National Seroprevalence and Risk Factors for Eastern Equine Encephalitis and Venezuelan Equine Encephalitis in Costa Rica

An Environmental Niche Model to Estimate the Potential Presence of Venezuelan Equine Encephalitis Virus in Costa Rica

“…The first report of an outbreak of VEEV in Costa Rica was documented in 1970, and this study also gave evidence indicating that subtype IE is endemic in the country [2]. An IgG seroprevalence study carried out in 2013 demonstrated that VEEV was circulating in the lowlands, less than 900 meters above sea level (m.a.s.l) and highlands (more than 900 m.a.s.l), with an overall seroprevalence of 35.9% (in 217 horses) [10]. In that study, altitude <100 m was the only variable considered a risk factor in the multivariate analysis, indicated that the lower altitude the higher IgG positives cases to VEEV [10].…”

“…This means that other conditions favor the occurrence of VEEV at higher elevations; one driver is the presence of different vector/reservoir species that may be more or less abundant. It was expected that the altitude variable would contribute more to the VEEV presence model since it was the one risk factor associated with antibodies to VEEV in the Costa Rican study [10]. Altitude also appeared to be the most important variable reported in an EEEV study [29], or for results reported for the vectors Culex.…”

“…VEEV is a neglected disease in Latin American countries. In Costa Rica few cases of people infected with this virus have been reported, despite the fact that based on serosurveys 36% of the horses have been in contact with this virus and cases are widely distributed throughout the country [10]. For this reason, it is important to determine the possible niches where cases could appear in the future.…”

“…We included two sets of VEEV positive data confirmed by two methodologies; the plaque reduction neutralization test (PRNT) and the IgM Enzyme-Linked ImmunoSorbent Assay ELISA from two different serological studies. In the first study, 217 horses were randomly selected across the country in the lowlands and highlands, 81 horses were IgG positive by ELISA and confirmed by PRNT [10]. The second study comprised passive surveillance carried out between 2009 and 2019 involving samples from animals with neurological signs that were taken and sent to the laboratory at the moment the animals present symptomatology to detect the presence of IgM antibodies to VEEV and other arboviruses.…”

“…An IgG seroprevalence study carried out in 2013 demonstrated that VEEV was circulating in the lowlands, less than 900 meters above sea level (m.a.s.l) and highlands (more than 900 m.a.s.l), with an overall seroprevalence of 35.9% (in 217 horses) [10]. In that study, altitude <100 m was the only variable considered a risk factor in the multivariate analysis, indicated that the lower altitude the higher IgG positives cases to VEEV [10]. An 11 years passive surveillance study finished in 2019, (in which animal health authorities did not actively search for cases but the samples were sent to the laboratory voluntarily by the animal owners), showed the presence of positive cases every year with apparent peaks every six years, one observed in 2009 and the second in 2015 during the evaluated period.…”