A cohort study of the effects of Vietnam service on testicular pathology of U.S. military working dogs.

Using histopathologic diagnoses made on necropsy material from 3,024 military working dogs (MWDs) who died from 1968 to 1973, we analyzed the effect of military service in the Republic of Vietnam on testicular pathology. Among 1,048 MWDs that died in Vietnam and had no reported developmental risk factors for testicular disease, significant excesses of testicular hemorrhage, epididymitis/orchitis, sperm granuloma, testicular degeneration, and seminoma were evident. Among 126 MWDs with prior Vietnam service who died at other duty stations outside Vietnam from 1968 to 1973, significant excesses of testicular degeneration and seminoma were likewise evident. Among 136 MWDs with prior Vietnam service that later died from 1974 to 1980, seminoma continued to be diagnosed in significant excess. In each instance, the odds ratio for the association between Vietnam service and seminoma was 2.0 or greater. Analysis of ever service by Corps Tactical Zones showed significant excesses of seminoma with each Corps area of service compared to Vietnam-era MWDs, but risk was highest in I Corps, particularly at Da Nang Port and Da Nang Air Base. This finding with respect to I Corps is consistent with certain human studies in Vietnam veterans and points to the need for further investigation of possible environmental exposures, particularly those associated to a greater extent with service in I Corps.