Lymphosarcoma (leukemia) in cattle, sheep and pigs in Great Britain

To investigate the incidence and characteristics of lymphosarcoma in foodproducing animals, a histologic survey of all neoplasms encountered in 100 abattoirs throughout Great Britain during 1 year was carried out in collaboration with the Ministry of Agriculture, Fisheries and Food. When lymphosarcoma was diagnosed, further investigations were undertaken on the farm of origin. The total numbers of slaughtered animals surveyed were 1.3 million (m) cattle, 4.5 m sheep and 3.7 m pigs. Of 302 bovine, 107 ovine and 139 porcine neoplasms receiyed, 75, 44 and 92, respectively, were lymphosarcoma. The overall incidence was 58 pm slaughtered cattle, 10 pm sheep and 25 pm pigs. Most bovine lymphosarcoma (53%) was of the thymic type while in sheep 75% and in pigs 62% was multicentric. A high incidence was found in young cattle: 35% under 2 years and 61% under 4 years of age. In pigs 58% occurred below 6 months of age while almost all affected sheep were adult. All cases of lymphosarcoma were isolated and sporadic. Blood samples from apparently normal cattle in 19 herds where lymphosarcoma had occurred showed no evidence of lymphocytosis. It is concluded that lymphosarcoma in cattle, sheep and pigs in Britain is a sporadic disease, further differing from the “enzootic” form of bovine lymphosarcoma in the age incidence, anatomic distribution of lesions and absence of lymphocytosis in other herd members. There is at present no epidemiological or experimental evidence of transmissibility of lymphosarcoma in the food-producing animals in Britain.