A statistical study on farm and village level on the possible relations between human leukaemia and bovine leukosis.

In order to further elucidate a possible relationship between bovine leukosis and human leukaemia a comparative statistical study on herd and village level was performed for an 11 year period in a Swedish county where bovine leukosis incidence as well as human leukaemia mortality were above the national mean. The addresses of the human leukaemia cases and bovine leukosis cases were traced. As control material were used farms and villages situated within 5 ± 0.1 km from each human case address. The difference between the addresses of human leukaemia cases and the control addresses with respect to the occurrence of bovine leukosis was not found to be statistically significant. There was no statistically significant difference in frequency between human cases with professions associated and not associated with farming with respect to the occurrence of bovine leukosis on the same addresses. A comparison between the frequency of addresses for human leukaemia and controls with respect to the occurrence of cattle on the addresses did not give statistically significant higher values for those human leukaemia addresses having housed cattle. A study of the time elapse between each human case and the bovine case(s) on the same address did not indicate a regular appearance earlier or later of the bovine case. The possibilities to evaluate with reliability a material of this kind are discussed.