Dogs that develop rabies post-vaccination usually manifest the paralytic subtype

Rabies infection can manifest as either encephalitic (furious) or paralytic (dumb) types, with a ratio of approximately 2:1 in dogs. The clinical type of rabies that develops post-vaccination has only been reported in studies from one country, all with similar findings. We report a study of 36 rabid dogs with obtainable vaccination history, presenting to The Queen Saovabha Memorial Institute, Bangkok, Thailand during 2002-2008. Dogs were classified into encephalitic or paralytic types. Of 22 non-vaccinated dogs, 16 (73%) had the encephalitic type. In contrast, of the 14 vaccinated dogs, 10 (71%) had the paralytic type, a difference that was significant (p=0.016). Recent studies on canine brains have shown that lymphocyte response is more pronounced in paralytic rabies at the brainstem level, whereas viral burden is greater in the encephalitic form. We postulate partial immune response in the vaccinated dogs might influence rabies to manifest as the paralytic type. These results can serve as a natural experiment that can help explain the basis for the differences between the paralytic and encephalitic forms of canine rabies.