key: cord-0008456-mg0pa1gx authors: Biuk-Rudan, N; Cvetnić, S; Madic, J; Rudan, D title: Prevalence of antibodies to IBR and BVD viruses in dairy cows with reproductive disorders date: 1999-04-01 journal: Theriogenology DOI: 10.1016/s0093-691x(99)00034-5 sha: 86f83ccc777aecd0db545e6cfe82dd096bdb025a doc_id: 8456 cord_uid: mg0pa1gx We determined the prevalence of antibodies to infectious bovine rhinotracheitis virus (IBRV) and bovine viral diarrhea virus (BVDV) in sera of dairy cows on 4 different farms in the Republic of Croatia. A high percentage (60.8%) of cows had various reproductive disorders. The results showed that seroprevalence of infectious bovine rhinotracheitis (IBR) was 85.8% and that of bovine viral diarrhea (BVD) was 79.2% in tested cows. Antibodies to both viruses were found in 80.8% of cows with reproductive disorders but in only 46.8% of cows without reproductive disorders. This difference was statistically significant (P<0.01), and indicated a connection between reproductive disorders and simultaneous infections with IBR and BVD viruses in dairy cows. Infectious bovine rhinotracheitis (IBR) and bovine viral diarrhea (BVD) are diseases with a worldwide distribution in domestic and wild r,~minants and result in severe economic losses to the cattle industry. Infectious bovine rhinotracheitis is caused by bovine herpesvirus 1 (BHV-1), which may also cause conjunctivitis, meningoencephalitis, infectious pustular vulvovaginifis and balanoposthitis, abortions and systemic infections (11) . Although there is no definite association between sub-type and the clinical entity, BHV-1 sub-types 1 and 2a are the main causes of the respiratory form of the disease and, frequently, of abortion. However, sub-type 2b is responsible for infectious pusmlar vulvovaginifis and infectious pusmlar balanoposthitis (23) . Abortions mostly occur during the third trimester of pregnancy. Infertility and shortened estrous cycles have been observed in nonpregnant cows inseminated at estrus with semen containing IBR virus. The IBR aCorrespondence and reprint requests: Department of Microbiology and Infectious Diseases, Faculty of Veterinary Medicine, University ofZagreb, Heinzelova 55, 10 000 Zagreb, Croatia. Fax: (+385 1 214-697) virus causes limited necroti~ing endometritis and neerottqin s oophoritis. Usually, both ovaries are affected by IBRV infection, although the most severe lesions begin on the coipus luteum (el; 17, lg, 19, 22) . The severity of bovine viral diarrhea in cattle ranges from transient acute infections, which may be unapparent or mild, to a mucosal disease that is inevitably fatal Venereal infection with BVD virus is shown to be an important factor in the transfer of virus to the fetus. Congenital infections can cause abortion, m,mmificatiun, stillbirth, malformation and the development of persistently viraemic calves (7) . Abortions usually occur between 50 and 100 d of gestation. Acute and persistently infected bulls may play a great role in the spread of BVD due to virus excretion by semen. Infection at the time of breeding through using BVDV-infected semen causes reduced conception rate, which is most probably due to reduced fertiliTation. Moreover, BVDV induces inflammation of ovaries and pustular lesions on genital organs, similar to BHV-1 (3, 4, 6, 12) . The mucosal disease arises from initial fetal infection with a non-cytopathogenic virus and the subsequent production of persistently viraemic calves. These calves may later develop mucosal disease as a result of superinfection with a "homologous" cytopathogenic virus (7) . Concurrent infections of BVD virus and other respiratory or enteric pathogens may produce a more severe disease than either pathogen alone because of the immlmosuppressive effect of BVD virus (1, 20) . With regard to the foregoing, the aim of this study was to determine seroprevalence to IBR and BVD viruses in the group of dairy cows with reproductive disorders and the group with no reproductive disorders. That is to say, in combined infections of IBR and BVD viruses the immunosuppressive effect of BVD virus may be a triggering factor for activation of IBR virus in latently infected carla. The sample for this study comprised 120 Holstein-Friesian cows, aged 2 to 9 yr, kept at 4 different dairy farms in the Repubfic of Croatia. Average annual milk production on these farms was 6,000 L per cow. These farms were chosen over others because of frequent reproductive problems that had occured over the few last years. We have tested for one group of cows with reproductive disorders and a second group without reproductive disorders from each farm. These groups were made by cluster random sampling, and cows within groups were chosen by systematic random sampling. Blood samples were collected from all dairy cows by puncture of the jugular vein into tubes without an anticoagulant. All blood samples were centrifuged in the laboratory at 1,200 rpm for 10 min to remove the sera, which were then heat-inactivated at 56 °C for 30 min prior to testing. Sera were examined for IBR and BVD viruses by serum-neutralization test. Antibodies were determined by the micro-method, using Linbro IS-FB-96 plates. Four serial two-fold dilutions of each serum were incubated in 50-#L volumes with equal volumes of the viral suspension containing 100 TCIDso of cytopathic Iowa strain of IBR virus and cytopathic Oregon-C24V strain of BVD virus. After I h of incubation at 37 *C, a suspension of an embryonic bovine trachea (EBTr) cell strain in Eagle's minimal essential medium (EMEM), with 10% fetal bovine serum (FBS), was added to make up a volume of 100 #L. Each test included a back titration of the vires, positive and negative serum control and cell culture control. The results were evaluated after 5 d of incubation at 37 *C in 5% CO2 in air. Virus neutralization antibody titres were expressed as the reciprocal of the 50% protection end point, calculated by the Spearman-Kgrber method. Sera with a titre -log10 SNT,o 0,9 or greater to IBR virus and -logto SNTso 1,0 or greater to BVD virus were considered positive. All the dairy cows in this study were examined vaginally and per rectum for reproductive disorders. Excluding clinical findings, data on abortions and fetal mortality were taken from reproductive ananmesis. Differences in antibody prevalence between groups with and without reproductive disorders for IBR and BVD viruses were tested by the Chi-square test. Antibody prevalence for IBR virus was 85.8%, and for BVD virus it was 79.2% in the tested cows from all dairy farms. Table 1 presents antthody prevalence for these viruses for each dairy farm. On the basis of the results we are able to say that the presence of anlfoodies to IBR and BVD viruses at these farm was approximately equal. Presence of IBR and BVD in dairy cows was considered in relation to their reproductive status ( Table 2 ). In the group of cows that proved positive for IBR and BVD viruses, a statistically si~ificant difference (P