Hygiene Protocols for the Prevention and Control of Diseases (Particularly Beak and Feather Disease) in Australian Birds

Department of the Environment and Heritage, 2006

2. Recommendation for a Quarantine Period to Avoid Spread of BFDV between Populations (TAP Action 2.4)

Quarantine means a place of isolation where birds of unknown health status may be maintained and subjected to health checks for a period before being introduced to a healthy population after passing the health checks. To eliminate the possibility of transferring pathogens to the "disease-free" breeding flock, the quarantine module is preferably separate to the facility where birds are maintained for breeding. A recommendation for a quarantine period necessary to avoid spreading pathogens, especially BFDV, between bird populations, will be recommended.

The quarantine described in this section is aimed at psittacine birds, but with slight modification can be adapted to any bird species.

BFDV is a non-enveloped virus and is extremely difficult to inactivate physically or chemically. A proposed quarantine period will be based on the detection of antigen and antibody for BFDV. Obviously, a quarantine protocol for an endangered species should not address BFDV alone. Other pathogens that can significantly affect the viability of a captive population and which are considered of quarantine importance include:

Incubation period of PBFD

Please read an explanation of how the Haemagglutination (HA) and Haemagglutination Inhibition (HI)(PDF - 34 KB) tests are conducted and interpreted.

With current knowledge and under natural conditions, it is not possible to place a maximum time on the incubation period for PBFD, since the time of infection is usually unknown. In nestling cockatoos, the incubation period of PBFD is a minimum of 21 to 28 days following the intravenous injection of the virus, and so will be variably longer for a natural infection, depending on the species and even among individuals of the same species (Raidal et al., 1993). Raidal (1994) reported that in susceptible galah chicks the onset of clinical signs ranged from 30 to 72 days, and with susceptible sulphur-crested cockatoo (SCC) chicks 28 days. Ignoring absence of powder downs (in those species that produce powder downs), a moult is necessary to express lesions in the plumage and this could take up to 12 months (as long as the bird is HI negative). Some infected birds remain feather lesion-free before they become stressed and succumb. Some infected birds can appear healthy and produce infected young (Raidal, 2005). Raidal (2005) advised that PCR screening of blood is the most sensitive way of detecting infection followed by PCR on feathers and HA testing of feathers or faeces. HI testing on a flock basis also reveals whether the flock is infected. The most practical recommendation for detecting BFDV antigen is a minimum of two separate blood and feather PCR tests at least 1 month apart (Raidal, 2005). However, some BFDV positive birds might remain undetected and a further test after 4 weeks is advisable. HA testing provides a quantifiable indication of virus excretion and, when used in conjunction with PCR, provides a valuable internal control mechanism for interpreting results. From a diagnostic view point it is advantageous to know both results. By applying all 4 tests on a flock basis (PCR blood, PCR feather, HA feather, HI blood) it is possible to detect early viraemia and antibody and antigen in feathers. If repeated 4-6 weeks later, any developing antigen or antibody can be detected. A further test 4-6 weeks later would detect late developing antigen or antibody.

Other tests being developed for antibody detection such as ELISA (enzyme-linked immunosorbent assay) and latex agglutination (LA) may provide more sensitive and accurate methods for assessing seroconversion in individual birds being held in quarantine and may be able to differentiate antibody response to experimental vaccination from natural infection.

Conclusion

A quarantine period of at least 63 days is recommended, with testing for BFDV at day 0, day 28 and day 56, leaving a week for results to be delivered.