APV INFECTION AND DISEASE IN ADULT PARROTS; THE PBFDV CONNECTION

APV readily infects adult parrots.30,36,44,48 Most infections, probably greater than 99.9% of then, are completely asymptomatic. These birds become infected, shed virus for a period of time, and never look or act ill. APV disease, however, has been documented in adult birds.24,25,46,50,58 So why do these few adult birds develop APV disease? The answer in most cases is that they are immunosuppressed with a concurrent infection of PBFDV.24,25,46 The author has documented an outbreak of APV disease in adult eclectus parrots.46 All birds had PBFDV. Disease has also been identified in adult cockatoos,24,25,34,58 again when these birds were tested for PBFDV, they have been found to be positive. I have previously mentioned that young adult lovebirds can die with APV disease. Again, concurrent infections with PBFDV may be the explanation for why. In the authors experience, on every occasion that APV outbreaks have occurred in lovebirds, PBFDV could also be found in the aviary.

PBFDV-infected birds are a common source for APV in an aviary.44 PBFDV-infected birds, like AIDS patients have a poorly functioning immune system. Therefore, if they become infected with APV they cannot clear the virus. Some of these birds will develop full blown APV disease and die. Most will become persistently infected. These persistently infected birds will then shed virus continuously from their skin and in their feather dust. This constant virus shedding contaminates the environment and makes it likely that it will be tracked into the nursery.

ARE CAIQUES MORE SUSCEPTIBLE TO APV INFECTION EVEN AS ADULTS, THAN OTHER PARROTS?

One of the first reports of APV disease in adult birds documented an outbreak where an eclectus, a painted conure, and 3 white-bellied caiques died.50 These birds clearly had APV-disease. They were not, however, tested for the PBFDV. So we do not know if this means that they were normal birds that have a predilection for APV disease, or were birds infected with PBFDV and were immunosuppressed. Since that time, the author has heard of a number of deaths in adult caiques. However, none of these birds were tested for PBFDV. Thus, the answer to this question remains elusive and requires further investigation. Because PBFDV may not cause histologic evidence of disease, the author feels that it is essential that when APV disease occurs in adult birds or in species where it is not normally a problem, that they be tested by DNA probes for the PBFDV.