Pathologic characterization of coinfection with Histomonas meleagridis,Marek’s disease virus, and subtype J avian leukosis virus in chickens

Histomonas meleagridis (H. Meleagridis ) is a trichomonad protozoan parasite, which can cause an important poultry disease known as histomoniasis; Marek’s disease virus (MDV ) and subtype J avian leukosis virus (ALV-J) usually cause avian oncogenic diseases. Although these diseases have been reported in single pathogen infection, information about their coinfection is scarce . This study reports a naturally occurring case of coinfection with H. meleagridis , MDV, and ALV-J in local chicken flock at the age of 150 days. Necropsy revealed necrosis and swelling in the liver and spleen. Histological analysis showed large areas of mild to severe necrosis of hepatocytes with numerous intralesional trophozoites of H. meleagridis by hematoxylin and eosin (H&E) and periodic acid-Schiff staining ; H&E staining showed pleomorphic and neoplastic lymphoid tumor cells in the liver and myeloid cells with eosinophilic cytoplasmic granules in the spleen. Coexpression of MDV and ALV-J a ntigens was detected in the liver by fluorescence multiplex immunohistochemistry staining . The   18S rRNA gene of H. meleagridis , meq gene of MDV, and gp85 gene of ALV-J were identified in mixed liver and spleen tissues by PCR and sequencing, respectively.