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Unformatted text preview: Lecture 2: Parasites of Wild Animals
Introduction More in Your Text Why Study Parasites? Host-Parasite Relationship Insights into the overall health of the host Evolutionary changes Environmental Changes Host/Parasite Changes Impacts on Human Health Definition -- Parasite
Organism that lives in or on another animal (host). The host provides a necessary nutrient for the parasite. Parasitism Symbiotic Relationship Parasitism: host does not gain Varying Degrees of Dependency Intracellular parasites Extracellular parasites Blood meal parasites Infection Vs Disease Infection: The host harbors parasites (and can compensate). Disease: The host is unable to compensate for the damage/drain caused by the presence of the parasites and "suffers" clinical disease Zoonotic Disease: Infection transmissible BETWEEN animals and man. Host/Parasite Interactions
In a "normal" host-parasite relationship, the host is infected with the parasite but does not suffer a parasitic disease. Disease or not? Factors Large numbers of parasites present Host is debilitated/unable to compensate Other sicknesses Nutritional Deficiencies Young or Old animals Parasite Excessively Pathogenic Situations Conducive to Disease Overcrowding High parasite exposure --- high parasite load Stress Other Diseases Nutritional Deficiencies Other Pathological Conditions Abnormal Host/Parasite Relationship Parasite Life Cycle
Inside the Host Adult Egg/Larva ______________________________________ Infectious Stage Outside the Host Direct Life-cycle Definitive Host Definitive Host The infectious stage from the definitive host (host with the adult stages of the parasite) can directly infect the new definitive host. Strongyle Life Cycle Indirect Life-Cycle
Definitive Host X Definitive Host Intermediate Host
The definitive hosts cannot be infected by the stages from the definitive host. Can ONLY be infected by the stages coming from the intermediate host (biological host). Parasite undergoes a change Heartworm Endoparasites Parasites which live INSIDE their host Nematodes Trematodes Cestodes Protozoa Nematodes Roundworms Direct or indirect life-cycles Cylindrical organisms tapered ends Separate sexes Females lay eggs or release living young Nematodes of Note Strongyles Wide number of different species Most commonly found Gastrointestinal parasites Ex: Abomasal parasites of white tailed deer High Parasite Loads - Overcrowding Haemonchus Infections Nematodes of Note Bayliascaris sp. Normal Host --- Raccoon
No pathology Intestinal parasite releases eggs Abnormal Host
Other mammals squirrels, rabbits, etc Humans --- children, especially --- zoonotic Aberrant migrations --- liver, brain Bayliascaris Life-cycle Baylisascaris -- Zoonotic Heartworm Adult worms live in right ventricle, pulmonary artery Release living larvae (microfilaria) Mosquito intermediate host injects microfilaria during blood meal Modified larvae enter new host when mosquito takes a blood meal Larvae migrate through body to get to lungs/heart Heartworms Life-Cycle Heartworm Emerging Zoonotic Disease Domestic and Wild dogs primary hosts Cats Smaller number of worms cause pathology Often occult infection no microfilaria released Larvae seen encysted in lungs Some immature worms seen in autopsy Humans Nematodes of Note Trichinella spiralis Wild animal cycle predators Adult worms in intestine
Release living young Young migrate to muscle NURSE CELL Infection occurs after eating infected meat Human exquisitely sensitive to damage & body's reaction to muscle stages Trichinella spiralis Trichinella spp. Nematodes of Note Parelaphostrongylus tenuis Indirect life-cycle involving snails Normal host --- White tailed deer
Migration: gut to spinal cord to brain Little or no pathology Abnormal hosts
Other deer, elk, moose, sheep, goats Reaction to migration of larvae Abnormal behavior, paralysis, death P. Tenuis Life cycle P. tenuis Trematodes -- Flukes Flatworms Hermaphroditic Two suckers Blind end digestive system Indirect life-cycles Generally involves at least one snail intermediate host Troublesome Trematodes Fascioloides magna Normal host White tailed deer
Live in pairs in cysts in the liver bile ducts No pathology Abnormal host Cow Little pathology --- flukes totally encysted Flukes wander in liver death of sheep Abnormal host Sheep Fascioloides magna Fascioloides magna Cestodes -- Tapeworms Segmented worms Hermaphroditic Indirect life-cycle Predator (adult stages) and prey (intermediate host) Indirect host cystic stages Cystic stages host/site specific Cestodes of Consequence Echinococcus multilocularis Fox/rodent SQ stages in rodent cancer-like masses Definitive host --- carnivore Cystic stages intermediate hosts ruminants, rodents Taenia spp. Taenia Life-Cycle Protozoa Unicellular organisms Generally live within the cells of the host Some may live free in the blood stream Direct and indirect life-cycles Biting insect often vectors for indirect cycles Problem Protozoa Fecal-Oral Transmission Toxoplasma --- intestinal parasite of cats Giardia Sarcocystis, cryptosporidia Toxoplasma transmission by ingestion of tissue stages Giardia Oocyst Giardia Beware the Beaver Toxoplasma Life Cycle Equine Protozoal Meningitis Problem Protozoa Trypanosomes African --- wild ruminants, tsetse fly American South America/Mexico Wild carnivores, reduviid bugs Babesia RBC parasite --- Anemia Wild ruminants, ticks Ectoparasites Parasites which live on or in the host's skin Insects Arachnids Direct damage Vectors for other diseases Insects 3 body parts: head, thorax, abdomen 6 legs Wings may or may not be present Flies Fleas Lice Flies Adult flies Irritants Blood suckers Vectors for diseases Maggots Bots Immature Stages Mosquitos Irritants Blood suckers Vectors Heartworm West Nile Virus EEE, WEE, St. Louis Encephalitis Arbovirus Cycle "New" Mosquito Tiger Mosquito West Nile vector "all day" biter Fleas Adults on animals Eggs roll off onto environment Develop off the host larvae, pupae, adults Irritants Blood suckers Vectors Plague Lice Adults cling to hairs, Eggs laid on hairs (nits) Transmission by direct contact Sucking Lice Pointed heads sucking mouth parts Vectors for disease (Typhus) Large heads mandibles for chewing Biting Lice Arachnids 2 body parts Cephalothorax Abdomen Adults 8 legs Ticks Mites Ticks Ticks Single to multi-host life-cycles Egg larval ticks (6 legs) adult Blood suckers Vectors for Disease Lymes Disease Rocky Mountain Spotted Fever Babesia Deer Ticks/Lymes Disease Ticks of Note Lone Star Tick Normally in SE/SW USA Carrier of Ehrlichiosis Zoonotic Hemorrhagic Disease Dogs, Humans Mites Generally microscopic Live on body surface or burrow into skin Ear mites crustiness in ear canal Skin mites surface mites Irritation, hair loss Major irritation, tissue fluid oozing Crustiness, secondary bacterial infection Intra-skin mites MANGE Mites/Mange Mange Parasites in Wild Animals Generally a symbiotic relationship with little pathology If disease occurs --- OTHER PROBLEMS Overcrowding Inadequate nutrition Other diseases Abnormal host Evolving Problems Human "incursions" New Zoonotic Diseases Movement of Animals & Parasites New Diseases of Concern Global Warming ...
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- Spring '11