Liver disease threatens egg production in free-range layer farms
Research from the University of Georgia shows Campylobacter hepaticus can infect multiple poultry breeds, causing liver damage, mortality and egg production losses.
Spotty liver disease has become an increasing concern for the global poultry sector, particularly in free-range egg production systems where outbreaks have been reported more frequently in recent years.
The disease is caused by the bacterium Campylobacter hepaticus, which triggers multifocal liver lesions, mortality in flocks and a drop in egg production, often appearing when hens reach peak laying performance. Because of its impact on productivity, the condition is drawing growing attention from researchers and poultry health specialists.
Scientists at the University of Georgia (United States) recently conducted experimental trials to determine whether different poultry breeds show varying levels of susceptibility to the pathogen. Their goal was to better understand how the disease behaves across commercial and breeding bird types.
The research evaluated five bird types commonly used in poultry production: Rhode Island White, Rhode Island Red, White Leghorn, broiler breeders and broilers.
A total of 30 birds per type were divided into groups and exposed to controlled doses of the pathogen. The birds were housed under similar conditions while researchers monitored clinical signs and disease progression.
To confirm infection, the team performed necropsies to identify liver lesions, alongside histopathology, microbiological tests and PCR analysis to detect the presence of the bacterium.
Results showed that Rhode Island Red and Rhode Island White birds developed the highest liver lesion scores, suggesting greater vulnerability to the disease. In contrast, White Leghorn hens showed significantly lower lesion scores, while broiler breeders and broilers presented levels similar to those observed in Leghorns.
Bacteriological testing indicated high prevalence rates-above 80%-in Rhode Island Red, Rhode Island White and broiler breeder birds. White Leghorn hens and broilers showed lower infection rates ranging between 40% and 50%, although the difference was not statistically significant.
These findings suggest that spotty liver disease can develop across multiple poultry breeds, indicating that no bird type is completely resistant to infection when exposed to the pathogen.
Persistent liver damage and treatment challenges
In a complementary study, researchers examined how long liver lesions remain in infected hens and whether they resolve without antibiotic treatment.
The trial involved 115 laying hens aged 24 weeks, with 80 birds receiving an oral challenge dose of Campylobacter hepaticus administered three times over consecutive days.
Sixteen days after infection, the hens were separated into two groups. One group received chlortetracycline through feed for five days, while the other group remained untreated.
To evaluate the spread of the disease, researchers introduced sentinel birds into both groups, allowing them to monitor potential horizontal transmission between infected and healthy hens.
The results showed that liver lesions remained present in birds that did not receive antibiotic treatment, confirming that the infection can persist within flocks. Birds treated with chlortetracycline displayed lower liver lesion scores, indicating that treatment reduced disease severity.
However, the antibiotic did not fully eliminate the bacterium nor stop transmission, as more than half of the treated and sentinel birds still tested positive during bacteriological analysis.
The research highlights that Campylobacter hepaticus can remain active within poultry flocks, reinforcing the need for stronger biosecurity strategies, flock monitoring and disease management practices to protect egg production systems.
