Evolutionary relationships of West Nile virus detected in mosquitoes from a migratory bird zone of Colombian Caribbean

Abstract

BackgroundWest Nile virus (WNV) is a member of the genus Flavivirus, and it is transmitted between Culex sp. mosquitoes and avian hosts. Equids and humans are commonly infected with WNV as dead-end hosts, and the signs and symptoms of infection range from mild illness to neurologic symptoms as encephalitis, meningitis and sometimes death. Previous phylogenetic studies have classified WNV into six genetically distinct lineages and provided valuable insight on WNV dispersal patterns within the Americas and its emergence in different geographic areas. In this study, we isolated, sequenced and genetically characterized the NS5 and envelope genes for two WNV strains detected from Northern of Colombia. Herein we describe the evolutionary relationships with representative WNV-strains isolated in a variety of epidemic outbreaks and countries, to define the phylogeographic origin and possible implications in the epidemiology of this emergent virus in Colombia.FindingsFragments of the NS5 and Envelope genes were amplified with RT-PCR and sequenced to obtain 1186-nt and 1504-nt portions, respectively. Our sequences were aligned with 46 sequences from WNV-strains collected in the U.S., Mexico and Argentina for phylogenetic reconstruction using Bayesian methods. Sequence analyses identified unique non-synonymous substitutions in the envelope gene of the WNV strains we detected, and our sequences clustered together with those from the attenuated Texas – 2002 genotype.ConclusionsA new strain closely related to attenuated strains collected in Texas during 2002 was identified from Colombia by phylogenetic analysis. This finding may explain the absence of human/equine cases of WNV-encephalitis or severe disease in Colombia and possibly other regions of South America. Follow-up studies are needed in ecosystems used by migratory birds areas and virological/entomological surveillance.

The Effects of Sampling Location and Predictor Point Estimate Certainty on Posterior Support in Bayesian Phylogeographic Generalized Linear Models

“…We specified a generalized time reversible substitution model following previous WNV studies 11 , 12 , 16 , 22 , 31 , 32 , also including invariant sites and a gamma heterogeneity (GTR + I + G) on our sequences. We set an uncorrelated lognormal relaxed molecular clock 33 following previous studies 11 , 22 , 34 with an initial mutation rate of 0.001 substitutions per site per year and specified a Bayesian Skyline prior 35 .…”

A four-year survey (2011–2014) of West Nile virus infection in humans, mosquitoes and birds, including the 2012 meningoencephalitis outbreak in Tunisia

“…Cx. pipiens mosquitoes are considered the most important vectors in transmitting WNV 43 , 49 , 50 . Entomological surveys conducted after WNV outbreaks in Tunisia showed the abundance and role of Cx.…”

Characterization of Puerto Rican West Nile Virus isolates in mice

“…In Colombia a similar situation was observed where a pathogenic phenotype which exhibited high virulence in Balb/c mice was observed from two WNV isolates from Colombia (COL 524/08, 9835/08) originally obtained from healthy captive American Flamingoes (Phoenicopterus ruber) [ 37 ]. However, two strains recently isolated from mosquito pools in Colombia were reported to be closely related to attenuated strains from Texas [ 38 ]. Although phenotypic characterization of these new Colombian strains has not yet been perform to confirm attenuation, Lopez et al, findings demonstrated the circulation in Colombia of genetic diverse WNV strains [ 38 ].…”

“…However, two strains recently isolated from mosquito pools in Colombia were reported to be closely related to attenuated strains from Texas [ 38 ]. Although phenotypic characterization of these new Colombian strains has not yet been perform to confirm attenuation, Lopez et al, findings demonstrated the circulation in Colombia of genetic diverse WNV strains [ 38 ]. Thus, it is possible that WNV strains isolated from both the Caribbean and Latin America have variable pathogenic capacities.…”