Spatial distribution and habitat characterization of mosquito species during the dry season along the Mara River and its tributaries, in Kenya and Tanzania

Abstract

BackgroundVector-borne diseases are increasingly becoming a major health problem among communities living along the major rivers of Africa. Although larger water bodies such as lakes and dams have been extensively researched, rivers and their tributaries have largely been ignored. This study sought to establish the spatial distribution of mosquito species during the dry season and further characterize their habitats along the Mara River and its tributaries.MethodsIn this cross-sectional survey, mosquito larvae were sampled along the Mara River, its two perennial tributaries (Amala and Nyangores), drying streams, and adjacent aquatic habitats (e.g. swamps, puddles that receive direct sunlight [open sunlit puddles], rock pools, hippo and livestock hoof prints, and vegetated pools). Each habitat was dipped 20 times using a standard dipper. Distance between breeding sites and human habitation was determined using global positioning system coordinates. The collected mosquito larvae were identified using standard taxonomic keys. Water physico-chemical parameters were measured in situ using a multiparameter meter. Mean mosquito larvae per habitat type were compared using analysis of variance and chi-square tests, while the relationship between mosquito larvae and physico-chemical parameters was evaluated using a generalized linear mixed model. The Cox-Stuart test was used to detect trends of mosquito larvae distribution. The test allowed for verification of monotonic tendency (rejection of null hypothesis of trend absence) and its variability.ResultsA total of 4001 mosquito larvae were collected, of which 2712 (67.8%) were collected from river/stream edge habitats and 1289 (32.2%) were sampled from aquatic habitats located in the terrestrial ecosystem about 50 m away from the main river/streams. Anopheles gambiae s.s, An. arabiensis, and An. funestus group, the three most potent vectors of malaria in Sub-Saharan Africa, together with other anopheline mosquitoes, were the most dominant mosquito species (70.3%), followed by Culex quinquefasciatus and Cx. pipiens complex combined (29.5%). Drying streams accounted for the highest number of larvae captured compared to the other habitat types. A stronger relationship between mosquito larvae abundance and dissolved oxygen (Z = 7.37, P ≤ 0.001), temperature (Z = 7.65, P ≤ 0.001), turbidity (Z = −5.25, P ≤ 0.001), and distance to the nearest human habitation (Z = 4.57, P ≤ 0.001), was observed.ConclusionsPresence of malaria and non-malaria mosquito larvae within the Mara River basin calls for immediate action to curtail the insurgence of vector-borne diseases within the basin. A vector control program should be conducted during the dry period, targeting drying streams shown to produce the highest number of larval mosquitoes.Electronic supplementary materialThe online version of this article (10.1186/s40249-017-0385-0) contains supplementary material, which is available to authorized users.

A Cross-Sectional Population Study of Geographic, Age-Specific, and Household Risk Factors for Asymptomatic Plasmodium falciparum Malaria Infection in Western Kenya

“…5 However, our finding that pfPR was similar in the areas abutting the lake than those that were more inland (39.3% versus 40.9%) suggests that breeding sites located closer to people's homes, such as slow-flowing streams, rain ponds, and vegetation, play an important small-area role in maintaining high malaria transmission patterns in both lakeshore and inland areas. 46 This reasoning is consistent with the observation that most mosquito vectors tend to breed near sites of human habitation 47 and that most fly relatively short distances (< 3 km) to find blood meals, 48 which is considerably shorter than the average distance across districts used to define lakeshore versus more inland areas. Our finding of high GMPD (∼1,000 parasites/μL) among asymptomatic children in the lake-endemic area may have public health relevance if we consider that GMPD > 1,000 parasites/μL may be a surrogate of carrying gametocytes.…”

Identification and characterization of immature Anopheles and culicines (Diptera: Culicidae) at three sites of varying malaria transmission intensities in Uganda.

“…This suggests that the same aquatic habitats targeted for Anopheles larval control programmes could also be targeted for culicine larvae control programmes. Previous studies have shown that Anopheles and culicine larvae are likely to occur in the same habitats [43]. Likewise, Anopheles early and late instars were highly correlated at the three sites.…”

Stability of the effect of silencing fibronectin type III domain-protein 1 (FN3D1) gene on Anopheles arabiensis reared under different breeding site conditions

“…Previous studies have established that bacteria in the breeding habitat constitute the main food source for larvae enhancing larval growth and the productivity and survival of the adult mosquitoes [8,9,17]. Studies have also demonstrated that higher dissolved oxygen favours the development of Anopheles mosquitoes [37,38].…”