1973 Volume 26 Issue 9 Pages 500-506
A survey on Marek's disease (MD) was conducted on the K Poultry Farm in Hokkaido over a period of 210 days beginning with the day of hatching. A total of 7, 287 chickens of strains No.731 and No.522 of High Line were surveyed and 892 dead and diseased birds examined pathologically.
The following results were obtained. The Selection rate was 12.24% including dead and condemned (birds) and the breeding rate 87.76%. The incidence of macroscopically diagnosed cases of MD and lymphoid leukosis (LL) was 10.40% (758/7, 287), and that of histopathologically diagnosed cases of MD 70.18% (353/503). The lesions of MD were classified as follows: Type TI, 11.13% type TII, 27.44% type TIII, 4.77%, and type R, 26.84%. The incidence of LL was 8.55% (43/503). LL was found among birds 120 or more days old.
The striking feature was a high incidence of visceral lymphoid tumors particularly those accompanied by swelling of peripheral nerves. Lymphoid tumors were found in the liver, spleen, proventriculus, lungs, ovary, kidneys, thymus, serosa, intestines, heart, skeletal muscles, bursa of Fabricius, adrenal glands, pancreas, and mesentery in the order of severity. The peak of occurrence of MD was found among chickens 90 to 180 (usually 140) days old. The gel precipitin reaction of MD was negative in 8.96%. In addition to lesions of MD and LL, 4 cases of nephroblastoma, 3 cases of myosarcoma, 3 cases of coli-granuloma, 2 cases of serositis, and 1 case of skin mucormycosis were observed.
