VACCINE-ASSOCIATED IMMUNE-MEDIATED HEMOLYTIC-ANEMIA IN THE DOG

Vaccination has been incriminated as a trigger of immunemediated hemol ytic anemia (IMHA) in dogs and in people, but evidence to support this association is lacking. In a controlled retrospective study, idiopath ic IMHA was identified in 58 dogs over a 27-month period. When compare d with a randomly selected control group of 70 dogs (presented for rea sons other than IMHA) over the same period, the distribution of cases versus time since vaccination was different (P < .05), fifteen of the dogs (26%) had been vaccinated within 1 month (mean, 13 days; median, 14 days; range, 1 to 27 days) of developing IMHA (P < .0001), whereas in the control group no marked increase in frequency of presentation w as seen in the first month after vaccination. The dogs with IMHA were divided into 2 groups based on time since vaccination: the vaccine IMH A group included dogs vaccinated within 1 month of developing IMHA; th e nonvaccine IMHA group included dogs that developed IMHA more than 1 month after vaccination. The recently vaccinated dogs with IMHA (vacci ne IMHA group) had significantly lower platelet counts (P < .05) and a trend towards increased prevalence of intravascular hemolysis and aut oagglutination when compared with the nonvaccine IMHA group. Similar m ortality rates were seen in the vaccine IMHA group (60%) and the nonva ccine IMHA group (44%), with the majority of fatalities (> 75%) occurr ing in the first 3 weeks after presentation. Persistent autoagglutinat ion was a negative prognostic indicator for survival in both groups (P < .05). Presence of icterus and hyperbilirubinemia were negative prog nostic indicators for survival in the nonvaccine IMHA group (P < .0001 and P < .01, respectively) but not in the vaccine IMHA group. In the recently vaccinated dogs, combination vaccines from various manufactur ers against canine distemper, adenovirus type 2, leptospirosis, parain fluenza, and parvovirus (DHLPP) were involved in each case. Vaccines a gainst rabies virus, Bordetella spp, coronavirus, and Lyme Borrelia we re administered concomitantly to some dogs. This study provides the fi rst clinical evidence for a temporal relationship of vaccine associate d IMHA in the dog.