Abstract
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.
Highlights
Bluetongue (BT) is an infectious, non-contagious disease caused by bluetongue virus (BTV), which is transmitted to domestic and wild ruminants by vectors [1]
We demonstrate for the first time that there is a high level of BTV circulation north of Manabí, with active infections on these farms
The species involved in BTV transmission are variable with the geographic area, but Culicoides sonorensis is the principal vector of BTV throughout much of North America, whereas Culicoides insignis is the major vector of BTV in the Caribbean Basin, Central and South America, and in Florida and the Gulf Coast region of the south eastern United States of America and is directly associated with the transmission of BTV between ruminant and non-ruminant natural hosts
Summary
Bluetongue (BT) is an infectious, non-contagious disease caused by bluetongue virus (BTV), which is transmitted to domestic and wild ruminants by vectors [1]. In Ecuador, there are four geographical zones, each with a different height above sea level and different climatic conditions They are: the coast to the east, the central region with the Andes Mountains, the Amazon Rainforest to the west, and the Galápagos Islands. More than 30% of the province’s livestock production is concentrated in the Chone municipality, north of Manabí province These herds are characterized by dual-purpose cattle in extensive and semi-intensive conditions. With the aim of assessing, for the first time, the circulation of the virus and the presence of active BTV infections in Manabí province, we conducted the present investigation in two parts: a cross-sectional serologic survey and a longitudinal study with sentinel calves in six selected seropositive farms from the Chone area
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