ATLANTA — A study by the Centers for Disease Control may shed light on which poultry are most vulnerable to Campylobacter infections.

CDC conducted the study at a Virginia poultry plant that employed about 1,000 workers and processed up to 350,000 birds per day. Between January 2008 and May 2011, researchers found 29 cases of laboratory-diagnosed Campylobacter infections in plant employees. Most of the cases occurred among employees who worked in the live-hang area where chickens are hanging by their feet in a shackle conveyor. Workers in the live-hang area were disproportionately infected with Campylobacter given that only 50 out 1,000 employees worked in that area.

"This area has a known high potential for contamination with Campylobacter spp. because the feathers, skin, crop, cloaca, and feces of birds brought to slaughter are often highly contaminated with Campylobacter spp.," according to the study.

"Pre-harvest practices by the plant and hatcheries may not be sufficient for controlling Campylobacter spp. contamination of live birds," CDC added. "The US Department of Agriculture has noted that high bacterial loads of Campylobacter spp. on live birds can undermine other in-plant interventions."

All but three of the infected employees were residents of a diversion center, according to CDC. Most of those cases had worked at the plant for less than a month for they got sick. Researchers findings of illness in new employees was comparable to other research which indicates "that for poultry workers, the highest risk for work-related Campylobacter infection is during the first weeks of work, after which the workers develop immunity that may be protective against future symptomatic infection," the study stated.

Finally, researchers said the number of Campylobacter cases was likely under-reported. "This may be due to an unwillingness to report illness because of the plant’s lack of paid sick leave and employees’ difficulty in accessing medical care," according to the study.

Based on the findings, researchers made several recommendations:

• Plant management should strengthen efforts to reduce Campylobacter contamination, particularly in the live-hang area through engineering controls such as improved sanitation, ventilation system modifications, and installation of hands-free soap dispensers and waste receptacles.

• Employee training (in English and Spanish) and compliance with plant policies related to hand hygiene and the use of personal protective equipment should be improved, especially among temporary employees.

"Poultry-processing plants should regularly review their illness records and work with local health departments to ensure that all cases and outbreaks of Campylobacter infection are reported," researchers said.