Effect of vaccination against bovine herpesvirus 1 with inactivated gE-negative marker vaccines on the health of dairy cattle herds.

The aim of this study was to estimate the effect of the bovine herpesvirus 1 (BHV-1) vaccination on herd health and production in BHV-1 infected Estonian dairy cattle herds. Seven herds vaccinated with inactivated gE-negative BHV-1 marker vaccines and seven matched non-vaccinated herds were selected. In vaccinated herds the calving interval was on average 7.01 days shorter compared to that in the non-vaccinated herds (coef=-7.01, 95% CI=-11.98, -2.03, p=0.008) during the study period (2007-2012). In non-vaccinated herds the insemination index had an increasing trend (coef(log scale)=0.03, 95% CI=-0.003, 0.06, p=0.054) and the first service conception rate decreased (coef=-2.19, 95% CI=-3.91, -0.47, p=0.015), whereas no significant changes occurred in vaccinated herds. Average yearly milk yield per cow increased (coef=145.30, 95% CI=-6.11, 296.71, p=0.065) and length of the dry period decreased in BHV-1 vaccinated herds (coef(log scale)=-0.02, 95% CI=-0.04, 0.004, p=0.056) compared to non-vaccinated herds during the study years. Youngstock and the cow culling rate due to respiratory disease was significantly lower in vaccinated herds compared to non-vaccinated herds (coef=-0.29, 95% CI=-0.47, -0.11, p=0.003 and coef=-0.15, 95% CI=-0.29, -0.007, p=0.043, respectively). These results suggest that vaccination against BHV-1 is associated with herd health and productivity.

Epidemiology and control of bovine herpesvirus 1 infection in Europe.

Bovine herpesvirus 1 (BHV-1) causes infectious bovine rhinotracheitis (IBR), infectious pustular vulvovaginitis, abortion and balanoposthitis, as well as neurological and systemic disease in cattle. The virus is endemic in cattle populations worldwide although in Europe six countries and several regions in other countries have achieved 'IBR-free' status by implementing control measures. According to European Union (EU) directives, all member states must comply with specific requirements related to BHV-1 infection status in semen and embryos. The requirement that 'IBR-free' states restrict the importation of cattle from endemically infected regions has motivated several European countries to instigate disease eradication programmes. Despite such control measures within the EU, outbreaks of IBR persist in 'IBR-free' states contiguous with infected countries. This review presents a summary of recent research on the epidemiology of BHV-1, highlights the control measures and surveillance systems in place, and discusses the challenges facing eradication schemes.

Neospora caninum in Estonian dairy herds in relation to herd size, reproduction parameters, bovine virus diarrhoea virus, and bovine herpes virus 1.

Cows infected with the tissue parasite Neospora caninum (Nc) are more likely to abort or give birth to calves with neurological disorders. The known infection routes are transplacentally and by consumption of oocysts shed by the definitive host, the dog. It has been hypothesised, that dormant stages of persistent Nc infection may be reactivated by immunosuppression mechanisms such as pathogenic invasions as bovine herpes virus 1 (BHV1) and bovine virus diarrhoea virus (BVDV). The study was set to give the first prevalence data on Nc from Estonian dairy herds in both animal as well as herd level. In addition, association between herd size and Nc, and association of Nc with abortion incidence (Ab), stillbirth incidence (Sb), insemination index (II), and calving interval (CaI) in the presence of BHV1 and BVDV was studied. Blood samples from 1973 animals from 100 herds were collected in 2006-2008, and 320 bulk tank milk (BTM) samples were collected in 2007. Antibodies against Nc was found in 2.5 ± 0.4% (95% CI) of the animals and at least one positive animal was found in 37.0 ± 4.7% (95% CI) of the herds. In addition, Nc antibodies were detected in 16.3 ± 2.0% (95% CI) of the tested BTM. Large herds (≥ 200 animals) were less likely to have seropositive animals for Nc. Logistic regression models showed that herds with more than one animal seropositive for Nc had significantly higher odds ratio of abortion incidence (OR: 11.92, 1.18-120.18 95% CI, p=0.036) and tendency of having more stillbirths (OR: 5.52, 0.87-35.02 95% CI, p=0.07). On the other hand one Nc seropostive cow in the herd was associated with lower odds ratio (OR: 0.22, 0.05-0.91 95% CI, p=0.04) of higher calving intervals. Estonian prevalence results reflect observations in the region. No evidence was found of the pathogens were affecting fertility variables through interactions but independently BHV1 and Nc had an impact on the abortion.

Association of herd BRSV and BHV-1 seroprevalence with respiratory disease and reproductive performance in adult dairy cattle.

BACKGROUND: The aim of this study was to detect the associations between bovine herpesvirus 1 (BHV-1) status of a herd and respiratory disease (BRD) occurrence and reproductive performance in pregnant heifers and cows. The association between management-related factors and higher BRD occurrence was also estimated. METHODS: Serum samples, collected from cows and youngstock from 103 dairy cattle herds, were analyzed for antibodies against BHV-1, bovine respiratory syncytial virus (BRSV), bovine viral diarrhoea virus (BVDV), and Mycoplasma bovis. A questionnaire was used to collect data concerning herd management factors and reproductive performance, as well as the occurrence of clinical signs of respiratory disease in the last two years, as evaluated by the veterinarian or farm manager. Multiple correspondence analysis (MCA) and logistic regression analysis were performed to identify and quantify the risk factors. RESULTS: A low to moderate prevalence (1-49%) of BRSV antibodies among youngstock was associated with a high occurrence of respiratory disease (OR = 6.2, p = 0.010) in cows and in-calf heifers. Employees of the farm may participate in the spread of such disease. Larger herd size, loose-housing of cows, housing youngstock separately from cows until pregnancy, and purchasing new animals were factors possibly related to a high occurrence of respiratory disease symptoms in pregnant heifers and cows. The highest risk of abortions (> 1.3%) and increased insemination index (number of inseminations per pregnancy) (> 1.9) occurred in herds with a moderate prevalence of BHV-1 antibodies (1-49%) in cows. CONCLUSIONS: BHV-1 was not associated with acute respiratory disease in adult dairy cattle, however was significantly related to reproductive performance. BRSV possesses the main role in respiratory disease complex in adult dairy cattle.

Eimeria and Cryptosporidium in Estonian dairy farms in regard to age, species, and diarrhoea.

Eimeria and Cryptosporidium are among the most common bovine parasites in the world, but little is known about them in Estonia. Basic field research is needed to gain insight into pathogen dynamics, providing knowledge for veterinarians and research. A survey of 45 Estonian dairy farms in 15 counties was carried out between 2006 and 2007. Three age groups: <3, 3-12, and >12 months old animals were sampled. Collected faeces were examined by quantitative flotation and Ziehl-Neelsen contrast staining, and species examined morphologically. Selected samples containing Cryptosporidium were additionally examined by polymerase-chain-reaction (PCR) and sequencing to determine genotypes. Twelve species of Eimeria were identified, seven previously unknown in Estonia. Main species in samples were E. bovis (30%), E. zuernii (23%), and E. ellipsoidalis (14%). All herds were infected and animals aged 3-12 months were more commonly infected with Eimeria oocysts (63%) than any other group. Calves <3 months shed most oocyst, but high counts were rare. A negative association (slope=-0.16, p<0.001) was found between the number of animals infected with Eimeria and the age category. Cryptosporidium were detected in 84% of the farms, and C. andersoni and C. parvum were successfully identified. Though prevalences of Cryptosporidium in the age groups were similar to the sample prevalence (30%) an increase in the infections was found with increasing age (p<0.001). Higher diarrhoea scores were negatively associated with Eimeria spp. infection (slope=-0.08, p<0.05), whereas Cryptosporidium could not be associated with the presence of diarrhoea. Frequent low intensity infections of animals in all age groups with both parasites apply a constant stress on the animals with impact on health and production. The Estonian results are different compared to available studies in regard of: older animals commonly being infected, finding of modest oocyst counts, and distribution of Eimeria species.