11 – Protozoa I Flashcards
What is the most common protozoan in shelter dogs in Canada?
- Cystoisospora
Protozoa of Vet Importance: categories (4)
- Flagellates
- Ciliates
- Apicomplexans
- Amoebae
Flagellates: categories
- mucosoflagellates
- haemoflagellates
Mucosoflagellates: general
- direct life cycle
- *only undergo asexual reproduction
- Ex. Giardia, Tritrichomonas
Giardia
- Fecal-oral transmission through water
- Pets can have host-specific genotypes as well as zoonotic genotypes
- *assume everything is zoonotic (people only get and give zoonotic genotypes)
- *old man with mustache hair
Life cycle of Giardia sp.
- Host: trophozoites attached to enterocytes and divide by binary fission
- Shedding is intermittent (can last for months)
- Feces: a few trophozoites, millions of cysts!
o Survive months-years in the environment
o *immediately infective
o Low dose (10 cysts) needed to infect a new host=CLEAN ENVIRONMENT - *PPP: 4-16 days
Giardia characteristics
- Ventral disk to attach to enterocytes
- Flagellum
Clinical signs of giardiasis
- Often asymptomatic
- Acute, chronic or recurring
- *diarrhea +/- mucous or fat (rarely blood)
- Flatulence
- Vomiting (occasionally)
- Nausea
- Abdominal pain
- Food allergies
Food allergies in giardiasis
- Dermatitis due to INCREASED PERMEABILITY of GIT wall to food antigens
Diagnosis of Giardia
- Only test diarrheic animals OR high risk households
- Multiple fecal samples (3 samples, over 2-3 day intervals)
What are some diagnostic test options?
- Hard to see on a direct, fresh fecal smear
- Zinc sulfate floatation (cysts)
- Immunofluorescent assay (IFA) (cyst antigen): DIAGNOSTIC LAB
- ELISA SNAP test (cyst antigen): IN CLINIC
- Genotyping difficult for vets
Control of Giardia
- ONLY treat diarrheic animals or high risk household
- Goal of treatment=decrease clinical signs and environmental contamination (NOT elimination of infection)
- Inform clients of zoonotic risk
- Sanitation (BATHE DOG and environment)
Sanitation of environment for Giardia
- Heat
- Dry
- Bleach
- Peroxide
- Quaternary ammonium
Drugs for control of Giardia
- Metronidazole
- Fenbendazole
- Ronidazole (off label use)
Epidemiology in pets (giardia)
- Subclinical common
- 7-40% in dogs
- 8-10% in cats
- *reinfection is common
What are some risk factors for Giardia?
- Young animals (<1 year)
- Suboptimal environment
- Stressed/immunocompromised
Tritrichomonas foetus
- Trophozoites=shed and infective stage (NO CYSTS!)
- NOT environmentally resistant (only lasts 3hrs)
Tritrichomonas foetus: cats that are at risk
- Cats less than 1 year old
- Catteries
- Purebreds (<30%)
Tritrichomonas foetus: ‘sign’ in cats
- CHRONIC, large-bowel diarrhea
Tritrichomonas foetus: diagnosis
- Culture and microscopy (InPouch TF)
- PCR
- More directional movement
Tritrichomonas foetus: treatment
- No labelled treatment
- Often self resolves
- Ronidazole, metronidazole
Haemoflagellates
- Arthropod-transmitted
- Bigger issue in warmer parts of the world
- *indirect life cycles
- Ex. Trypanosoma spp., Leishmania spp.
- *not in Canada unless imported with dogs (some in wildlife reservoirs)
Trpanosoma spp. transmitted by
- African: tsetse flies
- Others: kissing bugs, keds
Leishmainia spp. transmitted by
- Sand flies
Chagas disease: American Trypanosomiasis (Trypanosoma cruzi)
- In blood (Trypomastigotes) and heart (Amastigotes)
- Dogs from C. and S. America
- *hard to detect early on
Trypanosoma cruzi: indirect life cycle
- Asexual reproduction in cardiac and smooth muscles =blood feeds
- Asexual reproduction in gut of arthropod: shed in feces onto the skin of host (Trypomastigotes)
- Lick skin, eat or scratch and enters host
Dogs and humans clinical signs with Trypanosoma cruzi
- Dogs: Cardiomegaly
- Humans: *megaesophagus
Sporozoa/Apicomplexans: categories
- Coccidia: *sexual and asexual reproduction
- Haemosporidia
Coccidia: direct life cycle
- GIT
- Ex. Cystoisospora, Cryptosporidium
Coccidia: indirect life cycle
- Tissue cysts
- Ex. Toxoplasma
Cystoisospora
- Highly host specific
- Even GIT location specific
- *NOT zoonotic
- Common in shelters and young animals
Cystoisospora life cycle
- Infected by ingestion of paratenic host or direct ingestion of eggs
- Sporulated oocysts
- Merogony (Asexual cycle)
o ‘burst’ out of epithelial cells=bloody diarrhea
o Various rounds before moving on (species specific) - Gametogony (sexual cycle)
o Microgametocyte: burst out and go macrogametocyte=unsporulated oocyts which is shed in feces - Unsporulated oocyst undergoes sporogony (2-7 days) and then infective=sporulated oocyst
- PPP=5-10days (can have high bloody diarhea before you detect an oocyst)
Sporulated oocyst: diagnositic features
- 4 sporozoites in 2 sporocysts in the EGG
- *infective stage
- *environmentally resistant (last months in moist conditions)
- *see in OLDER FECES
Unsporulated oocyst
- Very small!
- 40x
- *what is often seen in feces
Pathogenesis of coccidiosis
- Young animals
- Asymptomatic
- Stress
- *heavily contaminated environment
- Destroy epithelial cells in PPP
- *diarrhea, dehydration, poor growth
- *watery sometimes bloody diarrhea (even in PPP)
Diagnosis of coccidiosis
- Clinical appearance
- Fecal floatation: numbers of oocysts significant
Control of coccidiosis
- Supportive (hydration)
- Environmental decontamination
- Goal is to reduce shedding!
- *treat high risk dogs and puppies at weeks 3, 5, 7
Drugs used to control coccidiosis
- Sulfonamides, furazolidone
- Toltrazuril, ponazuril
Cryptosporidium
- People can give it to pets, but rarely vice versa
- More common in young
- Most significant in immunocompromised
Cryptosporidium: intestinal life cycle
- Fecal-oral route
- *much quicker=can lead to an auto-infection
- Asexual and sexual
- *PPP=3-6 days
- *IMMEDIATELY infective eggs
- *very RESISTANT
Pathogenesis of Cryptosporidium
- Subclinical
- Self-limiting with secretory diarrhea (fluid loss in severe cases)
- More issues in immunocompromised
Diagnosis of Cryptosporidium
- Clinical appearance
- Fecal flotation=not very good
- Fluorescent Ab test/fecal antigen detection
Control of Cryptosporidium
- Supportive (hydration)
- Environmental contamination
- Few drugs are very effective
Epidemiology of cryptosporidium in small animals
- Hard to determine real prevalence
- Self limiting: subclinical or secretory diarrhea
- *most often human to animals zoonotic transmission
