Differences in Malaria Vector Biting Behavior and Changing Vulnerability to Malaria Transmission in Contrasting Ecosystems of Western Kenya
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Date
2023-10
Authors
Nzioki, Irene
Machani, Maxwell G.
Onyango, Shirley A.
Kabui, Kevin K.
Githeko, Andrew K.
Ochomo, Eric
Yan, Guiyun
Afrane, Yaw A.
Journal Title
Journal ISSN
Volume Title
Publisher
Parasites & Vectors
Abstract
Background Designing, implementing, and upscaling of efective malaria vector control strategies necessitates
an understanding of when and where transmission occurs. This study assessed the biting patterns of potentially
infectious malaria vectors at various hours, locations, and associated human behaviors in diferent ecological settings
in western Kenya.
Methods Hourly indoor and outdoor catches of human-biting mosquitoes were sampled from 19:00 to 07:00 for four
consecutive nights in four houses per village. The human behavior study was conducted via questionnaire surveys
and observations. Species within the Anopheles gambiae complex and Anopheles funestus group were distinguished
by polymerase chain reaction (PCR) and the presence of Plasmodium falciparum circumsporozoite proteins (CSP)
determined by enzyme-linked immunosorbent assay (ELISA).
Results Altogether, 2037 adult female anophelines were collected comprising the An. funestus group (76.7%), An.
gambiae sensu lato (22.8%), and Anopheles coustani (0.5%). PCR results revealed that Anopheles arabiensis constituted 80.5% and 79% of the An. gambiae s.l. samples analyzed from the lowland sites (Ahero and Kisian, respectively).
Anopheles gambiae sensu stricto (hereafter An. gambiae) (98.1%) was the dominant species in the highland site
(Kimaeti). All the An. funestus s.l. analyzed belonged to An. funestus s.s. (hereafter An. funestus). Indoor biting densities
of An. gambiae s.l. and An. funestus exceeded the outdoor biting densities in all sites. The peak biting occurred in early
morning between 04:30 and 06:30 in the lowlands for An. funestus both indoors and outdoors. In the highlands,
the peak biting of An. gambiae occurred between 01:00 and 02:00 indoors. Over 50% of the study population stayed
outdoors from 18:00 to 22:00 and woke up at 05:00, coinciding with the times when the highest numbers of vectors
were collected. The sporozoite rate was higher in vectors collected outdoors, with An. funestus being the main malaria
vector in the lowlands and An. gambiae in the highlands.
Conclusion This study shows heterogeneity of anopheline distribution, high outdoor malaria transmission,
and early morning peak biting activity of An. funestus when humans are not protected by bednets in the lowland sites. Additional vector control eforts targeting the behaviors of these vectors, such as the use of non-pyrethroids
for indoor residual spraying and spatial repellents outdoors, are needed.
Description
Article
Keywords
Malaria vectors, Biting behavior, Human behavior, Western Kenya
Citation
Nzioki, I., Machani, M. G., Onyango, S. A., Kabui, K. K., Githeko, A. K., Ochomo, E., ... & Afrane, Y. A. (2023). Differences in malaria vector biting behavior and changing vulnerability to malaria transmission in contrasting ecosystems of western Kenya. Parasites & Vectors, 16(1), 376.