Understanding and tackling Spotty Liver Disease in poultry

Understanding and tackling Spotty Liver Disease in poultry

RMIT researchers identified the bacterial species that causes Spotty Liver Disease in chickens and developed diagnostic tools for the serious issue that is affecting global egg production industries.

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Spotty Liver Disease chickens Campylobacter hepaticus egg production industry
Rob Moore profile photo he is smiling while wearing a suit and glasses

RMIT’s Professor Rob Moore is an internationally recognised veterinary microbiologist.

His research portfolio encompasses studies on bacterial pathogens, vaccination, genomics, gut microbiota, and probiotics. Moore’s research investigating host-pathogen interactions, and his collaborative work with industry includes significant contributions towards understanding the pathogenesis of Spotty Liver Disease in chickens.

Spotty Liver disease - the challenge

Spotty Liver Disease (SLD) in chickens is one of the most common and serious health issues for the Australian egg production industry. The infectious disease mainly affects free-range laying chickens, with outbreaks causing reduced egg production and increased mortality.

Monitoring of commercial poultry flocks has shown that the disease can cause up to a 15% increase in mortalities and 20% reduction in egg production. It is estimated that around 50 percent of flocks in Australia are currently being infected at some stage during their production cycle, resulting in around 9 million dozen eggs being lost each year. The direct cost of this issue for Australia’s $1.1 billion egg production industry is around $18 million per year.

Moore said that although SLD had been recognised for more than 50 years, its cause had remained a mystery.

“The disease remains an ongoing problem and all involved in the egg production industry are desperate to find a solution,” he said.

Successfully identifying the cause

In 2015, Moore’s team began a research program that aimed to identify the cause of the disease so that appropriate treatment options could be developed.

The team used a new high throughput DNA sequencing technology to provide clues about the bacterial pathogen that could be causing the disease.

By 2016 they had published research on successfully isolating, characterising, and naming a newly identified species of bacteria that they proposed was causing SLD, Campylobacter hepaticus. The team then published definitive proof that this species was the cause in 2017.

Recently, the group has isolated and identified a second novel species of Campylobacter, Campylobacter bilis, from a few SLD affected flocks in Australia. C. bilis is closely related but distinct from C. hepaticus.

Scanning electron micrographs of a colony of Campylobacter hepaticus. Scanning electron micrographs of a colony of Campylobacter hepaticus.

Developing tools to detect birds infected with Spotty Liver Disease

After identifying what was causing the disease, the team developed a sensitive and highly specific molecular test (PCR) for detecting the bacterial pathogen in clinical and environmental samples.

They also developed immunological assays to detect birds that have raised an immune response to infection.

For the first time globally, this allowed farmers and the egg production industry to accurately diagnose Spotty Liver Disease in flocks and to implement strategies to try and reduce its effects.

Moore said close collaborations with industry partners have been key throughout the research program.

Important collaborations included working with Scolexia Pty Ltd, a local veterinary consulting company that services a large proportion of the Australian egg layer industry.

“Scolexia have given us access to vital resources and information including clinical samples from the field, and knowledge about the disease, such as the extent and management of the disease in the poultry industry,” said Moore.

Research outcomes and impact

Identifying the global spread of the disease

Moore said the tests and assays developed by his team have allowed groups around the world to identify the disease, resulting in a new understanding of its global prevalence.

“Historically, Spotty Liver Disease was regarded as being an issue for farmers and the egg production industry mostly just in Australia and Britain,” he said. 

However, now that we can detect the bacteria and diagnose the disease correctly, it is being recognised as an issue around the world.

“In the last few years, reports have been published from the USA, New Zealand, Germany, Costa Rica, and Jordan.

“There are also anecdotal reports of cases being diagnosed in most European countries and many Asian countries that we hear about at conferences and through our network,” he said.

 

Understanding how the disease spreads, monitoring flocks, and reducing the risk

These diagnostic tools have also been used to complete epidemiological studies of SLD, allowing greater insights about when birds become infected and how the infection spreads. Insights include identifying that the faecal-oral route as the most likely means of transmission within a flock.

Moore said the tools have helped the poultry industry to monitor infections and assess the efficacy of biosecurity measures that they take to reduce the impact of the disease. Those now using the PCR test include laboratory services companies such as ACE Laboratory Services and local egg producing companies.

“The greatest impacts of our work so far have been enabling the poultry industry to identify and monitor the pathogenic agent,” he said.

“However, although the pathogen is most effectively managed using antibiotics, the animal production industries are rapidly moving away from using them, and so alternative methods of treatment are needed.

“The tools we have provided help to analyse the effectiveness of other approaches such as phytobiotics and probiotics, but to date no highly effective alternative treatment has been found.”

Transmission electron micrographs of Campylobacter hepaticus. Transmission electron micrographs of Campylobacter hepaticus.

Next steps – developing a vaccine against Campylobacter species

The research team is now collaborating with long-term partner Bioproperties Pty Ltd, a leading Australian manufacturer and a supplier of live vaccines to the worldwide farmed food animal industry.

The four-year $4 million Australian Research Council Linkage Project began in 2021 and aims to produce a general anti-Campylobacter vaccine for use in chickens. The London School of Hygiene and Tropical Medicine is also partnering with the team by providing technology for various aspects of the project.

The two streams of vaccine work include a focus on:

  1. Reducing Spotty Liver Disease in egg layers
    Vaccinating against Campylobacter hepaticus to reduce Spotty Liver Disease in flocks.
  2. Reducing Camplyobacter jejuni colonisation in broiler chickens
    Camplyobacter jejuni is well known to be the biggest cause of food poisoning in humans. Although this closely related species of bacteria doesn’t harm the chickens themselves, it causes food poisoning for humans that consume improperly prepared chicken meat.

The vaccine being developed is expected to be effective against both Camplyobacter jejuni and Campylobacter hepaticus.

The research was initiated by Professor Rob Moore and has been a long-term collaboration with Dr Hao Van, credited for the early laboratory work making the breakthroughs in culturing the bacteria. The early work that established a knowledge base has since been expanded with significant contributions from two RMIT PhD students, Canh Phung and Chithralekha Muralidharan.

Funding for this program of research has included support from Scolexia Pty Ltd, Australian Eggs, Poultry Hub Australia and from the Australian Government’s Innovation Connections scheme, Bioproperties Pty Ltd and an Australian Research Council Linkage Grant. 

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Acknowledgement of Country

RMIT University acknowledges the people of the Woi wurrung and Boon wurrung language groups of the eastern Kulin Nation on whose unceded lands we conduct the business of the University. RMIT University respectfully acknowledges their Ancestors and Elders, past and present. RMIT also acknowledges the Traditional Custodians and their Ancestors of the lands and waters across Australia where we conduct our business - Artwork 'Luwaytini' by Mark Cleaver, Palawa.

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aboriginal flag
torres strait flag

Acknowledgement of Country

RMIT University acknowledges the people of the Woi wurrung and Boon wurrung language groups of the eastern Kulin Nation on whose unceded lands we conduct the business of the University. RMIT University respectfully acknowledges their Ancestors and Elders, past and present. RMIT also acknowledges the Traditional Custodians and their Ancestors of the lands and waters across Australia where we conduct our business.

More information