A study of the effects of Marek's disease in a broiler flock

In a flock of 17000 broilers, characteristic Marek's disease (MD) paralysis, accompanied by increased mortality occurred during the fourth week of the flock's life. Cytolytic lesions and atrophy in the bursae of Fabricius, and the severity of lymphocytic infiltration of nerves, livers, proventriculus and brain are suggestive of the involvement of MD virus of greater pathogenicity than has been encountered previously in New Zealand.