Recent press reports have implicated feed as a vehicle of transmission in the Iowa SE outbreak and recall. Reports have indicated recovery of SE from the environment of the feed mill, from feed and from byproducts in the mill supplying affected flocks. Whether the animal protein ingredient was contaminated before delivery or acquired infection in the feed mill remains to be determined.
Central Bi-Products, a subsidiary of Farmers Union Industries, processed the “bone meal” (presumably meat and bone meal) at a rendering plant in Long Prairie, Minn. A spokesman for Central Bi-Products indicated that heat treatment during rendering would destroy salmonella and other vegetative bacterial pathogens. Unfortunately, post-rendering contamination does occur and animal proteins have a far higher rate of salmonella recovery than vegetable ingredients.
It is significant that Central Bi-Products stated that it does not render dead hens from the implicated farm. What might be more important is whether the company receives hens or breeders from any other source to be processed in its plant. A further complication is that the meal was handled by Superior Feed Ingredients in Waconia, Minn., and this company was the ultimate supplier to the Wright County complex.
According to an FDA spokesman, “investigation of the operation can help us understand the cause of the infection.” It is evidently too early to determine whether feed was contaminated at the rendering plant, during the intermediate stages in handling and transport or at the feed mill. News reports citing FDA investigations indicated suboptimal hygiene in the feed plant including “rodent contamination, the presence of wild birds and their droppings, holes in feed ingredient bins and uncovered feed tanks.”
SE has been a reality for the egg industry for almost three decades without feed being confirmed as a vehicle of either introduction or dissemination of infection. The absence of previous reports tend to suggest that recovery of SE from either feed samples or the environment of the implicated mill is a function of a general disregard for acceptable production practice with regard to suppression of pathogens. The presence of rodents in feed mills, although common is totally unacceptable since mice specifically serve as reservoirs of SE infection and their droppings will result in environmental contamination and introduction of various salmonella serotypes into feed.
Until a definitive report on the epidemiology of SE in the affected complex is released, it would be premature to accept that feed is a problem in relation to SE in egg producing operations although there is acceptance that other than Group-D salmonella serotypes have been introduced into vertically integrated swine and broiler operations in feed.
Irrespective of the final conclusions, it is obvious that the industry can no longer tolerate low standards of housekeeping, ineffective rodent control, lack of cleanliness and incomplete record keeping in feed mills. The Wright County episode has introduced a new paradigm for plants which will have to operate at a standard consistent with the realization that the FDA will closely monitor production facilities and practices with the media close behind.