Veterinary Parasitology I PDF Past Paper 2022

Veterinary Parasitology I 05/11/2022 Lebanese University Faculty of Agricultural & Veterinary Sciences PARASI...

Veterinary Parasitology I 05/11/2022 Lebanese University Faculty of Agricultural & Veterinary Sciences PARASITOLOGY 1 DR WALID DARWICHE 1 DEFINITIONS: PARASITES, PARASITISM AND PARASITIC DISEASES 2 Dr. Walid Darwiche 1 Veterinary Parasitology I 05/11/2022 One can form a close relationship with a tapeworm! Source:©Serre, C. (1984) Stuffing. Methuen London Ltd, London, UK DR. WALID DARWICHE 3 3 I. WHAT IS VETERINARY PARASITOLOGY? DR. WALID DARWICHE 4 4 Dr. Walid Darwiche 2 Veterinary Parasitology I 05/11/2022 Animal disease can have noninfectious or infectious origins.  Noninfectious diseases: Genetic defect Physiological abnormality Structural dysfunction External factors: injury, radiation or poisoning…  Infectious diseases are associated with invasive self-replicating agents that have evolved to occupy an animal body as their ecological niche in just the same way. DR. WALID DARWICHE 5 5 Studies in Infectious Diseases  Microbiology  Virology  Bacteriology  Mycology  Parasitology  Medical & Veterinary Protozoology: a subject that embraces the wide range of single-celled eukaryotic organisms that comprise the parasitic protozoa  Helminthology: which covers three main groups of parasitic worms – trematodes (flukes), cestodes (tapeworms) and nematodes (roundworms), as well as some minor groups such as the thorny-headed worms  Medical & Veterinary Entomology: the study of parasitic arthropods, including insects, ticks and mites DR. WALID DARWICHE 6 6 Dr. Walid Darwiche 3 Veterinary Parasitology I 05/11/2022 Parasites in Practice  In a veterinary practice how much effort & time is spent on Parasite issues?  What parasites are often diagnosed in a veterinary practice?  What parasites do veterinary practices often try to manage? DR. WALID DARWICHE 7 7 II. PARASITISM AND PARASITES DR. WALID DARWICHE 8 8 Dr. Walid Darwiche 4 Veterinary Parasitology I 05/11/2022 A. HOST–PARASITE RELATIONSHIPS Parasitism is part of a spectrum of intimate zoological relationships between unrelated organisms which includes: 1. Mutualism: describes a relationship in which both partners benefit from the association. Mutualism is usually obligatory, since in most cases physiological dependence has evolved to such a degree that one mutual cannot survive without the other. An alligator and a bird's symbiotic relationship is mutualism. The alligator gets its teeth cleaned by the bird. The bird gets its food from the alligators' teeth. DR. WALID DARWICHE 9 9 e.g., intestinal protozoa in termites. Termites feed on food that they do not digest but protozoa living in their intestine digest the food. Termites do not have the enzyme cellulase, but still feed on food that is rich in cellulose. Protozoa living in the intestine of termites synthesize the enzyme cellulase and help in digesting the food ingested by the termite. DR. WALID DARWICHE 10 10 Dr. Walid Darwiche 5 Veterinary Parasitology I 05/11/2022 2. Commensalism: one partner benefits from the association, but the host is neither helped nor harmed. The term means “eating at the same table,” and many commensal relationships involve feeding on food “wasted” or otherwise not consumed by the host. A remora (Echeneis naucrates) and its host, a zebra shark (Stegostoma fasciatum). By attaching itself to the shark, the remora is carried along by the shark, allowing the remora to travel to different areas without having to expend its own energy to swim. The shark is completely unaffected by the remora's presence. DR. WALID DARWICHE 11 11 DR. WALID DARWICHE 12 12 Dr. Walid Darwiche 6 Veterinary Parasitology I 05/11/2022 3. Parasitism: one of the participants, the parasite, either harms its host or in some sense lives at the expense of the host. Most parasites inflict a combination of these conditions on their hosts. DR. WALID DARWICHE 13 13 DR. WALID DARWICHE 14 14 Dr. Walid Darwiche 7 Veterinary Parasitology I 05/11/2022 4. Symbiosis: is association between two different organisms living in close physical association, be it mutualistic, commensalistic, or parasitic. The organisms, each termed a symbiont, must be of different species. Symbiosis can be obligatory, which means that one or more of the symbionts depend on each other for survival, or facultative (optional), when they can generally live independently. DR. WALID DARWICHE 15 15 5. Phoresis: is a relationship between two symbionts which are merely traveling together and without physiological or biochemical dependence on each other. One will be larger than the other and the smaller phoront will be mechanically carried by the larger phoront, for example, mites carried by beetles or bacteria on the legs of a fly. DR. WALID DARWICHE 16 16 Dr. Walid Darwiche 8 Veterinary Parasitology I 05/11/2022 B. PARASITE  Greek: parasitos: men sitting at King’s table tasting food in order to find out whether poison is in.  Since other people noted that these “parasitos” got their food without work, the term obtained a negative meaning which stands even today.  Later the term was transferred to people/animals which live on other than own costs.  An animal that lives completely at the expense of plants, animals, or humans is defined as parasite. Some authors also consider viruses, bacteria, and fungi as parasites. DR. WALID DARWICHE 17 17 C. CLASSIFICATION  The animal kingdom is divided into some 35 phyla (singular ‘phylum’), which in turn are subdivided successively into Class, Order, Family, Genus and Species, with a species being the basic replicating entity.  Subclass, Suborder and Superfamily groupings are also useful in some contexts. DR. WALID DARWICHE 18 18 Dr. Walid Darwiche 9 Veterinary Parasitology I 05/11/2022 Nomenclature  The identity of every organism is defined by using a combination of its genus and species names.  Thus, the protozoan parasite that causes Redwater fever in northern European cattle is Babesia divergens, while the related species Babesia bovis and Babesia bigemina cause similar diseases in warmer regions. -osis: disease caused by chu mnektub abla  By international agreement, the ending -osis is placed on a parasite name to indicate the disease caused by that parasite, e.g., babesiosis.  By tradition, the ending -iasis is sometimes preferred in human medicine and may occasionally be found in veterinary publications. DR. WALID DARWICHE 19 19 III. DIFFERENCES IN PARASITE LOCALIZATION DR. WALID DARWICHE 20 20 Dr. Walid Darwiche 10 Veterinary Parasitology I 05/11/2022 Parasites can be broadly categorized according to their location on or in the body of their host:  Ectoparasites: live or feed on the surface of the host or embed themselves into superficial or adjacent underlying tissues. Ectoparasites engage in host– parasite associations ranging from flies that land fleetingly to feed on secretions from the eyes, nose or other orifices to mites that spend nearly their whole lives in skin tunnels.  Endoparasites: live within the body of the host. Parasites may be found in every body tissue except, perhaps, bone and keratin. Those free in the lumen of the gastrointestinal tract are, technically speaking, lying outside of any host tissue, but they are nevertheless included in this category. Examples – roundworms, whipworms, heartworms. DR. WALID DARWICHE 21 21 Gastrointestinal parasites such as the worms depicted here in black are technically ‘outside’ of any body tissue. DR. WALID DARWICHE 22 22 Dr. Walid Darwiche 11 Veterinary Parasitology I 05/11/2022 IV. RELATIONSHIP OF THE PARASITE TO THE TISSUE IT INHABITS DR. WALID DARWICHE 23 23 A fundamental distinction that influences both the pathogenesis of infection and options for control is the relationship of the parasite to the tissue it inhabits:  Extracellular parasites: these live on or within host tissues but do not penetrate into host cells. Examples include almost all metazoan and also many protozoan parasites.  Intracellular parasites: these live inside a host cell modifying its genomic expression to satisfy for their needs, e.g., many protozoan parasites and at least one nematode genus (Trichinella). DR. WALID DARWICHE 24 24 Dr. Walid Darwiche 12 Veterinary Parasitology I 05/11/2022 V. CONCEPT OF MICRO AND MACRO PARASITES DR. WALID DARWICHE 25 25 Parasites can also be differentiated based on their reproductive behavior in the final host. This distinction is useful as it points towards fundamental biological differences that influence pathogenesis, epidemiology, control and treatment: A. Microparasites: these multiply within their host. Consequently, each organism that enters the body is capable of initiating a massive infection if not checked by host defenses or by chemotherapy. This category includes the parasitic protozoa (as well as microorganisms such as bacteria). DR. WALID DARWICHE 26 26 Dr. Walid Darwiche 13 Veterinary Parasitology I 05/11/2022 B. Macroparasites: these do not generally increase in number while they are on or within the final host. They may produce eggs or larvae, but these are dispersed into the environment. Thus, the number of mature parasites on or in the final host never exceeds the number of infective units that originally invaded the body. This category includes arthropods and helminths, although there are a few species that break the general rule by multiplying on or in the host (for example: lice, mites and a few nematodes, e.g. some Strongyloides species). DR. WALID DARWICHE 27 27 VI. DIFFERENT MODES OF PARASITISM DR. WALID DARWICHE 28 28 Dr. Walid Darwiche 14 Veterinary Parasitology I 05/11/2022 A. Obligate Parasite - This parasite is completely dependent on the host during a segment or all its life cycle, e.g., Lice, ear mites, some other mites. B. Facultative parasite – an organism that exhibits both parasitic and non- parasitic modes of living and hence does not absolutely depend on the parasitic way of life but can adapt to it if placed on a host. E.g., Ringworm in cats, calves. y3ne matlan ringworm fiyo y3ish barrat lbsen kamen rawa2 C. Accidental parasite – when a parasite attacks an unnatural host and survives. E.g., Heartworms in man, Crab louse in dogs. D. Erratic parasite - is one that wanders into an organ in which it is not usually found. E.g., Heartworm in eye, Cuterebra in brain heartworm usually bt3ish bl heart wl vessels DR. WALID DARWICHE 29 29 VII. HOSTS DR. WALID DARWICHE 30 30 Dr. Walid Darwiche 15 Veterinary Parasitology I 05/11/2022 A. Final (or definitive) host: a term used to identify the host in which the parasite reaches the adult stage, and sexual reproduction of the parasite takes place (the parasite reaches sexual maturity). B. Intermediate host: this is a host in which only immature stages grow and develop. Asexual replication may occur (but not sexual reproduction). It often acts as a vector of the parasite to reach its definitive host. For example, Dirofilaria immitis, the heartworm of dogs, uses the mosquito as its intermediate host until it matures into the infective L3 larval stage. C. Transport and paratenic hosts: host which the sexually immature parasite enters, does not undergo any development or reproduction, but remains infective to the definitive host. DR. WALID DARWICHE 31 31 D. Reservoir host: A primary host that harbors the pathogen but shows no ill effects and serves as a source of infection. Reservoir hosts do not get the disease carried by the pathogen or it is asymptomatic and non-lethal. Once discovered, natural reservoirs elucidate the complete life cycle of infectious diseases, providing effective prevention and control. E. Vector: this is a vague term for an insect, tick or other creature that carries (transmits) a disease-causing organism from one host to another. DR. WALID DARWICHE 32 32 Dr. Walid Darwiche 16 Veterinary Parasitology I 05/11/2022 VIII. PARASITIC DISEASES DR. WALID DARWICHE 33 33  A parasitic disease or parasitosis is an impairment of health.  Generally, a disease caused by a parasite ends with "-osis" (helminthosis, nematodosis, parasitosis, etc.) more rarely with "iasis".  It is necessary to study the etiology (cause of the disease) responsible for the symptoms (manifestations) caused by the pathogenesis (explanation of the mechanisms responsible for the disease).  These are the starting points for studying a disease. DR. WALID DARWICHE 34 34 Dr. Walid Darwiche 17 Veterinary Parasitology I 05/11/2022  It should also distinguish between infection and infestation.  Infection suggests a multiplication of the pathogen in the host, and therefore a pathogen cycle. Infestation is a notion specific to certain parasites that evolve in the host but do not multiply there: they are still responsible for disease. The cycle can take place in the external environment. (ex: Nematodes)  The pathogenic action of a parasite depends on its species, its sex (ex: In mosquitoes, only females bite), the evolutionary stage (ex: some stages are pathogenic, everything depends on the cycle), the degree of adaptation to its host. Very closely related species can have very different pathogenic manifestations. DR. WALID DARWICHE 35 35  Evolution leads to a state of equilibrium between host and parasite.  As a result, the oldest parasites are the least pathogenic, because there has been co-evolution of the host and the parasite.  Parasitic disease is a conflict between the pathogenic actions of the parasite (feeding, perforation, etc.), the host's defense reactions and the parasite's escape mechanisms compared to the host's defense reaction against him. DR. WALID DARWICHE 36 36 Dr. Walid Darwiche 18 Veterinary Parasitology I 05/11/2022 IX. TERMINOLOGIES USED IN PARASITIC DISEASES DR. WALID DARWICHE 37 37  Epidemiology is the study of a disease in relation to the population, aspects of disease such as incidence, prevalence and transmission in a population  Endemic disease refers to a disease that occurs with a predictable frequency with minor fluctuations in a population  Epidemic disease refers to diseases that occur at a higher level in a place at a time than expected for the disease in the place at that particular time  Sporadic diseases are those diseases that occurs irregularly with widely dispersed incidence or a disease that occurs infrequently  Pandemic is an epidemic occurring in a wide/larger area.  Incubation period is the time lapse between the entry of the parasite and the first appearance or onset of clinical signs.  Prepatent Period is the period between infection with a parasite and the production of eggs by a female; equivalent to the incubation period of microbial infections, but biologically different because the parasite is going through developmental stages in the host.. DR. WALID DARWICHE 38 mafrud n3refun 38 Dr. Walid Darwiche 19 Veterinary Parasitology I 05/11/2022  Hypobiosis refers to temporary cessation in the development of immature stages of some nematode parasites in the host due to adverse environmental conditions, for example, Ostertagia ostertagi in cattle  Hibernation (Winter Sleep) refers to low activity of parasites in winter.  Aestivation (summer sleep) is the period of low activity in summer  Diapause is a period of low activity in arthropods.  Parthenogenesis is a(Virgin birth) refers to formation of progeny without fertilization e.g., Haemaphysalis ticks and Strongyloides sp. of nematodes. DR. WALID DARWICHE 39 39  Schizogony is a type of asexual division/multiplication in protozoa where a parasite multiplies into numerous individuals by multiple fission. The nucleus of the parasites undergoes repeated division without cytokinesis. e.g., apicomplexan parasites.  Gametogony is the differentiation of gamonts in to male and female gametes  Syngamy is the union of the male and female gametes to form the zygote e.g., apicomplexan parasites  Sporogony is the differentiation of zygote to oocyst, sporocyst and sporozoites e.g., all apicomplexan parasites. DR. WALID DARWICHE 40 40 Dr. Walid Darwiche 20 Veterinary Parasitology I 05/11/2022 X. MODES OF TRANSMISSION DR. WALID DARWICHE 41 41  Parasites have distinct routes of entering a host.  Endoparasites enter the hosts in general through natural openings on the exterior of the body or through the skin.  Parasites are transmitted from one animal to another by  Ingestion  Skin penetration  Contact  Predation  Coitus  Transplacental/Transmammary transmission ex. toxacara canis: bas tkun female heblee b kun fi dormant larvae w byejo 3al foetus aw 3al 7alib w bynte2lo 3leyun DR. WALID DARWICHE 42 42 Dr. Walid Darwiche 21 Veterinary Parasitology I 05/11/2022 THROUGH INGESTION  The most common mode of transmission of parasites is through ingestion.  The host may become infected by direct ingestion of an infective stage through contamination of food and water or by ingestion of an intermediate host or transport host containing infective stages.  For parasites with direct life cycles, the infective stages: egg containing the second larval stage (ascarids), cysts (Entamoeba and Giardia) and oocysts (coccidia) find their way into the feed and water of the host thereby gaining access to the host, or the infective stages (third larval stage) may climb up the vegetations and wait for the host to ingest. l examples bukra mnshufun in details DR. WALID DARWICHE 43 43  For parasites with indirect life cycle, the host becomes infected by ingestion of an intermediate host or transport host containing infective stages.  In certain parasites, the definitive hosts are infected through ingestion of infective stages (larval stages) in intermediate hosts (fish for Diphyllobothrium latum and crabs for Paragonimus sp) and through ingestion of raw or undercooked meat/organs/milk of intermediate hosts (Taenia solium, Echinococcus granulosus). DR. WALID DARWICHE 44 44 Dr. Walid Darwiche 22 Veterinary Parasitology I 05/11/2022 THROUGH SKIN PENETRATION eza l host la2at l parasite w kenit ba3d mch infective=> ma fi disease  After mouth, skin is the most common route of entry for many parasites.  The infective stages of the parasite may actively penetrate the skin and in this process, the secretions of the parasite help to digest the host tissue (cercariae in schistosomes).  Penetration of the host’s skin is the predominant route by which the infective larvae of hookworms enter their hosts, although they also enter through the mouth.  Certain parasites enter the hosts via the bite of an intermediate host serving as a vector. These parasites develop in blood sucking insects and ticks and when these vectors feed to obtain the blood and tissue fluids from hosts, the infective stages of the parasites are introduced into the host. DR. WALID DARWICHE 45 45 CONTACT AND PREDATION  Parasites are transmitted between animals by contact especially when they are confined in shelters or houses. E.g. Lice infestation and mange is chiefly jarab transmitted between animals by contact.  Parasites are also transmitted during predation by a host. For example, when cats predate on rats, cats may acquire an infection with parasites. DR. WALID DARWICHE 46 46 Dr. Walid Darwiche 23 Veterinary Parasitology I 05/11/2022 ENTRY THROUGH NOSTRILS Oestrus ovis, the nasal bot fly, deposit its young larvae around the nostrils of the host, where upon they crawl upward and enter the nasal sinuses,  Naegleria fowleri, a freshwater amoebae present in surface water of polluted pools gains access to the hosts through the intranasal route. DR. WALID DARWICHE 47 47 ENTRY THROUGH EXTERNAL GENITALIA  Tritrichomonas foetus, the protozoan parasite that causes abortion in cattle and Trypanosoma equiperdum, the protozoa that causes dourine in horses are transmitted during coitus. DR. WALID DARWICHE 48 48 Dr. Walid Darwiche 24 Veterinary Parasitology I 05/11/2022 TRANSPLACENTAL/TRANSMAMMARY TRANSMISSION  Transplacental or prenatal infection refers to transmission from mother to fetus across the placenta.  Transcolostral or transmammary transmission refers to transmission from infected dams to nursing offspring via colostrum or milk as in Toxocara vitulorum or Toxocara cati. DR. WALID DARWICHE 49 49 XI. DISSEMINATION OF PARASITES DR. WALID DARWICHE 50 50 Dr. Walid Darwiche 25 Veterinary Parasitology I 05/11/2022  Most of the parasites leave the host passively through excretions of the host.  Many exit from the hosts through feces as eggs (ascarids, strongyles, flukes etc.), cysts (Entamoeba, Giardia) and oocysts (coccidia).  Few exit through urine (E.g., Schistosoma haematobium, Stephanurus dentatus) and some leave through genital discharges (E.g., Tritrichomonas foetus).  Some parasites are swallowed by arthropods inadvertently when they feed on a host (e.g., Malarial parasites transmitted by mosquitoes) while the extraintestinal stages of parasites may be removed from the host during predation and the parasite subsequently infects the predator and leaves it passively through their feces (e.g., Cyst forming coccidia). DR. WALID DARWICHE 51 51 DISSEMINATION OF PARASITES  Permanent ectoparasites such as louse and flea exit the hosts actively by either crawling or jumping on to another host during moments of contact between hosts.  Few parasites exit actively from the hosts (mother) to their fetuses through placenta (transuterine route) e.g., Toxocara canis, Toxoplasma gondii bt3ml cyst bl 3adal  Some parasites leave the host through the medium of milk to infect the young ones (transmammary route), e.g., Toxocara vitulorum, Toxocara cati. kamen toxocara canis DR. WALID DARWICHE 52 52 Dr. Walid Darwiche 26 Veterinary Parasitology I 05/11/2022 METHODS OF DISSEMINATION OF INFECTIVE STAGES OF PARASITES  Once parasites are outside the hosts, they have to survive in the environment until they find a suitable host. ex. ascaris, bl feces bytla3 eggs w lezim ykun 3ndun mane3a 3ala l environment (harara, humidity) wa ella b mouto  As the environmental conditions are generally unfavorable to their survival, the infective stages of parasites are resistant.  These resistant stages have the capability to survive the adverse conditions and remain infective to find a host.  Temperature and moisture are two important factors that facilitate or prevent parasite survival and development. ex. eza ktir shob w low humidity, l ticks bynzalo 3ala ka3b l 7ashish to survive wl 3aks kamen DR. WALID DARWICHE 53 53  Parasites generally do not develop below 10°C or above 40°C.  When climatic conditions are hostile (freezing temperatures), parasites by3mlo hypobiosis cease development in hosts (arrested development) and wait for the conditions to improve before they resume development and discharge their eggs in feces. DR. WALID DARWICHE 54 54 Dr. Walid Darwiche 27 Veterinary Parasitology I 05/11/2022 DISPERSAL OF PARASITES  Parasites are disseminated in the environment mechanically through the action of water and fomites beside human interventions.  Water is an important agent for dissemination of parasites especially for those that require an aquatic habitat for development (eggs of many trematodes, larvae of Dracunculus etc).  Trematodes whose intermediate hosts are aquatic snails are carried by the surface water into water bodies where they develop in aquatic snails. Similarly, larvae of Dracunculus require water bodies for gaining access to cyclops.  Parasites that require aquatic habitats for developments such as mosquitoes and black flies are carried to long distances by streams and rivers. DR. WALID DARWICHE 55 55  Human interventions such as construction of irrigation canals directly facilitate breeding of snails’ thereby aiding dissemination of trematode parasites besides aiding breeding of insects.  The use of sewage and sludge to fertilize pasture is another potential method of dissemination of parasites.  Fomites such as insects mechanically disseminate the parasites from one place to another.  The fungus Pilobolus aids in the dispersal of the lungworm infective larvae from fecal pats to the pasture thereby facilitating infection of cattle hosts.  Wild animal hosts may serve as a reservoir of infection for domesticated livestock.  Wild reservoir hosts are important factor in the epidemiology of Fasciolosis. Overcrowding of hosts also facilitates dispersal of parasites. DR. WALID DARWICHE 56 56 Dr. Walid Darwiche 28 Veterinary Parasitology I 05/11/2022 PARASITE INDUCED HOST BEHAVIORAL CHANGES  Metacercariae of Dicrocoelium enters the brain of ants and paralyze them thereby aiding dissemination of parasite infected ants for herbivores during grazing.  Grasshoppers infected with tetramers and beetles infected with cysticercoids of tapeworms become inactive thereby facilitating ingestion of definitive hosts.  Ruminants heavily infected with hydatid cysts become debilitated, making them easier prey for carnivores. DR. WALID DARWICHE 57 57 STRATEGIES ADOPTED BY PARASITES TO INFECT HOSTS  Some parasites employ certain strategies to augment their chances of finding a host. Liver fluke encysts on green parts of plants and on higher parts of the plants to facilitate ingestion by herbivore hosts. li fiyo eggs  As cattle are reluctant to feed on herbages near feces, the motile gravid segments of Taenia saginata leave the feces to contaminate the herbage and increase its chances of being eaten by an herbivore as against the non motile gravid segments of Taenia solium which does not have to leave the feces because pigs being coprophagic consume the feces and pick up the infection.  Some parasites are provided with sensory organs to locate hosts. Warmth, CO2, fatty acids, amines etc., serve as stimuli for parasites especially arthropods to locate hosts. DR. WALID DARWICHE 58 58 Dr. Walid Darwiche 29 Veterinary Parasitology I 05/11/2022 DR. WALID DARWICHE 59 59 Dr. Walid Darwiche 30