Population Dynamics of Malaria Vectors in Western Kenya Highlands

Ndenga, Bryson; Githeko, Andrew K.; Omukunda, Elizabeth; Munyekenye, Godwil; Atieli, Harrysonne; Wamai, Peter; Mbogo, Charles M.; Minakawa, Noboru; Zhou, Guobing; Yan, Guiyun

doi:10.1093/jmedent/43.2.200

Cited by 101 publications

(90 citation statements)

References 35 publications

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“…However in Marani, over the decade densities of An. funestus have increased threefold compared to a study by Ndenga et al [19]. Likewise, sporozoite rates of An.…”

Section: Discussionmentioning

confidence: 55%

Surveillance of malaria vector population density and biting behaviour in western Kenya

Ototo

Mbugi

Wanjala

et al. 2015

Malar J

Self Cite

107

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BackgroundMalaria is a great public health burden and Africa suffers the largest share of malaria-attributed deaths. Despite control efforts targeting indoor malaria transmission, such as insecticide-treated bed nets (ITNs) and deployment of indoor residual spraying, transmission of the parasite in western Kenya is still maintained. This study was carried out to determine the impact of ITNs on indoor vector densities and biting behaviour in western Kenya.MethodsIndoor collection of adult mosquitoes was done monthly in six study sites in western Kenya using pyrethrum spray collections from 2012 to 2014. The rotator trap collections were done in July–August in 2013 and May–June in 2014. Mosquitoes were collected every 2 h between 18.00 and 08.00 h. Human behaviour study was conducted via questionnaire surveys. Species within Anopheles gambiae complex was differentiated by PCR and sporozoite infectivity was determined by ELISA. Species distribution was determined and bed net coverage in the study sites was recorded.ResultsDuring the study a total of 5,469 mosquito vectors were collected from both PSC and Rotator traps comprising 3,181 (58.2%) Anopheles gambiae and 2,288 (41.8%) Anopheles funestus. Compared to all the study sites, Rae had the highest density of An. gambiae with a mean of 1.2 (P < 0.001) while Kombewa had the highest density of An. funestus with a mean of 1.08 (P < 0.001). Marani had the lowest density of vectors with 0.06 An. gambiae and 0.17 An. funestus (P < 0.001). Among the 700 PCR confirmed An. gambiaes.l. individuals, An. gambiaes.s. accounted for 49% and An. arabiensis 51%. Over 50% of the study population stayed outdoors between 18.00 and 20.00 and 06.00 and 08.00 which was the time when highest densities of blood fed vectors were collected. Anopheles gambies.s. was the main malaria parasite vector in the highland sites and An. arabiensis in the lowland sites. Bed net ownership in 2012 averaged 87% across the study sites.ConclusionsThis study suggests that mass distribution of ITNs has had a significant impact on vector densities, species distribution and sporozoite rate. However, shift of biting time poses significant threats to the current malaria vector control strategies which heavily rely on indoor controls.

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“…However in Marani, over the decade densities of An. funestus have increased threefold compared to a study by Ndenga et al [19]. Likewise, sporozoite rates of An.…”

Section: Discussionmentioning

confidence: 55%

Surveillance of malaria vector population density and biting behaviour in western Kenya

Ototo

Mbugi

Wanjala

et al. 2015

Malar J

Self Cite

107

View full text Add to dashboard Cite

show abstract

“…Houses used for the vector collections were two-roomed and occupied by bachelors, thus only one person slept in the house most of the times. Sporozoite rates used for the estimation, were obtained for the period beginning in 2003 to the end of 2004 [21] from mosquitoes collected from the same villages as in this study.…”

Section: Methodsmentioning

confidence: 99%

Topography and malaria transmission heterogeneity in western Kenya highlands: prospects for focal vector control

Githeko

Ayisi

Odada

et al. 2006

Malar J

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117

128

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Background: Recent resurgence of malaria in the highlands of Western Kenya has called for a more comprehensive understanding of the previously neglected complex highland vector ecology. Besides other drivers of malaria epidemiology, topography is likely to have a major effect on spatial vector and parasite distribution. The aim of this study was to determine the effects of topography on malaria spatial vector distribution and parasite prevalence.

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“…Rota is in a rural setting, on the marshes of Lake Victoria in Western Kenya, with a tropical climate and annual rainfall Ͼ1,000 mm. In all three highly endemic malaria localities, transmission is perennial, with inoculation rates of Ϸ200 (Tibati), Ϸ300 (Simbock), and 100-300 (Rota) infective bites per human per year (2,3,37). keys (6, 7), the mosquitoes were dissected in a saline solution on the morning of their collection in Cameroon and 1 week after collection in Rota to allow for the development of oocysts in infected females.…”

Section: Methodsmentioning

confidence: 99%

Population genetic structure of Plasmodium falciparum in the two main African vectors, Anopheles gambiae and Anopheles funestus

Annan

Durand

Ayala

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

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We investigated patterns of genetic diversity of Plasmodium falciparum associated with its two main African vectors: Anopheles gambiae and Anopheles funestus. We dissected 10,296 wildcaught mosquitoes from three tropical sites, two in Cameroon (Simbock and Tibati, separated by 320 km) and one in Kenya (Rota, >2,000 km from the other two sites). We assayed seven microsatellite loci in 746 oocysts from 183 infected mosquito guts. Genetic polymorphism was very high in parasites isolated from both vector species. The expected heterozygosity (HE) was 0.79 in both species; the observed heterozygosities (HO) were 0.32 in A. funestus and 0.42 in A. gambiae, indicating considerable inbreeding within both vector species. Mean selfing (s) between genetically identical gametes was s ‫؍‬ 0.33. Differences in the rate of inbreeding were statistically insignificant among sites and between the two vector species. As expected, because of the high rate of inbreeding, linkage disequilibrium was very high; it was significant for all 21 loci pairs in A. gambiae and for 15 of 21 pairs in A. funestus, although only two pairwise comparisons were between loci on the same chromosome. Overall, the genetic population structure of P. falciparum, as evaluated by F statistics, was predominantly clonal rather than panmictic, a population structure that facilitates the spread of antimalarial drug and vaccine resistance and thus may impair the effectiveness of malaria control efforts. malaria ͉ epidemiology ͉ evolutionary genetics ͉ Cameroon ͉ Kenya M alaria is the most significant and widespread vectortransmitted human disease, accounting yearly for several hundred million clinical cases and Ͼ2 million deaths, mostly affecting young children and pregnant women in subSaharan Africa (1). Prevention and cure of the disease are major publichealth challenges that are tackled by using several strategies, among them vector control. The transmission of Plasmodium falciparum, the agent of malignant malaria, involves a complex vectorial system consisting of Ϸ10 Anopheles species, colonizing different ecoclimatic settings, regions, and seasons in strongly variable relative abundances (2-5).The two most important vectors of malignant malaria in Africa are Anopheles gambiae and Anopheles funestus because of their widespread distribution, highly anthropophilic and endophilic behavior, and long life spans (6, 7). A. gambiae is the most important vector throughout Africa and the most extensively studied Anopheles species (8). The effectiveness of malaria transmission emerges from the complementary ecoclimatic attributes and seasonal patterns of both species. A. funestus breeds in permanent larval sites that enable this species, in regions of seasonal transmission, to extend parasite transmission far into the dry season, after the temporary breeding pools of A. gambiae have dried out (7, 9-11).Differences in the biology and ecology of these two main vectors might entail a differential impact on the genetic composition of the P. falciparum populations they harbo...

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Population Dynamics of Malaria Vectors in Western Kenya Highlands

Cited by 101 publications

References 35 publications

Surveillance of malaria vector population density and biting behaviour in western Kenya

Surveillance of malaria vector population density and biting behaviour in western Kenya

Topography and malaria transmission heterogeneity in western Kenya highlands: prospects for focal vector control

Population genetic structure of Plasmodium falciparum in the two main African vectors, Anopheles gambiae and Anopheles funestus

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