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Abstract

Objective

To further validate an antibody-capture ELISA for measuring bovine coronavirus (BCV) exposure (antibody seroresponse) in cattle and to explain the apparent loss of sensitivity of a BCV antigen-capture ELISA when testing feces from adult versus neonatal cattle.

Animals

98 adult cows from herds with and without winter dysentery; 10 gnotobiotic or colostrum-deprived calves.

Procedures

Results of an antibody-capture ELISA for BCV and a plaque reduction virus neutralization assay performed on paired serum samples from 24 cattle were compared with each other and with results of immunoelectron microscopy (IEM) of feces for BCV. For samples from 98 cattle, results of antibody-capture ELISA were compared with results of IEM. Calves were inoculated with feces ELISA-positive or IEM-positive for BCV and monitored for BCV infection. An ELISA was developed to detect BCV antigen-antibody complexes in feces and results were compared with results of an antigen-capture ELISA and IEM.

Results

Antibody-capture ELISA results correlated with neutralization assay results, but agreed more closely with results of IEM. Calves became infected with BCV following inoculation with either ELISA-positive or ELISA-negative but IEM-positive feces. Results of the antigen-antibody ELISA correlated with results of IEM and the antigen-capture ELISA.

Clinical Implications

In adult cattle, testing of paired serum samples by use of an antibody-capture ELISA may be a better indicator of recent BCV exposure than results of virus neutralization tests. Antigen-antibody binding in feces may interfere with results of antigen-capture ELISA for BCV. (Am J Vet Res 1998;59:956–960)

Free access
in American Journal of Veterinary Research

Abstract

Objective—To determine the prevalence, fecal shedding pattern, and association of bovine torovirus (BoTV) with diarrhea in veal calves at time of arrival and periodically throughout the first 35 days after their arrival on a veal farm.

Animals—62 veal calves.

Procedure—Fecal samples collected on days 0, 4, 14, and 35 after arrival were tested for BoTV by use of ELISA and reverse transcriptase-polymerase chain reaction (RT-PCR) assay. Paired serum samples obtained from blood collected on days 0 and 35 were analyzed for BoTV antibodies with a hemagglutination inhibition assay. Fecal samples were also screened for other enteric pathogens, including rotavirus, coronavirus, and Cryptosporidium spp.

Results—Fecal shedding of BoTV was detected in 15 of 62 (24%) calves by use of ELISA and RT-PCR assay, with peak shedding on day 4. A significant independent association between BoTV shedding and diarrhea was observed. In addition, calves shedding ≥ 2 enteric pathogens were more likely to have diarrhea than calves shedding ≤ 1 pathogen. Calves that were seronegative or had low antibody titers against BoTV (≤ 1:10 hemagglutination inhibition units) at arrival seroconverted to BoTV (> 4-fold increase in titer); these calves were more likely to shed virus than calves that were seropositive against BoTV at arrival.

Conclusions and Clinical Relevance—Shedding of BoTV was strongly associated with diarrhea in neonatal veal calves during the first week after arrival at the farm. These data provide evidence that BoTV is an important pathogen of neonatal veal calves. (Am J Vet Res 2003;64:485–490)

Full access
in American Journal of Veterinary Research