Some facts on south asian schistosomiasis and need for international collaboration.

In this review, we are discussing South Asian schistosomiasis; more specifically species which are responsible for schistosomiasis in India or South Asia -Schistosoma indicum, S. spindale, S. nasale, S. incognitum, S. gimvicum (S.haematobium), Bivitellobilharzia nairi, Orientobilharzia bomfordi, O. dattai, O. turkestanicum and O.harinasutai, their survival strategies such as mild pathology to the host, producing low egg number and utilizing fresh water snails (Indoplanorbis exustus and Lymnaea luteola) in stagnant water bodies like ponds, lakes, ditches, low laying areas, marshy lands and rice fields. Presently, correct identification of blood fluke species, their immature stages, male schistosomes and their intermediate host details like strain variations, susceptibilities, ecologies are not well studied. Species like B. nairi, O. bomfordi, O. harinasutai (Lymnaea rubiginosa intermediate host for O.harinasutai in Thailand) are also not well studied. Moreover, snail species like Oncomalania spp are not from South Asia, but species of Tricula or Neotricula are reported from this geography, which gives indications of S. mekongi like blood fluke presence in the area. Although in humans, cercarial dermatitis is rampant in rural population with occasional reporting of schistosome eggs in stools, human schistosomiasis is considered absent from this region, despite finding a foci (now dead) of urinary schistosomiasis in Gimvi village of Ratnagiri district, Maharashtra, India. There is great difficulty in diagnosing the infection in man and animals due to low egg production, hence development of a single step antigen detection test is the need of the hour. Interestingly, lethal effect of praziquantel was seen against S.haematobium and S.mansoni. However, this drug failed to cause significant reduction of S. incognitum and S. spindale experimentally suggesting some differences in the biology of two groups of the schistosomes. Triclabendazole showed adulticidal effect at a dose rate of 20 mg/kg body against female schistosome worms, but at lower dose (10 mg/kg body wt) of the drug, a dose that is used in treating bovine fascioliasis, it is providing chances of drug resistance of the persisting schistosomes against triclabendazole. Though the South Asian institutes have all the facilities to tackle issues related to existing schistosomes, it is recommended to develop an international collaboration by establishing an international centre on schistosomiasis in India.

Indian schistosomes: a need for further investigations.

India is uniquely positioned with regard to schistosomes and schistosomiasis-discovering seven new mammalian species with the existence of three more schistosome species: Orientobilharzia turkestanicum, O. harinasutai, and Schistosoma haematobium(?). An endemic focus of urinary schistosomiasis was reported from Gimvi village of Ratnagiri, Maharashtra with infrequent occurrence of schistosome eggs in human stools. Cercarial dermatitis has been reported to be more abundant in rural population using ponds, tanks, and so forth, for their domestic purposes. Few dermatitis cases were tested positive by CHR. Schistosome antigen was also detected in urine of five cases suggesting existence of active schistosomiasis in India. Nevertheless, human kind does not appear to be the usual host for Indian schistosomes in contrast to S. haematobium, S. mansoni, or S. japonicum. Various reasons for this phenomenon are discussed including evolution of Indian schistosomes, immune mechanisms, and environmental conditions. These and other aspects such as seasonal effect on the prevalence, snail infectivity, heterologous mating, existence of hybrids, and number of schistosomes in heterologous infections need further investigations with application of molecular techniques. Joint efforts by the national as well as international scientific community would be much more rewarding for better understanding of the parasite and the infection.

Cercarial dermatitis in central India: an emerging health problem among tribal communities.

Although cercarial dermatitis is an emerging disease world-wide, cases of such dermatitis may often go undiagnosed, especially in communities that are affected by various skin infections. Between August 2001 and July 2002, 1336 individuals from tribal villages in central India were examined for dermatitis. Skin scrapings were collected and examined for Sarcoptes scabiei and each subject's response to antiscabies treatment was recorded. Freshwater snails were collected from the local ponds used for bathing, and examined for cercariae. The recorded prevalence of dermatitis ranged between 2.1% and 12.5% during the study year, peaking at the end of winter (February-March) and during the rainy season (August-October). Snail positivity for cercariae peaked in the rainy season. The prevalence and the severity of dermatitis were both higher in children than in adults. As most recorded cases of dermatitis were associated with a rash that developed soon after bathing in the local pond, all the skin scrapings were negative for itch mites, and the response to antiscabies treatment was poor, most if not all of the dermatitis observed was probably cercarial. Cercarial dermatitis therefore appears to be a significant health problem among the tribal populations of central India.

Worm infestation and anaemia: a public health problem among tribal pre-school children of Madhya Pradesh.

A study to assess the status of intestinal parasitosis and anaemia was carried out among the pre-school children of Gond tribal community in Kundam block of Jabalpur district, Madhya Pradesh. A total of 985 pre-school children were covered. The results revealed that 48% pre-school children had intestinal parasitic infections. Common parasites observed among them were Hymenolepis nana, hookworms and roundworms. Mean epg for these parasites ranged from 371.2 to 1221.8. High prevalence of anaemia (86.7%) was also observed among them. This high prevalence of intestinal parasitic infections and anaemia could be due to indiscriminate defecation, low socio-economic status, ignorance and low standard of personal hygiene. Comprehensive control strategy with specific intervention measures need to be evolved and implemented specially in tribals as serious efforts are being madeby the Govt. for their overall development.

Human schistosomiasis in India?

It was a common belief in the first half of this century that human schistosomiasis would not become established in India, despite the regular introduction of the disease by soldiers returning from active campaigns. This was based on the absence of known intermediate hosts for Schistosoma spp, yet in 1952 a focus of human schistosomiasis was discovered in Gimvi village, Ratnagiri District, Maharashtra State. The focus seems to be in recession, but the proposed large irrigation schemes centering upon the Narmada River may exacerbate schistosomiasis in domestic stock, and possibly in humans. Here, Vaughan Southgate and Matesh Agrawal discuss the findings in Gimvi, and the possibilities of human schistosomiasis in India in the future.

Prevalence of sarcocysts of Sarcocystis capracanis in oesophagus and tail muscles of naturally infected goats.

The prevalence of sarcocysts of Sarcocystis capracanis in oesophagus and tail muscles of 76 goats slaughtered at Jabalpur, India, was found to be 67.10 and 46.05%, respectively. A total of 79.3% of oesophagi and 72.4% of tails had sarcocysts in older goats (greater than 1 year), but their prevalence in younger animals (less than 1 year) was 40.0% in oesophagi and none in tails. Therefore examination by biopsy of the tail muscles can be used to monitor the development of Sarcocystis sarcocysts in experimental infection without killing the animal.

Experimental infection of rhesus monkeys with Schistosoma incognitum and Orientobilharzia dattai.

Rhesus monkeys inoculated subcutaneously with 800-2500 cercariae of Schistosoma incognitum did not yield adult worms. Percutaneous exposures, however, resulted in the presence of adult flukes 21-35 days post infection. The infection became very mild (0-4 flukes) 45-100 days after exposure and no eggs were excreted. Monkeys percutaneously exposed to cercariae of Orientobilharzia dattai and treated with prednisolone yielded a very small number of flukes 22 days after exposure while non treated controls yielded no adult worms.

Stephanofilarial dermatitis in India.

Four species of Stephanofilaria have been reported from India causing various forms of dermatitis in cattle, buffalo, goat and elephant. However, additional work is needed to establish their identity as separate species. The lesions appear to flare up following reinfection, while the application of a petroleum jelly alone reduces them. In vitro tests have shown organophosphorous compounds to possess stephanofilaricidal action in addition to their insecticidal activity. Aspects where further work is needed are indicated.