Avian influenza in Australia: a summary of 5 years of wild bird surveillance.

BACKGROUND: Avian influenza viruses (AIVs) are found worldwide in numerous bird species, causing significant disease in gallinaceous poultry and occasionally other species. Surveillance of wild bird reservoirs provides an opportunity to add to the understanding of the epidemiology of AIVs. METHODS: This study examined key findings from the National Avian Influenza Wild Bird Surveillance Program over a 5-year period (July 2007-June 2012), the main source of information on AIVs circulating in Australia. RESULTS: The overall proportion of birds that tested positive for influenza A via PCR was 1.9 ± 0.1%, with evidence of widespread exposure of Australian wild birds to most low pathogenic avian influenza (LPAI) subtypes (H1-13, H16). LPAI H5 subtypes were found to be dominant and widespread during this 5-year period. CONCLUSION: Given Australia's isolation, both geographically and ecologically, it is important for Australia not to assume that the epidemiology of AIV from other geographic regions applies here. Despite all previous highly pathogenic avian influenza outbreaks in Australian poultry being attributed to H7 subtypes, widespread detection of H5 subtypes in wild birds may represent an ongoing risk to the Australian poultry industry.

Specificity of an immunochromatographic test for anthrax.

OBJECTIVE: To evaluate the specificity of an immunochromatographic test (ICT) for anthrax in cattle. DESIGN: A comparison of an ICT with blood smear and culture in uninfected cattle. PROCEDURE: Two hundred and forty blood samples were collected from dead cattle at two knackeries within Victoria and tested on-site with an ICT for the detection of protective antigen (PA) of Bacillus anthracis. Blood smears were prepared on-site and blood samples transported to the laboratory for aerobic and anaerobic culture. The results of the ICT were compared with blood smear and culture. Animals were regarded as not infected with B anthracis if the organism was not detected in a stained blood smear or on culture. Ten healthy yearling cattle were vaccinated with live spore anthrax vaccine and blood samples collected on days 0 to 7 and day 15 were tested in the ICT for the presence of PA. RESULTS: All blood samples from the 240 knackery cattle were ICT, smear and culture negative. All blood samples from the 10 vaccinated cattle were ICT negative. CONCLUSION: The ICT is a test with high specificity in cattle (98.5 to 100%; 95% CI) and recent vaccination of cattle does not give rise to positive reactions.

Detection of avian paramyxoviruses and influenza viruses amongst wild bird populations in Victoria.

OBJECTIVE: To isolate and characterise avian paramyxoviruses and other haemagglutinating viruses amongst Victorian wild bird populations. PROCEDURE: Tracheal and cloacal material was collected from wild duck, pigeon, quail and other wild birds throughout Victoria. Samples were processed and cultured in embryonating eggs. Viral isolates were characterised based on their haemagglutination and haemagglutination-inhibition activity using a panel of specific antisera. Reverse transcriptase polymerase chain reaction and DNA sequencing were used to characterise Newcastle disease virus isolates. RESULTS: Twenty-five nonpathogenic haemagglutinating viruses were isolated from 605 wild bird samples. The majority were characterised as APMV-6 or influenza A virus, H3N2. Two isolates were identified and characterised as APMV-1 (avirulent NDV) based on nucleotide and deduced amino acid sequence analysis at the F0 cleavage site. CONCLUSIONS: Twenty-five viruses were isolated, none of which resembled progenitor or virulent genotypes. This study provides valuable epidemiological information against which to compare future isolates from outbreaks of disease to determine their origin.

Molecular characterisation of Victorian Newcastle disease virus isolates from 1976 to 1999.

OBJECTIVE: To characterise Newcastle disease virus isolates obtained in Victoria from 1976 to 1999 and identify the diversity of FO cleavage signal. DESIGN: RT-PCR using viral RNA extracted from positive NDV allantoic fluid was performed to amplify a segment of the NDV F and HN genes. Molecular characterisation of the nucleotide and amino acid sequences within the FO cleavage site was undertaken. RESULTS: All isolates contained 'avirulent FO cleavage signal sequence of varied amino acid composition. CONCLUSIONS: Molecular characterisation of past and present NDV FO cleavage signal sequences will provide valuable epidemiological information and assist in understanding the genetic origins and relationships of outbreaks.