Spotty liver disease (SLD) affects free-range laying hens, leading to mortality and reduced egg production. Campylobacter species, including Campylobacter hepaticus, have been associated with SLD cases worldwide. However, the cause of SLD-like lesions found in broilers in Japan still remains unclear. The present study aimed to investigate the involvement of Campylobacter spp. in broiler SLD by conducting microbiological, molecular biological, serological, histopathological, and immunohistopathological examinations using specimens of liver, bile, cecum, and serum from SLD-like and non-SLD chickens. C. jejuni was predominantly isolated and detected in approximately 40% of both non-SLD livers and SLD-like livers, with no significant difference between them. However, C. hepaticus was neither isolated nor detected in this study. Gross and histopathology revealed multifocal necrotizing hepatitis, suppurative granulomatous hepatitis, and cholangiohepatitis. Hepatitis stages are classified as no hepatitis, subclinical, acute, and chronic hepatitis. C. jejuni was more frequently present in acute-stage SLD-like livers, and high IgG antibody levels were noted in both subclinical and SLD-like-affected chickens, indicating C. jejuni infection. Immunohistochemical examination also supported these findings. The findings suggest that C. hepaticus was not involved in SLD-like in broilers in Japan, but C. jejuni translocation from the intestines to the liver may be a contributing factor.

Spotty liver disease (SLD) affects free-range laying hens, leading to mortality and reduced egg production. Campylobacter species, including a novel strain, Campylobacter hepaticus, have been associated with SLD cases worldwide. However, the cause of SLD like lesions found in broilers in Japan is still remains unclear. The present study aimed to investigate the involvement of Cam-pylobacter spp. in broiler SLD by conducting microbiological, molecular, serological, histopatho-logical, and immunohistopathological examinations using specimens of liver, bile, cecum, and serum from SLD-like and non-SLD chickens. C. jejuni was predominantly isolated and detected in approximately 40% of both non-SLD livers and SLD-like livers, with no significant difference between them. While C. hepaticus was neither isolated nor detected in this study. Gross and his-topathology revealed multifocal necrotizing hepatitis, suppurative granulomatous hepatitis, and cholangiohepatitis. Hepatitis stages classified as no hepatitis, subclinical, acute, and chronic hepatitis. C. jejuni was more frequently present in acute-stage SLD-like livers, and high IgG an-tibody levels were noted in both subclinical and SLD-like-affected chickens, indicating C. jejuni infection. Immunohistochemical also supported these findings. The findings suggest that C. he-paticus was not involved in SLD-like in broilers in Japan, but C. jejuni translocation from the in-testines to the liver may be a contributing factor.