Mosquito-based xenosurveillance reveals circulation of Anaplasma and Neoehrlichia in livestock at a human–wildlife interface in Kenya

Background Hematophagous flies can serve as sentinels for detecting vertebrate pathogens or host antibodies present in the blood they ingest. Xenosurveillance, which uses blood-feeding insects as biological samplers, is emerging as a sensitive and minimally invasive approach for monitoring pathogens circulating among humans, livestock, and wildlife. However, despite its growing application in human health, the use of xenosurveillance for detecting pathogens in livestock systems, particularly within complex human–animal–wildlife interfaces, remains underexplored. To date, few studies have assessed whether mosquito blood-meals can reliably capture livestock-associated bacterial pathogens. Our study investigated whether blood-meals from mosquitoes could be used to detect infectious agents circulating in livestock in Kenya. Methods We collected a total of 4,673 mosquitoes, belonging to Culex , Anopheles , Aedes , Mansonia , and Coquillettidia genera around livestock enclosures in Kajiado and Naivasha counties, Kenya. Blood-fed mosquitoes were examined for the presence of Anaplasma , Ehrlichia , Rickettsia, Theileria , and Babesia pathogens using molecular tools and gene sequencing. Results Overall, we detected Anaplasma marginale in Culex pipiens (1/150; 0.7%) and Aedes hirsutus (2/11; 18.2%), Anaplasma sp. in Cx. pipiens (2/150; 1.4%) and Ae. hirsutus (1/11; 9.1%), and Candidatus Neoehrlichia mikurensis was found only in Mansonia africana (2/50; 4%). Pathogen detections showed strong host concordance where A. marginale was associated with cattle-derived blood-meals and Anaplasma sp. with goat-derived blood-meals, while Candidatus Neoehrlichia mikurensis was detected in Mansonia africana that had fed on cattle and on a host that could not be determined due to amplification failure. Conclusions Candidatus Neoehrlichia mikurensis is a recognized zoonotic pathogen, and detection represents the first report of its presence in mosquitoes in Africa. Although mosquitoes are not biological vectors of these pathogens, the presence of pathogen DNA in their blood-meals reveals circulation of the pathogens in livestock in Kenya. Our findings demonstrate that mosquito-based xenosurveillance offers a simple, scalable, and non-invasive method for detecting circulating vector-borne pathogens in livestock-human-wildlife ecosystems, supporting its value as an emerging tool for integrated biosurveillance.