Trichinosis primary prevention

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Overview

The best way to prevent trichinellosis is to cook meat to safe temperatures. Using food thermometers can make sure the temperature inside the meat is high enough to kill the parasites. There are currently no vaccines for trichinosis.

Primary Prevention

Food preparation:

• The best way to prevent trichinellosis is to cook meat to safe temperatures. A food thermometer should be used to measure the internal temperature of cooked meat. Do not sample meat until it is cooked. USDA recommends the following for meat preparation:
  • For Whole Cuts of Meat (excluding poultry and wild game)
    • Cook to at least 145° F (63° C) as measured with a food thermometer placed in the thickest part of the meat, then allow the meat to rest for three minutes before carving or consuming
  • For Ground Meat (including wild game, excluding poultry)
    • Cook to at least 160° F (71° C); ground meats do not require a rest time
  • For All Wild Game (whole cuts and ground)
    • Cook to at least 160° F (71° C)
  • For All Poultry (whole cuts and ground)
    • Cook to at least 165° F (74° C), and for whole poultry allow the meat to rest for three minutes before carving or consuming
• According to USDA, "A 'rest time' is the amount of time the product remains at the final temperature, after it has been removed from a grill, oven, or other heat source. During the three minutes after meat is removed from the heat source, its temperature remains constant or continues to rise, which destroys pathogens."
• Wash your hands with warm water and soap after handling raw meat
• Curing (salting), drying, smoking, or microwaving meat alone does not consistently kill infective worms; homemade jerky and sausage were the cause of many cases of trichinellosis reported to CDC in recent years
• Freeze pork less than 6 inches thick for 20 days at 5°F (-15°C) to kill any worms
• Freezing wild game meats, unlike freezing pork products, may not effectively kill all worms because some worm species that infect wild game animals are freeze-resistant
• Clean meat grinders thoroughly after each use

Pig farming:

• Keeping pigs in clean pens with floors that can be washed (such as concrete)
• Not allowing hogs to eat carcasses of other animals, including rats, which may be infected with Trichinella
• Cleaning meat grinders thoroughly when preparing ground meats
• Control and destruction of meat containing trichinae, e.g., removal and proper disposal of porcine diaphragms prior to public sale of meat

Education and training:

• Public education about the dangers of consuming raw and undercooked meat, especially pork, may reduce infection rates
• Hunters are also an at-risk population due to their contact and consumption of wild game, including bear
• As such, many states, such as New York, require the completion of a course in such matters before a hunting license can be obtained

Legislation:

• Laws and rules required of food producers may improve food safety for consumers, such as the rules established by the European Commission for inspections, rodent control, and improved hygiene
• Similar protocol exists in the United States in the USDA guidelines for establishment responsibilities in inspecting pork

Vaccine research

• There are currently no vaccines for trichinosis, although experimental mice studies have suggested a possibility
• In one study, microwaved Trichinella larvae were used to immunize mice, which were subsequently infected. Depending on dosage and the frequency of immunization, results ranged from a decreased larval count to complete protection from trichinosis
• Another study, used extracts and excretory-secretory products from first stage larvae to produce an oral vaccine. To prevent the gastric acids from dissolving the antigens before reaching the small intestine, scientists encapsulated the antigens in a microcapsule made of copolymers. This vaccine significantly increased CD4+ cells and increased antigen-specific serum IgG and IgA, resulting in a statistically significant reduction in the average number of adult worms in the small intestine of mice. The significance of this approach is that if the white blood cells in the small intestine have been exposed to Trichinella antigens (through vaccination) then, when an individual gets infected, the immune system will respond to expel the worms from the small intestine fast enough to prevent the female worms from releasing their larvae
• Another study tested a DNA vaccine on mice which "induced a muscle larvae burden reduction in BALB/c mice by 29% in response to T. spiralis infection"
• Researchers trying to develop a vaccine for Trichinella have tried to using either "larval extracts, excretory-secretory antigen, DNA vaccine, or recombinant antigen protein"