Protists (Exam 2)

Exam 2 of Parasitology is the Protists. Blue text is testable material, black text is general info or potential extra credit

Protists

Eukaryotes with a unicellular level of organization

Excavata (Flagellates)

Flagellum for locomotion during some life stages

Multiply via binary fission

Name this Protist and its defining features

Protists > Excavata (flagellates) > Trypanosomatida (hemoflagellates)

Long, spindle-shaped cells with posterior flagellum

Single nucleus near a large mitochondrion (kinetoplast)

Salivarian transmission

Spread through bite of arthropod

Stercorarian transmission

Spread through contamination by arthropod feces

Describe a typical Trypanosome Life Cycle

1. Lives in an arthropod vector in a Flagellated stage (trypomastigotes/promastigotes)

2. Transmitted to mammalian host (i.e. during a blood meal)

3. Flagellated (Trypomastigotes) or nonflagellated (amastigotes) in mammalian host bloodstream, multiply by binary fission

4. Arthropod vector takes a blood meal

Trypanosoma brucei and T. congolense: vectored by, disease

Protists > Excavata (flagellates) > Trypanosomatida > Trypanosoma

Sub-Saharan African trypanosomes

Glossina (tsetse fly) vector, spread trypomastigotes through bite

Nagana disease in domestic ruminants: Fever, weakness, paralysis, weight loss, inappetance. Can be fatal

Trypanosoma brucei gambiense and T. brucei rhodiense cause what disease?

Protists > Excavata (flagellates) > Trypanosomatida > Trypanosoma

Causes African sleeping sickness (African Trypanosomiasis) in humans: Fever, rash, lymphadenomegaly, confusion

Glossina (tsetse fly) vector, spread trypomastigotes through bite

Trypanosoma vivax: vectored by, clinical signs

Protists > Excavata (flagellates) > Trypanosomatida > Trypanosoma

Sub-Saharan African trypanosomes

Disease of livestock in Africa and Latin America

Mainly spread through tsetse flies

Can cause hemorrhage, anemia, and wasting in cattle, sheep, and goats

How was Trypanosoma vivax transported from Africa to South America?

Transported to South America with a tabanid fly mechanical vector, deer reservoir

Trypansoma evansi: vectored by, disease and clinical signs

Protists > Excavata (flagellates) > Trypanosomatida > Trypanosoma

Mechanical transmission by tabanids

Causes surra disease in domestic animals such as horses and cattle

Fever, weakness, lethargy, weight loss, anemia, edema, lymphadenomegaly, icterus, ataxia

Can be especially fatal in horses and camels

Name the disease associated with these clinical signs and the Trypanosome that causes it

Trypanosoma equiperdum

Dourine disease: Swelling of genitalia and mucoid discharge, depigmentation, flattened plaques on skin

Chronic emaciation, fever, death. Ocular disease and anemia can occur. Can cross blood brain barrier, leading to neurologic signs → High fatality rate

How is Trypanosoma equiperdum vectored and transmitted?

No vector required (easily spreads geographically)

Transmission via direct sexual contact

Protists > Excavata (flagellates) > Trypanosomatida > Trypanosoma

Diagnosis and Treatment of Dourine disease

Diagnosis: Parasite predominantly lives in tissues, and does not circulate in high numbers in blood. Organisms difficult to find in secretions → Low numbers found in urethral or vaginal mucus, genital fluids, or exudates from mammary glands

Serology can be helpful to support clinical suspicion

Treatment: No approved treatments

Trypanosoma cruzi causes what disease?

Chagas disease

Trypanosoma cruzi is distributed where in the world?

Texas, Arizona, New Mexico, California, Oklahoma, South and Central America

Protists > Excavata (flagellates) > Trypanosomatida > Trypanosoma

Trypanosoma cruzi is vectored by what and what is the mode of transmission?

Vectored by triatomin/assassin bugs

Insects infected via ingestion of trypomastigotes circulating in host blood (Reservoirs include opossums, armadillos, rats, guinea pigs, cats, raccoons, and monkeys)

Trypomastigotes passed in insect feces that contaminate bite wound or conjunctiva (stercorarian transmission)

Besides stercorarian transmission, Trypanosoma cruzi can also be transmitted how?

Can also be transmitted transplacentally or through blood transfusion, and ingestion of bugs in blended juices

Where do Trypanosoma cruzi amastigotes multiply in host body?

Amastigotes multiply by binary fission in macrophages, neural cells, glial cells, cardiac and smooth muscle cells

Trypanosoma cruzi infections can cause what clinical signs? Can it infect people?

Causes lymphadenopathy and acute myocarditis

Pale mucous membranes, lethargy, ascites, hepatomegaly, splenomegaly, congestive heart failure

Yes humans can be infected: Fever, headache, fatigue, vomiting, diarrhea, swelling near bite wound

How is Trypanosoma cruzi infection diagnosed? Treatment?

Diagnosis: Trypomastigotes and amastigotes on blood smear or lymph node aspirates, serology, PCR, histopathology

Treatment: No approved treatment, Benznidazole possible (not available in U.S.)

Affected dogs often euthanized

Trypanosoma theileri: host, vector, pathogenic or nonpathogenic?

Protists > Excavata (flagellates) > Trypanosomatida > Trypanosoma

Worldwide distribution

Nonpathogenic in cattle

Spread via tabanid flies

Trypanosoma melophagium: host, vector, pathogenic or nonpathogenic?

Protists > Excavata (flagellates) > Trypanosomatida >

Worldwide distribution

Nonpathogenic in sheep

Spread by Melophagus ovinus (ked)

How can you differentiate between a pathogenic vs a nonpathogenic trypanosomes/trypomastigotes?

Nonpathogenic species are double the size of pathogenic species

This Phlebotomine sandfly can vector what protist? How are the flies infected?

Protists > Excavata (flagellates) > Trypanosomatida > Leishmania

Flies infected via ingestion of amastigotes in macrophages of host

Besides spread through phlebotomine sandfly bites, Leishmania spp. can also be transmitted via what methods?

Vertical transmission described in dogs in the U.S.

Transmission also via blood contamination or venereally

Leishmania zoonotic or not?

Is zoonotic

Leishmaniasis disease: what breed of dogs overrepresented?

Foxhounds overrepresented

Cutaneous leishmaniasis: clinical signs

Clinical disease associated with antibody response → Immune-mediated mechanisms lead to disease pathogenesis

Exfoliative dermatitis, generalized or localized to face, ears, or limbs

Nodular lesions on face, ulcers over ears, alopecia

Visceral leishmaniasis: clinical signs and why

Amastigotes in macrophages of host lead to lymphadenomegaly and splenomegaly

Onychogryphosis can occur

Parasites in bone marrow can cause decreased RBC and platelet numbers

Ocular disease can also develop

Renal disease, colitis, lameness, muscle wasting also reported

Name the medical term for this condition

Onychogryphosis = abnormal nail growth

How is Leishmaniasis diagnosed? Treatment?

Amastigotes in macrophages on FNAs of lymph nodes, spleen, bone marrow. Serology (can cross react with Trypanosoma cruzi), PCR, Clin Path findings: anemia, thrombocytopenia, hyperproteinemia, hyperglobulinemia, hypoalbuminemia

Treatment: Allopurinol, miltefosine

Treated dogs remain reservoirs for life

Metronidazole: effective against what, MOA, toxicity

Part of nitroimidazole class of drugs (Related drugs: tinidazole, ronidazole, benznidazole)

Only metronidazole and tinidazole available in U.S.

Works by interacting with protozoal DNA, causing loss of helix structure and strand breakage

Effective against Trichomonas, amoebae, and Giardia spp.

FDA-approved for treatment of giardiasis in dogs

Also effective against some anaerobic bacteria (ex. Clostridium)

Can cause neurotoxicity in dogs at high doses → Ataxia, nystagmus, seizures, tremors, weakness

Extralabel use of nitroimidazoles is prohibited in food-producing animals in the US

Practice Question: What is the definition of stercorarian transmission?

Answer = Transmission through arthropod fecal contamination

Practice Question: How is this infection acquired?

Answer = Sexual contact with another infected host

Practice Question: Which is true regarding Trypanosoma cruzi?

Answer = Parasite can result in human infection

Practice Question: Which breed of dog is overrepresented for Leishmania infection in the US?

Answer = Foxhound

Practice Question: Which of the following is a potential side effect of metronidazole administration in dogs?

Answer = Ataxia

Trichomonads: morphologic characteristics, transmission

Protists > Excavata (flagellates) > Trichomonadida (mucosoflagellates)

Pear-shaped organisms

Single nucleus, rod-like axostylein posterior end

3-5 anterior flagella, one trailing flagellum

No environmentally resistant cyst stage

Transmission via infective trophozoite stages

Name this protist: where it is found in host, mode of transmission

Protists > Excavata (flagellates) > Trichomonadida > Tritrichomonas > Tritrichomonas foetus

Worldwide distribution

Found in reproductive tract of male and female cattle, and macerated fetuses

Infection not evident in males

Transmission during copulation

Infected bulls should be culled

Tritrichomonas foetus infection can result in what in cattle?

Results in infertility, abortion, fetal mummification, and pyometra

Often fetal loss in early gestation and return to estrus

After copulation, how long will Tritrichomonas foetus organisms be present in vaginal secretions?

Infected cows will have organisms in vaginal secretions first 2-3 weeks after copulation

How long should infected cows be sexually rested?

Infected cows should be given sexual rest for 4 months, after which trophozoites disappear

Less than 1% of infected cows become chronic carriers

Tritrichomonas foetus: diagnosis and treatment

Diagnosis: InPouch culture kit of preputial flush, PCR of penile scrapings or uterine/cervical fluid

No treatment available currently

Vaccine available, but not reliable

Name this protist: where does it live in the host?

Protists > Excavata (flagellates) > Trichomonadida > Tritrichomonas blagburni

Lives in large intestine of cats

Common in catteries and purebred cats

Can rarely occur in dogs

Tritrichomonas blagburni: mode of transmission, clinical signs

Likely fecal-oral spread

Causes chronic diarrhea and fecal incontinence in cats younger than 2 years

Many cats are asymptomatic

Most cats with Tritrichomonas blagburni infections have _____ of their diarrhea

spontaneous resolution (Can take up to 2 years though)

Tritrichomonas blagburni: diagnosis and treatment

Diagnosis: Trophozoites in fecal smears, InPouch culture, PCR. Fecal smears may miss low-level infections, InPouch culture improved sensitivity

No approved treatments → Off label ronidazole or metronidazole

Treatment failures common

Name the protist that causes this condition

Protists > Excavata (flagellates) > Trichomonadida > Histomonas

> Histomonas meleagridis

Histomonas meleagridis: where it lives in host

Lives in cecum and liver of turkeys, chickens, pheasants, and guinea fowl

Histomonas meleagridis: vectored by, transmission

Spread via nematode vector, Heterakis gallinarum

Birds infected via ingestion of nematode eggs in environment or earthworms containing nematode larvae

Histomonas meleagridis released from nematode larvae

Histomonas meleagridis: clinical disease

Histomonas migrate from cecal lumen to cecal wall and liver → Causes severe inflammation and necrosis in liver and cecum

High mortality in turkeys, low mortality in chickens (Raise turkeys and chickens apart)

No approved treatments (Ronidazole has been used effectively)

Name this protist: defining morphologic features

Protists > Excavata (flagellates) > Diplomonadida (mucosoflagellates) > Giardia

Tear-drop shaped trophozoites with two nuclei with large endosomes

Adapted for attachment to mucosa with sucking discs

Giardia: host, location in host, mode of transmission

Common intestinal commensal organism of dogs, cats, rodents, amphibians, birds, humans, etc.

Infection via oral ingestion of cysts in fecal-contaminated water, food, or fomites

Cysts can survive for months in the environment

Giardia cysts contain ___ trophozoites

Two

Are Giardia trophozoites or cysts the infectious form?

Cysts

Trophozoites can be passed in diarrheic feces but not considered infectious. Cysts are immediately infectious when passed

Giardia Assemblage A & B

Humans

Assemblage A shared by humans and some animals, but different subtypes, so zoonosis uncertain

Human infections primarily from other humans, dog to human transmission considered rare

Human assemblages have been found in dog fecal samples

Chinchillas have a high occurrence of Assemblage B, which affects humans

Giardia Assemblage C & D

Dogs

Giardia Assemblage E

Hoof stock (cattle, sheep, goats, pigs, horses)

Giardia Assemblage F

Cats

Giardia Assemblage G:

Rats

Giardia Assemblage H

Seals

Giardiasis: clinical signs

Trophozoites attach to and damage enterocytes in small intestine

Dogs and cats may develop mucoid diarrhea, but association not proven. Dogs may be subclinical. Puppies and debilitated dogs more likely to develop diarrhea

Humans can be asymptomatic or develop diarrhea, or irritable bowel syndrome

Calves can develop chronic diarrhea

Lambs have decreased weight gain

Giardia: Diagnosis

Diagnosis difficult due to intermittent shedding

SNAP Giardia test (ELISA)

Cysts on direct smear or fecal flotation with zinc sulfate “Falling leaf” motility

Iodine stain can aid in identification

Trophozoites may be present in wet mounts of diarrheic patients

PCR available

Giardia: Treatment, questions to consider

Consider if treatment is necessary: Is the dog experiencing clinical signs? Are there immunosuppressed individuals? Are there other animals that might be at risk?

Non-symptomatic patient with zoonotic assemblages should be treated. Non-symptomatic patients with non-zoonotic assemblages may not require treatment

In Dogs: If symptomatic, consider treatment with metronidazole, fenbendazole, or albendazole (bone marrow toxicosis possible)

Environmental decontamination such as bathing the animal and removing fecal matter are important

No approved treatments in Cats or Livestock

Benzimidazoles: examples of, MOA

Class of drugs, Dewormers, includes Albendazole, Fenbendazole, Febantel

Also useful against helminths

MOA: damages adhesive disc and microtubule cytoskeleton

Albendazole: effective against, side effects

More effective against against Giardia spp. than metronidazole

Available as oral suspension and paste

Can result in aplastic anemia due to myelosuppression in humans, dogs, and cats

Other side effects: Abortion, teratogenicity, anorexia, depression, ataxia, vomiting, diarrhea

Fenbendazole: safe for use in?, side effects

Available as paste and granules

Considered safe for use in pregnant animals, few side effects

One of the few drugs approved for use in zoo animals (ex. big cats, bears, wild ungulates)

Practice Question: How is Tritrichomonas transmitted between hosts?

Answer = Transmission during copulation

Practice Question: Which of the following is true regarding Tritrichomonas blagburni in cats?

Answer = Cats can spontaneously recover without treatment

Practice Question: Which is an organ system affected in turkeys by histomoniasis?

Answer = Liver

Practice Question: What is the infectious form of Giardia that is passed into feces?

Answer = Cysts

Practice Question: Which of the following is a potential side effect of albendazole administration?

Answer = Myelosuppression

Alveolates

Protists > SAR (Alveolates)

Large group encompassing many protists of veterinary importance

External surface covered with alveoli

Includes groups: Ciliates, Apicomplexa

Ciliates: morphologic characteristics

Covered with cilia, One macronucleus and one micronucleus

Apicomplexa: common name

Apicomplexa (“coccidians”): Often intracellular parasites, Apical complex in some life stages

Name this Alveolate: where it lives, hosts

Protists > SAR > Ciliophora (Ciliates) > Neobalantidium > Neobalantidium coli

Commensal organism of intestine in pigs, rats, primates, and humans

Reproduced by fission

Forms large cysts that pass in feces, Cysts are ingested in contaminated food and water

Pigs can act as reservoir for infection in humans

Neobalantidium coli: Disease

Usually harmless to pigs and humans

Can occasionally cause ulceration in human large intestine with diarrhea, Some pigs can experience diarrhea

Neobalantidium coli: Diagnosis

Cysts and motile trophozoites diagnosed in fecal smears

Cysts can be detected in fecal flotations

Zoite

Banana-shaped life stage

Oocyst

Environmentally resistant form passed in feces

Sporozoite

Infective forms found in oocysts

Merozoites/schizozoites

asexual reproductive forms

Tachyzoites

Rapidly dividing forms

Bradyzoites

Slowly dividing forms

Apicomplexa Life Cycle: Fill in the blank

1. Sporulated oocyst (ingested by host)

2. Sporocyst

3. Sporozoite (enter epithelial cells, mature to trophozoites in cells)

4. Schizont

5. Schizogony (trophozoites develop to schizonts via asexual reproduction)

6. Schizozoite (schizonts rupture, schizozoites invade new cells and continue dividing)

7. Microgamont (schizozoites develop to micro/macrogamonts)

8. Gametogony (microgametes fertilize macrogametes to form zygotes)

9. Macrogamont

10. Zygote (zygotes develop to oocysts)

11. Unsporulated Oocyst

12. Sporogony (oocysts shed in feces undergo sporulation in environment)

Name this Apicomplexa

Protists > SAR > Apicomplexa > Gregarines > Cryptosporidium

Cryptosporidium: Oocysts contain ____ sporozoites

4

Cryptosporidium: Oocysts are _____ infective when passed

Immediately

Cryptosporidium: where do sporozoites released from oocysts invade in the host?

Cells in microvillous border

Cryptosporidium: can cause _____infection

Oocysts can excyst before leaving the host leading to autoinfection

Cryptosporidium: Prepatent period

Short, 2-7 days in calves

Cryptosporidium parvum: host?

Calves younger than 30 days

Also in sheep, goats, and horses

Common zoonotic species

Cryptosporidium ryanae: host?

Calves up to 1 year of age

Cryptosporidium bovis: host?

Adult cows

Cryptosporidium andersoni

All ages of cattle, present in abomasum

Cryptosporidium: Disease

Often asymptomatic

Can develop diarrhea in cattle, usually due to C. parvum

Can develop mild diarrhea with C. andersoni

Cryptosporidium: Diagnosis

Colorless, transparent, and small oocysts (4-8um) on fecal flotations

Oocyst walls appear with pinkish hue

Cryptosporidium: Best solution for fecal flotations?

Sucrose

Cryptosporidium: Treatment

No specific effective treatment licensed in U.S.

Nitazoxanide, paromomycin, tylosin, azithromycin all used in U.S

Halofuginone lactate approved for prophylactic treatment in Canada and E.U.