Schistosoma PDF

Family Schistosomatoidea  Schistosoma spp. - The Blood Flukes General - Separate male and female worms exist in this group of flukes. The female is long and slender, the male is shorter, cylindrical and characteristically in-curved to form a gynecophoral groove in which the female repo...

Family Schistosomatoidea  Schistosoma spp. - The Blood Flukes General - Separate male and female worms exist in this group of flukes. The female is long and slender, the male is shorter, cylindrical and characteristically in-curved to form a gynecophoral groove in which the female reposes. Adult males are 22-1.8 mm long; females are 28-0.8 mm long. Ventral sucker pedunculated The female leaves the male to lay eggs in the small veins close to lumen of the intestine or bladder. Eggs are firmly wedged in, and spines present on the eggs facilitate their retention.  Schistosoma spp. - The Blood Flukes Life cycle - Eggs are released into fresh water; miracidia hatch. Miracidia penetrate snails and undergo essential developmental stages, leaving the snail as free-swimming cercariae. Free-swimming cercariae penetrate the skin of humans while they are swimming or bathing. Cercariae lose their tails upon penetration, travel through body via the bloodstream and develop to adults in blood vessels of the host. Schistosoma mansoni Site : mesenteric blood vessels Final host: human Intermediate host: Biomphalaria Schistosoma haematobium Site : blood vessels of urinary bladder Final host: human Intermediate host: Biomphalaria  Acute schistosomiasis (Katayama fever) -4 to 8 weeks after primary exposure Dry cough with changes on chest x-ray Fever Fatigue Muscle aches Malaise Abdominal pain Enlargement of both the liver and the spleen -lymphadenopathy,and eosinophilia  Chronic disease may appear many years later S.mansoni hepatomegaly splenomegaly portal hypertension esophageal varices  schistosomiasis haematobium inflammation and fibrosis obstruction Renal failure hematuria hydronephrosis uremia Characteristic eggs Apical spine: S. haematobium, S. bovis Lateral spine: S. mansoni S. Haematobium and bladder cancer Schistosomiasis  Swimmer itch schistosome cercarial dermatitis is a short-term immune reaction occurring in the skin of humans that have been infected by water-borne schistosomatidae. Symptoms, which include itchy, raised papules, commonly occur within hours of infection and do not generally last more than a week. It is common in freshwater, brackish and marine habitats worldwide. 14  Prevention No vaccine is available. The best way to prevent schistosomiasis is to take the following steps if you are visiting or live in an area where schistosomiasis is transmitted: Avoid swimming or wading in freshwater when you are in countries in which schistosomiasis occurs. Drink safe water. Although schistosomiasis is not transmitted by swallowing contaminated water Water used for bathing should be brought to a rolling boil for 1 minute to kill any cercariae, and then cooled before bathing. Vigorous towel drying after an accidental, very brief water exposure may help to prevent the Schistosoma parasite 15 from penetrating the skin.  Control 1. reducing the number of infections in people 2. eliminating the snails that are required to maintain the parasite’s life cycle. For all species that cause schistosomiasis, improved sanitation could reduce or eliminate transmission of this disease. Control measures can include mass drug treatment of entire communities and targeted treatment of school-age children. Some of the problems with control of schistosomiasis include: Chemicals used to eliminate snails in freshwater sources may harm other species of animals in the water and, if treatment is not sustained, the snails may return to those sites afterwards. 16