Pathogenesis

The pathogenesis and symptoms associated with trichinellosis vary with the number of viable larvae ingested. The human disease can be divided into two main phases. The first phase occurs approximately between the first week after infection until the eighth week after infection. The first symptoms to appear are fever and in most cases diarrhoea together with abdominal pain. These early symptoms are probably due to an inflammatory reaction in the small intestine that is parasitized by the adult nematodes. The symptoms then gradually move into the second phase which can continue for several years depending on the infection rate. The fever from the first phase decreases and the pain from the abdominal area is moved to the muscles most frequently used, such as the tongue, facial, diaphragm, neck muscles, and flexor muscles of the extremities. Movement of the muscles increases pain and the patients feel weak. These symptoms are due to the migration of the newborn larvae to the muscle cells and the penetration of these cells (reviewed by Pawlowski 1983). Once the larvae begin to encapsulate, symptoms in the patients subside, and eventually the cyst wall and larvae calcify. Modern medical treatment, such as different derivatives of benzimidazoles,

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helps in most cases, especially if they are given in an early stage of the infection, before the nematodes enter the muscle cells. Once the nematode has become encapsulated in the muscle cell, the treatment is less likely to be successful (reviewed by Campbell and Denham 1983).

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