The sand flies, which carry the parasites causing the disease, have grown resistant to chemicals used to eliminate them. This is likely to impact the eradication goals
Kala-azar or visceral leishmaniasis continues to be a major health challenge for India, with the country accounting for 65 million out of an estimated 200 million people who are at annual risk of the disease worldwide. Bihar is the “kala-azar epicentre of India”, and accounts for one third of the total cases in the country.
A study carried out in collaboration between experts from the Liverpool School of Tropical Medicine, United Kingdom, Indian Council of Medical Research, New Delhi and Rajendra Memorial Research Institute of Medical Sciences, Patna, says that the current method of spraying insecticides to eradicate kala-azar in Bihar is not of the highest standards. It highlights that the sand flies transmitting the parasites responsible for the disease have grown resistant to the chemical.
The team of researchers conducting the study, collected samples from walls and households of eight endemic Bihar districts to conduct a Quality Assurance (QA) test on DDT, the primarily-used insecticide for Indoor Residual Spraying (IRS). It was found that approximately 85 per cent walls were under-sprayed and sand flies were still in abundance.
"Monitoring of sand fly abundance indicated that the current IRS activities only had a positive impact on reducing sand fly abundance for a period of approximately four weeks,” concluded the data analysis. The root cause of this poor efficiency is yet to be determined.
The study notes that India is using WHO-established DDT dosages for mosquitoes carrying the malaria parasites as a surrogate standard to control sand flies, although there is no evidence for such an adoption. “WHO only has discriminating dosages for mosquitoes. They have not set these dosages for any insecticide for sandflies,” Janet Hemingway, one of the authors of the report told Down To Earth.
Moreover, there are a lot of issues surrounding the use of DDT because it belongs to a group of organic pollutants and adds high toxicity to the environment. The international agreement—Stockholm Convention—appeals for a complete phasing out of DDT but agrees upon its use against vector-borne diseases (diseases caused by insects carrying the parasites) when alternatives are not viable.
Besides India, East Africa and Brazil as well as India’s neighbours, Bangladesh and Nepal also report high number of kala-azar cases.
But even Bangladesh and Nepal have stolen a march over India in decreasing the incidences of kala-azar as well as doing so by using alternatives to DDT.
“Currently there are a number of pyrethroids, organophosphates and carbamates recommended by WHO for indoor residual spraying. Some, but not all of these are registered in India for this use,” said Hemmingway, further adding that Bangladesh and Nepal currently use pyrethroids for indoor residual spraying instead of DDT.
According to a WHO report released on June 2014, Bangladesh has witnessed a historical drop in kala-azar cases. A total number of 1,284 cases were reported to WHO in 2013 compared with 4,293 cases in 2009. Nepal too has seen some reduction in the disease but being a rural economy characterised by low human development and poverty, health is still a massive challenge for the country.
In Spetember, 2014, then-Union Minister for health, Harsh Vardhan had claimed that India would be free of kala-azar in 2015. But as the study indicates, it is not going to be so fast. Besides the quality of IRS, the study points out that the lack of diagnostic facilities in India’s healthcare, along with drug standards also account for the nation's failure in eradicating the disease.
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