Introduction to Parasites

Question 1

The main groups of parasites

Answer 1

protozoa, helminth, arthropods

Question 2

examples of protozoa

Answer 2

malaria, amoebic dysentery, leishmaniasis

Question 3

features of malaria

Answer 3

plasmodium species, mosquito vector

sporozoites are injected under the skin by mosquito, travel through blood to liver where they mature, re-enter circulation as merozoites, invade and destroy RBC’s using them to multiple, sexual forms are taken up by mosquito

Question 4

features of Amoebic dysentery

Answer 4

entamoeba hystolytica

trophozoite ingests red cells by pseudopodia

diarrhoea with blood/pus

protozoal cysts in stool samples

liver abscesses in late disease

Question 5

features of Leishmaniasis

Answer 5

several species

cutaneous or muco-cutaneous leishmaniasis causes skin/mucosal ulceration

visceral leishamiasis causes fever, weight loss and hepato-splenomegaly

spread by sandfly bites

Question 6

features of Nematodes - Ascaris lumbricoides

Answer 6

ingested eggs enter circulation, embryos hatch and pass through lungs, enter stomach and move to small intestine as adults

ova seen on microscopy of stool samples

often asymptomatic

can cause loefller’s syndrome

mass of worm can block bile duct

Question 7

features of trematodes - Shistosomiasis

Answer 7

eggs excreted in urine or faeces, miracidia released in fresh water, penetrate the body of a snail as an intermediate host, cercaria emerge from snail 4-6 weeks later, penetrate human skin, migrate through lungs to liver