Vol 27 No 2 December - The Indian Society for Parasitology
Vol 27 No 2 December - The Indian Society for Parasitology
Vol 27 No 2 December - The Indian Society for Parasitology
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74 Trematodes of public health importance<br />
JPD : <strong>Vol</strong>. <strong>27</strong> (2), 2003<br />
a patient who died in that city.<br />
and with irrigation and with increase in the population<br />
density of animals. <strong>The</strong> usual methods of human<br />
Family: Schistosomatidae<br />
exposure consist in wading, swimming, bathing or<br />
G:- Schistosoma<br />
washing cloths in shallow fresh water near the infected<br />
Sps : S.bovis (cattle, sheep, goat) -portal & mesentric<br />
snail hosts. Excreta of man and reservoir hosts<br />
Veins.<br />
containing viable Schistosoma eggs provide the<br />
inoculum which initiates the extrinsic phase of the life<br />
S. mattheei (Domestic and wild ruminants) - portal and cycle of the parasite. S. japonicum has many<br />
mesenteric veins as well as in the veins of the mammalian reservoirs, yet the use of human faeces as<br />
urogenital tract and stomach.<br />
fertilizer <strong>for</strong> crops in endemic areas probably<br />
S. intercalatum (wild and domestic ruminants , equines constitutes the most important source of infection. In<br />
and man) - portal and mescentric veins).<br />
certain foci in Africa baboons have been found to<br />
maintain infection with S. mansoni with out<br />
*S'. spindale (Ruminants & dogs ) - mesentric veins. involvement of humans (Faust et al., 1975).<br />
S. indicum (Ruminants, equines and camels) - portal Pathogenic changes resulting from blood fluke<br />
and mesentric veins.<br />
infection in a susceptible host are delivered into three<br />
S. japonicum (Man & animals) - portal & mesentric consecutive periods (1) Pre-patent period, from skin<br />
veins).<br />
penetration until the mature worms have arrived in the<br />
S. mekongi (Dog & Man) - mesenteric veins.<br />
venules of the intestine or urinary bladder and the<br />
females are already to oviposit; (2) acute stage, which<br />
S. nasalis (Buffaloes, cattle, sheep , goats and horses) - is one of active egg deposition and extrusion and (3)<br />
veins of nasal mucosa.<br />
Chronic stage, stable egg output, tissue proliferation<br />
<strong>The</strong> eggs in faeces or urine hatch in fresh water and the<br />
and repair.<br />
free swimming miracidia are released. If appropriate Adult parasites cause phelibitis in the mesenteric veins<br />
snails are found, the miracidia attack the snails soft and there is a proliferation of the tunica intima with<br />
tissues, penetrate and trans<strong>for</strong>m into first generation portal or complete occlusion of the lumen. As the<br />
sporocysts. Within each sporocyst several second - infection progresses the adult parasites shift away<br />
generation sporocysts are developed and on escape from their predilection site in the posterior small<br />
from the parent sporocyst migrate further into the intestine and anterior large intestines and lesions will<br />
snail's tissues. Broad <strong>for</strong>ktailed cercariae are produced be seen in other parts of the intestine as well as in other<br />
over a period of several weeks. On maturation these organs. In addition with S. mattheei lesions in the<br />
larvae escape from the second generation sporocysts, bladder are striking and common. Pathology of<br />
break out of the snail and swim about in the water. bladder is seen as linear granulomata or granular<br />
Infection of the definitive host is through active skin patches with associated haemorrhages. Adults of S.<br />
penetration of the cercariae although cercariae may mattheei and S. indicum may in heavy infections, be<br />
penetrate the wall of the lumen when swallowed with found in the pulmonary arteries.<br />
water. Skin penetration is assisted by the secretions of<br />
<strong>The</strong> hepatic syndrome is an immunological disease<br />
the cephalic glands, which digest the tissues. Cattle<br />
resulting from the host's cell -mediated immune<br />
and horses may become infected when standing in the<br />
response to Schistosome egg in the liver.<br />
shallow water of dams, rivers, etc., during the heat of<br />
the day. <strong>The</strong>se and other animals are also infected In heavy infections the development and healing of<br />
orally when water tanks and other source of drinking large numbers of these egg granulomas cause massive<br />
water become infected with snails and contaminated fibrosis in the portal triads of the liver and the<br />
with faecal material. <strong>The</strong> infection is most common in appearance of "Claypipestem" fibrosis.<br />
man and animals where the rainfall is highest; there is a S. nasalis causes nasal granuloma (snoring disease) of<br />
marked increase in incidence with increasing water cattle, goats and horses in India. I.H. are Lym. Luteola,<br />
conservation (the building of small and large dams) L. accuminata and Indoplanorbis exustus. <strong>The</strong> arasites