Schistosomiasis Pt 1 of 3 (1990)

[Music] this video is based on the work of two research teams one led by Dr Owen standon at the welcome Laboratories of tropical medicine in the early 50s and the mother led by Dr Diane McLaren in the late 80s at the National Institute for medical research Dr mcclaren's scanning and transmission electron micrographs of the schistosome are featured in our video this is the image seen in the microscope which is enlarged still further when processed photographically it should be appreciated that these electron micrographs represent a wide range of magnifications for example this adult male schistosome is magnified about 35 times when viewed on a 50 cm television screen his ventral sucker 500 times and this spiny Inside Edge of the sucker 7,000 times some of our images are magnified around a quarter of a million times like this section showing the outer surface of a lval schistosome it was with the aid of this electron microscope that Dr McLaren was able to unravel one of the most puzzling stages in the life cycle of the Chism The crucial process is involved in the transformation from free living organism to a parasitic way of life these happy children are playing in water that is more than likely to be infected by one of the world's most damaging parasitic diseases schistosomes are parasitic flukes that live in the bloodstream of man they cause the disease schistosomiasis probably better known as bartsia a major health problem for hundreds of millions of people in many tropical and subtropical regions of the world a male schistosome is seen here with a female partly held in his gynecophoric Canal the male is about a cenm long and uses the lateral folds of his body to form the gynecophoric canal with he Embraces the longer more slender female incidentally the scientific name chista means Clift bodied this is the anterior part of the Clift which surrounds the head end of the female here are the paired schistosomes in the portal vein of an experimentally infected hamster the flukes migrate as far as they can into the mesenteric veins and the female extend tends out of the gynecophoric canal to deposit her eggs into the smaller blood vessels the eggs then work through the tissues into the Lumen of the intestine in this species of schistosome the eggs pass out later with the feces here's an egg in a fecal smear the earliest records of urinary schistosomiasis are to be found in the EAS Papyrus dated around 1,900 BC although the ancient Egyptians did not know the cause of the disease they recognized and clearly Illustrated the urinary symptoms in their hieroglyphics calcified schistosome eggs have also been identified in the kidneys of mummies more than 3,000 years old it was not until 1851 that the German pathologist Theodore billhartz identified chistosa hematobium as the causative agent of urinary schistosomiasis in Egypt in 1904 katsurada described the life cycle of japonicum and in 197 sambon described mansai as a separate species in 1934 Fisher recorded the existence of intercalatum and as recently as 1978 Vogue Brookner and Bruce discovered mongi today 18 species are recognized of these mansai japonicum and he iium probably infect more people worldwide than any of the other species mansoni lives chiefly in the veins of the large intestine and this part of the portal circulation is also infected by japonicum the passage of eggs through the intestinal tissues causes ulceration thickening and fibrosis of the bowel wall eggs can be seen in this much thickened region of The Superficial layers of the intestine also at the bases of the Villi those eggs which enter the Lumen of the gut are discharged with the feces chistosa hematobium differs from the other two species it inhabits the blood vessels of the bladder and its eggs are discharged with the urine the main clinical sign is hematuria But ultimately fibrotic lesions May develop throughout the whole of the urogenital system bladder cancer is not an uncommon development in advanced stages of the disease schistosomiasis is currently endemic in 75 countries hematobium is present in 53 countries mostly in Africa but also in the Eastern Mediterranean mansai shows a similar distribution except that it's also found in South America notably Brazil where it was probably carried with the slave trade japonicum on the other hand is confined to countries of the Far East China Indonesia and the Philippines Japan where the parasite was originally found has now been freed from the disease mongi occurs in Southeast Asia and intercalatum is found in Central and West Africa worldwide some 200 million people are infected with the schistosomes and 500 to 600 million are at risk the highest infection rates are found in Brazil Egypt and the Sudan freshwater snails play an essential role in the transmission of the disease since each schistosome will spend part of its life cycle in the tissues of a snail species of bulinus are intermediate hosts for hematobium biomphalaria carries Manson and enom Melania carries japonicum wholesale destruction of the snail hosts with chemical mides is one obvious method of reducing the incidence of schistosomiasis but since the snails are hemaphrodite possessing both male and female sexual organs it needs only one individual to survive a control program of this kind for an entire area to be repopulated within a single season moreover development projects such as hydroelectric schemes like the gigantic Kuba Dam on the zambesi have created large bodies of water and consequently enable the snails to flourish in recent years although most infected people carry only small numbers of schistosomes treatment with an effective drug not only reduces the prevalence of the disease it also reduces morbidity przi quantel is currently the drug of choice since a single dose affects all the main species of schistosome that infect man and it produces High cure rates oxamniquine is also used for mansen especially in South America while metrifonate is valuable for the treatment of hematobium it's man's primitive habits with regard to urination and defecation which maintain the disease in the community obviously the separation of urine and feces from Waters inhabited by the snails is vital in the control of infection in the third world this is easier said than done however in Zimbabwe the Blair Research Laboratories have produced some interesting designs for simple water pumps and lavatories this one is a strong shelter built over a deep pit it has an odor pipe fly traps and is easy to keep clean and here are some variations on the basic design