Effect of indoor residual spraying on sandfly abundance and incidence of visceral leishmaniasis in India, 2016-22: an interrupted time-series analysis and modelling study.

Coffeng, Luc E, de Vlas, Sake J, Singh, Rudra, James, Ananthu, Bindroo, Joy, Sharma, Niteen, Ali, Asgar, Singh, Chandramani, Sharma, Sadhana and Coleman, Michael ORCID: https://orcid.org/0000-0003-4186-3526 (2024) 'Effect of indoor residual spraying on sandfly abundance and incidence of visceral leishmaniasis in India, 2016-22: an interrupted time-series analysis and modelling study.'. The Lancet. Infectious diseases, Vol 24, Issue 11, pp. 1266-1274.

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Abstract

Background
Efforts to eliminate visceral leishmaniasis in India mainly consist of early detection and treatment of cases and indoor residual spraying with insecticides to kill the phlebotomine sandfly Phlebotomus argentipes that transmits the causative Leishmania protozoa. In this modelling study, we aimed to estimate the effect of indoor residual spraying (IRS) on vector abundance and transmission of visceral leishmaniasis in India.

Methods
In this time-series analysis and modelling study, we assessed the effect of IRS on vector abundance by using indoor vector-abundance data (from 2016 to 2022) and IRS quality-assurance data (from 2017–20) from 50 villages in eight endemic blocks in India where IRS was implemented programmatically. To assess a potential dose–response relation between insecticide concentrations and changes in sandfly abundance, we examined the correlation between site-level insecticide concentrations and the site-level data for monthly sandfly abundances. We used mathematical modelling to link vector data to visceral leishmaniasis case numbers from the national Kala-Azar Management Information System registry (2013–21), and to predict the effect of IRS on numbers of averted cases and deaths.

Findings
IRS was estimated to reduce indoor sandfly abundance by 27% (95% CI 20–34). Concentrations of insecticides on walls were significantly—but weakly—associated with the degree of reduction in vector abundance, with a reduction of –0·0023 (95% CI –0·0040 to –0·0007) sandflies per mg/m2 insecticide (p=0·0057). Reported case numbers of visceral leishmaniasis were well explained by trends in vector abundance. Village-wide IRS in response to a newly detected case of visceral leishmaniasis was predicted to reduce disease incidence by 6–40% depending on the presumed reduction in vector abundance modelled.
Interpretation
Indoor residual spraying has substantially reduced sandfly abundance in India, which has contributed to reductions in visceral leishmaniasis and related deaths. To prevent the re-emergence of visceral leishmaniasis as a public health problem, surveillance of transmission and sandfly abundance is warranted.

Item Type:	Article
Subjects:	WC Communicable Diseases > Tropical and Parasitic Diseases > WC 715 Visceral leishmaniasis WD Disorders of Systemic, Metabolic or Environmental Origin, etc > Animal Poisons > WD 430 Insects WR Dermatology > Parasitic Skin Diseases > WR 350 Tropical diseases of the skin. Mucocutaneous leishmaniasis. Leishmaniasis
Faculty: Department:	Biological Sciences > Vector Biology Department
Digital Object Identifer (DOI):	https://doi.org/10.1016/S1473-3099(24)00420-1
SWORD Depositor:	JISC Pubrouter
Depositing User:	JISC Pubrouter
Date Deposited:	12 Sep 2024 10:25
Last Modified:	18 Nov 2024 16:01
URI:	https://archive.lstmed.ac.uk/id/eprint/25220

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