Riscos do exercício profissional dos Médicos Veterinários Inspectores Higio Sanitários e outros trabalhadores de matadouros de aves

Oncogenic virus exposure, poultry industry

Certain viruses naturally infect and cause cancer in chickens and turkeys. They include the avian leukosis/sarcoma viruses (ALSV), reticuloendotheliosis viruses, and Marek’s disease virus. Some of these viruses are among the most potent cancer-causing agents known in
animals [that is, avians]. Humans are widely exposed to these viruses from contact with live poultry and their raw products, including eggs; from ingestion of raw or inadequately cooked products; or through vaccination with vaccines grown in eggs, such as measles, mumps, influenza, yellow fever, and typhus vaccines. It has been shown that
exogenous ALSV-contaminated yellow fever vaccines caused malignant tumors when injected into chickens. Some but not all studies have reported the presence of antibodies to these viruses in the sera of poultry workers and subjects in the general population.

A study by Felini et al. published lately in Annals of Epidemiology [Felini et al. (2011) Annals of Epidemiology 21:755-766] was designed to test the hypothesis that exposure to poultry oncogenic viruses that widely occurs occupationally in poultry workers and in the general
population may be associated with increased risk of death from liver and pancreatic cancers, and also to identify new risk factors. The source population for this case-cohort study consisted of 30 411 poultry workers and 16 408 non-poultry workers.

The conclusions are that slaughtering of chickens at work and catching live chickens at work were significantly associated with pancreatic cancer. Slaughtering of chickens at work was significantly associated with liver cancer.

—
communicated by: Nati Elkin Nati@poultrymed.com

[The paper described above by Martin Felini and colleagues is entitled
“A pilot case-cohort study of liver and pancreatic cancers in poultry
workers” and was published in Annals of Epidemiology, Volume 21, Issue
10 , Pages 755-766, October 2011
.

The purpose was to test the hypothesis that exposure to poultry
oncogenic viruses that widely occurs occupationally in poultry workers
and in the general population may be associated with increased risk of
death from liver and pancreatic cancers, and to identify new risk
factors. A pilot case-cohort study of both cancers within a combined
cohort of 30 411 highly exposed poultry workers and 16 408 control
subjects was conducted, and risk was assessed by logistic regression
odds ratios (OR) and proportional hazards risk ratios.

New occupational findings were recorded respectively for
pancreatic/liver cancers, for slaughtering of poultry (odds ratio (OR)
= 8.9, 95 per cent confidence interval [CI]: 2.7-29.3)/OR = 9.1, CI:
1.9-42.9); catching of live chickens (OR = 3.6, CI: 1.2-10.9)/OR =
1.0, CI: 0.1-8.5); killing other types of animals for food (OR = 4.8,
CI: 1.5-16.6)/OR = 2.0, CI: 0.2-18.2), and ever having worked on a pig
raising farm (OR = 3.0, CI: 1.0-8.2) for pancreatic cancer only.

It is concluded that this study provides preliminary evidence that
exposure to avian oncogenic viruses may possibly be associated with
the occurrence of liver and pancreatic cancers. Case-control studies
nested within occupational cohorts of highly exposed subjects of
sufficient statistical power may provide an efficient and valid method
of investigating/confirming these findings.

Felini et al. [In Occup Environ Med doi:10.1136/oemed-2011-100310
http://oem.bmj.com/content/early/2011/10/17/oemed-2011-100310.abstract]
have also described a case-cohort study of lung cancer in poultry and
control workers demonstrating that excess deaths from cancer at 11
different cancer sites including lung cancer were observed in the
poultry workers.

The authors believe that these results may have important public
health implications, since the general population is also exposed to
these poultry viruses. Similarly elevated risks were observed for
non-poultry-related occupational exposures such as working in a
stockyard, working in a chemical plant, use of chemicals to kill
moulds, and working in plants where plastic products were
manufactured. These preliminary findings indicate that full scale
epidemiological studies of adequate statistical power are needed to
examine the role of occupational exposures in cancer occurrence in
poultry workers.

However, it must be stressed that these analyses contain no
virological component. While it is true that avian leukosis/sarcoma
viruses (ALSV), reticuloendotheliosis viruses, and Marek’s disease
virus are potent cancer-forming agents, their oncogenic potential is
restricted to avians to a large extent. It has been just over 100
years since Peyton Roux discovered Rous sarcoma virus, the 1st
oncogenic virus, and it has remained a uniquely avian virus.

Nonetheless, this study is a useful attempt to identify risk factors
associated with employment in the poultry industry. – Mod.CP]