Bluetongue (BT) is a viral disease transmitted by Culicoides (Diptera: Ceratopogonidae) to domestic and wild ruminants. Infections in cattle are mainly subclinical, but severe necrotic and hemorrhagic illness and death may occur depending on the strain of the virus and other factors; cattle act as a reservoir for the virus. Although the Ecuadorian coast has climatic conditions that favor the presence of the vector, there are few serologic or virologic BTV studies available. Manabí is a coastal province in which livestock farming is mostly implemented in the northern part. We conducted two studies to assess, for the first time, the presence of active BTV infections in Manabí province. We collected 430 serum samples from 38 randomly selected farms between March and July 2019 to perform BTV competitive ELISA. In addition, six seropositive farms were selected to place eight sentinel BTV-naive calves. All these calves were blood sampled and the presence of BTV RNA and antibodies was tested for by RT-PCR and competitive ELISA, respectively, once a week for 6–8 weeks until seroconversion was evidenced. A high individual seroprevalence (99%) was obtained, and all investigated farms had BTV seropositive animals. All sentinel calves became BTV viremic and seroconverted. The first viremia appeared after 2–5 weeks from arrival at the farm; they seroconverted 1–3 weeks later. We demonstrate for the first time that there is a high level of BTV circulation north of Manabí, with active infections on these farms. Integrated control strategies such as hygienic measures on farms to reduce midge populations would be advisable for the owners as mitigation measures.
Vesicular stomatitis virus (VSV) is an arbovirus causing vesicular stomatitis (VS) in livestock. There are two serotypes recognized: New Jersey (NJ) and Indiana (IND). The virus can be transmitted directly by contact or by vectors. In Ecuador, in the year 2018, an outbreak of Vesicular Stomatitis (VS) in cattle, caused by VSV-NJ and VSV-IND, was recorded with 399 cases reported distributed over 18 provinces. We determined the phylogenetic relationships among 67 strains. For the construction of phylogenetic trees, the viral phosphoprotein gene was sequenced, and trees were constructed based on the Maximum Likelihood method using 2004 outbreak strains from Ecuador (Genbank) and the 2018 sequences (this article). We built a haplotype network for VSV-NJ to trace the origin of the 2004 and 2018 epizootics through topology and mutations connections. These analyses suggested two different origins, one related with the 2004 outbreak and the other from an enzootic transmission source in 2018. Our analysis also suggests different transmission patterns with several small and independent outbreaks, most probably transmitted by vectors in the Amazon, and in the Andes and Coast region by the movement of livestock. We recommend further research for vectors and vertebrate reservoirs in Ecuador to clarify the mechanisms of the reemergence of the virus.
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