Exploring the impact of cattle on human exposure to malaria mosquitoes in the Arba Minch area district of southwest Ethiopia

Abstract

Background: The success of indoor interventions that target mosquitoes for malaria control is partially dependent on early evening and outdoor biting behaviours of mosquito vectors. In southwest Ethiopia, people and cattle live in proximity, which calls to investigate whether the presence of cattle increase or decrease bites from malaria mosquito vectors. This study assessed both host-seeking and overnight activity of malaria mosquito vectors given the presence or absence of cattle in Chano Mille village, Arba Minch district, Ethiopia. Methods: Anopheles species density and activity time was compared when a calf was: (i) placed inside; (ii) 1 m away from; or (iii) absent from a tent with a human volunteer resting insides using hourly human landing catches (HLC) conducted from 18:00-0:00 h for 3 months. This trial was performed close to the shore of the Lake Abaya to minimize the interference of other animals on mosquito movement. The overnight activity of malaria vectors was assessed within a Chano village from 18:00-6:00 h with collections carried out both indoors and outdoors by HLC. Generalized estimating equations were used to statistically assess differences. Results: Anopheles pharoensis was significantly more prevalent when a calf was present either inside (42%, P < 0.001), or adjacent to (46%, P = 0.002) a tent relative to a tent without a calf present. The presence of a calf did not affect densities of the primarily anthropophilic species A. gambiae (s.l.), or An. tenebrosus. Anopheles gambiae (s.l.) (P < 0.001) and An. pharoensis (P = 0.015) both had a tendency for early evening biting between 19:00 h and 20:00 h. Anopheles gambiae (s.l.) was mainly biting humans outdoors in the village. Conclusions: The presence of calves within and close to human dwellings acts to draw malaria mosquitoes toward the human occupant with the potential to increase their risk of malaria. Hence, deployment of cattle far from human residence could be recommended to reduce human exposure. Outdoor and early evening biting could threaten the success of current indoor-based interventions. Hence, tools could be designed to reduce this threat.

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

“…Further studies are required to elucidate how this apparent Households with higher numbers of cattle and sheep had higher anopheline activity and a higher number of human-fed malaria vectors, suggesting that the abundance of non-human hosts, particularly cattle, in the study area may increase human-feeding rate, as previously reported [83][84][85]. 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][86][87]. In contrast, the presence of livestock at households has also been shown to reduce human-feeding rates [77,88,89].…”

A Retrospective Analysis of Malaria Trends in Maksegnit Health Center over the Last Seven Years, Northwest Ethiopia: 2014-2020

“…As a result, such outdoor activities increase the risk of malaria due to the incidence of outdoor mosquito biting is increased following the vector's host-seeking behavior being changed as recent evidence indicated [ 35 ]. Moreover, having frequent contact and proximity with cattle increases the probability of biting with mosquitoes malaria vector and has a behavior of attracted by cattle [ 36 ]. In this study, showing the burden of malaria cases over the last seven years with a large sample size considered as a positive side unable to address the bottlenecked factors which trigger and reaggravating the severity of malaria in recent times is the main limitation of the study.…”

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.…”