If you haven't read Rosemary's most recent article on the inhumane slaughter of poultry, you should do so. You may question or change your eating habits! Poultry Slaughter Lawsuit.
Two important issues surfaced from accounts of the U.S. district court ruling that allows for lawsuits against the U.S. Department of Agriculture for excluding poultry and other birds from the Humane Methods of Slaughter Act. Not only are current methods of poultry slaughter inhumane, but they also risk contaminating poultry with organisms that cause human disease. I'll leave the humanity issue to Rosemary to pursue, and will discuss the contamination risks instead. For those of you who would like to know more about current slaughter methods, and more humane alternatives, visit Downbound.com. And, vote in the poultry contamination poll on the Science and Nature homepage Poll.
Poultry processors slaughter birds using methods such as shackling, electrically stunning them into paralysis, and sometimes drowning conscious birds in tanks of scalding water. A press release issued by the Humane Society Suit suggests that these methods increase the risk of carcass contamination with human pathogens during processing. My curiosity caused me to investigate the accuracy of this allegation. The Humane Society indicated that current slaughter methods increase the risk that the birds inhale feces in the water, leading to higher intestinal bacteria level that may result in food poisoning after consumption of undercooked meat. Additionally, dirt, dust and feces spread by birds trying to escape can increase the risk, not only of emotional distress on processing plant workers, but also an increased risk of infection to plant workers.
Reportedly, Salmonella and Campylobacter account for over 90% of cases of bacteria-related food poisoning (gastroenteritis) world-wide. Although all livestock are reservoirs of infection, poultry - particularly chickens - account for the majority of human infections. Most retail chicken is contaminated with Campylobacter - studies suggest contamination rates of 70-98%. Studies have also shown Salmonella contamination rates of up to 40% in retail chicken. Contamination rates may be even higher in game fowl, while somewhat lower, but still a significant concern, turkey. Not only is the meat a concern - infection can also occur from Campylobacter and Salmonella contamination from both the external and internal surfaces of packaging of the meat.
Horizontal transmission from environmental sources is the primary route of flock infections by Campylobacter, while horizontal and vertical transmission occurs with Salmonella. Horizontal transmission is that which occurs from bird to bird; whereas, vertical transmission occurs from mother to progeny through infected eggs. Many Salmonella outbreaks are caused by contaminated shell eggs, including eggs used in eggnog, Caesar salad, lightly cooked eggs in omelettes and French toast.
Campylobacter and Salmonella are commensal in chickens - usually forming part of the gut flora as early as 3 days after birth, and contaminating chicken carcasses at slaughter. Bacterial counts on carcasses are likely to increase during slaughter and processing - transportation of birds to the slaughter facility, defeathering, and removal of intestines and internal organs have all been associated with increasing bacterial counts, with highest rates in the latter. Contamination can occur by fecal spillage, fecal contamination in dust and dirt, ingestion of feces from dunking of inverted shackled birds, and cross-contamination through the hands of processing plant workers.
There are also many critical control points identified in the processing plant which reduce contamination including temperature controls (washer and product), chemical interventions, water replacements and counter-flow technology in the scalder and chiller, and equipment maintenance. An inspection checklist used by the Canadian Food Inspection Agency identifies numerous processing critical check-points. Inspection
It is unlikely that humane slaughter techniques will prevent human gastrointestinal infection; however, it's possible that it may reduce carcass contamination during slaughter. Less stressed birds may be more docile during slaughter so that feces and fecal contamination through dust and dirt is reduced.
However, significant reductions in poultry contamination leaving the plant can likely only be achieved by delivering birds to the plant that are free of human pathogens. Unless producers find ways to prevent commensal intestinal colonization of chickens with Salmonella and Campylobacter, consumers will have to continue to use care when handling and cooking poultry. There was seasonal variation in the level of Campylobacter contamination of fresh chicken, with a peak in June and the lowest positive rates in January, March, and December.
Prevention of human infection requires an understanding of the numerous points in the food chain where contamination can be introduced. Special attention to careful hand-washing and cleaning of surfaces where poultry and poultry packaging, has been handled, and thorough cooking of poultry and eggs are essential to preventing human infection.
For more information:
Humane Slaughter - Controlled-Atmosphere Killing of Poultry
Emerging Foodborne Diseases: An Evolving Public Health Challenge
Judy Arbique - I graduated from Medical Laboratory Technology training in 1979 and since then obtained advanced recognition in clinical microbiology from ...
