Vaccination strategies for PBFD

Psittacine Beak and Feather Disease (PBFD) is regarded is a key pathogen of parrots, cockatoos and other psittacine birds throughout Australia. The development of a vaccine to control the disease has been a high priority for the Threatened Species Strategy (2015) especially for the Orange-bellied Parrot (Neophema chrysogaster) which was identified as a species for emergency intervention following the re-emergence of unique BFDV genotypes in this species. PBFD is considered a high threat in captive breeding flocks of endangered species not only because of its direct effect on susceptible birds but also because of the immunosuppressive effect it may have on a flock. Secondary threats due to opportunistic microbial infections have all recently contributed to mortalities and ill-health in captive Orange-bellied Parrots. Since 1993 vaccination has been shown experimentally to be useful for preventing PBFD but the development of a reliable and safe antigen supply has been hampered by an inability to grow the virus in cell culture. Difficulties in reliably producing synthetic antigen using recombinant technologies also impeded advances in vaccine research. Producing this protein synthetically has presented a number of challenges to researchers such as low endogenous expression and poor solubility and stability. Working closely with Tréidlia Biovet, we have produced consistent batches of vaccine to conduct field trials with more than 300 vaccine doses administered. Vaccine reactions have been minimal with no adverse skin or muscle lesions detected so far. Preliminary serological data provides good confidence that the vaccine is tolerated producing an effective immune response in both none infected and early PCR positive birds. As expected vaccination of parrots already affected by chronic PBFD had little effect on the infection status but we did detect a reduction in virus load in some individuals. More importantly we detected a clearance of virus infection in 2 out of 3 lorikeets that were clinically PBFD-affected. Preliminary results also indicate that otherwise clinically normal Orange-bellied parrots and Bourke’s parrots with early signs of BFDV infection (PCR positive) might be able to clear the infection and mount a HI antibody response. This was an unexpected result which can have a significant beneficial change in management practices to the captive recovery program.