Salmonella event isolated from a mass mortality of birds

Grillo T, Cox-Witton K, Gilchrist S and Ban S.

In October 2016, more than 30 birds were found dead within the grounds of a pet shelter in an inner Melbourne suburb. Daily mortalities of house sparrows (Passer domesticus) and at least two dead spotted turtle-doves (Streptopelia chinensis) presented dead or moribund over a period of more than one month.

Dead birds were submitted to the Victorian veterinary diagnostic laboratory, AgriBio (Bundoora) for investigation. Gross pathology of examined birds included enlarged livers with multifocal pallor and enlarged spleens. Avian influenza (AI), avian paramyxovirus and Chlamydia spp. were excluded by PCR testing.

Histopathological lesions included histiocytic and lymphoplasmacytic hepatitis and splenitis with numerous intracytoplasmic and extracellular gram negative coccobacilli. A Salmonella isolate recovered from the liver and faeces of submitted birds (both P. domesticus and S. chinensis) was referred to the Microbiological Diagnostic Unit Public Health Laboratory (Melbourne University) for identification, where it was identified as Salmonella enterica subsp. Enterica serotype Typhimurium DT160 (S. Typhimurium DT160). The Department of Health and Human Services was notified.

This is the first diagnosis of S. Typhimurium DT160 in wild birds in Victoria (and in mainland Australia). S. Typhimurium DT160 is considered enzootic in Tasmania and has been diagnosed in 13 investigations involving house sparrows. Infected wild birds (for example, sparrows) have the potential to be sources of infection for humans, domestic animals and native animal and bird species. S. Typhimurium has significant zoonotic potential, with a small number of human cases diagnosed in Australia to date.