Although larvae encyst only in striated muscle, inflammatory lesions may develop in the heart, lungs, and central nervous system. Fatalities usually result from myocarditis. Symptoms generally abate slowly after the third week of infection. Infections with T. pseudospiralis may be associated with years of myositis. Serologic tests are positive in most patients with acute infection, but diagnostic antibody titers may not be detectable until the third week of infection.
Definitive diagnosis requires demonstration of larvae in muscle.
A portion of the biopsied muscle should be submitted for histopathological examination. In addition, another portion should be compressed between glass slides and examined microscopically for larvae. Because a larger volume of muscle can be examined by this technique, it is more sensitive than histopathological examination for detecting larvae. Differentiation of Trichinella species can be based on the absence of larval encystment with T. pseudospiralis and on DNA-based molecular biologic techniques. The triad of periorbital edema, myalgias, and eosinophilia strongly suggests the diagnosis of trichinellosis.