Prevalence of serum antibodies to bovine herpesvirus-1 and bovine viral diarrhea virus in beef cattle in Uruguay

Our objective was to determine the prevalence of serum antibodies to bovine herpesvirus-1 (BHV-1) and bovine viral diarrhea (BVD) virus in beef cattle in Uruguay. A random sample of 230 herds selected with probability proportional to population size based on the number of cattle was chosen from a list frame of all registered livestock farms as of June 1999. Sera from up to 10 heifers, cows and bulls (up to 30 sera total per herd) were collected on selected farms between March 2000 and March 2001 and evaluated by means of enzyme-linked immunosorbent assays (ELISAs). Overall, 6358 serum samples were evaluated. We also collected data on previous diagnosis of BHV-1 or BVD infections and on the use of vaccines against these agents.

The estimated prevalence of exposure to BHV-1 and BVD at the herd level for the Uruguayan beef population was 99% and 100%, respectively. Approximately 37% of beef cattle in Uruguay have been exposed to BHV-1 and 69% to BVD virus. Only 3% of beef herds in Uruguay regularly (typically, annually) use vaccines against either of these agents.     

A rapid, quantitative assay for titration of bovine virus diarrhoea-mucosal disease virus

An end point dilution microtitration assay is described that can be used for the titration of both cytopathic and non-cytopathic isolates of bovine virus diarrhoea-mucosal disease virus. Indirect immunofluorescence is used to detect infected MDBK cells in the wells of Terasaki plates. The virus titre is derived from the number of uninfected wells, using the Poisson distribution. The assay is simple, fast and economical. Titres of cytopathic virus determined by the microtitration assay and standard plaque assay are equivalent.     

Prevalence and specificity of antibodies to bovine respiratory syncytial virus in sera from feedlot and range cattle

The specificity of serum antibodies for the polypeptides of bovine respiratory syncytial virus (BRSV) was examined, using sera obtained from feedlot and range cattle. Test results in sera from feedlot cattle indicated a 60% rate of seroconversion and 95% seropositivity to BRSV, associated with lack of clinical signs indicative of respiratory tract disease. Exposure to other common respiratory tract viruses also was high (greater than or equal to 92% to bovine herpesvirus type 1, bovine viral diarrhea virus, and para-influenza virus type 3). Test results in sera from range cattle indicated BRSV seropositive rates of 28% in calves, 49% in yearling cattle, and 70% in mature cows; clinical signs of respiratory tract disease were not observed in these cattle. Antibodies to BRSV in sera from cattle in both environments reacted predominantly with polypeptides of molecular weight 80,000 through 85,000, 40,000, and 28,000. Reactivity to a glycoprotein of molecular weight between 43,000 and 44,000 and to several glycopolypeptides of smaller molecular weight increased in serum specimens obtained from feedlot cattle between time of entry into the feedlot and slaughter.     

Prevalence of Borna disease virus antibodies in healthy Japanese black cattle in Kyushu

Epidemiological studies have demonstrated that asymptomatic infection of Borna disease virus (BDV) is found in various species of animals in Japan. Recent reports have also revealed that neurological diseases caused by this virus could exist in horses, cattle, a dog, and cats in this country. In this study, we investigated seroprevalence of BDV antibodies in Japanese black cows reared in Kyushu, the southernmost main island of Japan, using ELISA and Western-immunoblotting. Of 101 serum samples, 11 (10.9%) and 21(20.7%) sera were identified as having antibodies to the BDV N and P antigens, respectively. Among the positive sera, three cows (2.9%) were seropositive for both of the antigens. Furthermore, interestingly, only female cows showed antibodies to P, whereas N antibodies were detected in male and female cows with a comparative ratio. Together with previous studies, our results indicate that BDV might be widely spread in cattle raised in Japan. Furthermore, this is the first report to show that beef cattle, Japanese black cattle, have antibodies against a possible zoonotic pathogen, BDV.     

Bovine virus diarrhoea-mucosal disease virus-induced fetopathy in cattle: Efficacy of prophylactic maternal pre-exposure

Maternal immunity was produced in Jersey heifers by exposing them to bovine virus diarrhoea-mucosal disease virus before conception. In the following pregnancy this immunity protected the fetuses from transplacental infection arising from challenge of the dams at 100 days gestation with homologous virus. Unprotected Jersey heifers showed a high incidence of death and fetal intrauterine growth retardation associated with transplacental viral infection. Functional normality of the locomotor system was assessed retrospectively from ciné films of each calf after birth, and scored for each of an overlapping series of clinical signs. The progeny of non-immune dams scored significantly lower than calves from the vaccinated heifers.     

Pathogenesis of bovine viral diarrhoea-mucosal disease (BVD-MD) virus infection in tracheal organ cultures

Bovine foetal tracheal organ cultures were infected with two strains of BVD-MD virus and observed for 35 days. The effect of the virus was assessed by observing ciliary activity in gross tissue explants and histological changes in haematoxylin and eosin stained sections. Decrease in ciliary activity and mild epithelial degeneration were first observed at 4 days post infection (p.i.), the epithelial degeneration progressing to complete destruction by day 35 p.i. Viral titres in extracellular fluids rose sharply from day 4 p.i., reached peak levels (10⁵ TCID₅₀/ml) between 15 and 18 days p.i., and eventually declined but persisted at lower titres up to day 35 p.i., when observations were terminated.     

Prevalence of antibodies to four bovine rotavirus strains in different age groups of cattle

Neutralizing antibody titers to four bovine rotavirus strains, representing three serotypes, were measured in 160 sera from cattle of different age groups. Age-specific seroprevalence analysis revealed serotype 6, represented by bovine rotavirus (BRV) NCDV, as the predominant rotavirus serotype infecting German cattle and serotype 10, represented by BRV V1005, as the least prominent. Infections with serotype 8, represented by BRV 678, occurred with intermediate frequency. Antibodies of young calves distinguished between NCDV and UK virus, two serotype 6 BRV strains differing in VP4 antigen.     

The effects of bovine viral diarrhoea-mucosal disease (BVD) virus on the ovine foetus

Bovine viral diarrhoea-mucosal disease (BVD) virus has been incriminated as a cause of abortion, hairy birth coat and unthriftiness in sheep. Intravenous inoculation of 40 ewes 34 to 45 days pregnant with the V/TOB strain of virus produced death in two of four foetuses 9 days after inoculation and in all but one of 31 foetuses between 11 and 56 days. The highest levels of virus in placentomes and foetal tissues occurred between 9 and 15 days after inoculation and in foetal fluids between 11 and 18 days. Virus was not detected in any foetus later than 21 days after inoculation. Groups of 10 ewes infected between 59 and 62 days (Group B) and 70 and 76 days (Group C) of gestation had 73% and 62%, respectively, of abortions or perinatal foetal deaths. Birth weights of lambs born to infected ewes in groups B and C were significantly lower than those born to uninfected control ewes. Virus was recovered consistently from the cotyledons of the foetal membranes of live lambs, and irregularly from the tissues of full term foetuses that were dead at birth but on no occasion from mummified foetuses. There were no specific gross or microscopic lesions in tissues selected from aborted foetuses and the results highlight the difficulties associated with the diagnosis of BVD abortions and perinatal death of foetuses under field conditions.     

Prevalence of bovine leukemia virus antibody in seven herds of Holstein-Friesian cattle

Sera from 959 Holstein-Friesian cattle in 7 herds were tested for antibody to bovine leukemia virus, using the agar gel immunodiffusion test with glycoprotein antigen. Seropositive cattle were found in 6 herds; 120 (12.5%) were reactors. In 1 of the herds, the prevalence of seropositive cattle was significantly greater in purebred than in grade cows. Purebred cows raised on the premises and an overall antibody prevalence similar to purchased purebred cows. Purebred cattle more than 2 years old had a significantly greater prevalence of reactors than younger cattle. There was no difference in prevalence by sex.     

Prevalence of bovine viral diarrhoea virus antibodies in bulk tank milk of industrial dairy cattle herds in suburb of Mashhad-Iran

Bulk milk for the presence of antibodies against bovine viral diarrhea virus (BVDV) from 38 industrial dairy cattle herds complexes with 250-3000 Holstein dairy cows in suburb of Mashhad-Iran was tested. None of the herds were vaccinated against BVDV. Commercial indirect ELISA-kit for the detection of specific antibodies was used. The result could be read visually where the optical density (OD) was measured at 450 nm. The percent positivity (PP) values >or=7 and <7 interpreted positive and negative, respectively. According to this study the apparent and the true prevalence of BVDV antibody-positive herds was 89.47 and 93.98%, respectively. The range of PP was 1.59-107.66 among the herds. The OD in 52.63% bulk milk of the herds was very high. It is concluded that exposure to BVD virus was widely distributed in the dairy cattle herds in suburb of Mashhad-Iran.