Editor's note: The following research reports are from the 42nd National Meeting on Poultry Health and Processing held in Ocean City, Md. Although this annual meeting concentrates on broiler production with an emphasis on the Delmarva Peninsula, information was presented which has direct importance to egg production.
Anatomy of a Foodborne Illness Outbreak
Dr. Jurgen Schwarz of the University of Maryland Eastern Shore outlined the role of PulseNet in identifying clusters of foodborne infection with specific emphasis on E coli infection and salmonellosis. Laboratories affiliated with PulseNet are equipped to apply a sensitive analytical technique, Pulsed Field Gel Electrophoresis (PFGE), to characterize specific isolates of foodborne pathogens. This is used by public health investigators and the CDC to establish epidemiologic relationships between sources of contaminated food and the isolates derived from individual patients involved in outbreaks. FoodNet, which is an active surveillance system, now incorporates 15 percent of the U.S. population with participation by state laboratories in Connecticut, Georgia, Maryland, Minnesota, New Mexico, Oregon, Tennessee and large urban counties in California, Colorado and New York. Dr. Schwarz outlined the actions involved in detection and characterization of the Listeria outbreak attributed to processed turkey meat emanating from plants in Michigan in 1998 and Pennsylvania and New Jersey in 2002.
The implication for egg producers is that any outbreak of SE which involves 10 or more cases, constituting a cluster in any of the states participating in the FoodNet program, will be identified and trace back to farms of origin will be inevitable. The implication of identifying and elimination of any foci of SE is obvious. Outbreaks attributed to a complex or integrator will result in tort claims and action by state agencies and ultimately the FDA when proposed regulations are promulgated.
Predictive Microbiology Information Portal
The Microbial Food Safety Research unit of the Eastern Regional Research Center, USDA-ARS, located in Wyndmoor, Pa., functions as an interdisciplinary team of scientists. The laboratory cooperates with commercial entities, universities and research institutes in the United States and six foreign countries to investigate technology to prevent foodborne infection. The research interests of the affiliated scientists include Salmonella, Listeria and E coli, in relation to food products. The institute has obvious expertise in food safety centering on the molecular biology of food borne pathogens and extending to microbial modeling and pilot scale validation of commercial interventions to limit food borne infection.
Avian influenza (AI) has the potential to disrupt production in the United States and to curtail availability of eggs on domestic and export markets. Compartmentalization was reviewed by Dr. T.J. Myers, deputy director for science and technology, USDA-APHIS. The concept, now accepted by OIE, allows regulators to designate a specific company or complex as being free of AI or some other notifiable disease subject to acceptable biosecurity procedures. The compartmentalization programs, which must be approved in advance of a disease outbreak, will include the definition of a compartment, proof of epidemiologic separation from high risk zones, full documentation of activities and ongoing surveillance for designated diseases including diagnostic capability and emergency response plans.
With increasing prevalence of H7N2, low pathogenic AI in the live bird market and possibly in backyard flocks, the probability of entire regions being affected by LPAI should be considered in relation to maintaining the output and interstate movement of product. For instance, a diagnosis of H7N2 on a farm operated by a contractor supplying eggs from non-confined flocks would most probably involve blanket quarantine over a multi-county area in California or Ohio, where a high density of hens in proximity to other avian species exist. If producers comply with the principles of compartmentalization, the highly restrictive quarantines and restrictions required under geographic "zoning" would be avoided.
ILT persists as a widespread infection which depresses performance in broiler flocks. Invariably, all U.S. layer flocks are vaccinated (but not necessarily immunized) against ILT using tissue culture origin vaccines administered by eyedrop during the early and mid-rearing periods. Chicken egg origin ILT vaccines as used in the broiler industry are responsible for field outbreak of clinical disease, based on PCR-RFLP analysis followed by sequencing of the variable genome regions.
There is a clear distinction between the serotypes prevalent in backyard flocks and those encountered on commercial farms. It is apparent that a newly introduced fowlpox-vectored recombinant ILT vaccine may provide uneven protection due to the presence of antibodies against the vector virus.
It is possible that a new HVT-vectored recombinant ILT vaccine will become available to the industry. This product has been registered for in-ovo and subcutaneous administration. The important question will be whether producers will pay the extra cost for the innovative vaccine given that there does not appear to be an obvious clinical problem of ILT in rearing flocks or subsequently during egg production. Life-time protection may require administration of both the HVT vectored ILT vaccine at day old followed by a tissue culture origin vaccine during rearing.
Innovative HVT-Vectored Vaccines
The use of HVT vector vaccines was viewed by Dr. David Shapiro, previously a scientific coordinator for Hoechst Roussell, and now affiliated to Perdue Farms. USDA-licensed recombinant HVT vaccines are now available to protect flock against ND, ILT and IBD. The commercial egg industry does not use in-ovo vaccination for obvious reasons but HVT vector vaccines can be administered by subcutaneous injection usually in combination with SB1 or with Rispens strain MDV at day old.
When the deleterious immunosuppressive effects of early exposure to IBD become apparent, egg producers may adopt new and more effective vaccines. The principle of combining disease protection by vaccination and chick service (beak treatment) at the hatchery will overcome the deficiencies and the cost of administering vaccines and also manual handling for beak treatment during the early brooding period. Quality control and the use of Nova-Tech equipment will contribute to pullet flocks with greater uniformity and the potential to achieve genotype during subsequent production.