Endemic and Epidemic Human Alphavirus Infections in Eastern Panama: An Analysis of Population-Based Cross-Sectional Surveys.

Madariaga virus (MADV) has recently been associated with severe human disease in Panama, where the closely related Venezuelan equine encephalitis virus (VEEV) also circulates. In June 2017, a fatal MADV infection was confirmed in a community of Darien Province. We conducted a cross-sectional outbreak investigation with human and mosquito collections in July 2017, where sera were tested for alphavirus antibodies and viral RNA. In addition, by applying a catalytic, force-of-infection (FOI) statistical model to two serosurveys from Darien Province in 2012 and 2017, we investigated whether endemic or epidemic alphavirus transmission occurred historically. In 2017, MADV and VEEV IgM seroprevalences were 1.6% and 4.4%, respectively; IgG antibody prevalences were MADV: 13.2%, VEEV: 16.8%, Una virus (UNAV): 16.0%, and Mayaro virus: 1.1%. Active viral circulation was not detected. Evidence of MADV and UNAV infection was found near households, raising questions about its vectors and enzootic transmission cycles. Insomnia was associated with MADV and VEEV infections, depression symptoms were associated with MADV, and dizziness with VEEV and UNAV. Force-of-infection analyses suggest endemic alphavirus transmission historically, with recent increased human exposure to MADV and VEEV in Aruza and Mercadeo, respectively. The lack of additional neurological cases suggests that severe MADV and VEEV infections occur only rarely. Our results indicate that over the past five decades, alphavirus infections have occurred at low levels in eastern Panama, but that MADV and VEEV infections have recently increased-potentially during the past decade. Endemic infections and outbreaks of MADV and VEEV appear to differ spatially in some locations of eastern Panama.

Implementation of bamboo and monkey-pot traps for the sampling cavity-breeding mosquitoes in Darién, Panama.

Despite the importance of Aedes, Haemagogus and Sabethes in the transmission of yellow fever virus (YFV) and the public health impacts of recent YFV epidemics in the Americas, relatively little has been reported on the biology and ecology of these vectors. Many Aedes, Haemagogus and Sabethes spp. in the American tropics inhabit and develop in the forest canopy and are difficult to sample with conventional entomological surveillance methods. We tested the utility of two previously developed phytotelmata-style oviposition traps (bamboo Guadua angustifolia) and (monkey-pot Lecythis minor), for collecting immature forms of these mosquitoes in a forest near the community of Aruza Abajo, Darién Province, Panama. Our results showed distribution of mosquito species emerging from the two types of traps was found to be significantly different (X2 = 210.23; df = 14; P < 0.001), with significantly greater numbers of Sabethes (Peytonulus) aurescens (Lutz) and Sabethes (Peytonulus) undosus (Coquillett) emerging from the bamboo traps. More females of Sabethes (Sabethes) cyaneus (Fabricius) were captured in the monkey-pot traps, although the difference was not significant. No differences were observed in the average time to emergence for the two traps. These results suggest that various phytotelmata-style traps, including monkey-pot and bamboo, could be used to improve entomological surveillance of YFV vectors in the American tropic.