P.PSH.2054-Abattoir survey of ovine pneumonia pathogens in Australian sheep flocks

Summary

Pneumonia in sheep (Ovine Respiratory Complex, ORC) is a complex disease involving the interaction of pathogen, host and environmental factors. During 2018–19 Joan Lloyd Consulting Pty Ltd and Meat & Livestock Australia co-funded pilot research on ORC pathogens circulating in Australian sheep flocks (P.PSH.0814). This project was focused on method development, including culture and Polymerase Chain Reaction (PCR), but also revealed widespread infection with Mycoplasma ovipneumoniae in Australian slaughter sheep sampled at abattoirs in SA and NSW.

A recommendation from the pilot research project was a larger abattoir survey of respiratory pathogens in Australian slaughter sheep be undertaken. The current project is an abattoir survey of respiratory pathogens in Australian slaughter sheep. The aim of the project was to build on the research findings of Project P.PSH.0814 and provide further information on the prevalence of the ovine respiratory pathogens circulating in sheep flocks in Australia, including sheep from NSW, Queensland, SA, Tasmania, Victoria and WA.

Objectives

The objective of this project was to provide information on the prevalence of the common ovine respiratory pathogens circulating in sheep flocks in south-eastern Australia.

Key findings

The project has revealed widespread infection with M. ovipneumoniae in Australian slaughter sheep, with 64.4% of abattoir lots testing positive for the bacterium. Abattoir lots positive for M. ovipneumoniae originated in NSW, Queensland, SA, Tasmania, Victoria and WA. Of the abattoir lots tested, 39.8% were positive for M. haemolytica and 15.3% were positive for P. multocida. Small numbers of abattoir lots tested positive for ovine Respiratory Syncytial Virus (2.4%) and ovine Parainfluenza Virus 3 (2.0%).

Benefits to industry

Previously the role of M. ovipneumoniae in pneumonia in Australian sheep has been overlooked, with emphasis instead placed on the easier-to-culture bacteria M. haemolytica and P. multocida. New diagnostic methods based on PCR have allowed this project to detect much wider infection with M. ovipneumoniae in Australian sheep than recognised to date.

Pleurisy/pneumonia is common in Australian slaughter sheep. The project finding of widespread infection with M. ovipneumoniae in Australian sheep will help sheep producers and their veterinarians put in place appropriate management and treatment strategies to better control outbreaks of disease. Better control and/or prevention of outbreaks of pleurisy/pneumonia will have animal welfare and economic benefits for industry.

MLA action

To achieve full value from the project, a communications strategy for the key project finding of widespread infection with M. ovipneumoniae should be developed. It is recommended that information on the project findings be included on the Meat & Livestock Australia and Animal Health Australia websites, as well as an article in the Meat & Livestock Australia Feedback magazine, and for existing resources on pneumonia in sheep to be updated to include information on M. ovipneumoniae.

Future research

In the immediate future, a well-designed comparison of the various options to control respiratory disease in feedlot sheep is recommended, with assessment to include clinical, abattoir and meat science parameters. A contract research organisation experienced in conducting pharmaceutical and vaccine efficacy assessments would be best placed to conduct this study for industry.

In the longer term, consideration could be given to funding research on the feasibility of test and segregation for control of M. ovipneumoniae infection in flocks or mobs of sheep.
Mycoplasmal infections are notoriously difficult to eliminate with antibiotic treatments, whereas vaccination is complicated by the immunopathological mechanisms that contribute to the disease processes associated with infection. Test and segregation may provide a viable alternative to reduce the prevalence of Mycoplasma ovipneumoniae infection in the Australian sheep flock and the significant economic cost the current high prevalence of infection is undoubtedly causing. A series of individual farm case studies with highly motived producers is one approach to consider for this work.