A Pilot Case-Cohort Study of Brain Cancer in Poultry and Control Workers

Abstract

We conducted an exploratory study to investigate which exposures (including poultry oncogenic viruses) are associated with brain cancer in poultry workers. A total of 46,819 workers in poultry and nonpoultry plants from the same union were initially followed for mortality. Brain cancer was observed to be in excess among poultry workers. Here we report on a pilot case-cohort study with cases consisting of 26 (55%) of the 47 brain cancer deaths recorded in the cohort, and controls consisting of a random sample of the cohort (n = 124). Exposure information was obtained from telephone interviews, and brain cancer mortality risk estimated by odds ratios. Increased risk of brain cancer was associated with killing chickens, odds ratio (OR) = 5.8 (95% confidence interval, 1.2-28.3); working in a shell-fish farm, OR = 13.0 (95% CI, 1.9-84.2); and eating uncooked fish, OR = 8.2 (95% CI, 1.8-37.0). Decreased risks were observed for chicken pox illness, OR = 0.2 (95% CI, 0.1-0.6), and measles vaccination, OR = 0.2 (95% CI, 0.1-0.6). Killing chickens, an activity associated with the highest occupational exposure to poultry oncogenic viruses, was associated with brain cancer mortality, as were occupational and dietary shellfish exposures. These findings are novel.

Lack of Evidence That Avian Oncogenic Viruses Are Infectious for Humans: A Review

“…A potential is present for information bias for the risk factors in Felini et al (46) and in Gandhi et al (48). The respondents for the risk factors for the cases were of necessity only next of kin (the cases were already dead).…”

“…On the other hand, authors can still indicate the numbers of risk factors tested so that the, albeit partial, list of significant risk factors declared in the abstract is put into perspective; this was not done in any of the four primary studies reviewed. In addition, Gandhi et al (48) found only 13 significant risk factors even at their unadjusted alpha of 5%, and listing all 13 might well have been possible. However, the abstract listed only 5 of the 13 (including the only one related to poultry) without warning of another 8 significant risk factors or that the questionnaire from which the risk factors were derived contained 646 questions.…”

“…Four recent primary epidemiological studies (46,48,68,71) have offered information on this topic; all are from the same research group and were made possible because of good access to union records for workers that included people in the livestock/abattoir industry in various states. There is also one recent review on this topic (69) from the same research group.…”

“…Johnson (68) and Johnson and Ndetan (71) were careful to indicate the ICD codes used to identify the various outcomes. However, Felini et al (46) failed to do so, and Gandhi et al (48) specified nothing more than the very general ICD code for ''brain tumor'' (without regard to, e.g., histopathological type or location within the brain).…”

“…In a recent review paper, Tischer and Osterrieder (140) also concluded that there is no formal proof or even likelihood of infection of humans with MDV. However, based on recent epidemiological studies, concerns have once more been raised that MDV and avian retroviruses can cause cancer in humans (33,48,69,72) and that MDV or the closely related herpes virus of turkeys (HVT), one of the MDV vaccine strains, may be the cause of multiple sclerosis (MS) (21, 88,89,90,92,93). In this paper we will first analyze examples of the epidemiological evidence that these viruses are causative agents for human cancer, followed by description of the relevant key characteristics of ALV, REV, and MDV.…”