Causes of morbidity and mortality of wild aquatic birds at Billabong Sanctuary, Townsville, North Queensland, Australia.

Infectious diseases are common causes of significant morbidity and mortality events of wild aquatic birds (WABs) worldwide. Reports of Australian events are infrequent. A 3-yr passive surveillance program investigating the common causes of morbidity and mortality of WABs was conducted at Billabong Sanctuary near Townsville, North Queensland, from April 2007 to March 2010. Forty-two carcasses were obtained and evaluated by clinico-pathologic, histologic, bacteriologic, and virologic (molecular) examinations. Morbidity and mortality were sporadic and more commonly observed in chicks and juvenile birds in April than other months of the year. Morbid birds were frequently unable to walk. Hemorrhagic lesions and infiltration of lymphocytes in various organs were the most common findings in dead birds. Identified bacterial diseases that could cause bird mortality were colibacillosis, pasteurellosis, and salmonellosis. Salmonella serotypes Virchow and Hvittingfoss were isolated from an Australian white ibis (Threskiornis molucca) chick and two juvenile plumed whistling ducks (Dendrocygna eytoni) in April 2007. These strains have been previously isolated from humans in North Queensland. A multiplex real time reverse transcriptase-PCR (rRT-PCR) detected Newcastle disease viral RNA (class 2 type) in one adult Australian pelican (Pelecanus conspicillatus) and a juvenile plumed whistling duck. No avian influenza viral RNA was detected from any sampled birds by the rRT-PCR for avian influenza. This study identified the public health importance of Salmonella in WABs but did not detect the introduction of the high pathogenicity avian influenza H5N1 virus in the population. A successful network was established between the property owner and the James Cook University research team through which dead birds, with accompanying information, were readily obtained for analysis. There is an opportunity for establishing a long-term passive disease surveillance program for WABs in North Queensland, an important region in Australian biosecurity, thus potentially significantly benefitting public health in the region and the country.