The bio-ecology of key mosquito vector species in Botswana: implications for shifting environments

Mosquitoes account for significant morbidity and mortality globally, with the African

region being most affected. In many arid regions, including Botswana, mosquitoes are

increasingly becoming problematic, harbouring pathogens and parasites that cause debilitating

infectious diseases to differential host species. The risk of mosquito proliferation and burden is

accelerated when affected societies have knowledge gaps coupled with climatic mediated global

change scenarios. In Botswana mosquito research is skewed towards malaria and associated

anopheline vector species, neglecting other mosquito taxa, despite their economic significance

as disease vectors for humans, domestic animals and wildlife. The national vector control

programme in the country is mainly focused on adult mosquito species with management of

juveniles (e.g., larvae) largely disregarded. Cognisant of these shortcomings, the thesis was thus

aimed at bridging knowledge gaps in mosquito bio-ecology within the Central district, Botswana,

a largely neglected region on vector mosquito bio-ecology. Knowledge, attitude and practices of

local communities were assessed on mosquitoes across sub-districts of malaria endemic and non endemicity status, with communities largely exhibiting limited knowledge on aspects of

mosquito bio-ecology. Mosquito communities across the region were also assessed with key taxa

species of medical (Anopheles, Aedes and Culex species) and veterinary (Culiseta longiareolata)

importance identified throughout the study areas. The study also reports for the first time in the

country, a globally important and medically significant invasive vector species, Ae. aegypti from

Palapye sub-district. Using a mesocosm approach, the effects of anthropogenic activities were

tested on mosquito breeding. The degradation associated with cattle dung nutrification in aquatic

environments favoured oviposition by mosquito vector species. With the aim to assess natural

predator (Lovenula falcifera and Anisops sardea) mosquito control potential, their predation on

larvae of the abundant mosquito species (Culex pipiens) were quantified using a functional

response (FR) approach. Both predators exhibited Type II FRs and typically contributed

additively to prey risk, with synergistic impacts evident on prey of intermediate sizes. In

complementing this approach, multiple predator effects by notonectid predators, A. sardea and

Enithares chinai, were quantified across a habitat complexity gradient. Enithares chinai

exhibited significantly greater consumption rates than A. sardea, both as individuals and

conspecific pairs. Each predator type displayed Type II FRs across experimental treatments, with

synergistic multiple predator effects displayed in the absence of habitat complexity. Effects of

increasing habitat complexity modified multiple predator effects differentially between species

given behavioral differences. Whilst the ecosystem services provided by natural predators for

mosquito biological control are evident, understanding how climate change-induced

environmental perturbations may corrode these services remains largely unknown. Here, critical

thermal limits of key predator-prey participants across instar stages (as above) were explored.

All predators generally had lower activity limits and narrower thermal windows compared to

their larval mosquito prey. These results point to significant predator-prey mismatches under

environmental change, potentially adversely affecting natural mosquito biocontrol given

projected shifts in temperature fluctuations in the study region. The information gleaned from

the various chapters will be useful for practitioners dealing with the various human, biological

and ecological components of pest mosquito control and emerging threats in the region.