Week1-parasitology.pdf

Veterinary Parasitology VET 3003 1 Parasitology ▪Study of relationship between parasite and host. History ▪Father of Parasitology – Platter ▪Father of modern Parasitology – Francesco Redi An Italian scientist who identified and described many impo...

Veterinary Parasitology VET 3003 1 Parasitology ▪Study of relationship between parasite and host. History ▪Father of Parasitology – Platter ▪Father of modern Parasitology – Francesco Redi An Italian scientist who identified and described many important parasites. Francesco Redi  Branches of Parasitology 1- Structural Parasitology Study of structures of proteins from parasites. Determination of parasitic protein structures may help to better understand how these proteins function differently and may helpful in the process of drug discovery. 2- Quantitative Parasitology Parasites exhibit an aggregated distribution among host individuals. It involves the use of statistics to draw meaningful conclusions from observations of the prevalence and intensity of parasitic infection. 3- Protozology Scientific study of protozoa. Protozoa are unicellular, heterotrophic eukaryotes. Example: Coccidia in birds Coccidia Paramecium Protozoa i- Veterinary Protozology: Study the protozoa that cause disease in animals. Example: Piroplasmosis is disease caused by the Babesia equi (horses, donkeys, mules). - East coast fever also call Theileriasis caused by Theileria annulata (cattle), Theileria parva (sheep) and Theileria ovis (goat). ii- Medical Protozology: Study the protozoa that cause disease in human. Example: Amoebiasis caused by Entamoeba histolytica - Leishmaniasis caused by Leishmania 4- Helminthology Scientific study of parasitic worms (helminths). Example: Echinococcus granulosus, Taenia solium, ▪3 types of helminths: Nematode, Trematode, Cestode Helminths i- Veterinary Helminthology: Study of helminths (parasitic worms) that cause disease in animals. Example: Ascaridia galli (birds), Fasciola hepatica (ruminants) ii- Medical Helminthology: Study of helminths (parasitic worms) that cause disease in humans. Example: Ascaris lumbricoides, Schistosoma mansoni 5- Entomology ▪Scientific study of insects. Example: Acarus siro (mite) Tick (Ixodidae) Insects, Ticks and Mites i- Veterinary Entomology: Study of insects that cause disease or that are vectors of organisms that cause disease in animals. Example: Ornithonyssus sylviarum (bird mite) Damalinia limbata (goat louse) ii- Medical Entomology: Study of insects and arthropods that impact human health. Example: Aedes albopictus (mosquito), Cimex lectularius (bed bug)  Parasite ▪An organism that lives on or in its host, which is usually a larger organism that provides physical protection and nourishment. ▪Parasites affect the host by many ways ▪If producing a disease the pathogenesis can be in the form of ▪ Trauma ▪ Nutrient robbing ▪ Toxin production ▪ Interaction with immune system  Taxonomy ▪Scientific Classification of Parasites The Kingdoms ▪Protista – Single-celled organisms ▪ Amoeba ▪ Coccidia ▪ Giardia ▪ Toxoplasma ▪Animalia – Multi-cellular animals ▪ Most parasites we will cover are here ▪ Most animals are free-living, not parasitic 3 Phyla of Kingdom Animalia ▪These 3 phyla have the parasites we will cover this semester ▪Phylum Platyhelminthes – flatworms & tapeworms ▪Phylum Archelminthes – roundworms (nematodes) ▪Phylum Arthropoda – arthropods  Parasite are categories on the basis of 1- Location on the Host 1- Location on the Host 2- Amount of Time on the Host Ectoparasite On outside surface of body of host Examples – fleas, mosquitoes, horse flies Endoparasite Live in body of host Examples – roundworms, whipworms, heartworms  2- Amount of Time on Host i- Temporary ii- Stationary ii- Stationary Spends definite period of time in or on host iii- Permanent Most parasites Periodic – leaves host to complete development i- Temporary (example – Cuterebra) Visits host for food Examples Ticks Mosquitoes iii- Permanent ▪Spends entire life on host, except when transferring to another host ▪Examples ▪ Ear mites ▪ Lice Types of Parasites 1- Incidental Parasite 2- Erratic (Aberrant) Parasite 3- Obligate Parasite 4- Facultative Parasite 5- Pseudoparasite 1- Incidental Parasite 3- Obligate Parasite ▪Appears in unusual hosts ▪Must lead parasitic existence ▪Examples – ▪No free-living stages ▪ Heartworms in man ▪Examples ▪ Lice ▪ Crab louse in dogs ▪ Ear mites ▪ Some mites 2- Erratic Parasite ▪Aberrant parasite 4- Facultative Parasite ▪Seen in unusual locations in hosts ▪Free-living organism that can become parasitic in certain hosts ▪Examples – ▪Examples ▪ Heartworm in eye ▪ Cuterebra in brain ▪Chigger mite larvae (microscopic) ▪Ringworm in cats, calves 5- Pseudoparasite ▪Organisms that appear to be parasites, but are not parasite ▪Examples – grain mites in fecals,, pollen grain and air bubbles  Types of Hosts 1- Definitive Host: The host in which the parasite goes through its sexual cycle (I.e., fertilization & meiosis) Example: mosquitoes serve as definitive hosts of the malaria parasite (Plasmodium spp.) Example: snakes (~30 species) serve as definitive hosts of Sarcocystis singaporensis, a disease of mammals 2- Intermediate Host: Host in which the parasite replicates but does not go through its sexual cycle Example: mammals, including humans, serve as intermediate hosts of the malaria parasite (Plasmodium spp.) Example: mammals (~30 species, including humans) serve as intermediate hosts of Sarcocystis singaporensis 3- Reservior Hosts: The reservoir host is the population in which a parasite resides when it isn’t affecting a population that we care more about Example: the rabies virus normally is passed back and forth among wild mammals (these serve as the reservoir hosts—the populations that we don’t much care about) Occasionally, however, rabies can infect pets, and thereby us (the population we do care about) To prevent the latter (i) we vaccinate pets, (ii) avoid handling wild animals, and (iii) otherwise attempt to reduced the incidence of rabies in reservoir pops.  4- Incidental/ Accidental host ▪Wrong host species for this parasite ▪If man – parasite is a zoonosis ▪ Raccoon roundworms ▪ Heartworms in cats.  Symbiosis ▪Any association between at least 2 different living organisms of different species. ▪Each partner is called ‘’Symbiont’’ ▪‘’Sym’’ means ‘together’ and ‘’biosis’’ means ‘living’ thus ‘’living together’’ ▪Example: Act of a human owning a dog and living with that dos is a type of symbiotic relationship. Types of Symbiotic Associations ▪5 type of symbiotic relationships: Predator-prey relationship, Phoresis, Mutualism, Commensalism, Parasitism ▪If we consider the degree of the association, then phoresis and commensalism represent “loose” associations, where as mutualism and parasitism indicate “intimate” associations  1- Predator-prey relationship ▪Extremely short relationship and one symbiont benefits at the expense of other. ▪Predator -The bigger animal ▪Prey -The smaller or weaker animal ▪Example: Loin (predator) kill the zebra (prey). The prey pays with its life and serves as a food source for predator.  2.Phoresis (Phoresy) In this type of relationship, the phoresis has been regarded as a type of symbiotic relationship in which one organism(smaller called phorant) is mechanically carried on or in another species(larger called host) Phoresis means “to carry.” In phoresis, there is no physiologically or biochemically dependence on the part of the host or symbiont Example: Moraxella bovis (cause bovibe keratoconjunctvitis or pinkeye of cattle) is mechanically carried from eye of one cow to other by sticky foot pads of Musca autumnalis (face fly)  3. Commensalism Means “eating at the same table” Association in which one member of the associating pair receives all the benefit and the other member is neither benefited nor harmed Example: Relationship between Shark and Remora (suckerfish), which attaches underside of shark and hitches a ride. Remora also eats food scraps or leftover of shark meal. Remora gets benefit from this relationship and shark neither harm nor benefits.  4. Mutualism Association in which both organism in symbiotic relationship get benefits. Mutuals are metabolically dependent on one another; one cannot survive in the absence of the other. Example: Microbes living in rumen of cow. Cow provides them food, warm and liquid environment and microbes break down cellulose for cow.  Honey bee take juice from plants and in return pollens stick on bee and spread pollens of plants Honeybee bringing pollen to a desert shrub  5. Parasitism Intimate relationship between two heterospecific organisms, in which the parasite lives on or within the host and may cause harm. Parasite metabolically Gastrointestinal Parasites of Cattle - Digestive System dependent on the host. Example: Helminth living in gastro-intestinal tract of host.  Parasite Transmission ▪How parasites transfer from one host to another ▪Passive transmission ▪ Parasite does not travel to host ▪ Ingested by the host ▪ Example – ascarids (roundworms) ▪Active transmission ▪ Parasite travels to host and/or aggressively penetrates host ▪ Examples – fleas, hookworm larvae Inoculative Transmission ▪Vector/ Intermediate host “injects” parasite into definitive host ▪ Often takes blood from definitive host ▪ Often has “sucking mouthparts” ▪ Examples – mosquitoes, ticks  Vectors A living organism that carries and transfer a disease-causing organism to new Hosts. Example: Anopheles mosquito is a vector for the parasitic disease malaria because we care more about the health of the human host than that of the mosquito However, in addition, the malaria parasite has a much greater impact on the health of the human host than it does on the health of the mosquito vector  Biological Vector: The vector where parasite undergoes some stages/ aspect of its life cycle. Example: Plasmodium (cause malaria) gone through developmental stages in mosquito. Mechanical Vector The vector where parasite does not undergo some aspect of its life cycle and it transport parasite to a second host. Example: Flies are mechanical vectos of feces- born pathogens such as Salmonella Disease Vectors ▪Mosquitoes ▪ Heartworms ▪ West Nile Virus ▪ Equine encephalitis ▪ Equine infectious anemia (EIA) ▪Ticks ▪ Lyme disease ▪ Rocky mountain spotted fever ▪Fleas ▪ Feline infectious anemia Parasitic nutrition Parasitic nutrition is a mode of heterotrophic nutrition: Parasite lives on the body surface or inside the body of host and the parasite obtains nutrition directly from the body of the host. Since these parasites derive their nourishment from their host, this symbiotic interaction is often harmful to the host. Parasitic nutrition Parasites are dependent on their host for survival, since the host provides nutrition and protection. As a result of this dependence, parasites have considerable modifications to optimise parasitic nutrition and therefore their survival.  Environmental Constraints on Transmission Examination of the parasitic life cycle often explains why a given parasitic disease is found in one area of the world and not another. For example, the transmission of schistosomiasis depends on an intermediate snail host that is not present in North America or Europe. Thus, viable eggs in the stool or urine of infected persons cannot produce the forms infective for humans because there are no intermediate snail hosts in which the parasite can mature. For that reason, human schistosomiasis is not endemic in these countries and will not be, unless an intermediate snail host becomes established. Harmful Effects of Parasites Harmful Effects of Parasites ▪Blood loss ▪Secondary invasion of pathogens ▪ Hookworms, fleas ▪ Bacterial infections after primary disease has ▪Hypersensitivity (allergy) begun ▪ Example – generalized demodectic mange ▪ Flea allergy dermatitis (FAD) ▪ 15% of dogs & cats ▪Disease transmission ▪ Heartworms? Eosinophilia as high as 20% ▪ Parasite vectors – carry disease to host ▪Toxicity ▪Worry ▪ Maggots ▪ Horse flies in the barn  Parasite Life Cycles ▪ The entire sequence of stages in the life of a parasite, from adults of one generation to adults of the next generation. ▪Parasite may be “Species Specific” ▪ Affect only 1 species of host ▪ Lice – species specific; fleas – not ▪2 types of life cycle ▪ Direct life cycles ▪ Indirect life cycles  1- Direct Life Cycles ▪Parasite transfers from one host to another host of same species ▪ Dog to dog to dog, etc. ▪No intermediate hosts Direct Life Cycle-Fleas ▪Examples – fleas whipworms ▪Direct Life Cycle-Fleas Direct Life Cycle – Whipworms  2- Indirect Life Cycles ▪Parasite requires at least 1 intermediate host to complete its life cycle ▪Intermediate host harbors immature parasite ▪Definitive host harbors adult parasite ▪Examples – heartworms, all tapeworms, flukes ▪Best way to stop life cycle is to eliminate intermediate host Always have intermediate hosts Indirect Life Cycle – Tapeworms ▪Some parasites have both a direct as well as indirect life cycle ▪Examples – roundworms, hookworms Parasites with Both Life Cycles 52