Parasite - Environment Factors

Compare how environmental survival, development, and intermediate-host availability affect transmission of the parasites covered. Use parasite stage, exposure history, and timing of infection to select and interpret diagnostic tests. Explain why detecting a parasite does not always establish it as the cause of an animal’s clinical signs. Recommend prevention and control measures that address both the infected animal and its source of exposure. Assess potential public-health risks based on transmission routes and the evidence for shared exposure or zoonotic transmission.

Flagellated protozoan, small intestine, has cysts and trophozoites

Giardia spp.

What hosts can Giardia infect?

Humans, small mammals, birds and ruminants

How do Giardia produce? What kind of lifecycle do they have?

Binary fission, direct

What is a coccidia?

Common name for apicomplexan

What is a good diagnostic test for identifying Cryptosporidia oocysts and Giardia cysts?

Immunofluorescent assays

Outside of immunofluorescent assays, what are other ways to test for Giardia?

Wet mount (fresh sample), immunodiagnostics, centrifugal flotation

Why might you need to retest for Giardia if symptoms persist, but a snap test and fecal float are negative?

intermittent shedding

Where does excystation for Giardia cysts occur?

Small intestine

Where does encystment of trophozoites occur? What triggers it?

as organisms travels down GI tract. Dehydration and cholesterol deprivation

What is a prepatent period?

Time from ingestion of cysts to shedding cysts in feces

Clinical signs of Giardia? How does it cause these?

chronic diarrhea, weight loss, lethargy, flatulence. Trophozoites attach to enterocytes in small intestine

How do we control/prevent giardia?

Combination of febantel, pyrantel pamoate and praziquantel

Why is reinfection such a risk for Giardia?

It can persist in the environment, self grooming or contact with area not disinfected can cause reinfection

Causes GI disease in SA, devastating repro effects in herd animals, highly regulated in bulls

Tritrichomonas blagburni

Highly species specific, Apicomplexan, oocyst sporulates in the environment to become infected

Cystoisospora and Eimeria

Common liver fluke, trematode, lives in liver/bile ducts, common hosts are ruminants, horses, pigs

Fasciola hepatica

How are trematodes detected?

sedimentation, serology

Do Fasciola hepatica have a direct lifecycle? If not, what is their intermediate host?

No, snails. Infection relies on an environment where snails can live

Which phase of Fasciola hepatica penetrates the snail host?

Miracidium

Which phase leaves the snails? What phase encycsts on grass?

Cercariae leave the snail, encyst on grass and become infective metacercariae in 6 weeks to months

Acute signs of Fasciola hepatica infection

migration of immature flukes causes hemorrhage and inflammation, abdominal pain, hepatomegaly, fever, weight loss, inappetence, anemia, sudden death

Chronic signs of Fasciola hepatica

Secondary bacterial infections, biliary obstruction and inflammation, fibrotic changes over time, submandibular edema, emaciation, ascites

What species do we typically see chronic signs of Fasciola hepatica in?

Cattle

Pathogenesis of Fasciola hepatica

Immature flukes destroy liver parenchyma, liver fibrosis forms, hyperplastic cholangitis from sever necrosis of biliary mucosa, calcification of bile ducts, aberrant migration to lungs

What is a species that relies heavily on close contact and cannot survive long at all in the environment due to it’s single life stage? What is it’s one life stage?

Tritrichomonas blagburni, trophozoite

Which pathogen relies on becoming infections once they are in the environment?

Coccidia - Eimeria and Cytoisospora

Which pathogen relies on having environment for an intermediate host and be combated by pasture rotation?

Fasciola hepatica