Human cancer in households containing cats with malignant lymphoma

Since feline malignant lymphoma is viral in nature, a retrospective case‐control study was done to assess if there was any additional risk of cancer for human members in households with cats histologically diagnosed as having that disease. The 221 households identified as having owned cats that developed the disease were matched with control ones on the basis of index cat age, sex and breed. Various compared human demographic factors indicated close agreement in makeup between groups. Tests for association of human cancer with feline malignant lymphoma were negative. Association was sought in two ways: (1) by a case‐control comparison, controlling human household cancer risk and length of time the index cat was in the household; and (2) by a comparison of the last five years' occurrence of human cancer in both groups compared to the expected. The expected numbers were calculated for the population‐at‐risk from human age‐ and sex‐specific incidence rates published for this area. The specific occurrence of human cancers of the lymphatic and hematopoietic systems was examined. The validity of the study results and extension of these results to cat ownership in general were discussed.