Histomoniasis in turkeys: pathological observations and PCR detection

Histomoniasis was detected and described in naturally affected 35 turkeys. A polymerase chain reaction, which amplified a 209 bp region from the small subunit ribosomal RNA gene of H. meleagridis, was used and compared to the detection by histopathological observation of the histomonad trophozoits. In gross examination, typical histomoniasis lesions of hyperaemia and thickening of the cecal wall with grayish-yellow cecal cores were seen. In livers and kidneys, variably sized multiple foci of circumscribed necrotic areas were observed. Microscopically, varying amounts of histomonad trophozoits were detected in cecum (100%), liver (91.4%), kidney (17.1%), spleen (11.4%), proventriculus (5.7%) and bursa of Fabricius (2.8%). Mononuclear cell infiltration often containing giant cells in ceca, livers, kidneys and a proventriculus was observed. Lymphoid depletion was present in spleen and bursa of Fabricius. PCR assay detected the agent in cecum (100%), liver (100%), kidney (31.4%), spleen (25.7%), proventriculus (11.4%), bursa of Fabricius (11.4%) and lung (17.1%). This study describes histomoniasis lesions especially in several unusual locations such as kidney, spleen, bursa of Fabricius and proventriculus and could provide a help in the diagnosis of the natural histomoniasis in turkeys. It was also shown that PCR based detection was a more sensitive technique than detection based on histopathological observation.