Protozoal Infections

Question 1

Malaria (Plasmodium sp: P. falciparum, P. vivax, P. ovale, P. malariae)

Answer 1

• Mosquito-born, hemolytic, febrile illness.
• obligate intracellular parasite-replicate, kill human cells
• Equitorial regions (tropics)
• P. falciparum tends to be worst.
• Human reservoire; gametocytes are in human blood and taken up by mosquito
• Reproduce sexually in mosquito = > sporozoites
• Trasmitting to human via bite; go to the liver and form merozoite, perform asexual division.
• Merozoites can invade/multiply within/destroy RBCs. => hemosiderin-laiden Macrophages seen.
• Hepatosplenomegaly
• clumped, infected erythrocytes block blood vessels–hemorrhages, obstruction–acute renal failure with renal blood vessels, intravsascular hemolysis leads to hemoglobinuric nephrosis (blackwater fever)

Question 2

Babesiosis

Answer 2

• Tick-born, malaria-like disease.
• Typically non fatal (self-limited) in healthy; but immuncompromised/splenectomy => complications
• Reproduce in red blood cells (hemolytic anemia), where they can be seen as cross-shaped inclusions (fourmerozoites asexually budding
• Seen in Europe and North America

Question 3

Toxoplasmosis (T. gondii)

Answer 3

• obligate intracellular pathogen
• mostly asymptomatic, problem for immunocompromised and fetus-necrotizing disease.
• Undercooked pig meats, cat litter, cats shed oocysts in their feces.
• Convert to tachyzoites inside intermeidate-host and replicate inside specialized vacuoles
• Immune response causes conversion to bradyzoites, which are associated with cyst formation, especially in CNS and muscle.
• Associated with developmental defects in fetus and neuropsychiatric disorders.
• Encephalitis produced in immunocompromised hosts
• Lymphadenopathy in immunocompetent hosts

Question 4

Amebiasis (Entamoeba histolytica

Answer 4

• Active form (trophozoite) in human and feces
• Cyst form is usually ingested from environment / fecal oral.
• Large Intestine, bleeding more likely.
• Invasive => May feature bloody / leukocytes in stool, metastisis = >Liver
• ameboma: complication, when amebae invade through intestinal wall-inflammatory thickening of bowel resembling colon cancer.

Question 5

Cryptosporidiosis (Cryptosporidium parvum)

Answer 5

• extracellular enteric infection
• most common diarrheal infection in HIV positive patients.
• self-limiting, unless immunocompromised
• AIDS patients, etc, develop chronic infection with persistent chronic diarrhea that can lead to death

Question 6

Giardiasis (Giardia lamblia)

Answer 6

• aka “Beaver Fever” and “Backpacker’s Bug”
• usually self-limited, normally commensual protozoa
• Small Intestine, watery diarrhea.
• Symptoms of GI infection + bloating, excessive gas, and burping (often sulfurous)
• Malabsorption, structural and chemical changes to brush border.
• Watery diarrhea
• IgA deficiency?

Question 7

Leishmaniasis (Leishmania spp.)

Answer 7

• Via sandfly bite.
• proliferate in macrophages–amastigotes
• Tropic/Subtropic, overcrowding.
• Skin soars, may progress to disseminated disease, splenomegaly.
• immunocompromised-diffuse cutaneous leishmaniasis.
• mucocutaneous late complication: disfiguring larynx, nasopharynx, anus, vulva (highly damaging)
• kala azar=visceral leishmaniasis “black sickness”-viscera overwhelmed by build up of infected macrophages–disrupts organ architecture with sheets of parasitized macrophages.
• kala azar is fatal: Requires treatment if disseminated.

Question 8

Chagas Disease (American Trypanosomiasis)

Answer 8

• Rural areas of Mexico, Central America, and South America;
• Flagellate protozoan, insect born zoonosis (kissing bug).
• Bite => Invasion of macrophages / nodular ‘chagoma’
• lesion => dissemination
• Acute illness may kill via myocarditis / encephalitis
• Chronic illness involes GI dysfunction and autonomic nerve degeneration and cardiac failure–years to decades

Question 9

African Trypanosomiasis (Trypanosoma brucei rhodesiense)

Answer 9

• Tetse fly
• Acute febrile progresses to life threatening meningoencephalitis-3 to 6 months
• Humans only reservoir of T. brucei
• evade immune system by altering glycoprotein antigen coat–genetically determined pattern (not mutation)
• Disruption of sleep, neurological problems.
• Fatal if untreated

Question 10

Primary Amebic Meningoencephalitis

Answer 10

• Naegleria fowleri “Brain eating ameoba”: free-living, soil ameba
• Rare, but almost always rapidly fatal: fulminant disease-fever, nausea, vomiting, headache to deterioration of mental status in matter of hours.
• invades via nasal epithelium/olfactory bulbs.
• Swimming pools
• Neti-pots (for cleaning out your sinuses)