Listen to Story Spraying insecticide inside homes in Indian villages to combat sandflies, which transmit visceral leishmaniasis (kala-azar), was found to reduce their numbers by 27% between 2016 and 2022, according to a study. The study, which included researchers from CARE India and AIIMS Patna, suggests that using the insecticide alpha-cypermethrin in homes where visceral leishmaniasis cases are reported could potentially decrease the prevalence of this vector-borne disease by 6-40%. This insecticide is commonly used on crops like cotton, cereals, and soybeans.
Conducted in 900 homes across 50 villages in Bihar, Jharkhand, and West Bengal, regions where kala-azar is endemic, the research was part of an elimination program initiated in 2015. The study's findings were published in The Lancet Infectious Diseases journal. Visceral leishmaniasis is caused by leishmania parasites, transmitted through the bites of phlebotomine sandflies.
It primarily affects internal organs such as the liver, bone marrow, and spleen, leading to symptoms like fever, weight loss, and anemia. If left untreated, the disease can be fatal. According to the World Health Organisation (WHO), most cases occur in Brazil, East Africa, and India.
Visceral leishmaniasis is caused by leishmania parasites, transmitted through the bites of phlebotomine sandflies. (Photo: Getty Images) The study also noted that kala-azar accounts for 12.5% of the cost of indoor insecticide spraying to control vector-borne diseases in India, second only to malaria, which accounts for 76%.
However, the researchers pointed out that there is limited evidence on the cost-effectiveness of indoor spraying in significantly reducing disease cases. Despite this, indoor spraying consumes 70-80% of India's budget for eliminating visceral leishmaniasis. The researchers analysed three datasets for their study.
The first dataset tracked the number of sandflies present in each home, with data collected biweekly from 2017 to 2022 using light traps provided by the US Centers for Disease Control and Prevention (CDC). Approximately 2,30,000 sandflies were captured. The second dataset assessed the quality of indoor insecticide spraying in these homes, while the third dataset comprised surveillance data on visceral leishmaniasis cases from January 2013 to December 2021, sourced from the Kala-Azar Management Information System (KAMIS), India's national case registry.
The study found that indoor insecticide spraying in 11 villages across four blocks in Bihar led to a 27% overall reduction in sandfly numbers. The researchers' model also predicted that three years of sustained indoor spraying could lead to a significant reduction in new cases of visceral leishmaniasis and related deaths. Specifically, a 30% decrease in sandfly numbers due to spraying was estimated to result in a 17% reduction in new cases and a 9% decrease in deaths over the same period.
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