Serological screening of patients with clinical suspicion of trichinellosis in Belgrade from 2009 to 2018

Introduction. Trichinellosis is one of the most important foodborne diseases in Serbia. Most patients with suspected trichinellosis in Belgrade are referred to the Clinical Center of Serbia for diagnosis and treatment, as are unclear and complicated cases from all across Serbia. Materials and Methods. A retrospective study of trichinellosis serology was carried out from 2009-2018 and included all outpatients and hospitalised patients from the Clinic for Infectious and Tropical Disease, Clinical Center of Serbia, who were serologically tested for Trichinella by the Parasitological Laboratory (n=1,565). Trichinella-specific IgG antibodies were detected in sera by a commercial ELISA test. We analysed the seroprevalence of Trichinella-specific IgG antibodies, antibody detection kinetics and cross-reactivity with other nematodes. Results and Conclusions. The number of patients who reported for serological testing varied greatly per year and month. Most patients were tested in December and March, which coincides with the months with the most confirmed cases of trichinellosis. A total of 17.4% patients who were tested for trichinellosis had other parasitic infections. Altogether, 223 (14.2%) of tested patients were finally diagnosed with trichinellosis. We detected anti-Trichinella IgG in 68.8% (223) of patients with suspected trichinellosis on admission, which increased to 86.5%, 91.5% and 92.4% after later second, third and fourth testing, respectively. Final diagnoses of toxocariasis, strongyloidiasis, filariasis, and dirofilariasis were made for 2.4%, 0.3%, 0.3% and 0.1% of patients, respectively. Concurrent seropositivity for Trichinella and Toxocara was observed in 18.9% (7/37) of patients with clinical presentation of trichinellosis and who were also tested for toxocariasis. In 3/5 patients with imported filariasis, we found cross-reactivity with Trichinella. Potential cross-reactivity of this ELISA test with antibodies to the autochthonous nematode Toxocara canis demands the introduction of Western blot technology. Trichinellosis must be diagnosed by the combination of clinical, laboratory and epidemiological criteria.