The value of systematic screening for Trichinella antibodies among individuals with eosinophilia in recognizing outbreak events: a seroprevalence study from Croatia

Although trichinellosis represents one of the most significant global foodborne zoonotic diseases, human seroprevalence studies are scarce. Due to its endemicity in Croatia, the aims of this study were to establish the general prevalence of Trichinella infection in Croatian individuals presenting with eosinophilia during a 5-year period, and to assess the value of such screening endeavours for early detection/differentiation of outbreaks. A total of 1342 serum samples were collected from male and female subjects presenting with peripheral blood eosinophilia between 2013 and 2017, and tested for Trichinella IgG antibodies by employing commercial qualitative ELISA and Trichinella Excreted/Secreted (E/S) Western blot methods. The overall positivity was 3.65%, ranging from 0.49% to 1.50% between 2013 and 2016, but rising to 10.98% in 2017; such ten-fold increase in seroprevalence forecasted the epidemic situation in Croatia. Overall the prevalence of the infection rose with the increasing age and the rate was highest among those older than 40 years of age (p=0.003), without any significant sex-based differences (p=0.438). Considering the early appearance of eosinophilia in the infected individuals, this type of systematic screening can be seen as an additional epidemiological tool to unveil the trichinellosis outbreak in a timely manner.