Trichina, << trih KY nuh, >> is a small roundworm that causes the disease trichinosis, also known as trichinellosis. The worm is a parasite. That is, it lives in and feeds on other animals.
The trichina infects human beings and other animals, especially rats, hogs, and bears. Most infections of trichinosis in the United States and Canada result from eating infected pork that has not been cooked enough. Trichinosis in rats, hogs, and bears usually results from eating garbage that contains infected meat.
The larvae (early form of the worms) live in microscopic cysts (sacs) in the muscles of the animals that they infect. They usually live in the animal’s chest and neck muscles.
If an animal infected by the larvae is allowed to live, the cysts eventually harden, and the larvae die. But sometimes infected animals are killed for meat. In such cases, the larvae can be killed by thoroughly cooking or freezing the meat. However, if the larvae are not killed and the meat is eaten, the larvae are freed from the cysts during digestion. The larvae attach themselves to the intestine of the individual who eats the meat. They become adult worms in about 3 or 4 days. The largest are only about 1/4 inch (6 millimeters) long.
The adult females burrow into the wall of the intestine, where they produce large numbers of larvae. The larvae enter the blood and are carried to many parts of the body. They eventually leave the blood and form new cysts in the muscles.
Some people carry trichina worms in their bodies for many years and never have severe symptoms. But in other people, the worms irritate the intestine and cause diarrhea, nausea, and vomiting. When they pass through the blood, fever, headache, and muscular pain occur. After they reach the muscles, they cause swelling of the face and other parts and bleeding under the skin. The worms may form their cysts in the diaphragm (chief muscle used for breathing) and make breathing painful. The disease occasionally is fatal.
The prevention of trichinosis involves several steps. Garbage containing meat scraps may carry trichina worms, so it should be cooked before it is fed to hogs. Meat packers should freeze pork to kill any worms the pork may carry. Finally, cooks should be sure the central section of pork is held at a temperature of at least 137 °F (58 °C) for 5 minutes or more.
