Protozoal Infections

Question 1

Protozoa

Answer 1

• single-celled eukaryotes

- amebae (pseudopods), flagellates (flagella), or sporozoites

Question 2

Malaria

Answer 2

• mosquito borne, hemolytic, febrile illness
• P. falciparum, P. vivax, P. ovale, P. malariae
• destroy human erythrocytes
• life cycle requires both human and mosquito hosts
• merozites feed on Hgb, grow and reproduce in RBCs
• P. falciparum - malignant malaria, no secondary hepatic stage, parasitizes RBCs of any age, can have several parasites in a single RBC, and alters flow characteristics and adhesive properties of infected RBCs
• hepatosplenomegaly as RBCs are sequestered by fixed mononuclear phagocytes

Question 3

Babesiosis

Answer 3

• transmitted by hard bodied ticks

- malaria like - invade and destroy RBCs

Question 4

Toxoplasmosis

Answer 4

• T. gondii protozoa
• final host is the cat, which allows oocysts to sporulate in feces and sporozoites which may enter humans
• lymphadenopathy in immuno competent
• serious for fetus (meningoencephalitis) or immunocompromised (encephalitis)
• tachyzoites and bradyzoites

Question 5

Amebiasis

Answer 5

• Entamoeba histolytica
• involves the colon (ulcerates) and liver
• causes slowly expanding necrotizing abscesses
• trophozoite, precyst, cyst

Question 6

Cryptosporidiosis

Answer 6

• causes diarrhea in immunocompromised

- remain extracellular and attach to mucosal surface

Question 7

Giardiasis

Answer 7

• Giardia lamblia, flagellated protozoa
• can be acquired from wilderness water sources
• trophozoite and cyst stages
• attach to intestinal wall and live on villous surfaces within crypts
• usually harmless commensal

Question 8

Leishmaniasis

Answer 8

• transmitted to humans from sand flies
• reproduce within macrophage as amastigotes
• 1) localized cutaneous - ulcerates with Leishman-Donovan bodies
• 2) Mucocutaneous - ulcer appears and resolves but years later another ulcer will develop
• 3) visceral - infection of monocyte/macrophage system and normal organ architecture is replaced by sheets of parasitized macrophages

Question 9

Chagas Disease

American Trypanosomiasis

Answer 9

• T. cruzi, zoonotic infection
• usually in heart (myocarditis, heart failure) and GI tract (mega esophagus, megacolon)
• reduviid bug
• form localized nodular inflammatory lesions (chagomas)

Question 10

African Trypanosomiasis

Answer 10

• sleeping sickness
• T. brucei gambiense or T. brucei rhodesiense
• hemoflagellate protozoa transmitted by tsetse flies
• meningoencephalitis - formation of immune complexes and autoantibodies against galactocerebrosides
• can form primary chancres at site of inoculation, then systemic infection, then brain invasion with destructive vasculitis

Question 11

Primary Amebic Meningoencephalitis

Answer 11

• Naegleria fowleri
• inoculate in nasal mucosa near cribriform plate, invade olfactory nerves and proliferate in meninges and brain
• thrombosis and destruction of blood vessels with extensive hemorrhaging