Malaria is endemic in many regions of East Africa where climate and environment together present conditions suitable for malaria vectors and parasites . The main vector species in western Kenya are Anopheles gambiae Giles sensu stricto
An. arabiensis Patton and An. funestus Giles. Anopheles gambiae and An. arabiensis are commonly found in clear sunlit pools of water, man-made shallow water bodies, in polluted water and along the shores of large water bodies such as Lake Victoria [2–8]. Anopheles funestus prefers rather permanent water bodies (8). In the last decade an increasing number of cases of malaria in formerly malaria-free areas and highland areas have become common [9–11]. Several hypotheses have been proposed to explain the increased malaria transmission in the highlands, including land-use changes, global climate changes, increased drug resistance, cessation of malaria control activities, and demographic changes [11–13]. Cox  estimated that 34 million individuals were at risk of malaria in the East African highlands. In these highlands, transmission is probably much more focal in its distribution than in many lowland areas, as breeding sites are more common in the valley floor than on the steep valley slopes . In addition, studies report that human activities in these highlands have subsequently created potential mosquito breeding habitats [7, 11, 16].
In the Ugandan highlands, the elimination of papyrus swamps created a habitat for An. gambiae and An. funestus, leading to increased malaria transmission . In the highlands of western Kenya, An. gambiae was found only in cultivated farmland habitats but not in original forest and swamp habitats . These differences in larval distribution were attributed to the fact that farmland habitats received more sunlight, and hence water temperatures were conducive for An. gambiae breeding. In Ethiopia, changes in land use and climate expose the highland areas to unexpected malaria epidemics, presumably due to expansion of environmental conditions suitable for malaria transmission .
Research on malaria in the highlands has mainly focused on the development of early-warning systems to identify when epidemics are expected [18–20] and on the effects of changes in climatic variables [13, 21, 22]. The core idea behind these systems is that when parameters indicate a malaria epidemic is likely, resources can be channeled to prevent or contain the epidemic . However, in sub-Saharan Africa, malaria epidemics arise suddenly in mostly remote, disadvantaged settings without effective alert systems . In resource-limited countries such as those of highland East Africa, an all-or nothing approach to interventions such as insecticide spraying or bed net distribution, often results in complete coverage for some areas and no coverage for others when funds run out . Thus, regular vector control activities targeted at the malaria risk areas are more cost effective than emergency interventions that often face delays in mobilization . In addition, because full coverage of control measures is hardly achieved, integration of larval source management (LSM) into Integrated Vector Management (IVM) program will be advantageous to the fight against malaria.
In western Kenya highlands, for instance, since the implementation of the roll back malaria initiative , malaria control has been based on insecticide treated nets (ITNs), indoor residual spraying (IRS) and the use of anti-malarial drugs for the treatment of malaria parasites. Following the adoption of RBM, there are indications that malaria morbidity and mortality is on a decline as a result of scaled up use of ITNs [26, 27] and increased availability of antimalarial medicines . However, with increased use of interventions targeting indoor resting mosquitoes, the vectors are bound to develop evading mechanisms or even change their biting behavior. Exophily of the commonly known endophilic species has recently been reported [29, 30], in addition to development of resistance in the malaria vector and parasites. There is need development and integration of complementary tools to target outdoor vectors [31, 32].
Microbial larvicides have been proven efficient in the control of anopheline mosquito larvae and the reduction in adult mosquito densities [33–36]. However, access to microbial larvicides is still a challenge for developing countries, thus calling for development of alternative larval control strategies that can utilize locally available resources. In the current study, an integrated larval source management comprising of habitat manipulation, source reduction in comparison to the application of microbial larvicides and the use predatory fish were used. The hypothesis being habitat manipulation and source reduction are as effective as the application of Bti and the use of predatory fish for mosquito larval control.