Protozoan Parasites

Lectures 34, 35, 36, and 37

The following general features match which type of parasite:

• single celled organisms

• small scale (microscopic)

• parasitic in all vertebrate hosts

• parasitic in all host tissues/systems

• variable life cycles

• reproduction based on asexual, sexual, combination/alernation involving both modes, and allelic sequence heterogeneity

protozoan

What is the living, motile form of protozoan parasites?

Trophozoite

What is the environmental transmission form of protozoan parasites?

cyst/oocyst

How do protozoan parasites cause disease?

• feed on solid tissues directly or after liquefying them

• compete with the host for ingested food

• destroy host cells by growing in them

• production of various toxic substances (hemolysins, histolysins, anticoagulants) that aid in their ability to enter host tissues, feed, or reproduce

• cause various host reactions such as allergic, inflammatory, hyperplasia, thrombocytopenia

• reduce host resistance to other diseases and parasites

What are the major protozoan groups?

flagellates and coccidia

Which species is described by the following:

• single cell, flagellate protozoan parasite

• First described in 1681 by Antoine van Leeuwenhoek in his own diarrheic stool

• significant confusion with naming the parasite by different parasitologists

• ICZN review to determine its “real” identity

• Primarily associated with waterborn outbreaks

• occupational risk for veterinarians and techs

Giardia spp

What are the three species of Giardia?

• G. lamblia

• G. duodenalis

• G. intestinalis

These images match which species?

Giardia sp

The following lifecycle matches which species:

• direct lifecycle

• trophozoites live free (extra cellular) or attach via ventral sucking disk in lumen of proximal small intestine

• Multiply by binary fission with genetic diversity by allelic sequence heterogeneity

• Cysts passed in the feces following a 7 to 14 day incubation period

• Host infection/re infection via fecal oral contamination and ingestion of immediately infective cysts

Giardia spp

Describe a syptomatic infection of giardia spp in dogs and cats.

• watery diarrhea in acute phase (5 days post infection)

• voluminous, maldorous stools with mushy consistency

• gas, flatulence

• cysts appear in stools 7 to 14 days post infection

• Clinical signs may persist for 2 to 6 weeks before resolution in immunocompetent animals

Describe a symptomatic infection of giardia spp in humans.

• voluminous watery diarrhea

• gas, flatulence, greasy stools that float

• abdominal discomfort, anorexia, nausea, vomiting, weight loss, fatigue

• symptoms appear 7 to 14 days post infection

• illness duration 2 to 6 weeks, may be self limiting if immunocompetent

What is the host range of genotype assemblage A within Giardia duodenalis/intestinalis?

humans, livestock, dogs, cats, beavers, guinea pigs

What is the host range of genotype assemblage B within Giardia duodenalis/intestinalis?

humans, dogs, beavers

What is the host range of genotype assemblage C and D within Giardia duodenalis/intestinalis?

Dog

How do we manage giardia infections in companion animals?

• diagnosis by ZnSO4 flotation

• supportive care to restore electrolyte imbalances

• Treatment with Panacur or Metronidazole

• Bathe pet at beginning and end of treatment protocol to remove imediately infective cysts

• disinfection os pet reisdential environment usin chlorine bleach at a high concentration, lysol, or quaternary ammonia compounds

What do we have to worry about when treating giardia infections with prolonged use of metronidazole?

neurotoxicity

The following description matches which species:

• flagellate protozoan parasite in large intestine of cats

• causative agent of chronic diarrhea (long duration, cats otherwise healthy)

• Lymphoplasmacytic/neutrophilic colitis, crypt abscess, increased mucous production, generalized erosionof colonic mucosa

Tritrichomonas blagburni

Which species was formerly known as T foetus until molecular genetic confirmed identity as a distinct species?

Tritrichomonas blagburni

These images match whcih species?

Tritrichomonas blagburni

How do we diagnose infection with Tritrichomonas blagburni ?

• microscopically by direct smear to differentiate from Giardia

• PCR specific assay to identify organism isolated from infected animals

• Fecal culture and isolation in commercially available media will increase sensitivity

How do we treat infections of Tritrichomonas blagburni?

• No FDA approved treatment but can use Ronidazole or Metronidazole despite neurotoxicity (although reversible) has been reported with use of both drugs

How do we prevent infection of Tritrichomonas blagburni?

• suspected transmission between hosts by fecal oral route

• no environmentally resistant cyst stage

• trophozoites may survive outside of host for variable times

• segregate infected cats, separate litter boxes

• not known to be zoonotic

The followng description matches which species:

• flagellate protozoan parasite in the reproductive tract of cattle

• morphologically indinstinguishable from T. blagburni and other Trichomonad protozoa

• causative agent of bovine genital trichomoniasis

• bulls are generally symptomatic and responsible for herd level infections

• diagnosis by PCR and culture methods

Tritrichomonas foetus

What are the symptoms of bovine genital trichomoniasis?

• infertility

• spontaneous abortion in first trimester

• generalized reproductive tract infection

Blood and tissue flagellates are broadly classified as what?

Trypanosomes

The following description matches which type of protozoan parasite:

• family members wekk known as causative agent of Affrican Sleeping Sickness and Chagas Disease

• Flagellate trophozoite stage circulating in blood/lymph known as Trypomastigote, which is infective for the vertebrate host

• classified by mode of transmission (anterior station vs posterior station)

Blood and Tissue Flagellates (Trypanosomes)

These images match which type of protozoan parasite?

Blood and Tissue Flagellates (Trypanosomes)

These general lifecycle features match which type of protozoan parasites:

• arhtropods intermediate host and are infected during blood meal

• epimastigotes divide and multiply in intermediate host

• develop into Trypomastigotes in intermediate host

• tansferred to human/animal host

• multiplication in human/animal host

Blood and Tissue Flagellates (Trypanosomes)

Which disease is decribed by the following:

• T brucei and T gambiense

• live in blood, invade lymph nodes, intercellular spaces

• generally produce anemia from imune mediated processes and mechanisms (depressed erythropoiesis, hyperplasia bone marrow and spleen, erythrophagocytosis because trypanosome antigens attach to RBCs)

• animal production limited to areas where disease is not prevalent

African Trypanosomiasis

Which species is the causative agent of Chaga’s Disease or American Trypanosomiasis?

Trypanosoma cruzi

What are the obligate intermediate hosts for Trypanosoma cruzi?

Triatomin/Reduviid bugs

What are the reservoirs for Trypanosoma cruzi?

armadillo, monkeys, dogs, cats, opossum, rodents, raccoons

How is Trypanosoma cruzi transmitted by vectors?

• active defecation by intermediate host

• ingestion of intermediate host

How is Trypanosoma cruzi transmitted by something other than vectors?

• blood transfusion

• organ/tissue transplantation

• congenital

• lab exposure

• fecal contamination of food items

How does genotypic variation affect Trypanosoma cruzi?

• geographics

• host associations

• transmission

• disease potential

• response to treatment

What is Romana’s sign?

edema and inflammatory response resulting from trypomastigotes defecated on host and rubbed into eye

Trypomastigotes proliferate asexually in histocytes as what?

amastigote stage organisms

How do we diagnose Chaga’s disease?

serology and PCR

What are clinical signs of Chaga’s disease in dogs?

• lymphadenopathy

• myocarditis

• pale mucous membranes

• tachycardia

• splenomegaly

Which protozoan parasite species is described by the following:

• parasites infecting macrophages of vertebrate hosts

• Amastigote stages only and transmitted by sand fly bite

• Associated with visceral disease, mucocutaneous disease, cutaneous disease depending on species

Leishmania sp

Which species of Leishmania sp are associated with visceral disease?

• L. donovoni

• L infantum (L. chagasi)

Which species of Leishmania sp are associated with muco-cutaneous disease?

L mexicana

Which species of Leishmania sp are associated with cutaneous disease?

L. tropica

T cruzi infection should be on the differential diagnosis for dogs presenting with symptoms of what?

cardiac disease including lymphadenopathy, tachycardia, ascites, hepatomegaly, splenomegaly

Leishmania infections should be on the differential diagnosis doe dogs presenting with symptoms of what?

dermatologic disease and infection including lymphadenopathy, hepatomegaly, splenomegaly

A SNAP test for giardia tests for what?

fecal antigen

Which species of protozoan parasite does not have a cyst stage?

Tritrichomonas blagburni

The following general features match which type of protozoan parasite:

• intracellular parasites of intestinal epithelium, endothelium blood vessels, organs, and other tissues

• gliding locomotion

• tropozoites with apical complex

• asexual and sexual replication in vertebrate and invertebrate hosts

• 1 host lifecycles are monoxenous and may use a paratenic host

• 2 host lifecycles are heteroxenous and can be obligate or facultative indirect

Coccidia

These images match which type of protozoan parasite?

Coccidia

Which species of coccidia are intestinal?

• cryptosporidium

• eimeria

• cystoisospora

Which species of coccidia are found in tissues?

• toxoplasma

• neospora

• sarcocystis

Which species of coccidia are found in blood?

• hepatozoon

• babesia

• cytauxzoon

Which coccidia species matches the following description:

• primarily associated with waterborne outbreaks

• foodborne outbreaks can be ue to homemade, natural unpasteurized apple cider or from bottled water for pediatric colic

• occupation risk

• metabolically divergent from other Apicomplexa (Lack Krebs cycle so unable to synthesize fatty acids, lack plastid bodies for mannufacturing food, unresponsive to drugs)

• host specificity is variable

• oocysts passed in feces, are immediately infective, and morphologically indistinguishable

• able to survive in the environemtn and water treated with chlorine

Cryptosporidium spp

This image matches which species?

Cryptosporidium spp

The following lifecycle matches which species:

• direct lifecycle

• sexual and asexual replication occur in the small intestinal epithelium (inter-cellular)

• oocysts passed in the feces following 3-5 day incubation period

• immediately infective

• host infection via fecal oral contamination and ingestion of oocysts

• infectious dose with as few as 9 oocysts

• infections can be asymptomatic or symptomatic

Cryptosporidium spp

What are the clinical features of a symptomatic infection with Cryptosporidium spp?

• voluminous watery diarrhea

• mucous present, rarely blood/leukocytes

• abdominal discomfort, anorexia, nausea, vomiting, weight loss, fatigue, fever

• mean illness duration 12 days but may be self limiting if immunocompetent

In which animals do we usually see apparent infections of Cryptosporidium?

Dairy calves 1-3 weeks of age

What can act as a persistent source of reinfection for Cryptosporidium in animals?

oocyst contamination of bedding environment

Are Cryptosporidium infections seen in companion animals zoonotic?

Only in immunocompromised persons

How do we diagnose Crypotsporidium infection?

Sucrose fecal flotation focused immediately below the coverslip

What is the therapy protocol for animals infected with Cryptosporidium spp?

• no consistently effective, approved pharmaceutical for use in animals

• not cost effective for use in cattle/calves

• supportive care to restore electrolyte imbalance from diarrhea

What is the therapy protocol for humans infected with Cryptosporidium spp?

• Nitazoxanide which interferes with anaerobic energy metabolism of parrasite

How do we disinfect areas where Crptosporidium spp have been found?

• ammonia compounds, ethylene oxide, methyl bromide, and ozone appear to be most effective

• hydrogen peroxide and formaldehyde containing compounds show promise with increased contact times

• oocysts in milk and water killed by commercial pasteurization

• chlorine not effective

Which species of coccidia matches the following description:

• intestinal

• direct lifecycle (ingestion of sporulated oocysts, 4 sporocysts each with 2 sporozoites)

• domestic livestock, birds, and grazing wildlife are definitive hosts

• asexual replication in small intestine

• diarrhea associated with destruction of enterocytes by developing oocysts sexual reproduction in fresh uninfected cells of large intestine

Eimeria sp

What is the term for disease that is associated with onset of sexual replication in host tissues and causes mechanical disruption of mucosal cells by gametes (sexual stage)?

Coccidiosis

These images match which coccidia species?

Eimeria

Coccidiosis is a function of what?

• age

• nutrition

• stress

• sex

• season

• gestational status

• inherent pathogenicity

What species causes coccidiosis in sheep and goats?

Eimeria ovinoidalis

What species cause coccidiosis in cattle?

• Eimeria bovis

• Eimeria zuernii

Risk of disease with coccidia species is a function of what?

• environmental contamination

• moderate levels of infection

• stress in the host population

How do we prevent coccidiosis?

• environmental hygiene (removal of manures, keep surfaces dry and clean)

• chemoprophylaxis (targets asexual stage of replication)

All treatment decisions for coccidiosis need to be based on what?

holistic assessment of environmental contamination, health status of herd, risk of exposure to susceptible hosts, and production goals

Which drugs arrest development at specific stages of the lifecycle but allow parasites to remain alive in the tissues so withdrawal of the drug allows the parasite to resume development and completion of the lifecycle?

Coccidiostatic drugs

Which drugs kill or damage the parasite irreversibly so there is no disease relapse following drug withdrawal?

Coccidiocidal drugs

Which drugs may have static and cidal properties depending on dose of the drug and length of parasite exposure to the drug?

Anticoccidial drugs

Which drug is decribed by the following:

• coccidostatic activity

• administered as feed additive for 28+ days for prevention of coccidiosis

• acts on sporozoite stage

• no activity against adult parasites

• not approved for lactating cattle, laying poultry

Decoquinate (Deccox)

Which drug is decribed by the following:

• coccidiostatic activity

• administered in drinking water for 21 days at 5mg/kg for PREVENTION of coccidiosis

• administered in drinking water for 5 days at 10mg/kg for TREATMENT of coccidiois

• acts on first generation schziont in the intestinal cell wall to prevent differentiation into metrozoites

• has ability to suppress sexual stages and sporulation of ocysts

• not approved for lactating cattle, laying poultry

• more effective as preventative than treatment

Amprolium (Corrid)

Which drug is decribed by the following:

• coccidiocidal activity

• FDA approval for prevention of coccidiosis in poultry

• extra label use for control in cattle, sheep, goats dogs, and cats

• acts on “apicoplast” organelle involved in biosynthesis of fatty acids and amino acid metabolism

• has ability to suppress sexual stages and sporulation of oocysts

• not approved for lactating cattle, laying poultry

Diclazuril (Clincox)

Which drug is decribed by the following:

• coccidiocidal activity

• FDA approval for prevention of EPM (Sarcocystis neurona) in horses; neosporosis (Neospora caninum) in cattle

• acts on “apicoplast” organelle involved in biosynthesis of fatty acids and amino acid metabolism

• has ability to suppress sexual stages and sporulation of oocysts

• not approved for lactating cattle, laying poultry

Ponazuril (Marquis)

Which drug is decribed by the following:

• coccidiocidal activity

• Not available in US with FDA approval

• acts on “apicoplast” organelle involved in biosynthesis of fatty acids and amino acid metabolism

• has ability to suppress sexual stages and sporulation of oocysts

• not approved for lactating cattle, laying poultry

Totazuril (Baycox)

Which drug is decribed by the following:

• coccidiostatic and coccidiocial actviity

• active against folic acid pathway and interfere with folate biosynthesis

• significant negative effects on gut microbiota

• TMS potentially teratogenic so must weigh benefit vs risk adverse effects

Sulfonamides (Sulfadiazene, Sulfadimethoxine aka Albon, Trimethoprim/Sulfaiazine aka TMS, Tribrissen)

Watery diarrhea in a SINGLE young animal at 1-4 weeks of life with emaciation is suggestive of what?

cryptosporidiosis

What are the usual differential diagnosis for older animals with diarrhea?

coccidia (Eimeria spp) in animals 21 days and older or Ostertagia (anorexia, poor growth) in animals <2 years of age and having chronic presentation

What is your differential diagnosis for 1-4 day old calves presenting with acute and lethal hemorrhagic diarrrhea?

colibacilliosis

What is your differential diagnosis for multiple cases of viral diarrhea?

• rotavirus if animals are 5 days to 2 weeks of age

• coronavirus if animals are 4 to 30 days of age

Which species of coccidia is described by the following:

• intestinal

• faculative direct/indirect lifecycle (ingestion of sporulated oocysts, 2 sporocysts each with 4 sporozoites)

• cats, dogs, pigs and some birds are definitive hosts

• mice, birds, rodents are paratenic hosts

• sexual/asexual replication in small intestine

• diarrhea associated with destruction of enterocytes

• prepatent period 6-12 days

Cystoisospora spp (synonymous with Isospora spp)

Which Cystoisospora spp affect dogs?

• C canis

• C ohioensis

Which Cystoisospora spp affect cats?

• C felis

• C rivolta

Which Cystoisospora spp affecting the dog is teardrop shaped and 40 × 30 micrometers?

C canis

Which Cystoisospora spp affecting the cat is teardrop shaped and 40 × 30 micrometers?

C felis

Which Cystoisospora spp affecting the dog is round and 25 micrometers in diameter?

C. ohioensis

Which Cystoisospora spp affecting the cat is round and 25 micrometers in diameter?

C rivolta

How do we manage intestinal coccidia infections in companion animals?

• diagnosis by centriful ZnSO4 or sucrose flotation

• supprtive care to restore electrolyte balances

• Treat dogs with Albon

• Treat cats with Trimethoprim sulfadiazene

• bathe pet at beginning and end of treatment protocal to remove immediately infective cysts

• remove feces daily

Which species is an unequivocally zoonotic parasite, immediately infective, and is associated with waterborne outbreaks?

Cryptosporidium

How do intestinal coccidia cause disease?

by invasion and mechanical destruction of cells in the intestinal tissues of their host species

Which species is tiny with 4 naked sporozoites, immediately infective?

Cryptosporidium

Whcih species is characterized by 4 sporocysts each with 2 sporozoites?

Eimeria

Which species is characterized by 2 sporocysts each with 4 sporozoites?

Cystioisospora

Sporulated oocysts must be ingested via what route to infect the host?

fecal oral

What is a function of limited asexual replication and a single generation of sexual replication in their hosts?

Expression of disease