Serodiagnosis by fluorescent antibody staining of an outbreak of trichinosis in Lebanon.

The opportunity offered by a recent outbreak of trichinosis in Lebannon was utilized to evaluate the applicability of an indirect fluorescent antibody (IFA) test for early diagnosis. Freeze-dried T. spiralis sonicated larval antigen fragments were used, together with human test serum and monospecific anti-human IgG, IgM and IgA fluorescein conjugates. Diagnostic IgG levels of 1/100 and above were observed in serum obtained some time during the acute phase of illness from nine out of ten patients. Diagnosis was made in seven cases within 30 days after the onset of symptoms. IgM antibodies were demonstrated in occasional samples. No IgA antibodies were detected. IgG levels of 1/100 were present in only four out of ten samples obtained 150 days after the clinical onset. These observations suggest that freeze-dried larval antigens make the IFA test an easy and useful procedure in the diagnosis of acute trichinosis. In chronic cases the efficacy of the method appears to be poor.