Abstract
The epidemiology of Spotty Liver Disease (SLD) was investigated by assaying 1,840 samples collected from layer chickens and the environment in poultry farms across Australia for the presence of Campylobacter hepaticus, the agent responsible SLD in chickens. A C. hepaticus specific PCR and bacterial culture were used. Results showed that birds could be infected with C. hepaticus up to 8 weeks before clinical SLD was manifested. In addition, birds could be infected long before laying starts, as young as 12 weeks old, but the peak period for SLD outbreaks was when the birds were 26–27 weeks old. Campylobacter hepaticus DNA was detected in motile organisms such as wild birds and rats and so these organisms may be vectors for C. hepaticus dissemination. Moreover, water, soil, mites, flies, and dust samples from SLD infected farms were also found to be PCR-positive for C. hepaticus DNA. However, it still remains to be determined whether these environmental sources carry any viable C. hepaticus. The indications from this study are that environmental sources are a likely transmission source of C. hepaticus. Therefore, biosecurity practices need to be strictly followed to prevent the spread of SLD amongst and between flocks. Also, a rapid, molecular detection method such as PCR should be used as to monitor for C. hepaticus presence in flocks before clinical disease is apparent, and therefore inform the use of biosecurity and therapeutic measures to help prevent SLD outbreaks.
Highlights
Spotty Liver Disease (SLD) has been a persistent problem in the Australian and UK poultry industries for several decades and its presence in North America has recently been confirmed [1,2,3]
Clinical SLD outbreaks were observed in two of the three farms that were monitored over 10 weeks
SLD occurred during peak-laying age at 26 and 28 weeks of age; this timing agrees with previous reporting of the most common age at which disease is seen [4]
Summary
Spotty Liver Disease (SLD) has been a persistent problem in the Australian and UK poultry industries for several decades and its presence in North America has recently been confirmed [1,2,3]. In Australia, SLD was first noted in the 1980s [4, 5] and the disease is regarded as one of the most important disease challenges for the Australian egg industry [6]. SLD outbreaks most commonly occur when the birds are reaching the peak of lay and the outbreaks can happen all year round [1, 4]. SLD has been recognized for many years, perhaps as early as 1954 in the USA [7], the etiology of the disease was only determined recently, when a novel Campylobacter was isolated The disease is prevalent in free-ranging flocks but sporadically occurs in other housing systems such as conventional cages, controlled environmental cages, and barn systems [4].
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