Modified haemagglutination inhibition assay for the detection of canine parvovirus type 2 antibodies in dog sera

•Evaluation of passive immunity facilitates effective vaccination in puppies.•A haemagglutination inhibition assay was modified to improve interpretation.•Pre-treatment of sera with red blood cells prevented nonspecific hemagglutination.•Lowering the concentration of red blood cells prevented artefactual precipitation. Canine parvovirus type 2 (CPV-2) infection is associated with severe gastroenteritis in puppies. Quantification of CPV-2 specific antibodies before vaccination can reveal the presence of interfering maternal-derived immunity and facilitate timing of effective immunisation. Inhibition of haemagglutination (HI) is commonly used to measure CPV-2-specific antibody levels in serum. However, the presence of nonspecific agglutinins in canine serum and artefactual precipitation of red blood cells (RBC) are both limitations of the assay. In this study, we compared the standard HI protocol with a refined HI protocol, in which canine serum was pre-incubated with porcine RBC for 12 h to remove nonspecific agglutinins and a lower concentration (0.1% vs. 0.8%) of porcine RBC suspensions was used to limit artefactual precipitation of RBC. A panel of canine sera, collected from 80 dogs of different ages and with different neutralising antibody titres, was analysed. Nonspecific agglutinins were identified in most (97%) serum samples from puppies