The goal of measuring serum antibody titers in companion animals is to provide a rational way of establishing whether an individual animal has an adequate antibody response to a given disease agent, and of using this information as a practical indicator of the need for revaccination. Antibody titers in this study population of dogs were likely a result of prior immunization combined with any natural exposure, and suggest that these dogs had adequate immunologic memory, the mechanism that provides animals with protection from clinical disease upon natural viral challenge.

Results of the present study indicate that adequate antibody titers to CPV were found slightly less consistently than to CDV. The number of dogs with an inadequate CPV titer but an adequate CDV titer (53 of 71; 75%) was significantly higher than the number of dogs with an inadequate CDV titer but an adequate CPV titer (15 of 33; 45%). Several factors may explain these findings. Some of the dogs with inadequate CPV titers may have been inadequately immunized as puppies. This occurs when maternally derived antibodies are at a high enough concentration to interfere with vaccination, but not high enough to provide protection. This could explain their poor immunologic response to revaccination as adults. In addition, certain breeds of dogs (e.g., Rottweiler, Doberman pinscher, Labrador retriever, Alaskan sled dog, pomeranian, and American Staffordshire terrier) have difficulty mounting an appropriate immune response to CPV. Serology could be performed after puppies in these susceptible breeds are vaccinated to determine whether an adequate immune response has been established.

Some dogs never appear to mount an adequate antibody response to vaccination, but remain healthy, presumably because of persistence of immune memory cells and development of cell-mediated and mucosal immune responses, or alternatively, lack of exposure to infectious virus. It may be appropriate to stop vaccinating these dogs, especially if they had experienced adverse reactions to vaccination in the past.

By measuring serum antibody titers annually, one can assess the level of a given dog’s humoral immune response to CPV and CDV. Results of the present study indicate that a large percentage of healthy dogs have serum antibody titers to CPV and CDV, regardless of duration of time since last vaccination. Moreover, of the dogs with a known CPV and CDV vaccination history, 133 of 142 (93.7%) and 127 of 136 (93.4%) dogs, respectively, had serum antibody responses even though they had last received a vaccine more than 2 years ago. These results support the contention that annual vaccination for these viral diseases is unnecessary in most cases.

References: Tizard, I and Ni, Y, JAVMA 213: 54-60, 1998; Shultz, RD, Vet Med 93: 233-254, 1998; Scott, FW and Geissinger, CM, Am JVet Res 60: 652-658, 1999; Dodds, WJ, Adv Vet Med 41: 715-732, 1999; Twark, L and Dodds, WJ, JAVMA 217: 1021-1024, 2000.