Swine Practitioners Enlisted to Help with Enhanced Classical Swine Fever Surveillance Plan

September 7, 2005 — Robyn Fleck (Ed. Harry Snelson)

Classical Swine Fever (CSF) surveillance has been an ongoing effort since the disease was eradicated in the 1970's. Now, with the advent of a new validated PCR test, the CSF surveillance plan has been reworked to include routine samples submitted by veterinarians to diagnostic labs. Soon, practitioners will be able to submit fresh tonsils and nasal swabs to diagnostic labs and they may be tested for CSF for free.

As part of their focus on integrated and comprehensive surveillance, the USDA has developed a CSF surveillance plan. The first objective of the plan, which is for rapid detection of CSF in the United States, has received approval for recurrent funding. Implementation will begin the end of 2005 in states with a high risk for introduction of CSF, including Puerto Rico. The majority of the funding will be used for sample collection and CSF testing at National Animal Health Laboratory Network (NAHLN) diagnostic laboratories. A PCR test will be used as a screening test rather than a serum antibody test, since the number of false positives is greatly reduced with the PCR, unlike the serum antibody test. False positives play havoc with trade relations and thus are not well tolerated in programs that require the routine testing of a large number of samples. The serum antibody test will still be run at FADDL and will only be used for FAD investigations and for very high risk populations where additional monitoring is required. Any sample testing inconclusive or positive on the PCR will be immediately forwarded to FADDL for confirmation as outlined in the CSF Response Plan developed by Emergency Programs staff. The samples for which the PCR test has been validated are fresh tonsil and nasal swabs. As of this writing, twelve laboratories are certified to run the PCR test for CSF and at least fifteen additional laboratories will come on line during 2006.

Eighteen states and Puerto Rico have been designated as high risk for a variety of reasons, including: the feeding of waste food (garbage), presence of feral swine, travel between or proximity to CSF positive countries and the presence of a large commercial swine population. These states are AZ, CA, HI, IA, KS, NE, NM, OK, TX, WA, FL, GA, IL, IN, MN, NJ, NY and NC. The goal of the program is to collect and test approximately 17,000 tonsil samples and 7000 serum samples annually.

Over half of the samples collected and tested will come from slaughter plants in these high risk states. Swine condemned for Erysipelas or septicemic disease will be the most common source of tonsils. Slaughter samples may be taken by either APHIS employees in the plants, FSIS or by state inspectors. Five plants buying hogs from very high risk areas in Texas and Florida will randomly sample pigs, regardless of the animal's condemnation status. Overall, the postmortem sampling will represent 95.8% of all hogs slaughtered in the high risk states and 68% of the total U.S. hog slaughter.

A little less than one half of samples will come from diagnostic laboratory specimens in high risk states. As of this writing, the NAHLN diagnostic laboratories approved to run CSF samples are FL, GA, WI, NY, NC, AZ, CA, IA, CO, LA, WA and TX. Any fresh tonsil and nasal swab samples submitted to these high risk states will be submitted for testing, with the exception of Iowa and Minnesota. Since Iowa and Minnesota receive the bulk of swine diagnostic submissions, tonsil and nasal swab samples will be submitted when they meet the appropriate selection criteria. If any one of the following are noted on the history and samples are available, CSF PCR will be performed: 1) dramatic acute septicemic disease 2) abortions with deformed piglets 3) porcine dermonecrosis and nephropathy syndrome or 4) undiagnosed CNS disease esp. congenital tremors. The current plan calls for funds to reimburse collection and shipping of tonsils and nasal swabs from high risk states. If a veterinary diagnostic laboratory in a high risk state is not approved to run the CSF test but has an eligible sample, funding will be available to forward the sample to an approved diagnostic lab. If a fresh tonsil sample or nasal swab is selected for testing, the veterinary diagnostic laboratory will credit the submitting veterinarian's account by $50.00. Veterinarians will be encouraged to submit fresh tonsil and nasal swabs as a routine diagnostic specimen and to include a detailed case history with each submission.

The USDA will also fund a communications plan in order to educate veterinarians and producers on CSF and the importance of early detection. The education program will also cover collection of diagnostic samples and the CSF suspect case description.