Schistosoma SPP Flashcards
Classification
Metazoa
Indirect or direct
Hosts
Indirect life cycle
Snail intermediate host
Human final host
Various other animals are reservoirs.
Transmission and life cycle
In the water eggs hatch and release miracidia. Miracidia infect snails.
The stages in the snail include two generations of sporocysts and the production of cercariae.
Upon release from the snail, the cercariae penetrate the skin of the human host.
The schistosomulae migrate through the circulation to the lungs, then the heart and develop in the liver.
They exit from the liver via the portal vein when they are matured.
Male and female adult worms replicate sexually in the mesenteric venules, the location which varies by species.
Mansoni is often found in the bowel. Haematobium is often found in the bladder. The eggs are excreted by feces or by urine.
Symptoms are caused by the body’s reaction to the eggs. Continuing infection may cause granulomatous reactions and fibrosis in the affected organs (liver and spleen) with associated symptoms.
Diagnosis
Microscopic identification of eggs in stool or urine. But eggs can be present in the stool in infections with all schistosoma species.
Antibody detection can be useful in travelers in whom eggs cannot be detected in fecal or urine specimens.
