Genomic characterization and seroprevalence studies on alphaviruses (Togaviridae) in Uruguay

BURGUEÑO A, FRABASILE S, CABRERA A, DIAZ LA, PISANO MB, RIVAROLA ME, MARTINEZ MS, CONTIGIANI MS, DELFRARO A

Cádiz

Congreso; XIV Congreso Nacional de Virología; 2017

Sociedad Española de Virología

Objective: to investigate the status of Alphavirus infections inUruguayin mosquito vectors and hosts.Materials and Methods: A total of 3575 mosquitoes werecollected at rural and suburban localities and pooled bylocality, genus/species, sex, engorged/not engorged females.From years 2006 to 2014, 266 pools were analyzed. TotalRNA extraction was done, followed by retro transcription andamplification of partial NSP4 gene by a generic nested -polymerase chain reaction. Amplified fragments werefurtheridentified by sequencing and characterized byphylogenetic analysis. Serologic studies were done on horsesera collected during 2007 from 18 departments of the country.A total of 425 horse samples were screened and further titratedby plaque reduction neutralization test (PRNT). Sera weretested against reference strains of WEEV, Eastern equineencephalitis virus (EEEV) and Venezuelan equine encephalitisvirus (VEEV) subtypes I, IV and VI.Results and Conclusions: Seven genera of mosquitoes werecaptured, the majority were identified as Culexpipiensaccounting for 82.9% of the captures. Two poolesresulted positive for alphavirus: one collected in 2006 in FrayBentos city, near the Uruguay river at the limit with Argentina,and a second pool, collected in 2014 at Las Toscas locality(Canelones department) in Southern Uruguay. Phylogeneticanalyses (Bayesian and maximum likelihood) were done. FrayBentos mosquitoes resulted positive for EEEV and groupedwith high statistical support with strains of the North Americanlineage I. The second pool resulted positive for VEEV andclustered with subtype VI (Rio Negro virus), closely relatedwith Chaco and Tucumán strains from Argentina. PRNTassays showed the presence of antibodies to VEEV, EEEV andWEEV. The highest seroprevalences were to Rio Negro virus,ranging from 2.3% to 20% and detectable in 10 of 18departments. VEEV subtype I was detected in 5/18departments, with seroprevalences ranging between 4.6-13%.Pixuna virus and WEEV were only detected in Cerro Largodepartment, with low seroprevalences (3.1%). For EEEV, fourdepartments resulted positive, with seroprevalences around4%. Serological studies showed that VEEV subtype VIexhibited the highest seroprevalence, a wide geographicdistribution and its genome was also detected in Culex pipiensmosquitoes. Notably, EEEV had a low seroprevalence inequines, but an epizootic lineage typical of North America wasdetected in Culex mosquitoes. Taken together our results showthat alphaviruses are present in our territory with variableoccurrence and geographical distribution, being a potentialthreat for human health and equine sanity.