In some cases patients also have respiratory difficulties and red blotches appear on the skin. This phase terminates 5-7 days following the onset of symptoms. During the migration phase, which can result in the larvae appearing in almost any tissue, they can cause pneumonia, pleurisy, encephalitis, meningitis, nephritis, deafness, peritonitis, eye damage and so on. Ten days after the initial symptoms,the larvae penetrate the muscle fibres, the resultant symptoms are dependant on the intensity of the infection. In addition weakening of the pulse accompanies, lower blood pressure, damage to the heart and the onset of nervous disorders such as hallucinations.
Death can occur through heart failure, respiratory complications, toxaemia or kidney failure.
Some work has been done on the effects of trichinella infections on the behaviour of infected mice and has correlated the muscle phase of the infection with the host behaviour. Mice, with low grade infections change their activity patterns and become less active and submissive to other uninfected mice. This could be reversed if mice were given anti-inflammatory drugs. More recently studies of trichinella infections in wild populations of deer mice have also shown behaviourial modifications likely to make them more susceptible to predation. Diagnosis usually requires a biopsy of muscle or examination of the suspected contaminated food.