Epidemiological characteristics of streptococcus suis infection

Abstract

Streptococcal infections have a significant impact on pig farming worldwide, including in Ukraine, resulting in significant economic losses for livestock farmers. Streptococcus is considered one of the primary zoonotic diseases in pigs, often causing meningitis, septicemia, or arthritis, and can also be dangerous for humans. For many years, experts have managed to control the spread of this infection quite effectively. However, in recent years, due to antibiotic resistance, this infection is becoming more widespread. Given the importance and danger of this pathogen for pigs, this problem is still relevant in pig farming. The main etiological factor of streptococcal infections in pigs is Streptococcus suis (S. suis), which are gram-positive bacteria that are either aerobic or facultatively anaerobic. Most streptococci have capsules, do not form spores, and cannot move. The structure of the streptococcal antigen is complex and consists of three primary components, namely groupspecific antigen, type-specific antigen, and nuclear protein antigen. β-type hemolytic streptococcus has highly pathogenic properties, and there are 35 serotypes based on different characteristics of the capsular antigen. S. suis serotype 2 is commonly isolated from clinically ill piglets and is considered the most virulent subtype of the organism. The pathogenicity of this bacterium for animals is related to its primary pathogenic factors, including the capsule, toxin, and enzymes. S. suis is widespread, and newborn piglets, suckling piglets, and pregnant sows are most susceptible to infection, while adult pigs are more resistant. S. suis tends to peak during weaning and mating, and piglet susceptibility to S. suis decreases with age. S. suis occasionally infects dogs, cats, rodents, cattle, sheep, and horses. It can also infect humans and has become a serious endemic threat to public health. The primary modes of transmission are alimentary and respiratory infections. People typically become infected by contacting sick animals. Infected animals often show symptoms such as pneumonia, wet dermatitis, meningitis, peritonitis, osteomyelitis, arthritis, and pharyngitis, among others. Outbreaks of the disease caused by S. suis usually occur throughout the year without any significant seasonal patterns.