The development and standardization of an enzyme-linked immunosorbent assay for the detection of antibodies to bovine herpesvirus 2

First Demonstration of Bovine Herpesvirus 2 Infection among Cattle by Neutralization Test in Japan

Seroepidemiological surveys were performed on neutralizing antibody to bovine herpesvirus 2 (BoHV-2) among cattle in Japan. A total of 1,819 sera were collected from cattle in 27 prefectures from 1997 to 1998. Antibodies were detected in only 18 sera collected from 4 prefectures. However, the most prevalent areas of the infection were found in two islands located in the subtropical zone. Additional 353 sera were collected in three including these islands in 1999-2001. The antibody-positive rates in the farms in these islands ranged from 10% to 81.1%. It was confirmed that BoHV-2 was prevalent in these areas. However, the infection seemed to be latent, because no diseases have been noticed. This is the first report showing the presence of BoHV-2 infection among cattle in Japan.

Significance of Neospora caninum in British dairy cattle determined by estimation of seroprevalence in normally calving cattle and aborting cattle

A case control study was conducted to evaluate the significance of Neospora caninum infections in cattle in England and Wales. The prevalence of N. caninum in normally calving cattle (the control group; n = 418) and aborting cattle (n = 633) was estimated using a commercial antibody-detection ELISA. Prevalence estimates for bovine virus diarrhoea virus, infectious bovine rhinotracheitis virus and Leptospira hardjo were also obtained by serology. The prevalence of N. caninum was significantly higher (P < 0.0001) in the aborting group (18%; 95% confidence interval: 15%, 21%) than in the control group (6%; 95% confidence interval: 4%, 8%); the latter is the first estimate, to date, of the national seroprevalence of N. caninum in dairy cattle in England and Wales. Prevalence estimates for bovine virus diarrhoea virus, infectious bovine rhinotracheitis virus and L. hardjo were not found to be higher in the aborting cattle than in the control group. With N. caninum, a strong association between seropositivity and abortion was found, with seropositive cows being 3.5-times more likely to abort than seronegative cows (odds ratio = 3.49; 95% confidence interval: 2.16, 5.69). Furthermore, 12.5% of abortions in dairy cattle in England and Wales may be attributable to N. caninum, as indicated by estimation of the population aetiological fraction.

Evaluation of the immunogenicity of attenuated feline calicivirus vaccines by ELISA

An ELISA test was developed to measure the levels of IgG antibody in specific-pathogen-free (SPF) cats immunised with two doses of an attenuated feline calicivirus (FCV) vaccine. All eight vaccinates were protected from virus challenge, but four out of five non-vaccinates were not. There was a significant difference in respect of protection from virus challenge between SPF cats with and without three-fold or greater increase in antibody units (P = 0.01). Each serum absorbance was standardised against the reference positive which has an arbitrary value of 100 antibody units. In SPF cats, the 99% confidence level for seropositivity to FCV was determined as greater than or equal to 2.5 antibody units. The results suggest that the sensitive ELISA test can be used to monitor the antibody status of SPF cat colonies prior to FCV vaccine trials, and to measure the immunogenicity of attenuated FCV vaccines. Thus, the ELISA test may replace the need for virus challenge, with consequent reduction in animals used in future FCV vaccine trials.