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. 2019 Dec 27;18(1):445.
doi: 10.1186/s12936-019-3076-4.

Impact of vector control interventions on malaria transmission intensity, outdoor vector biting rates and Anopheles mosquito species composition in Tororo, Uganda

Alex K Musiime  1   2 , David L Smith  3 , Maxwell Kilama  4 , John Rek  4 , Emmanuel Arinaitwe  4 , Joaniter I Nankabirwa  4   5 , Moses R Kamya  4   5 , Melissa D Conrad  6 , Grant Dorsey  6 , Anne M Akol  7 , Sarah G Staedke  8 , Steve W Lindsay  9 , James P Egonyu  7   10
Affiliations

Impact of vector control interventions on malaria transmission intensity, outdoor vector biting rates and Anopheles mosquito species composition in Tororo, Uganda

Alex K Musiime et al. Malar J. .

Abstract

Background: Long-lasting insecticidal nets (LLINs) and indoor residual spraying of insecticide (IRS) are widely recommended for the prevention of malaria in endemic regions. Data from human landing catches provide information on the impact of vector control on vector populations. Here, malaria transmission indoors and outdoors, before and after mass deployment of LLINs and IRS in Uganda was compared.

Methods: The study took place in Tororo district, a historically high transmission area where universal LLIN distribution was conducted in November 2013 and May 2017 and 6 rounds of IRS implemented from December 2014 to July 2018. Human landing catches were performed in 8 houses monthly from October 2011 to September 2012 (pre-intervention period) and every 4 weeks from November 2017 to October 2018 (post-intervention period). Mosquitoes were collected outdoors from 18:00 to 22:00 h and indoors from 18:00 to 06:00 h. Female Anopheles were tested for the presence of Plasmodium falciparum sporozoites and species identification performed using gross dissection and polymerase chain reaction (PCR).

Results: The interventions were associated with a decline in human biting rate from 19.6 to 2.3 female Anopheles mosquitoes per house per night (p < 0.001) and annual entomological inoculation rate from 129 to 0 infective bites per person per year (p < 0.001). The proportion of mosquitoes collected outdoors increased from 11.6 to 49.4% (p < 0.001). Prior to the interventions the predominant species was Anopheles gambiae sensu stricto (s.s.), which comprised an estimated 76.7% of mosquitoes. Following the interventions, the predominant species was Anopheles arabiensis, which comprised 99.5% of mosquitoes, with almost complete elimination of An. gambiae s.s. (0.5%).

Conclusions: Mass distribution of LLINs and 6 rounds of IRS dramatically decreased vector density and sporozoite rate resulting in a marked reduction in malaria transmission intensity in a historically high transmission site in Uganda. These changes were accompanied by a shift in vector species from An. gambiae s.s. to An. arabiensis and a relative increase in outdoor biting.

Keywords: Biting rates; Indoor residual spraying; Long-lasting insecticide nets; Malaria vector; Transmission.

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Conflict of interest statement

The authors declare that they have no competing interests.

Figures

Fig. 1
Fig. 1
Monthly pattern of daily human biting rate by female Anopheles mosquitoes (red) and rainfall (blue) before and after intensive vector control interventions in Nagongera sub-county, Tororo district
Fig. 2
Fig. 2
Proportions of hourly indoor mosquito catches before (blue) and after (red) intensive vector control interventions in Nagongera sub county, Tororo district
See this image and copyright information in PMC

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References

    1. Bhatt S, Weiss D, Cameron E, Bisanzio D, Mappin B, Dalrymple U, et al. The effect of malaria control on Plasmodium falciparum in Africa between 2000 and 2015. Nature. 2015;526:207. doi: 10.1038/nature15535. - DOI - PMC - PubMed
    1. Tukei BB, Beke A, Lamadrid-Figueroa H. Assessing the effect of indoor residual spraying (IRS) on malaria morbidity in Northern Uganda: a before and after study. Malar J. 2017;16:4. doi: 10.1186/s12936-016-1652-4. - DOI - PMC - PubMed
    1. Eastman RT, Fidock DA. Artemisinin-based combination therapies: a vital tool in efforts to eliminate malaria. Nat Rev Microbiol. 2009;7:864. doi: 10.1038/nrmicro2239. - DOI - PMC - PubMed
    1. Oguttu DW, Matovu JKB, Okumu DC, Ario AR, Okullo AE, Opigo J, et al. Rapid reduction of malaria following introduction of vector control interventions in Tororo District, Uganda: a descriptive study. Malar J. 2017;16:227. doi: 10.1186/s12936-017-1871-3. - DOI - PMC - PubMed
    1. Nankabirwa JI, Briggs J, Rek J, Arinaitwe E, Nayebare P, Katrak S, et al. Persistent parasitemia despite dramatic reduction in malaria incidence after 3 rounds of indoor residual spraying in Tororo, Uganda. J Infect Dis. 2018;219:1104–1111. doi: 10.1093/infdis/jiy628. - DOI - PMC - PubMed