Anti-BVDV2 E2 gp53 monoclonal antibody, clone 58K2

Many viral diseases are endemic in cattle populations worldwide. The ability of many viruses to cross the placenta and cause abortions and fetal malformations is well understood. There is also significant evidence that viral infections have additional actions in dairy cows, which are reflected in reduced conception rates. These effects are, however, highly dependent on the time at which an individual animal first contracts the disease and are less easy to quantify. This paper reviews the evidence relating to five viruses that can affect fertility, together with their potential mechanisms of action. Acute infection with non-cytopathic bovine viral diarrhea virus (BVDV) in mid-gestation increases abortion rates or causes the birth of persistently infected calves. BVDV infections closer to the time of breeding can have direct effects on the ovaries and uterine endometrium, which cause estrous cycle irregularities and early embryo mortality. Fertility may also be reduced by BVDV-induced immunosuppression, which increases the susceptibility to bacterial infections. Bovine herpesvirus (BHV)-1 is most common in pre-pubertal heifers, and can slow their growth, delay breeding, and increase the age at first calving. Previously infected animals subsequently show reduced fertility. Although this may be associated with lung damage, ovarian lesions have also been reported. Both BHV-1 and BHV-4 remain latent in the host following initial infection and may be reactivated later by stress, for example associated with calving and early lactation. While BHV-4 infection alone may not reduce fertility, it appears to act as a co-factor with established bacterial pathogens such as Escherichia coli and Trueperella pyogenes to promote the development of endometritis and delay uterine repair mechanisms after calving. Both Schmallenberg virus (SBV) and bluetongue virus (BTV) are transmitted by insect vectors and lead to increased abortion rates and congenital malformations. BTV-8 also impairs the development of hatched blastocysts; furthermore, infection around the time of breeding with either virus appears to reduce conception rates. Although the reductions in conception rates are often difficult to quantify, they are nevertheless sufficient to cause economic losses, which help to justify the benefits of vaccination and eradication schemes. (C) 2020 THE AUTHORS. Published by Elsevier LTD on behalf of Chinese Academy of Engineering and Higher Education Press Limited Company.

Understanding risk factors for bovine viral diarrhoea (BVD) transmission is important for planning national disease control programmes. However, traditional statistical approaches may miss important features of BVD epidemiology due to the highly correlated nature of many farm-level risk factors. In this cross-sectional study, we used data collected from 304 cattle herds in New Zealand during 2015/2016 to compare the results from multivariable logistic regression with Bayesian network (BN) analysis. Blood samples from 15 heifers from each farm were pooled and analysed with an antibody ELISA test to classify BVD virus exposure status. Farmers were surveyed about their general management practices, knowledge about BVD, and risk factors for disease transmission, including onto- and off-farm movements, within- and between-farm contacts, and whether they implemented BVD control measures for their service bulls. Multiple imputation was used to infer missing values in the dataset prior to statistical analysis. The results showed that 57/116 (49.1%) beef farms and 95/188 (50.5%) dairy farms were likely to be actively infected with BVD virus. Almost 60% of farms had movements of heifers/cows onto the premises and 13.8% of farmers reported contact with cattle from other farms. The results of the multivariable logistic regression showed that farms where heifers/cows had been moved onto the premises during all or most of the past five years were at higher risk of being BVD seropositive than farms without those movements (OR 2.21, 95% CI 1.29-4.24). Farms where cattle had occasional or rare contacts with cattle on other farms were also at increased risk compared with farms without any animal contacts between farms (OR 2.63, 95% CI 1.33-541) although this association was not frequency-dependent. Only close animal contacts between farms was directly associated with BVD status in the BN model, however, this approach further untangled other complex associations between correlated management factors, and provided additional important insights into BVD epidemiology. Compared to other countries with intensive production systems, over the fence contact appeared to play a more important role in New Zealand pastoral-based production systems and should be considered when developing strategies for a national BVD control programme.