Question

distinguish between the three Schistosoma species that most commonly parasitize humans using both structural and clinical observations

Answer 1

Schistosomes are important human and animal parasites throughout Africa, Asia and South America, predominantly in rural areas. The three Schistosoma species that are medically relevant are S. japonicum, S. haematobium and S.mansoni. Schistosomiasis (or bilharziasis) is unusual amongst helminth diseases for two reasons:

• much of the pathogenesis is due to the eggs (rather than larvae or adults);
• and most of the pathology is caused by host immune responses (delayed-type hypersensitivity and granulomatous reactions).

S. japonicum

Species	Definite host	Site of infection	Egg excretion	Endemic Area	Worm morphology	Egg Morphology
S.Japonicum	Humans, Ruminants, Carnivores	Intestinal mesenteric veins	Faeces	China,East Asia,	Color: Yellow or Yellow brown. measure approx:2cm by 0.5mm Females are larger than males	round eggs (70-100 x 50-70µm) with a rudimentary lateral spine
S. haematobium	Humans, Primates	veins of Urogenital system	Urine	Africa,Middle east		Mostly red, can be dark grey in color. oval eggs (110-170 x 40-70µm) with a sharp terminal spine.
S.mansoni	Humans, Rodents	Intestinal mesenteric veins	Faeces	Africa, South America, Caribbean, Middle East	Color: males are white and females are grey measure approx 1cm by 0.015	oval eggs (115-175 x 45-7µm) with a sharp lateral spine