Expanding understanding of urban Rift Valley fever risk and associated vector ecology at slaughterhouses in Kisumu, Kenya

Authors: GERKEN, KELI - Stanford University; OWUOR, KEVIN - Kenya Medical Research Institute; NDENGA, BRYSON - Kenya Medical Research Institute; WAMBUA, SAMMY - Pwani University Biosciences Research Centre; WINTER, CHRISTABEL - Kenya Medical Research Institute; CHEMUTAI, SALOME - Pwani University Biosciences Research Centre; OMUKUTI, RODNEY - Pwani University Biosciences Research Centre; ARABU, DANIEL - Pwani University Biosciences Research Centre; MIRING’U, IRENE - Pwani University Biosciences Research Centre; Wilson, William - Bill; MUTUKU, FRANCIS - Technical University Of Mombasa; WAGGONER, JESSE - Emory University, School Of Medicine; PINKSY, BENJAMIN - Stanford University; BOSIRE, CARREN - Technical University Of Mombasa; LABEAUD, ANGELLE - Stanford University

Submitted to: Pathogens
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/3/2024
Publication Date: 6/8/2024
Citation: Gerken, K.N., Owuor, K.O., Ndenga, B.N., Wambua, S., Winter, C., Chemutai, S., Omukuti, R., Arabu, D., Miring’U, I., Wilson, W.C., Mutuku, F., Waggoner, J.J., Pinksy, B., Bosire, C., Labeaud, A.D. 2024. Expanding understanding of urban Rift Valley fever risk and associated vector ecology at slaughterhouses in Kisumu, Kenya. Pathogens. 13(6). Article 488. https://doi.org/10.3390/pathogens13060488.
DOI: https://doi.org/10.3390/pathogens13060488

Interpretive Summary: The mosquito transmitted Rift Valley fever virus (RVFV) is an important pathogen of domestic livestock and humans present in Sub-Saharan Africa. This study surveyed two urban slaughterhouses and nearby mosquitoes during a predicted ideal conditions for a disease outbreak. Although no mosquitoes tested positive for RVFV using a lateral flow assay, 8.5% of the 923 anaimals tested were positive for antibodies to RVFV. The paper demonstrates the potential for using slaughterhouse samples for RVF surveillance.

Technical Abstract: Rift Valley fever virus (RVFV) is an extremely adaptable arbovirus demonstrating more potential host-vector interactions than any other virus of medical importance. Peri-urban outbreaks of RVFV have just recently been documented in East Africa. We previously reported a low-level exposure in urban communities in Kenya and highlighted that live animal importation carries great risk of introduction. On February 16th, 2022, the Food and Agriculture Organization (FAO) early warning system triggered a RVF alert for Eastern Africa, indicating ideal weather conditions for an outbreak. We deployed a slaughtered animal testing framework at two urban slaughterhouses and simultaneously trapped mosquitoes for RVFV and blood meal testing. Out of 923 animals, 8.5% were IgG seropositive but no evidence of recent livestock exposure was detected. Mosquito species abundance varied greatly by slaughterhouse site which explained 52% of the variance in blood meal data. We captured many Culex spp., a known RVFV amplifying vector, at one of the sites (p<0.001) and this species had the most diverse blood meals. No mosquito pools tested positive for RVFV antigen using rapid VecTOR test assay. These results expand understanding of potential RVF urban disease ecology, and highlight that slaughterhouses are key locations for future surveillance and monitoring efforts.