Another hazard in undercooked pork - danger of toxoplasmosis

Science News, July 19, 1986 by Janet Raloff

Another hazard in undercooked pork

For decades mothers have admonished their young to beware of pink pork. Their concern has been that if the meat was undercooked and infected with the trichina worm, the diner might develop trichinosis. As a result of such caution, this disease is relatively rare in the United States today. Moreover, U.S. pork producers -- through more stringent inspection and improved animal breeding -- are working toward meat certified as trichina-free, notes veterinarian Jitender P. Dubey at the Agriculture Department's Animal Parasitology Institute in Beltsville, Md.

These trends worry him because they may lead to complacency. And this is especially dangerous, he suggests, because a study he and his colleagues recently completed indicates that undercooked pork can harbor a far more serious potential health hazard than trichinosis.

The researchers recently reported the first finding of the protozoa Toxoplasma gondii in commercial cuts of pork. Like the parasitic trichina worm, T. gondii can be killed by cooking meat or edible organs (like the brain and heart) to an internal temperature of 158[deg.]F. However, with trichinosis scares on the wane, Dubey worries that consumers may be tempted to serve rarer pork -- a practice that has been advocated in some areas of the world, including France.

Humans ingesting the live T. gondii parasite may contract toxoplasmosis. In a developing fetus or an immuno-compromised individual -- including those with AIDS or undergoing cancer therapy -- this disease can eventually lead to blindness, mental retardation, even death. Of the estimated 3,300 U.S. infants born each year with this infection (contracted through the mother), about 6 percent soon die, according to National Institutes of Health-sponsored research. How many of the rest develop related problems later in life is not known.

Implications of the new pork finding are described in a related report by Dubey in the July 15 JOURNAL OF THE AMERICAN VETERINARY MEDICAL ASSOCIATION. (In the May 1 issue of the journal, Dubey's group reported the initial discovery of T. gondii in pork.) According to Dubey, an estimated one in three pigs may be infected with the parasite. Though cat feces have long been considered the leading source of human infection, Dubey notes in the new report that "fresh pork may be the main meat source of T. gondii infection in the United States." However, he says, because an estimated 6 percent of all hamburger may also be contaminated with pork during grinding, many people who eat rare or raw ground beef may also risk picking up the T. gondii infection.