mosquitoes), we pursued evidence of enzootic transmission and human spillover events. Overall, CHIKV seropositivity in 2014 was 13.4% (9/67). Antibodies reactive against closely related onyong-nyong computer virus (ONNV) occurred; however, neutralization titers were too low to conclude ONNV exposure. Seroprevalence for the flavivirus dengue was also detected (28%), mostly near Kwale, suggesting possible spillback from humans to baboons. Almorexant HCl CHIKV antibodies in some juvenile and subadult NHPs suggested recent blood circulation. We conclude that CHIKV is usually circulating in western Kenya, despite the 2004 human outbreaks only being reported coastally. Further work to understand the enzootic ecology of CHIKV Almorexant HCl in east Africa is needed to identify sites of human spillover contact where urban transmission may be initiated. INTRODUCTION CHIKV, a mosquito-borne alphavirus (family spp. mosquitoes, has been analyzed extensively in West and South Africa.17,18 However, there is no direct evidence for such an enzootic cycle in east Africa. In addition, east African CHIKV isolates from human outbreaks are of a different phylogenetic lineage than those in West or South Africa.6,11,19 The nature of any adaptations needed to initiate efficient interhuman transmission, leading to the originating strains of the 2004 Kenya outbreak assuming they emerged from an enzootic source, is also unknown. Antigenically and genetically, CHIKV is usually closely related to another alphavirus, ONNV, with disparate transmission ecology by spp. vectors20,21; ONNV has been sporadically reported in Kenya,22,23 and nearby in Uganda24 and Tanzania.25,26 It is therefore important to distinguish neutralizing antibodies generated by infection with these viruses when considering computer virus exposure, particularly since human seroprevalence for ONNV is believed to be high in coastal Kenya.22 Understanding when and where the hypothesized transition from enzootic to urban blood circulation occurred during or before the 2004 CHIKV outbreak could inform future interventions to prevent pandemic emergence. We therefore conducted field studies to understand the enzootic blood circulation of African alphaviruses. Here we focus on NHP serosurveys to gain an indication of likely foci for enzootic CHIKV blood circulation in Kenya. MATERIALS AND METHODS Collection of samples. In the beginning, the Institute of Primate Research, Kenya, provided 252 NHP sera from their selections, which had been taken from three different species: (olive baboon), (vervet monkey), and (blue monkey), across eight sites in three regions of Kenya between 1985 and 2000 (Physique 1, Table 1). Open in a separate window Physique 1. Summary of plaque reduction neutralization test (PRNT) results from archived non-human primate (NHP) samples (1985C2005), mapped by region in Kenya. The location of 2014 sampling (Kwale and Kakamega County) is also indicated. This physique appears in color at www.ajtmh.org. Table 1 Origin and quantity of biobanked NHP samples screened for chikungunya computer virus = 21)Mtito Andei (= 60)Tana (= 60)Mt.Elgon (= 23)Watumu (= 31)Kakamega (= 5)Lamu (= 21)Buyangu (= 31) Open in a separate windows NHP = non-human primate. In 2014, to provide a more recent picture of CHIKV exposure, NHPs were captured and sampled from three sites in the Kakamega forest province of western Kenya (August 2014) and two sites in the Shimba Hills (Kwale) CSF3R region of coastal Kenya (December 2014). Species caught were (red-tailed monkey) and (western Kenya), and (yellow baboon) (coastal Kenya); other species including and spp. (black and white colobus monkey) were also targeted but not successfully captured during the program. Animals were captured alive, bled once, marked, and released back to their habitat. Pregnant females, lactating mothers, and infants were not sampled. Capture was done under the auspices of wildlife study permits from your Kenya Wildlife Support and according to the Kenya Medical Research Institute (KEMRI) Ethics Review Committee guidelines. Animals were Almorexant HCl caught using rectangular metal cage traps (1.5 m in height and 0.9 m in width), fixed with sliding trap doors, and baited with banana or corn. Captured animals were anesthetized with a 3:7 mixture.