Veterinary session

Today, the use of antibiotics in large-scale pig farming has become significantly restricted, in line with the One Health principle. Thus, the prevention, like vaccination against infectious diseases, is becoming more and more important. However, for preventive measures to be effective, adequate and detailed data collection and analysis using an appropriate testing method are essential. Streptococcus suis (S. suis) is a major pathogen in pig production and a zoonosis of growing importance. Several serotypes occur worldwide, but some serotypes have different significance in different geographical areas. Knowledge of the serotype is important for the evaluation of epidemiological data and for the selection of appropriate vaccine strains. The prevalence and significance of each serotype is known in several European countries, but no relevant national data are available.

The aim of my studies was to obtain a more detailed picture of the diversity and prevalence of S. suis serotypes in Hungarian pig farms and to compare the serological method commonly used for serotype identification with an alternative molecular test. In our retrospective studies, 253 preserved strains isolated from pigs and identified as streptococci at the Production Animal Diagnostic Centre in 2020, 2021 and 2022 were used. The species of the isolates and the serotype of S. suis were determined by classical microbiological, serological or different molecular methods.

Over the 3 years studied, 210 S. suis isolates were identified from 45 farms of 42 holdings throughout the country. Among the 210 S. suis isolates, 19 serotypes were detected, the most frequent being serotypes 2 (31.1%), 9 (17.8%), 7 (15.6%) and 1/2 (8.9%). Based on literature data, the serotypes more prevalent in Hungary are among the most virulent strains and may pose an occupational health risk to pig farmers and veterinarians. Our data may help to estimate the risk associated with serotypes and thus to better target the strains of colony-specific vaccines, consequently helping to improve the effectiveness of disease control.

Of the 186 serological tests performed, 157 cases were serotyped, giving a serological success rate of 157/182 (86.2%) for strains typable by the method, and a PCR success rate of 52/53 (98.1%) for 53 S. suis strains not serotyped or not typed, respectively. Our results are in line with those of other authors and – despite the small sample size – highlight the advantages of the molecular method.