Induction of spotty liver disease in layer hens by infection with Campylobacter hepaticus.

Spotty liver disease (SLD) in chickens can present with variable impacts on mortality and production, ranging from sporadic mortalities of individual birds and no notable impact on production to severe reduction in egg output and increased mortality in layer flocks of greater than 1% per day. It was first described over 60 years ago and there have been sporadic reports of the disease throughout the intervening decades, particularly in the US, UK and Germany. Recently it has become of increasing concern as outbreaks of the disease have occurred more frequently, particularly in the Australian poultry industry. An understanding of the causes of the disease has proven elusive. However, recent studies of SLD have strongly implicated a novel Campylobacter species, Campylobacter hepaticus, as the causative agent. Here we demonstrate that C. hepaticus is highly invasive in LMH cells, an immortalised chicken hepatoma cell line, and can induce disease when orally delivered to mature layer birds. Challenged birds developed liver lesions, typical of those seen in field clinical cases, within 5days of challenge. The bacterium used to challenge the birds could be recovered from the diseased liver and from bile, thus demonstrating that C. hepaticus is the causative agent of chicken SLD.

Campylobacter hepaticus sp. nov., isolated from chickens with spotty liver disease.

Ten strains of an unknown Campylobacter species were isolated from the livers of chickens with spotty liver disease in Australia. The strains were Gram-stain-negative, microaerobic, catalase- and oxidase-positive and urease-negative. Unlike most other species of the genus Campylobacter, most of the tested strains of this novel species hydrolysed hippurate and half of them could not reduce nitrate. All strains showed resistance, or intermediate resistance, to nalidixic acid and most of them were resistant to cephalothin. Examination of negatively stained cells under transmission electron microscopy revealed that they were S-shaped, with bipolar unsheathed flagella. Phylogenetic analyses based on the 16S rRNA gene and the heat shock protein 60 (hsp60) gene sequences indicated that the strains formed a robust clade that was clearly distinct from recognized Campylobacter species. Unusually, they had a DNA G+C content of 27.9 mol%, lower than any previously described Campylobacter species, and they showed less than 84 % average nucleotide identity to the nearest sequenced species. Taken together, these data indicate that the strains belong to a novel Campylobacter species, for which the name Campylobacter hepaticus sp. nov. is proposed. The type strain is HV10T (=NCTC 13823T=CIP 111092T).