A paper presented by Ducatelle et al of Ghent University presented at the XVII World Veterinary Poultry Association meeting in August 2011 is currently circulating on the web. It is stressed that the paper deals with control of Salmonella in general although extensive reference is made to Salmonella Enteritidis.(SE) infection in egg production.
In the context of the U.S. egg production industry it is clear that existing modalities are effective. This is confirmed by the low incidence rate of infection in flocks and the fact that since August 2010 there have been no major recalls associated with SE.
It is clear from the overview presented by the researchers in Belgium that vaccination is effective. It is noted that from January 1, 2008 producers in the EU were required to administer approved vaccines to laying flocks if contamination was detected. Epidemiologic data in the U.S. suggest that since introduction of comprehensive programs of vaccination have been beneficial. Current practice incorporates both live attenuated mutant Salmonella Typhimurium (ST) vaccines during early rearing, coupled with one or more inactivated oil emulsion Salmonella Enteritidis vaccines prior to transfer. It is generally accepted by poultry health professionals that vaccination has reduced both shed rate in flocks and has interdicted vertical transmission.
Rodent control has most certainly limited dissemination of SE especially in multi-house complexes with a range of flocks extending from 16 through 110 weeks. Both vaccination and rodent control are especially important in high-rise houses constructed during the 1970’s which have extensive wood in construction and where flocks are housed above their manure. Pits provide a suitable habitat for mice since manure accumulates from as little a week to 6 months or more depending on the program of disposal and the season.
In an attempt to further suppress intestinal colonization with SE many producers have adopted either probiotics or prebiotics alone or in combination as an added level of “insurance”. Reputable manufactures will claim that their products “serve as an aid in preventing intestinal colonization”. Any supplier suggesting that their products are a “sure fire” or “single product” solution to SE infection are either misinformed or unethical. Producers confronted with choices are advised to request results of comparative trials conducted under controlled conditions in order to assess the efficacy of probiotics and prebiotics. Published literature in peer reviewed journals clearly demonstrates reduction in intestinal colonization using many of these products. All have in common the conclusion that there is no single product or method offering absolute eradication.
The paper by Ducatelle and his colleague is a useful overview, with references relating to the challenge of Salmonella infection caused by Groups B, C and D Salmonella serotypes. The approach to control in the presentation dealt with both eggs and broilers for which there are different modalities based on the production systems for these industries.