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Trichinosis, also called trichinellosis, is a parasitic disease caused by eating raw or undercooked pork and wild game products infected with the larvae of a species of worm Trichinella spiralis, commonly called trichina. Infection occurs worldwide, but is most common in areas where raw or undercooked pork, such as ham or sausage, is eaten.
Signs and symptoms
Nausea, diarrhea, vomiting, fatigue, fever, and abdominal discomfort are the first symptoms of trichinosis. Headaches, fevers, chills, cough, eye swelling, aching joints and muscle pains, itchy skin, diarrhea, or constipation follow the first symptoms. If the infection is severe, patients may experience difficulty coordinating movements, and have heart and breathing problems. In severe cases, death may occur.
For mild to moderate infections, most symptoms subside within a few months. Fatigue, weakness, and diarrhea may last for months.
Incubation time
Abdominal symptoms can occur 1-2 days after infection. Further symptoms usually start 2-8 weeks after eating contaminated meat. Symptoms may range from very mild to severe and relate to the number of infectious worms consumed in meat. Often, mild cases of trichinosis are never specifically diagnosed and are assumed to be the flu or other common illnesses.
Life cycle
When a human or animal eats meat that contains infective Trichinella cysts, the acid in the stomach dissolves the hard covering of the cyst and releases the worms. The worms pass into the small intestine and, in 1-2 days, become mature. After mating, adult females lay eggs. Eggs develop into immature worms, travel through the arteries, and are transported to muscles. Within the muscles, the worms curl into a ball and encyst (become enclosed in a capsule). Infection occurs when these encysted worms are consumed in meat.
Risk factors
Eating raw or undercooked meats, particularly pork, bear, wild feline (such as a cougar), fox, dog, wolf, horse, seal, or walrus puts one at risk for trichinosis.
Infection can only occur by eating raw or undercooked meat containing Trichinella worms. It is not transmitted from one person to another
Diagnosis
A blood test or muscle biopsy can identify infection with trichinosis.
Treatment
Several safe and effective prescription drugs are available to treat trichinosis. Treatment should begin as soon as possible and the decision to treat is based upon symptoms, exposure to raw or undercooked meat, and laboratory test results.
Epidemiology
Infection was once very common; however, infection is now relatively rare. From 1991-1996, an annual average of 38 cases per year were reported in the USA. The number of cases has decreased because of legislation prohibiting the feeding of raw meat garbage to hogs, increased commercial and home freezing of pork, and the public awareness of the danger of eating raw or undercooked pork products. Cases are less commonly associated with pork products and more often associated with eating raw or undercooked wild game meats.
Prevention
- Cooking meat products until the juices run clear or to an internal temperature of 170°F (76°C).
- Freezing pork less than 6 inches thick for 20 days at 5°F (-15°C) to kill any worms.
- Cooking wild game meat thoroughly. Freezing wild game meats, unlike freezing pork products, even for long periods of time, may not effectively kill all worms.
- Cooking all meat fed to pigs or other wild animals.
- Not allowing hogs to eat uncooked carcasses of other animals, including rats, which may be infected with trichinosis.
- Cleaning meat grinders thoroughly when preparing ground meats.
Curing (salting), drying, smoking, or microwaving meat does not consistently kill infective worms.
References
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