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.

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  • Additional Information
    • Source:
      Publisher: Elsevier Science Country of Publication: United States NLM ID: 101130150 Publication Model: Print-Electronic Cited Medium: Internet ISSN: 1474-4457 (Electronic) Linking ISSN: 14733099 NLM ISO Abbreviation: Lancet Infect Dis Subsets: MEDLINE
    • Publication Information:
      Original Publication: New York, NY : Elsevier Science ; The Lancet Pub. Group, 2001-
    • Subject Terms:
      Leishmaniasis, Visceral*/prevention & control ; Leishmaniasis, Visceral*/epidemiology ; Leishmaniasis, Visceral*/transmission ; Insecticides*/pharmacology ; Phlebotomus*/drug effects ; Phlebotomus*/parasitology ; Insect Control*/methods; India/epidemiology ; Animals ; Humans ; Incidence ; Insect Vectors/drug effects ; Insect Vectors/parasitology ; Psychodidae/drug effects ; Psychodidae/parasitology ; Models, Theoretical
    • 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/m 2 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.
      Funding: Bill & Melinda Gates Foundation.
      Translation: For the Hindi translation of the abstract see Supplementary Materials section.
      Competing Interests: Declaration of interests We declare no competing interests.
      (Copyright © 2024 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 license. Published by Elsevier Ltd.. All rights reserved.)
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    • Accession Number:
      0 (Insecticides)
    • Publication Date:
      Date Created: 20240812 Date Completed: 20241025 Latest Revision: 20241207
    • Publication Date:
      20241209
    • Accession Number:
      PMC11511677
    • Accession Number:
      10.1016/S1473-3099(24)00420-1
    • Accession Number:
      39134082