Clinical cases resembling strangles are regularly seen in some areas of Croatia. However, there are no data on the prevalence of infection and the clinical forms or geographic distribution of the disease. The aim of this study was to determine the seroprevalence of Streptococcus equi subspecies equi in horses resident in Croatia, in order to estimate the geographic distribution of infection. The study included 291 horse sera from the eight counties where the majority of Croatian horses are kept. Sera were tested by indirect ELISA (iELISA) for the presence of serum antibodies against S. equi protein A (SEQ_2190) and protein C (SeM). Positive horses were detected in all counties. Overall seroprevalence was 16.5 per cent (48/291), ranging from 7.1 to 29.6 per cent. A positive association was observed between the population size of the horses in the counties and the seropositivity rates: the larger the population, the higher the seropositivity. The results of this study suggest that S. equi infection is widespread in Croatia. Further investigation of the clinical manifestations, circulating strains and other characteristics of the disease in Croatia and raising awareness of the disease among horse owners are now required.
Keywords: Croatia; Streptococcus equi; horse; seroprevalence; strangles.