34-35 - Protozoa

How do protozoan cause disease?

• Feed on solid tissues or after liquefying them

• Absorb host’s ingested food

• Grow inside host cells and destroy them

• Produce toxic substances like hemolysins, histolysins, anticoagulants

• Reduces host resistance to other diseases/parasites

What are the two major protozoan groups?

1. Flagellates

2. Coccidia

What is giardia?

Single cell, flagellate protozoa

Giardia

• Tear-drop shape

What is associated with giardia outbreaks?

• Water

• Outdoor recreation

What is the lifecycle of giardia?

• Trophozoites live free or attach via sucking disk to the SI lumen

• Cysts passed in feces after 7-14 days of incubation

How is giardia transmitted?

Fecal-oral

Ingestion of immediately infective cysts

What are the symptoms of giardia?

• Asyptomatic or symptomatic

• Watery diarrhea (acute phase)

• Voluminous, malodorous stools with mushy consistency

• Gas, flatulence

• Cysts in stools after 7-14 days

• Clinical signs don’t subside for 2-6 weeks (immunocompetent animals)

Are giardia trophozoites able to live outside the body?

No, only cyst stage can live in water

Who are most at risk for giardia?

• Animals in high-volume facilities (shelters, boarding etc.)

• Daycare workers

• International travelers

Giardia

• Cyst-like

How is giardia treated?

• Supportive care → elecrolytes

• Panacur

• Metronidazole → toxicity if you prolong use!

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

• Disinfect enviornment with bleach, lysol, ammonia

How is giardia diagnosed?

• Fecal float

• SNAP test

• Direct smear → only with diarrhea

What is Tritrichomonas blagburni?

Flagellate protozoan parasite in the LI of cats

What are the symptoms of Tritrichomonas blagburni?

• Chronic diarrhea

• Cats otherwise healthy!

• Fecal incontinence

• Lymphoplasmacytic/neutrophilic colitis

• Crypt abscess

• Increased mucosus production

• Erosion of colonic mucosa

Tritrichomonas blagburni

• Large nucleus

• Flagella from anterior and posterior

• Fusiform body/spindle shape

Tritrichomonas blagburni

How can you tell the difference between Tritrichomonas blagburni and Giardia?

• Tritrichomonas → more spindle shaped, moves around quickly

• Giardia → more tear-drop shape, moves slowly

How is Tritrichomonas blagburni treated and prevented?

• No FDA approved therapy

• Ronidazole or Metronidazole → can cause neurotoxicity

• Segregate infected cats with separate litter boxes

Is Tritrichomonas blagburni zoonotic?

No

Can Tritrichomonas blagburni trophozoites and/or cysts survive the environment?

• Trophozoites → yes (water, urine, cat food)

• Cysts → yes

What species is indistinguishable from Tritrichomonas blagburni?

Tritrichomonas foetus

What is Tritrichomonas foetus?

Flagellate protozoan in repro tract of cattle

Symptoms of Tritrichomonas foetus

• Bovine genital trichomoniasis

• Infertility

• Spontaneous abortion in 1st trimester

• Repro tract infection

• Bulls → asymptomatic, typically responsible for herd infections

Tritrichomonas foetus

• ungulating membrane

What causes African sleeping sickness and Chagas disease?

Trypanosomes (T. cruzi)

What is the flagellate trophozoite stage of Trypanosomes that circulates in blood/lymph? What does it infect?

Trypomastigote

• Infective for vertebrate host

• Other stages are developmental in arthropod IH

How are Trypanosome of Anterior and Posterior stations different?

• Classified by mode of transmission

• Anterior → bite of infected teste fly

• Posterior → feeding rejuvidae bugs defecate and pass parasites

Trypanosome - blood/tissue flagellate

What are Trypanosomes?

Blood-Tissue Flagellate Protozoa

Life cycle of Trypanosome

• Arthropods IH infected during blood meal

• Epimastigotes divide and multiply in IH

• Develop into Trypomastigotes

• Transferred to Human/Animal Host

• Multiplication in host

What are the symptoms of Trypanosome?

• Hyperplasia of bone marrow/spleen

• Trypanosome antigens attach to RBCs → erythrophagocytosis → decreased erythropoiesis → anemia

How is Trypanosoma cruzi transmitted?

Vectors

• IH defication

• Ingestion of IH

Non-Vector

• Blood transfusion

• Organ/tissue transplantation

• Congenital

• Lab exposure

• Fecal contamination of food

What are the symptoms of Trypanosoma cruzi?

• Romona’s sign (edema and inflammation from trypomastigotes fecating on host and rubbed into eye)

• Dogs → acute dz

  • Lymphadenopathy

  • Myocarditis, tachycardia

  • Pale MM → anemia!

  • Splenomegaly

How is Trypanosoma cruzi treated?

No effective intervention!

Pathogenesis of Trypanosoma cruzi?

• Trypomastigotes proliferate asexually

• Spread via lymphatics enter tissues and continue to proliferate

• Acute and can become deadly after 2-4 weeks