Aim: To evaluate the value of indirect fluorescent antibody test (IFAT) in diagnosing trichinosis.
Methods: IFAT using frozen section of the purified Trichinella larvae as antigen was employed to detect anti-Trichinella antibodies in sera from mice infected with Trichinella spiralis and the patients with trichinosis. Sera from patients with trichinosis were collected at different time intervals after onset of the disease and after treatment with albendazole. Sera from patients with other parasitic diseases and healthy individuals were used as control.
Results: The anti-Trichinella antibodies were detected in 15 infected mice as early as 2 weeks after infection, and in 86.5% of 467 patients with trichinosis. Sera from patients with filariasis, echinococcosis and healthy controls were all negative. 8 of 48 (16.7%) cases with paragonimiasis showed positive cross reaction. The antibody positive rate of patients with trichinosis was 70.2% one week after onset of disease and increased to 91.0%, 95.8% and 100% at two, three and four weeks after onset, respectively. The frozen section of the larvae can be stored at -20 degrees C for 5 years without loss of antigenicity. The IFAT positive rate was increased from 87.5% before treatment to 100% one week after treatment, and the serum antibody titers were elevated as well. The antibody negative conversion rate of the patients was 24% at one month after teratment and increased to 75% at four months after treatment.
Conclusion: IFAT using frozen section of the purified Trichinella larvae as antigen is highly sensitive and specific for the diagnosis of trichinosis and evaluation of the therapeutic effect.