India's widespread dependence on indoor spray of the insecticide DDTto combat kala azar mightironicallybe derailingefforts to eliminate this menacing disease,stillprevalent in eastern states, particularly Bihar, health experts have cautioned.
A comprehensivestudythat examined indoor DDT spraying practices in Bihar has revealed that about 85 per cent of sprays did not contain enough concentrations of DDT to kill sand flies - the insect that spreads kala azar parasites through their bites.
The studycarried out jointly by experts at the Rajendra Memorial Research Institute of Medical Sciences, Patna, and the Liverpool School of Tropical Medicine, UK,also found DDT resistance in sand flies, implying that even high concentrations of DDT may not kill the insects.
Thenorthern districts of Bihar account for 85 per cent of the total kala azar cases in the country. It is also the second largest parasitic killer disease in the world after malaria.At least 20,000new cases are reported from the stateevery year.
Janet Hemingway, the British parasitologist who worked on the study said: "Spray monitoring relies on visual inspections. This just tells you whether something has been sprayed, not whether the correct amount of DDT has been sprayed."
"DDT resistancein sand fliesis now extensive throughout Bihar," she told The Telegraph. "It would be better to spray an insecticide to which there is no resistance."
The "indoor residual spraying quality assurance" study was carried out in 560 households acrosssixdistrictsinBihar - Begusarai, Gopalganj, Khagaria, West Champaran, Saharsa and Samastipur - last year. Its findingswere publishedthis yearin areputedscientific journal.
The studyrecommendsreplacing DDT with a synthetic "pyrethroid deltamethrin," somethingsuggested earlier by other experts in India,but not implemented yet.
"Our proposal to the Union health ministry to replace DDT with deltamethrin has been accepted, however, it can be implemented only in phases, saidPradeep Das, director of Rajendra Memorial Research Institute of Medical Sciences, the regional branch oftheIndian Council of Medical Research.
He admitted that DDT sprayingismostly carried out by local municipal bodies,as a result of which thequality of sprayingisoftennot up to mark. "Till the time a new pesticide replaces DDT completely,we're trying to supervise spraying activitiesthrough the district health authorities to ensurethat the programme is effective, and is carried out through the prescribed standard operating procedures," he said.
The Centre had in 2006 expanded theNationalVector Borne Disease Control Programme to coverkala azar andhad set 2015-16as the target date for its elimination from 33 districts in Bihar.
But health officials both in the Centre and in the state admitthe target may be pushed byat least anothertwo years.
P.K. Sinha,theformer director of the Patna-based institute and an expertonkala azar, said though thenumber of new cases of kala azar had beencontinuously declining every year, the governments have to adoptimprovedstrategies to tackle it.
"In terms of both prevention and cure of the disease, there is a lot that can be done and therefore studies like these should be taken into consideration for framing new policies," he said.
