Canine Fatalities Associated with the use of a Modified Live Vaccine Administered during Late Stages of Pregnancy

Abstract

Commencing in November 1992, tissue samples from 10 cases of canine abortion were submitted to the Washington Animal Disease Diagnostic Laboratory for analyses. A common feature was a history of vaccination of the pregnant dam, 34 weeks prior to whelping, with a modified live virus (MLV) multi-component canine vaccine (MLV canine distemper, adenovirus type 2, Parainfluenza , and parvovirus) reconstituted with a killed canine coronavirus vaccine. A cytopathic agent was identified in Vero cells and Crandell feline kidney (CrFK) cells (after repeated passage) inoculated with tissues originating from the dams. No evidence of the usual abortigenic agents of dogs, such as Brucella canis and canine herpesvirus, was found from histopathology, virology, or bacteriology. 6,9 Because the common link among the cases was the use of the MLV vaccine during late-term pregnancy, it was speculated that disease resulted from a virulent component of the vaccine, such as canine parvovirus (CPV). Although isolation attempts were negative for CPV, multiple other viruses isolated had properties consistent with members of the family Reoviridae. 1 In this paper, we present the laboratory findings from 3 naturally occurring cases of canine disease associated with the administration of an MLV canine vaccine during late stages of gestation. This study was a collaborative project with investigators at the Veterinary Biologics Laboratory (National Veterinary Services, Ames, IA). An adjunct report on the properties of the viral isolate and its subsequent identification as bluetongue virus are the subject of a separate report. 15