Virus-like Particles in Blood Lymphocytes in Acute Marek's Disease

Abstract

DURING a preliminary survey by electron microscopy of blood from cases of acute Marek's disease in chickens, virus-like particles were observed within cytoplasmic vesicles of lymphocytes. The experimental disease was induced by the intraperitoneal inoculation into day old chicks of a commercial broiler breed of heparinized whole blood obtained from cases of acute Marek's disease from a field outbreak in November 1965. Blood was withdrawn from the wing vein of eight of these experimentally injected birds which showed the paralysis or tumours typical of the disease and from one bird which had been similarly injected but showed no signs of involvement. The birds were killed and the diagnosis was confirmed by macroscopic and histological examinations. As control material, blood was obtained from six uninjected and apparently healthy birds of the same breed which had been reared apart from the treated group. Blood was also obtained in a similar manner from two broilers from the Lebanon which were affected with spontaneous acute Marek's disease and from three spontaneous cases of classical Marek's disease occurring in Brown Leghorns from the stock at the Poultry Research Centre. Leucocytes were prepared for electron microscopy by a method based on that of Anderson¹.