Evidence for Marek's disease in turkeys in Germany: Detection of MDV-1 using the polymerase chain reaction

Since 1994 tumorous lesions have been monitored in turkeys on three farms i n Germany. On one of these farms, chickens also had tumorous lesions. Affec ted turkeys were retarded in growth, apathic, pale and almost unable to mov e. The older the animals got, the more indistinct the clinical signs became . Mortality started at an age of 5 weeks and reached between 20% and 60% by the end of the fattening period of about 20 weeks. The aetiological differ ential diagnosis includes reticuloendotheliosis (RE), lymphoproliferative d isease (LPD), lymphoid leukosis (LL) and Marek's disease (MD). Repeated ser ological examinations did not establish the presence of antibodies against REV, LLV or MDV-1. Cloacal swabs were negative for LL P27 antigen in ELISA. Solid tumors of various sizes as well as diffuse infiltrations were predom inantly seen in the liver, spleen and kidney. Pleomorphic cell infiltration was rarely noted in the plexus brachialis and nervus ischiaticus. Herpesvi rus of turkeys (HVT) was the only virus isolated from buffy coat cells deri ved from affected turkeys in chicken embryo kidney cell (CEK) and chicken e mbryo fibroblast (CEF) cultures. Use of polymerase chain reaction (PCR) for the amplification of the 132 bp repeat region provided evidence for the pr esence of MDV-1 DNA in tumor tissue from several diseased turkeys. No evide nce was found for the presence of REV.