Biting patterns of malaria vectors of the lower Shire valley, southern Malawi

Monicah M. Mburu, Themba Mzilahowa, Benjamin Amoah, Duster Chifundo, Kamija S. Phiri, Henk van den Berg, Willem Takken, Robert S. McCann

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

Assessing the biting behaviour of malaria vectors plays an integral role in understanding the dynamics of malaria transmission in a region. Biting times and preference for biting indoors or outdoors varies among mosquito species and across regions. These behaviours may also change over time in response to vector control measures such as long-lasting insecticidal nets (LLINs). Data on these parameters can provide the sites and times at which different interventions would be effective for vector control. This study assessed the biting patterns of malaria vectors in Chikwawa district, southern Malawi. The study was conducted during the dry and wet seasons in 2016 and 2017, respectively. In each season, mosquitoes were collected indoors and outdoors for 24 nights in six houses per night using the human landing catch. Volunteers were organized into six teams of two individuals, whereby three teams collected mosquitoes indoors and the other three collected mosquitoes outdoors each night, and the teams were rotated among twelve houses. All data were analyzed using Poisson log-linear models. The most abundant species were Anopheles gambiae sensu lato (primarily An. arabiensis) and An. funestus s.l. (exclusively An. funestus s.s.). During the dry season, the biting activity of An. gambiaes.l. was constant outdoors across the categorized hours (18:00 h to 08:45 h), but highest in the late evening hours (21:00 h to 23:45 h) during the wet season. The biting activity of An. funestus s.l. was highest in the late evening hours (21:00 h to 23:45 h) during the dry season and in the late night hours (03:00 h to 05:45 h) during the wet season. Whereas the number of An. funestuss.l. biting was constant (P = 0.662) in both seasons, that of An. gambiaes.l. was higher during the wet season than in the dry season (P = 0.001). Anopheles gambiae s.l. was more likely to bite outdoors than indoors in both seasons. During the wet season, An. funestus s.l. was more likely to bite indoors than outdoors but during the dry season, the bites were similar both indoors and outdoors. The biting activity that occurred in the early and late evening hours, both indoors and outdoors coincides with the times at which individuals may still be awake and physically active, and therefore unprotected by LLINs. Additionally, a substantial number of anopheline bites occurred outdoors. These findings imply that LLINs would only provide partial protection from malaria vectors, which would affect malaria transmission in this area. Therefore, protection against bites by malaria mosquitoes in the early and late evening hours is essential and can be achieved by designing interventions that reduce vector-host contacts during this period.

LanguageEnglish
Article number105059
JournalActa Tropica
Volume197
DOIs
Publication statusPublished - 1 Sep 2019

Fingerprint

Malawi
malaria
Malaria
valleys
dry season
Culicidae
wet season
Bites and Stings
vector control
Anopheles gambiae
volunteers
control methods
linear models
Volunteers
Linear Models

Keywords

  • Anophelines
  • Biting
  • Culicines
  • HLC
  • Indoors
  • Malawi
  • Outdoors

Cite this

Mburu, M. M., Mzilahowa, T., Amoah, B., Chifundo, D., Phiri, K. S., van den Berg, H., ... McCann, R. S. (2019). Biting patterns of malaria vectors of the lower Shire valley, southern Malawi. Acta Tropica, 197, [105059]. https://doi.org/10.1016/j.actatropica.2019.105059
Mburu, Monicah M. ; Mzilahowa, Themba ; Amoah, Benjamin ; Chifundo, Duster ; Phiri, Kamija S. ; van den Berg, Henk ; Takken, Willem ; McCann, Robert S. / Biting patterns of malaria vectors of the lower Shire valley, southern Malawi. In: Acta Tropica. 2019 ; Vol. 197.
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Biting patterns of malaria vectors of the lower Shire valley, southern Malawi. / Mburu, Monicah M.; Mzilahowa, Themba; Amoah, Benjamin; Chifundo, Duster; Phiri, Kamija S.; van den Berg, Henk; Takken, Willem; McCann, Robert S.

In: Acta Tropica, Vol. 197, 105059, 01.09.2019.

Research output: Contribution to journalArticleAcademicpeer-review

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T1 - Biting patterns of malaria vectors of the lower Shire valley, southern Malawi

AU - Mburu, Monicah M.

AU - Mzilahowa, Themba

AU - Amoah, Benjamin

AU - Chifundo, Duster

AU - Phiri, Kamija S.

AU - van den Berg, Henk

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AU - McCann, Robert S.

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AB - Assessing the biting behaviour of malaria vectors plays an integral role in understanding the dynamics of malaria transmission in a region. Biting times and preference for biting indoors or outdoors varies among mosquito species and across regions. These behaviours may also change over time in response to vector control measures such as long-lasting insecticidal nets (LLINs). Data on these parameters can provide the sites and times at which different interventions would be effective for vector control. This study assessed the biting patterns of malaria vectors in Chikwawa district, southern Malawi. The study was conducted during the dry and wet seasons in 2016 and 2017, respectively. In each season, mosquitoes were collected indoors and outdoors for 24 nights in six houses per night using the human landing catch. Volunteers were organized into six teams of two individuals, whereby three teams collected mosquitoes indoors and the other three collected mosquitoes outdoors each night, and the teams were rotated among twelve houses. All data were analyzed using Poisson log-linear models. The most abundant species were Anopheles gambiae sensu lato (primarily An. arabiensis) and An. funestus s.l. (exclusively An. funestus s.s.). During the dry season, the biting activity of An. gambiaes.l. was constant outdoors across the categorized hours (18:00 h to 08:45 h), but highest in the late evening hours (21:00 h to 23:45 h) during the wet season. The biting activity of An. funestus s.l. was highest in the late evening hours (21:00 h to 23:45 h) during the dry season and in the late night hours (03:00 h to 05:45 h) during the wet season. Whereas the number of An. funestuss.l. biting was constant (P = 0.662) in both seasons, that of An. gambiaes.l. was higher during the wet season than in the dry season (P = 0.001). Anopheles gambiae s.l. was more likely to bite outdoors than indoors in both seasons. During the wet season, An. funestus s.l. was more likely to bite indoors than outdoors but during the dry season, the bites were similar both indoors and outdoors. The biting activity that occurred in the early and late evening hours, both indoors and outdoors coincides with the times at which individuals may still be awake and physically active, and therefore unprotected by LLINs. Additionally, a substantial number of anopheline bites occurred outdoors. These findings imply that LLINs would only provide partial protection from malaria vectors, which would affect malaria transmission in this area. Therefore, protection against bites by malaria mosquitoes in the early and late evening hours is essential and can be achieved by designing interventions that reduce vector-host contacts during this period.

KW - Anophelines

KW - Biting

KW - Culicines

KW - HLC

KW - Indoors

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KW - Outdoors

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