Spotty Liver

Introduction:

Spotty Liver Disease (SLD) caused by the Campylobacter hepaticus and/or Campylobacter Bilis is a common disease in free-range and barn egg production chickens. The incidence of SLD in Australian and New Zealand flocks has steadily increased as the non-caged production sector has increased. It has previously been reported as a ‘summer’ disease, however it is widely noted that SLD outbreaks can occur year-round.

How does it cause disease?

The cause and pathogenesis of the disease are yet to be determined. Significant amount of research is underway to identify risk factors associated with SLD outbreaks to determine how Campylobacter causes disease.

The faecal-oral route of infection is a known route of transmission and is consistent in the presentation that SLD mostly occurs in free-range and barn birds that have access to manure.

C.Hepaticus is found throughout the small intestine and is in high abundance in the cecum. Despite the clinical signs being primarily focused on the liver, the bacteria do not reside in the liver and cultures of the liver will not result in detection. It is speculated that the liver damage (white spots) may be a result of a hepato-toxin produced by the bacteria that results in small necrotic areas which disrupts liver function.

Clinical Signs:

The disease has variable impacts on performance and mortality, ranging from low impact to significant mortality figures of 15%, and a 35% reduction in egg production. The impact on mortality and productivity of the flock has a substantial economic impact for egg producers that are expanding into the free-range and barn layer sector.

On post-mortem of affected birds, a clinically diagnostic and obvious manifestation of the disease is the appearance of small whitist-grey spots on the surface of the liver, generally impacting all the liver lobes. Additional findings may include ascites (fluid around the heart), and general peritonitis.

When do we see it?

Commonly, the disease often becomes clinically evident when the flocks are approaching the peak lay period typically around 25-30 weeks of age. Despite this, SLD can occur at any age especially if they experience operational, environmental or husbandry stressors. A significant feature of SLD is that disease outbreaks can reoccur multiple times throughout a single batch, requiring long-term repeat treatments.

To control and treat SLD, antibiotic treatment using Chlortetracycline, Amoxicillin or Lincospectin in water and feed, or a combination of both has been effective. It must be noted that resistance of SLD to these treatments is increasing which reduces the effectiveness of treatment in future outbreaks.

Currently, the best approach to minimising the impact of SLD is to maintain high standards of biosecurity and minimising husbandry and environmental stressors. Reducing standing water in the range, control pests and rodent populations and reduce environmental stressors will provide the greatest protection against an SLD incursion.

Feed additives including organic acids, short and medium chain fatty acids, probiotics and phytobiotics have been used in affected flocks with limited success.

Autogenous vaccines are being utilised in Australia as a mitigation strategy, with varying degrees of success.

Risk Factors

The risk of SLD increases substantially when the birds have access to a scratch area as opposed to a fully slatted house. Scratch area allows closer contact of the birds with manure and fecal droppings which increases the likelihood of the birds ingesting the bacteria. A fulyl slatted floor restricts this access.

Current unpublished research also suggests correlations with temperature controlled sheds around the peak of lay period, and the nest box density ratios and the occurrence and severity of SLD outbreaks.

Economic Impact

In a cost model study presented by Courtice and Jenner (2022), a flock of laying hens that experienced an outbreak of SLD, resulting in a mortality of 6%, and a 7.2% egg production drop, the net economic cost to the outbreak resulted in a loss of AUD $4.24 per hen. This impact to a commercial operation is significant and costly for the producer.

To work on a treatment plan please reach out to the Hatch House Veterinarians through our contact page. We stand ready to help you with your animal health needs.

Written by Hatch House Senior Veterinarian

Alex-Kate Langfield BVetBiol/BVSc