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Poultry Health & Disease
on August 11, 2010

What is the prevalence of SE among caged flocks?

Validity of statistics is questionable

California Act 1437 mandates that any eggs imported into California after January 2015 would have to be produced in compliance with the requirements of Proposition 2. When first proposed the obvious response was that this item of legislation would be unconstitutional since it interfered with interstate commerce. The framers of the legislation, obviously influenced by the principles of HSUS, consider that validity will rest on the provision that legislation can be validly enacted which “promotes the health and welfare of citizens.” The rationale advanced to support this presumption is at best scientifically unproven.

The challenge facing the U.S. egg industry at large is to clearly demonstrate that confined hens are not inherently more susceptible to Salmonella enteritidis infection than their non-caged counterparts. Alternatively it would be even more desirable to prove that in the context of the U.S. production, caged systems are superior with respect to prevalence rate of intestinal salmonella colonization and vertical transmission than non-confined and free-ranged flocks. A number of outdated studies have been cited to support 1437. The oft repeated but outdated axiom of “one egg in 20,000” contamination rate is totally spurious and reflects the period following introduction of SE in the early 1980s before the advent of vaccination, and EQAPs.

The egg industry has a window of approximately one year in which to clearly define the epidemiology and SE status of commercial confined flocks and the equivalent prevalence rates in barn-housed and free-range operations. Extrapolating data from Europe is totally irrelevant to the U.S. situation since prevalence rates vary from double digits in northern Europe to over 25% in Mediterranean nations of the EU. Preliminary data in the U.S. suggest that the prevalence rate of environmental contamination in recent years is between 5% and 7% and falling rapidly.

It is further noted that environmental contamination does not necessarily directly correlate with vertical transmission since vaccination and the use of non-stressful molting procedures have reduced the possibility of vertical transmission even in flocks housed in units shown to have environmental contamination.

The task facing producers in the Midwest who historically have supplied approximately a third of the egg requirements for California will be to establish rates of environmental contamination and egg transfer of SE. It will be possible to challenge the “health and safety” justification of 1437 by conducting scientifically valid epidemiologic studies. These would compare both on-belt manure batteries and conventional high rise cage systems in comparison to non-confined units operated in the same areas and subjected to the same vaccination and management practices.

It is ironic that the California egg industry invoked SE as a justification for opposing Proposition 2 during the pre-election campaign in 2008. It now appears the same issue has been turned around and is being used to promote an anti-cage agenda. Unless the U.S. industry gathers and correctly interprets data relating to SE prevalence in the environment of egg production facilities and eggs the forces aligned against intensive egg production will continue to present, manipulate and distort EU data of questionable validity and to raise false concerns regarding SE among consumers faced with state ballot initiatives.

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