Central nervous system syndrome associated with Marek's disease in Hubbard broilers

Marek's disease (MD) has a high economic impact in poultry production worldwide. MD consists of several pathologic syndromes of which the most commonly encountered are lympho-proliferative syndromes such as acute MD. Sporadically, MD leads to central nervous system syndromes characterized by non-neoplastic brain pathology. In this case report, an onset of neurological signs on two different broiler farms, housing 'slow-growing' Hubbard JA 757 broilers, is described. On the first farm, clinical signs were observed from 42 days of age onwards and on the second farm, respectively from 42 (stable 1) and 30 days (stable 2) of age onwards. The neurological symptoms consisted of acute central nervous system signs, which started with flaccid neck paralysis. Histopathological examination revealed multifocal perivascular cuffing of CD3 positive mononuclear cells in the brain tissues. These findings pointed towards the development of transient paralysis. qPCR analysis confirmed the diagnosis. In broiler flocks, which only have a limited life span, vaccination is not common practice. In flocks of slow-growing breeds, outbreaks of MD might become more important again. Therefore, vaccination of slow-growing broilers against MD seems recommended.