BANFF, Alta. – More cases of salmonella enteritidis linked to eggs has scientists scouring for causes and cures.
“Poultry salmonella problems tend to rise and fall independent of what people try to do,” said poultry specialist Richard Gast.
In the last five years, the majority of reported salmonella cases were linked to eggs, said Gast, of the United States Department of Agriculture.
An egg nutrition symposium held in Banff discussed the problem of salmonella contamination in eggs.
Illness caused by salmonella enteritidis most often happens because of improper cooking, cross contamination of eggs and improper temperature control.
Read Also
VIDEO: British company Antler Bio brings epigenetics to dairy farms
British company Antler Bio is bringing epigenetics to dairy farms using blood tests help tie how management is meeting the genetic potential of the animals.
And, for unknown reasons, the incidence of the problem has increased in the last two decades, said Gast.
In 1989, salmonella outbreaks peaked. An outbreak is defined as two or more people getting sick from the same source. This has declined, but every year there are at least three or four outbreaks in the U.S. Canadian statistics are similar, said Gast.
Improper refrigeration
In 1997 the most cases were found in restaurants where improperly cooked eggs were not refrigerated properly.
A case in a Maryland breakfast bar showed a number of health violations when scrambled eggs were left sitting in improperly heated pans and raw eggs were not refrigerated.
Also, if raw eggs were left over at the end of the day, the staff mixed those in with the next day’s supply.
The bacteria starts with the hen and affects the birds differently than other salmonella types. Typically, an infected chicken will suffer gastrointestinal problems. The infection is systemic and is found in the intestines, ovaries, ovary ducts and liver.
Studies show a wide range of salmonella types appear on shells. Under the right conditions they can penetrate the shell and contaminate the internal parts of the egg.
However, the incidence of salmonella is not high. Other studies revealed when salmonella was detected in laying flocks, the infection showed up in fewer than three eggs per 10,000 samples.
When outbreaks first appeared, the government insisted on a traceback system. Flocks were destroyed and about one billion eggs were pasteurized. This didn’t work well so USDA has embarked on another approach of heightened biosecurity.
Common controls today urge producers to regularly check their flocks for infection. They are encouraged to use chicks certified as uninfected, thoroughly clean facilities between flocks, promptly refrigerate and wash eggs and control mice in the hen houses.
“We found in heavily infected flocks, a high number of mice,” said Gast.
They don’t know if the mice were the carriers or caught the bacteria from the chickens. But when the mice were controlled, the problem declined.
“Rodent control has a direct correlation between control and contamination,” he said.
They also found forced molting of laying hens tends to alter the birds’ immune systems making them more susceptible to the bacterial
infection.
Vaccines work but don’t provide a complete disease barrier.
