policymakers in India swear by the insecticide ddt to contain sand fly, the kala-azar vector. There are alternatives to using chemicals, a group of researchers has found by studying 50 villages in five kala-azar endemic districts in Bihar. The disease is most prevalent in the state. Critics say the study is not foolproof.
Various theories exist on sand fly's habitat. It is said that sand flies live in crevices in the grass walls of huts, multiply in alluvial soil and cow dung. The ph and the composition of the soil affect its breeding habits. V K Saxena, the lead author of the Bihar study, says a thorough understanding of sand flies' habitat and breeding habits is essential to find ways to control the menace that transports the killer pathogen (Leishmania donovani) to millions of people.India's National Vector Borne Disease Control Programme estimates that about 165 million people face the risk of kala-azar in Bihar, Jharkhand, Uttar Pradesh, and West Bengal.
The researchers studied 851 soil samples from damp areas surrounding cattle shelters and houses in Darbhanga, Muzaffarpur, Samastipur, Patna and Vaishali, the five endemic districts. The villages had similar features--houses were close to cattle sheds and made of mud-plastered walls with thatched roofs and the high-plasticity soil in sheds was laden with dung and urine.
Research methods included assessment of breeding preferences (through soil incubation) of the sand fly and measuring the ph of each soil sample. Breeding of sand flies was detected in 7.3 per cent of the samples examined. Soil from the cattle sheds was found to be infested more than houses. A type of sand fly, called the Phlebotomus argentipes, preferred to breed in the alkaline soil of cattle sheds, while another variety, Phlebotomus papatasi, gelled well with the neutral ph soil found in the vicinity of houses, said the study which will be published in the journal Acta Tropica.
|Researchers suggest that using weed to make the soil acidic could control the kala-azar vector|
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