Parasite Basics Flashcards
Basic Classification of Parasites
- Protozoa (Amoeba, flagellates, ciliates, sporozoa)
- Helminths (cestodes, trematodes, nematodes)
- Ectoparasites
Difference between animalia and protozoa
Protozoa are unicellular
Giardia life cycle
cysts are ingested, excyst into 2 trophozoite in the small intestine. Trophozoites adhere to the intestinal mucosa and either divide asexually or become cysts. Cysts passed into the environment are cold-hardy and infective.
Entamoeba histolytica life cycle
Cysts are ingested, they excyst in the small intestine, then the trophozoites move to the large intestine where they divide or encyst. Trophozoites can also invade tissue and move to other parts of the body.
Plasmodium life cycle
Sporozoites get into the blood after a bite from a female Anopheles mosquito. It then goes to the liver to reproduce asexually. Hepatic cells rupture, merozoites go infect blood cells to eat hemoglobin, become ring forms, make more merozoites OR gametocytes. Gametocytes can be taken up by another mosquito. Sexual reproduction happens in the stomach, then the sporozoites go to the salivary glands until the next bite.
Giardia
- Incubation time
- Pathogenesis
- Immunity
- Symptoms
- 7-14 days
- Disruption of microvilli and crypts
- Partial IgA immunity with chronic exposure
- Foul smelling, fatty stools; abdominal discomfort, malaise
Plasmodium falciparum
- incubation time
- Pathogenesis
- Symptoms
- Diagnosis
- 14-21 days
- Inflammation caused by lysis of RBCs, and making RBC cells knobbly so that they stick to vessels and cause organ ischemia
- Fever q48h, headache, general malaise
- Diagnosis is with thin and thick blood films
Entamoeba histolytica
-symptoms
- 90% asymptomatic
- amoebic dysentery
- extraintestinal infection, most common liver abcesses
- mimics chronic IBD
Ascaris lumbricoide lifecycle
Swallow egg, hatches in small intestine, larvae gets into blood, then lung and matures there, then crawls up the bronchiole tree and is swallowed and lives in intestine. When male and female worms are both present, fertilized eggs are passed and must mature in soil before becoming infective.
Enterobius vermicularis lifecycle
Egg is ingested larvae hatch in small intestine and mature in large intestine. When male and female worms are present, eggs are laid on perianal fold which becomes pruritic. The eggs are then transmitted fecal/orally
Strongyloides stercoralis life cycle
Eggs are passed to soil by infected individual, hatch into larva, grow up and lay more eggs. A different form of larvae penetrates the skin on your foot, goes to lung, is swallowed and lives in intestine. Can replicate inside humans, or inside soil
Necator americanus life cycle
Larvae enter skin, go to lung, are swallowed, live in small intestine. Eggs are passed in stool, hatch in soil.
Ascaris Lumbricoides
- signs
- Dx
- Eosinophillic pneumotitis may occur during lung stage
- Stool O&P
Enterobius vermicularis
- signs
- Dx
- Most commonly itchy anus in children
- Diagnosed but putting a piece of tape on perianal fold then sending to lab
Strongyloides stercoralis
- timeline for symptoms
- Dx
- usually asymptomatic until immunocompromised
- Stool O&P
