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Egg Yolk Antibody Controls Vertical Transfer of Salmonella in Eggs and Chicks

Opinion

Salmonella is a Gram-negative, facultative intracellular pathogen that is capable of causing gastroenteritis and typhoid fever in the affected host. Salmonella infections are reported as the second leading cause of foodborne illnesses in the United States. Salmonella has the potential to cause fatal bacterial infections in infants, the elderly and individuals with a suppressed immune system.

The majority of foodborne Salmonella serovars can colonize in the intestinal tracts of poultry. One of the major routes of human salmonellosis is believed to be consumption and handling of contaminated poultry and poultry products. According to surveillance data from the U.S. Department of Agriculture’s Food Safety and Inspection Service (FSIS), Salmonella accounts for 23 percent of foodborne outbreaks and 31 percent of illness. Salmonella enterica serovar Enteritidis (S. Enteritidis) is the most common serovar, causing 27 percent of salmonellosis. The top of the list of the commodities to which S. Enteritidis outbreaks were attributed was egg and laying hens.

If Salmonella colonizes in the gut of laying hen heavily, a some eggs can be contaminated with the bacterial cells. If even a few eggs used for hatching are contaminated, then a limited number of chicks come out from the egg with bacterial contamination (called vertical transfer), but then it can be spread in millions of chicks within few days via horizontal transfer.

The most common and available current option for reducing established Salmonella colonization in poultry flocks is the addition of antibiotics to poultry feeds and water. However, due to the emergence of microorganisms resistant to multiple classes of antibiotics, there are some concerns that such practices may cause dissemination of antibiotic-resistant human pathogens and increase untreatable human disease. In addition to this, the cost of antibiotics puts increasing pressure on the search for new ways to control colonization of Salmonella in the gut of laying hens and stopping the vertical transfer of Salmonella to chicks and eggs. Further antibiotic use is not allowed in organic/pasture poultry.

Recently, it was found that the yolk of immunized chickens is a rich and inexpensive source of polyclonal antibodies that decrease the attachment of Salmonella onto chicken cells. Using specific bacterial antigen antibodies provides protection against pathogens. When the feed of the laying hens is supplemented with these antibodies, the newly hatched chicks from these hens carry the antibodies from the mother via the egg. Antibodies derived from the egg yolks of immunized hens have the added benefit that large quantities of antibodies can be produced less expensively than with mammalian sources. Further, the collection of eggs is much less invasive and stressful to the animals as compared to using a needle to obtain blood, and purification is also a relatively simple process involving the removal of the lipoprotein fraction from the egg yolk.

Polyclonal antibodies derived from egg yolks have the potential for broader spectrum applications such as feed supplements to control contamination of eggs with S. Enteritidis and vertical transfer from eggs to chicks.

© Food Safety News
  • Eric Gingerich, DVM

    Concerning the 29Aug12 opinion article by Debabrata Biswas on the use of egg yolk antibodies for Salmonella enteritidis (SE) control, someone needs to educate this person on normal practices used in the egg industry. We DO NOT use antibiotics for control of SE nor have ever used them for control of SE. We do utilize vaccination which establishes high levels of antibody in the hen itself and the egg to prevent infection and reduce SE growth in the eggs after laying. The production of an SE specific antibody egg yolk preparation for feed use has been attempted but is not economically nor biologically useful.