Impact of cattle on the abundance of indoor and outdoor resting malaria vectors in southern Malawi

Abstract

Background Understanding the blood feeding preferences and resting habits of malaria vectors is important for assessing and designing effective malaria vector control tools. The presence of livestock, such as cattle, which are used as blood meal hosts by some malaria vectors, may impact malaria parasite transmission dynamics. The presence of livestock may provide sufficient blood meals for the vectors, thereby reducing the frequency of vectors biting humans. Alternatively, the presence of cattle may enhance the availability of blood meals such that infectious mosquitoes may survive longer, thereby increasing the risk of malaria transmission. This study assessed the effect of household-level cattle presence and distribution on the abundance of indoor and outdoor resting malaria vectors. Methods Houses with and without cattle were selected in Chikwawa district, southern Malawi for sampling resting malaria vectors. Prokopack aspirators and clay pots were used for indoor and outdoor sampling, respectively. Each house was sampled over two consecutive days. For houses with cattle nearby, the number of cattle and the distances from the house to where the cattle were corralled the previous night were recorded. All data were analysed using generalized linear models fitted with Poisson distribution. Results The malaria vectors caught resting indoors were Anopheles gambiae sensustricto (s.s.), Anopheles arabiensis and Anopheles funestuss.s. Outdoor collections consisted primarily of An. arabiensis. The catch sizes of indoor resting An. gambiae sensulato (s.l.) were not different in houses with and without cattle (P = 0.34). The presence of cattle near a house was associated with a reduction in the abundance of indoor resting An. funestuss.l. (P = 0.04). This effect was strongest when cattle were kept overnight ≤ 15 m away from the houses (P = 0.03). The blood meal hosts varied across the species. Conclusion These results highlight differences between malaria vector species and their interactions with potential blood meal hosts, which may have implications for malaria risk. Whereas An. arabiensis remained unaffected, the reduction of An. funestuss.s. in houses near cattle suggests a potential protective effect of cattle. However, the low abundance of mosquitoes reduced the power of some analyses and limited the generalizability of the results to other settings. Therefore, further studies incorporating the vectors’ host-seeking behaviour/human biting rates are recommended to fully support the primary finding.

Prevalence of malaria and its risk factors in Lake Tana and surrounding areas, northwest Ethiopia

“…The result of this study showed sleeping in the same house with cattle was the main determinant factor for malaria (p = 0.031). This finding is in agreement with other similar study conducted in Malawi [ 78 ]. The availability of alternative hosts such as livestock near or inside residential houses could make suitable mosquito breeding sites as well as could attract more mosquitoes towards the house.…”

High Vector Diversity and Malaria Transmission Dynamics in Five Sentinel Sites in Cameroon

“…In contrast to the north, several biting peaks were recorded at the southern sites, where two rainy seasons are observed yearly, except during the short dry season from November to January. Interestingly, all the vectors showed outdoor biting patterns throughout both years and at all sites, even though several animal shelters were found in the northern sites, which could drive the mosquitoes outdoors [32,33]. Furthermore, the endophagic rates recorded in Gounougou and Simatou were lower than those of the southern sites because of the presence of great number of cattle farms.…”

Seasonal variation in abundance and blood meal sources of primary and secondary malaria vectors within Kilombero Valley, Southern Tanzania

“…In situations in which livestock are kept close to humans, the presence of animals may increase the risk of human-biting simply through the cattle attracting mosquitoes to the general proximity [ 85 – 87 ]. In contrast, the presence of livestock at households has also been shown to reduce human-feeding rates [ 77 , 88 , 89 ]. These contradictory observations may be attributed to variations in host preference and abundance of the dominant vector species, as well as in the distance of livestock from households [ 90 ].…”