Location: Animal Parasitic Diseases Laboratory
Project Number: 8042-32420-007-09-I
Project Type: Interagency Reimbursable Agreement
Start Date: Sep 1, 2015
End Date: Aug 31, 2020
Pigs with access to the outdoors are at substantial risk of infection with the zoonotic parasite Trichinella spiralis. The historical problem of Trichinella infection in pigs is responsible for strict federal control of methods used to prepare ready-to eat pork products in the U.S., and for expensive carcass inspection requirements for U.S. pork destined for Europe. These regulations are still in effect in the Code of Federal Regulations and in the Directives of the European Union. Currently, U.S. pork cannot be exported to major markets without individual carcass testing for trichinae. While most countries provide specific training to technical personnel in the performance of Trichinella testing, the measures which are followed to assure that the test continues to be performed properly vary greatly. For quality assurance, the proficiency of a technician performing the digestion assay should be regularly assessed using one or more samples of ground meat containing a known number of Trichinella muscle larvae (proficiency samples). APDL will provide ongoing support to the AMS Export Certification Program for pork and horsemeat by providing a verified proficiency sample program for certified laboratory analysts to allow continuous quality control of approved testing laboratories, and continued export of U.S. pork to international markets.
The Beltsville strain of Trichinella spiralis (ISS 4) will be pass into female Sprague-Dawley rats by oral inoculation of 5000 muscle larvae (ML). After 60 days, ML within nurse cells will be recovered from eviscerated rat carcasses by artificial digestion. The number of intact nurse cells will be determined by dilution counting using a stereomicroscope; at least three samples will be counted to assure accuracy. The suspension will be searched for nurse cells containing multiple larvae; these will be manually removed with a Pasteur pipette. This will be accomplished by spotting the parasites under the dissecting microscope and coaxing them into the pipette tip by means of hand-eye coordination, then deposit by pressing down on the piston. Ground pork meat will be purchased commercially (0.45 kg each batch) and placed in a chilled stainless steel bowl attached to a stand mixer with a paddle attachment. Four indentations will be made in the meat, and the nurse cell suspension will be placed in the indentations and manually covered with ground meat. The meat will be mixed at room temperature for 2 hours, divided into 5 gram samples, packaged into meat cups, and 6 coded samples (including 3 larvae-free controls) will be mailed to each certified analyst on a quarterly basis along with a scoring sheet to record the digestion counts from each coded sample. Analysts will be instructed to perform individual sample digestions in acidified pepsin following the standard magnetic stirrer protocol described in the ICT Guidelines of Quality Assurance in Digestion Testing Program for Trichinella. Analysts will return the completed scoring sheets to APDL, and in consultation with AMS, analysts will be cleared to continue to perform the artificial digestion procedure at the plant location.