Life Cycle of the Trichina Worm

Trichina is a type of roundworm that infects rats, pigs and humans. It is responsible for a condition known as trichinosis, which can cause abdominal pain, fever, diarrhea and sometimes vomiting. Most cases of trichinosis are subclinical, meaning that the symptoms are so mild that they are never noticed by the host.

Trichinella spiralis, or the trichina worm, is responsible for causing this infection.

Early Stage

T. spiralis begins life as an embryo, hatching in the uterus of the female adult trichina worm. The immature trichinella are discharged into the host's intestinal tract as second stage larvae. The discharge will usually contain between 1,000-2,000 larvae, which will bore into the intestinal lining and enter the bloodstream, where they make their way their way through the circulatory system to the heart, where they are pumped into the blood vessels of striated muscle tissue. Straited muscles include skeletal muscles and the heart itself. If, by the chance, a larva becomes wayward and cannot find its way to this specific muscle type it will die and be absorbed by the host's body.

Maturation

After lodging in the muscle tissue, the larvae will continue to grow, reaching an approximate length of 1mm and will then enter into a dormant state, encasing themselves in a protective casing called a cyst. A trichina worm can stay in this dormant state for up to 10 years.

Adulthood

The trichina larvae will remain inactive in the intermediate host's muscle fibers until consumed by the new primary host. The cyst walls are broken down during the digestive process and the larvae then escape into the new host's digestive system where they complete the maturation process and begin the process over again.

Symptoms of Infection

As the larvae begin their migration through the intestinal wall and into the circulatory system of the intermediate host, a person will begin to experience generalized symptoms including: fever, swelling of the face, especially around the eyes, nonspecific rash, bleeding of the nail beds, retinas and the whites of the eyes, and a dry cough. In mild cases, these may be the only symptoms, if there are any symptoms at all. In more severe cases of trichinosis, inflammation of the heart, lungs and/or brain is possible. Death contributed to trichinosis is rare, but has been documented.

As the larvae begin to form cysts in the muscle tissues, usually after two to three weeks after the initial infection occurs, the host will begin to experience signs of muscle inflammation, pain and generalized weakness. The most frequent complaint is pain around the eyes, jaw, neck, upper arm, lower back and diaphragm.

Recovery

Symptoms of trichinosis will reach their peak three weeks after infection and will then begin to subside slowly. Recovery is extremely gradual and symptoms may last as long as three months after the initial infection. Fatigue and muscle pain may take several more months to subside.

Causes of Trichinosis

Trichinosis is caused by eating undercooked pork. Cooking pork, and all meats, thoroughly will destroy any cysts that may be lurking within the meat.

References

• State University Encyclopedia