Writer: Robert Burns, (903) 834-6191, rd-burns@tamu.edu
Contact: Dr. Billy Hargis, (979) 845-8989, bhargis@tamu.edu
COLLEGE STATION — Inoculating baby chicks with a special mixture of harmless bacteria dramatically reduces the chances of their becoming infected with salmonella bacteria, according to research findings at Texas A&M University.
Developed by a joint U.S. Department of Agriculture (USDA) and Texas A&M research team, the treatment has reduced the contamination of salmonella in chickens up to a hundred fold in laboratory tests, said Billy Hargis, veterinary pathologist with the Texas A&M Agricultural Experiment Station.
In preliminary field trials, the reduction was not as dramatic as in the lab tests, but was still “quite encouraging,” Hargis said.
Salmonella, which resides in chicken and turkey’s intestines, cuts producer profits and raises costs to consumers at the meat counter. Salmonella can find its way into the processed chicken carcass, where it can cause serious health risks to humans.
In humans, severe cases of salmonella poisoning can kill. Particularly at risk are small children, the elderly, those whose immune systems are already overwhelmed, and pregnant women and their unborn children.
Less severe salmonella poisoning causes abdominal cramps, diarrhea, fever, nausea, and vomiting. These non-lethal symptoms usually disappear within one to seven days, but there may be other effects. Medical experts now believe that long-term symptoms of arthritis (chronic back and joint pain) may follow an episode of salmonellosis.
Exact counts of human death and illness due to salmonellosis are not known, but it is generally accepted that the number of outbreaks have steadily increased in the last few years. From 1985 through 1989, there were 217 outbreaks in the United States of salmonellosis caused by only one of the more than 2,000 known species of salmonella, according to Hargis. The particular species of salmonella accounts for about 40 percent of the outbreaks in a typical year.
Hargis noted that though these numbers may seem large, the United States still has the cleanest meat and poultry in the world.
“The total salmonella mortality in the United States rarely exceeds 10 people a year,” Hargis said.
The 217 outbreaks resulted in 44 deaths and nearly 7,400 reported illnesses. Epidemiologists estimate the total economic cost of salmonellosis, in terms of lost work time, doctor visits and hospital stays and preventive measures adds up to more than $3 billion annually, Hargis said.
Viewed in this light, the research team’s work could have a long- term effect on human health.
“This means we can now produce fewer chickens and turkeys that are contaminated with salmonella. Fewer contaminated chickens and turkeys means fewer contaminated processed carcasses. Fewer contaminated carcasses means fewer cases of human infection,” Hargis said.
The inoculation developed by the team is a selection of about 30 bacterial species from the hundreds normally found in a chicken’s intestine. The bacteria are harmless to both chicken and humans. Baby chicks do not commonly become hosts to the harmless bacteria until later in life.
Though harmless to chickens and humans, the 30 strains of bacteria are beneficial to each other. Once in the chick’s intestine, they work together and thrive.
Salmonella is also a bacterium that lives in the intestines of chickens. Like the harmless bacteria, salmonella must attach to molecular receptor sites of the intestinal lining to live and multiply. The bacteria, both salmonella and the harmless variety, fit these receptor sites the way a key matches a lock. The harmless bacteria work filling up most of the key receptor sites, thereby excluding the salmonella bacteria.
Hargis said the team’s findings come at a critical time. Incidences of salmonellosis caused by a particularly virulent salmonella subspecies, Salmonella enteritidis phage IV, have rapidly risen worldwide, according to a recent survey by the World Health Organization.
As with salmonellosis caused by other species, Salmonella enteritidis phage IV is rarely fatal to humans. The likelihood of healthy people becoming sick is much higher, however, according to Hargis.
To date, there has only been one outbreak of the salmonella subspecies in commercial poultry industry in the United States and that outbreak was contained. But Hargis and other pathologists believe it’s only a matter of time before it becomes common in the United States as well.
Though not tested in conjunction with the new subspecies, there’s no reason why the microbial treatment shouldn’t offer just as effective control for Salmonella enteritidis phage IV as it does the other species, Hargis said.
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