Epidemiologic relationships of the bovine population and human leukemia in Iowa

Data from the Third National Cancer Survey and data collected under the auspices of the National Cancer Institute's Surveillance, Epidemiologic and End Results (SEER) Program were used to perform a descriptive epidemiologic study of leukemia in Iowa. Data were also collected on livestock population patterns in the state, and a survey was performed to locate cases of lymphosarcoma within the cattle population. Ecologic relationships between human leukemia, livestock populations and bovine lymphosarcoma were investigated. Iowa has higher rates than the national average for human leukemias. The lymphoid leukemias make up the majority of the excess leukemias. Excessive acute lymphoid leukemia (ALL) is seen in the ages under 20 years and over 60 years. The excess ALL is in males living in rural counties. There is no sex difference for chronic lymphoid leukemia (CLL), but there is a slight urban-rural differential. There is a high positive correlation between ALL in males and cattle density. This relationship is greater for daily cattle than for beef cattle. There is an additional positive relationship between counties with excessive ALL and the presence of dairy herds affected with bovine lymphosarcoma.