2004 Swine Research Review

Herd Health and Management

Meat Processing Technologies May Help Block Toxoplasma Transmission

Helping consumers reduce the risk of contracting toxoplasmosis from infected pork requires a multi-faceted approach that includes on-farm prevention procedures and processing and preparation procedures.

In studies at the U.S. Department of Agriculture's (USDA) Agricultural Research Service, Beltsville, MD, Agricultural Research Center (BARC), researchers have identified that injection of pork loins with solutions commonly used in meat processing to improve pork quality and palatability can prevent the spread of Toxoplasma gondii (Tg), the parasite responsible for toxoplasmosis infections.

A protozoan parasite, Tg infects nearly one-third of the human population. For most adults, it does not cause serious illness. But it can cause blindness and mental retardation in congenitally infected children and devastating disease in immunocompromised individuals.

USDA estimates that 50% of Tg infections in the U.S. are linked to consumption of raw or undercooked meat products containing Tg tissue cysts.

Pork for human consumption has been shown to contain Tg tissue cysts, and the cysts can be found in virtually every edible cut at retail.

Commonly, retail cuts of pork are enhanced with salt solutions to improve flavor and texture, and to extend product shelf life by reducing microbial contamination.

To test the effectiveness of commonly used meat enhancement solutions on the viability of Tg tissue cysts, BARC researchers experimentally infected pigs with the parasite.

Loins were collected from the infected pigs and injected to 110% of the original weight of the loin with solutions containing sodium chloride (1 and 2%), sodium diacetate (0.1 and 0.2%), sodium tripolyphosphate (0.25 and 0.5%), potassium lactate (1.4 and 1.96%) or sodium lactate (1.4, 1.5 and 2.0%). These solutions were used alone or in combination.

The treated pork loins were then stored for 7, 28 or 45 days at 39∞ F. before feeding to Tg-seronegative cats.

The feces of cats fed the parasite were examined for 14 days to assess oocyst (parasite eggs) shedding.

The study demonstrated that injection of pork loins with solutions of 2% sodium chloride or 1.4% or greater potassium or sodium lactate, alone or in combination with other components, successfully prevented transmission of Tg to cats.

Researcher: Dolores Hill, U.S. Department of Agriculture, Agricultural Research Service, Animal and Natural Resources Institute, Animal Parasitic Diseases Laboratory. Phone Hill at (301) 504-8770 or (202) 334-3192; fax (301) 504-6273; or e-mail dhill@anri.barc.usda.gov.