Silent Circulation of the Saint Louis Encephalitis Virus among Humans and Equids, Southeast Brazil.

Saint Louis encephalitis virus (SLEV) is a mosquito-borne flavivirus that occurs throughout the Americas, and is considered a public health threat. In Brazil, SLEV has been detected from human cases associated with dengue-like disease, but no neurological symptoms were reported. Furthermore, the epidemiology of SLEV in human populations is still poorly explored in the country. We reported serological and molecular detection of SLEV in a healthy population of equids and humans from rural areas in Southeast Brazil. A plaque reduction neutralization test was applied, and neutralizing antibodies were detected in 11 individuals (4.6%) and 60 horses (21.5%). A qPCR targeting the 5'UTR region and reverse transcription-PCR (RT-PCR) targeting the non-structural protein (NS5) gene were performed and three individuals tested positive in both assays. Subsequent phylogenetic analysis confirmed SLEV circulation and its findings suggest the occurrence of an asymptomatic or subclinical presence in human and animal cases, correlating with the risks for outbreaks and consequently burden of SLEV infections to public health. Preventive strategies should include improved surveillance in regions with a high probability of SLEV occurrence, improvement in diagnostic methods, and evaluation of exposure/risk factors that can favor SLEV emergence.

Molecular detection of bovine immunodeficiency virus in water buffaloes (Bubalus bubalis) from the Amazon region, Brazil.

Bovine immunodeficiency is a chronic progressive disease caused by a lentivirus that affects cattle and buffaloes. Although the infection has been described in cattle in some countries, including in Brazil, there are only two reports of infection in buffaloes: one in Pakistan and one in Cambodia. The aim of the present study was to survey the occurrence of bovine immunodeficiency virus (BIV) in water buffaloes from the Amazon region, Pará state, Brazil. BIV proviral DNA was surveyed in 607 whole blood samples of water buffaloes from 10 farms located in the state of Pará using semi-nested polymerase chain reaction (PCR) (PCR-SN) to amplify the pol region of the viral genome. Of the 607 samples tested, 27 (4.4 %) were positive for BIV proviral DNA. The amplified fragments were confirmed by sequence analysis after cloning and nucleotide sequencing. The sequence obtained had 99 % similarity to the reference strain (R-29). The present study provides important epidemiological data because BIV was detected for the first time in water buffaloes in Brazil. Further, the results suggest the possibility of the virus being a risk factor for herd health because it may be a potential causal agent of chronic disease and, also may be associated to other infectious diseases.