Abstract
Dengue virus (DENV) circulates in two distinct transmission cycles: one, termed the sylvatic cycle, is enzootic to canopy-living hosts, including non-human primates and primatophilic mosquitoes, and the other, initiated by spillover from the sylvatic cycle, is endemic to humans and anthropophilic mosquitoes. Transmission dynamics of sylvatic DENV in non-human hosts has not been well characterized, and the identity of reservoir and amplification hosts is still to be determined. We investigated the role of the three common species of monkeys in the Kédougou region of Senegal in the sylvatic transmission cycle of DENV. Longitudinal surveillance of primatophilic mosquitoes in this region dating back to the 1970s revealed that sylvatic DENV-2, the only one of the four DENV serotypes found to circulate in a sylvatic transmission in West Africa, is amplified cyclically at intervals of approximately eight years based on the isolation of the virus from mosquitoes. Subsequent to the detection of DENV-2 in primatophilic mosquitoes in Kédougou in 2008, 737 monkeys, including 3 species: Chlorocebus sabaeus (n = 219), Erythrocebus patas (n = 78), and Papio papio (n = 440) were captured from 2010 to 2012 for the current study. Their age was determined using dentition and other morphological measurements. Evidence of DENV-2 infection was detected via neutralizing antibody in sera, and the annual hazard of DENV-2 infection was estimated per species using catalytic models. These analyses revealed annual hazard ranging from 0.09 to 0.42 across the three species, consistent with high levels of transmission in these populations. Furthermore, seroprevalence was moderate in individuals under one year of age, despite the lack of detection of DENV-2 in primatophilic mosquitoes for up to three years prior, suggesting that non-primate hosts contributed to the maintenance of sylvatic DENV in this region.