Saint Louis Encephalitis Virus in Mato Grosso, Central-Western Brazil

Abstract

The dengue virus (DENV), which is frequently involved in large epidemics, and the yellow fever virus (YFV), which is responsible for sporadic sylvatic outbreaks, are considered the most important flaviviruses circulating in Brazil. Because of that, laboratorial diagnosis of acute undifferentiated febrile illness during epidemic periods is frequently directed towards these viruses, which may eventually hinder the detection of other circulating flaviviruses, including the Saint Louis encephalitis virus (SLEV), which is widely dispersed across the Americas. The aim of this study was to conduct a molecular investigation of 11 flaviviruses using 604 serum samples obtained from patients during a large dengue fever outbreak in the state of Mato Grosso (MT) between 2011 and 2012. Simultaneously, 3,433 female Culex spp. collected with Nasci aspirators in the city of Cuiabá, MT, in 2013, and allocated to 409 pools containing 1-10 mosquitoes, were also tested by multiplex semi-nested reverse transcription PCR for the same flaviviruses. SLEV was detected in three patients co-infected with DENV-4 from the cities of Cuiabá and Várzea Grande. One of them was a triple co-infection with DENV-1. None of them mentioned recent travel or access to sylvatic/rural regions, indicating that transmission might have occurred within the metropolitan area. Regarding mosquito samples, one pool containing one Culex quinquefasciatus female was positive for SLEV, with a minimum infection rate (MIR) of 0.29 per 1000 specimens of this species. Phylogenetic analysis indicates both human and mosquito SLEV cluster, with isolates from genotype V-A obtained from animals in the Amazon region, in the state of Pará. This is the first report of SLEV molecular identification in MT.

Natural infection by Culex flavivirus in Culex quinquefasciatus mosquitoes captured in Cuiabá, Mato Grosso Mid‐Western Brazil

“…Culex quinquefasciatus was identified as naturally infected and is a competent vector for arboviruses, especially to Flavivirus (Hoch et al, 1987;Segura & Castro, 2007;Heinen et al, 2015;Serra et al, 2016).…”

Natural transovarial transmission of dengue virus 4 in Aedes aegypti from Cuiabá, State of Mato Grosso, Brazil

“…This pathogen was recently detected in three patients with dengue and in Culex spp. from Cuiabá, MT (12). However, the cycle of transmission of this virus in the city is poorly understood.…”

“…Additionally, one human case was reported in Ribeirão Preto, and the virus was detected in three patients from Mato Grosso (12) (15) (16) . Additional evidence of SLEV circulation in Brazil among humans, equines, mosquitoes, birds, and vectors in the Amazon region, the State of São Paulo, and the southern Pantanal has also been reported (17) (18) (19) .…”

“…Most of the cases occurring in 2012 were reported in Cuiabá, the state capital (10,742 cases, two fatal). All four DENV serotypes were detected in the city throughout this year, but DENV-4 was responsible for the vast majority of the cases (12) .…”

Mayaro virus and dengue virus 1 and 4 natural infection in culicids from Cuiabá, state of Mato Grosso, Brazil

“…Cuiabá is the capital of MT and a significant number of confirmed or suspected dengue cases are reported annually in the city ( Acendino 2013 ). Studies involving patients with acute febrile illness during a large dengue outbreak demonstrated the hyperendemicity of DENV and the circulation of SLEV and MAYV in Cuiabá during 2012 ( Zuchi et al 2014 , Heinen et al 2015a , b ). However, until the present, studies to evaluate the genetic diversity and frequency of these viruses are lacking.…”