A Cross-Jurisdictional Model for Targeted Surveillance of Wild Bird Species

Abstract

Between 1/11/05 and 30/6/06 the laboratory processed 47 submissions of wild birds, comprising 103 individuals of 20 species, and encompassing 20 mass mortality events, as well as six individual bird mortalities. Diagnoses for the mass mortality events included:

• Organophosphorus compound (fenthion, fenamiphos and diazinon) poisoning
• Botulism
• Misadventure
• Necrotic enteritis

Just under half of the mass mortality events remained undiagnosed. This was attributed to a combination of poor sample quality and incomplete diagnostic workup as a consequence of funding constraints. In particular, the routine use of pesticide screens in these cases requires a formal cost-sharing agreement.

Most birds were tested at Biosecurity Sciences Laboratory (BSL) for the presence of Avian Influenza (AI) viruses using a real time RT-PCR developed at Australian Animal Health Laboratory (AAHL). Samples from a small number of healthy wild birds were also included for AI surveillance during an investigation into one of the larger mass mortality events. Two of 155 samples, derived from76 birds, gave low reactivity by PCR at BSL, but subsequently tested negative at AAHL. No AI viruses were isolated, and AI was excluded as a cause of mortality in all cases.

About half the submissions were screened for Newcastle Disease (ND) viruses, also using a real time RT-PCR developed at AAHL. All samples were negative. However, a ND virus was isolated, as an incidental finding, from cloacal swab samples which had tested consistently negative in the real-time PCR at both BSL and AAHL. The isolated virus was also consistently PCR-negative. This led to the suspension of the PCR for NDV screening of wild birds, pending the development of more appropriate primers.

Selected cases were investigated for the presence of West Nile Virus, with negative results. Material has also been referred to the Australian Registry of Wildlife Health for continuing investigations.

Cross-jurisdictional collaboration improved over the course of this project, with a greater range of participants than originally anticipated. This model was considered effective in gaining surveillance data on AIV in sick and dead wild birds. It was less effective in providing alternate diagnoses, and thereby increasing confidence in negative AIV findings. Some specific recommendations are made to improve the diagnostic rate and enhance disease surveillance; adequate funding is foremost amongst these.