Aspectos epidemiológicos de diarreia viral bovina, rinotraqueíte infecciosa bovina, neosporose e leptospirose em rebanhos bovinos leiteiros no Rio Grande do Sul

Abstract

Reproductive failures are present in cattle herds, causing considerable economic losses. It is estimated that infectious agents are responsible for more than 30% of gestational losses in cattle and, among the agents, the following stand out: bovine herpesvirus type-1 (BoHV-1), bovine viral diarrhea virus (BVDV), Leptospira spp. and the protozoan Neospora caninum. The aim of this study was to verify the prevalence of specific antibodies against N. caninum and against the viruses of Infectious Bovine Rhinotracheitis (IBR), Bovine Viral Diarrhea (BVD), and the prevalent serovars of leptospira in whey samples from dairy cattle from different farms in the state of Rio Grande do Sul.Risk factors for the prevalence of N. caninum and serovar Djasiman were evaluated. This experiment was carried out in two stages. In the first stage, 435 blood samples were collected from dairy cattle in October and November 2019. In the second stage, 148 samples were collected in November 2022. Commercial ELISA kits were used to detect specific antibodies against N. caninum, IBR and BVD. The prevalence obtained for Neospora, IBR and BVD in the first stage was 9.9%, 68%, 13.3% respectively and in the second stage was 19.6%, 85.8% and 4.7%, with a significant increase in neosporosis, demonstrated in the association with the reproductive problems observed as abortion in the middle and end of pregnancy, delivery problems such as placental retention, stillbirths and birth of weak calves. In the second experiment, the mean prevalence of antibodies against leptospires diagnosed was 73.6% (320/435), indicating a high prevalence of leptospirosis in the region studied and the prevalent serovars/serogroups were Djasiman (Djasiman), Hardjoprajitno (Serjoe) and Hardjobovis (Serjoe) with 18.1%,14.1% and 9.4%, respectively. In the statistical analysis by the chi-square test, the association between the positivity of serovar Djasiman and reproductive and childbirth problems was observed. The prevalences observed demonstrate the presence of these agents in the region, reinforcing the attention to neosporosis because there is no effective vaccine. Djasiman serovar is not in vaccine formulations, demonstrating its importance and the need for further studies. In the analyzed regions, it is suggested to carry out control and prevention measures to minimize the reproductive disorders observed.