being felt by many countries and most particularly, although not exclusively, by developing countries. 3. Apart from causing human suffering, morbidity and mortality, zoonoses hamper agricultural production, decrease availability of food, inhibit the generation of capital needed for investment and create barriers to international trade. Very evident in the great changes of the current times, especially the increasing urbanization, most of which is inadequately planned, large movements of populations, opening up of badly needed new areas for food production, the increasing trade in meat, milk and other products of animal origin, the vastly increasing number and speed of vehicles, and tourism have contributed to making the problem of zoonoses not only rural and characteristic of defined areas, but regional and worldwide. 4. The developing countries suffer much loss than technically developed countries. This is attributable to the lack of adequately organized public health and veterinary services, poor Page 49 of 49  hygiene, poor facilities for prompt diagnosis, poor standard of living and poverty and to particular social customs prevailing in the predominantly agricultural societies of developing countries. 5. Besides causing economic losses (related to treatment, immunization, loss of wages, loss of man- hours and manpower), morbidity and mortality in humans, zoonosis causes considerable loss of livestock, their productivity (dairy products, protein food, and animal by-product industries) and reproductivity. 6. Zoonosis acts as a double-edged weapon affecting social aspects and economic development. The socio-economic losses of zoonoses though, significant, are difficult to quantify completely, because as with other human diseases, the actual costs in terms of lives and suffering cannot be measured. In addition, the losses in export and investment opportunities and the consequent losses in foreign exchange by countries because of zoonoses cannot be estimated. 7. Developing countries and especially the poor, whether they are livestock owners, labourers working with animals, livestock owners, consuming products from their animals or non- livestock owners consuming these products, suffer special consequences. a. First being that, many of these diseases are fatal and cause disability in humans, the prevention of which is often through their control in animals. This requires the availability of appropriate veterinary and animal health technologies and their delivery to and accessibility by the people. - Human Sleeping Sickness caused by Trypanosoma brucei rhodesiense is an example in which mass treatment of cattle significantly reduces the risk of disease in humans. - Another example is Human Epilepsy in which neuro- cysticercosis caused by the intermediate host of the pork tapeworm (Taenia solium) is considered the main cause. b. The second feature is that, while there are some zoonoses to which a large section of any given human population is equally susceptible, the poor and the developing countries are at particularly at risk to many of them. Example include cysticercosis in pig in which poor sanitation is the underlying cause for which the knowledge and resources to adopt preventive measures are limited or absent. Another example is Leptospirosis in which rats play an important role in the maintenance of infection and rats often thrive in poor and dirty environment. Page 50 of 50 c. The third and possibly the most important of these features is that, the lower down the income scale, the more likely is the high risk of multiple zoonoses. Examples can be found in some rural and peri urban settlements where animals co-exist with families struggling for survival. There is potential risk of human brucellosis and Tuberculosis from cow. The risk of multiple zoonoses is a factor poor purchase of cheap animals or meat that have not been inspected, lack of knowledge and resources to protect their dogs from rabies. d. Some humans are more at risk than others; like infants and small children (with immature immune systems, poor hygiene), pregnant women (immune systems are more susceptible and there are additional fatal hazards), elderly persons (whose immune systems may be impaired), immune-compromised people (undergoing cancer therapy, AIDS/HIV patients, people who have received organ or bone marrow transplant, people born with congenital immune deficiencies, Veterinarians, farm workers, zoo/wildlife workers and other animal health care workers. (Treat this topic as an area of concentration for your exams)! GOOD LUCK! END OF OUR LITTLE STORIES! HOPE YOU WILL REMEMBER THEM. OUR NEXT LECTURE IS REVISION. I WISH YOU ALL THE BEST IN YOUR STAY AND STUDIES AT VERITAS UNIVERSITY! MAY EACH OF YOU BRING ABUNDANT JOY AND CELEBRATIONS TO YOUR FAMILIESS, AT THE END OF YOUR STUDIES HERE, AND BEYOND! AMEN! AMEN! AMEN!!! Page 51 of 51