Page 9 - NPN0922

Spotty liver disease in poultry
SPOTTY liver disease is an emerging disease in extensively housed poultry.
been recognised for over 60 years, it is only in the past decade that the disease has become a significant issue for the layer industry, with the change away from cages to extensive production systems.
Flocks can recover from low level inci- dences of SLD sponta- neously or in more sig- nificant outbreaks after therapeutic intervention following treatment with chlortetracycline.
rial species that we have named campylobacter hepaticus – see Figure 2.
It’s most commonly seen in free range layer hens but has also been reported in broiler breeders.
Commonly, the disease becomes clinically evi- dent when flocks are ap- proaching peak lay.
A feature of SLD is that disease outbreaks can re- occur multiple times, re- quiring repeat treatment.
We have developed PCR-based methods for the specific detection of c hepaticus in complex biological samples, for example intestinal con- tents.
The signs of disease are variable, ranging from low bird mortality with minimal impact on pro- duction to a sudden onset of significant mortality with a reduction in egg production.
SLD can occur at any age but particularly when layer production flocks are experiencing husbandry or environ- mental stressors.
Despite decades of looking for the aetio- logical cause of SLD, it was only in 2015 that the bacterial cause of the disease was identi- fied – first by an English research group and then confirmed and charac- terised more extensively here in Australia.
The collaborative part- ners have established an experimental disease- induction model that produces typical clinical SLD in layers and this is now being used to study the mechanisms of dis- ease pathogenesis.
Such impacts on bird health and productivity have serious economic consequences for egg producers in the expand- ing free range layer sec- tor in Australia.
When mortalities are investigated the birds are found to have lesions in the liver – usually the surfaces of all lobes are covered in 1-2mm pale spots, as per Figure 1.
Collaborative research carried out by RMIT University and Scolexia Pty Ltd led to the isola- tion and characterisation of the bacterial patho- gen responsible for caus- ing SLD in Australian flocks.
Recognising the nega- tive impact to the layer industry, Australian Eggs is supporting the collaborating partners to use their disease mod- el to evaluate potential ways to control the dis- ease or lessen its impact.
Figure 1. Liver lesions seen in a typical field case of spotty liver disease.
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Additional to these productivity losses is the costs associated with treatment during out- breaks of SLD and cur- rent attempts at imple- menting non-antibiotic in-feed preventative pro- grams.
It is assumed that the pathogenesis of SLD, which results in damage to the liver, is causally associated with the de- pressed egg production and increased mortali- ties.
The pathogen has been identified as a new bacte-
Vaccine formulations are being developed by ACE Laboratories and tested in the disease model and various non- antibiotic feed additives – such as short and me- dium chain fatty acids, probiotics and plant ex- tracts – are being evalu- ated for their efficacy in preventing or ameliorat- ing the impact of SLD.
Though the disease has
Figure 2: Transmission electron micrograph of campylobacter hepaticus. Note the typical s-shaped cell and bipolar flagella.
With a continued dedi- cated research effort and support from Austral- ian Eggs, industry and other funding bodies, we aim to understand more about the disease and develop control methods that poultry farmers can implement to improve the health, welfare and productivity of their egg production flocks.
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National Poultry Newspaper, September 2022 – Page 9