Epidemiological and spatial characterization of BVDV and BoHV-1 infections in bovides from the Paraíba State, Northeastern Brazil.

Abstract

This thesis is composed of three chapters. In Chapter I, a cross-sectional study based on a planned sampling was carried out to determine herd- and animal-level seroprevalences and to identify risk factors for Bovine Viral Diarrhea Virus (BVDV) infection in cattle from the State of Paraíba. The state was divided into three sampling strata, and for each stratum, the prevalence of herds infected with BVDV and the prevalence of seropositive animals was estimated by a two-stage sampling survey. In total, 2443 animals were sampled from 478 herds. In Chapter II, the study aimed to identify the risk factors associated with BVDV and Bovine Herpesvirus Type 1 (BoHV-1) infection in buffaloes in the State of Paraíba using 136 female buffaloes ≥ 24 months old from 14 herds. For the serological diagnosis of the BoHV-1 and BVDV infections, the virus-neutralization test was used and in each herd, an epidemiological questionnaire was applied in order to obtain data used in the risk factor analysis. In Chapter III, the study aimed to identify spatial clustering of positive herds by BVDV and BoHV-1 in cattle in the State of Paraíba, using the Cuzick-Edwards‘ k-nearest neighbor method and spatial scan statistics. The herd- and animal-level prevalences for BVDV in cattle in the state were 65.5% (95% CI =61.1–69.7%) and 39.1% (95% CI =33.1–45.6%), respectively, and the risk factors identified were: more than six calves aged ≤12 months (OR = 3.72; 95% CI=2.08–6.66), animal purchasing (OR = 1.66; 95% CI=1.08–2.55), pasture rental (OR = 2.15; 95% CI=1.35–3.55), and presence of veterinary assistance (OR = 2.04; 95% CI=1.10–3.79). In buffaloes, of the 136 animals 86 (63.2%) were positive for BoHV-1 and 12 (8.8%) for BVDV. The presence of watering points (OR = 17.68; 95% CI = 3.74–83.04) was identified as risk factor for BoHV-1, and animal purchasing was a risk factor for both BoHV-1 (OR = 68.64; 95% CI = 12.28–383.73) and BVDV (OR = 3.64; 95% CI = 1.04–12.76). Six significant clusters were detected for BVDV, a primary cluster (11 herds, 24.10 km, RR = 2,21; p <0.001) covering the eastern Sertão region, and five smaller significant clusters, involving one or two herds in Agreste/Zona da Mata region, near the border of the Borborema region. A significant clustering of BoHV-1 positive herds (p <0.001) was detected in Agreste/Zona da Mata region (103 cases, 77,17 km, RR=1.27). The findings suggest that the implementation of control and prevention measures should be adopted for cattle and buffaloes in the Paraíba state, with the aim of preventing dissemination of the agents in those herds.