Disease intervention targets for porcine Streptococcus suis infections in Vietnam
Streptococcus suis causes high morbidity and mortality in the pig industry, which affects economics, animal welfare, and food security within both commercial and small-scale farming. S. suis is also the leading cause of human meningitis in Vietnam. There are no commercial vaccines available for this disease, and control of infections in pigs relies heavily on the use of antibiotics — but antimicrobial resistance is becoming increasingly prevalent. One of the major barriers to vaccine commercialization is the lack of protection of experimental vaccines against more than one serotype. Specific strategies to ensure prudent use of antimicrobials in swine do not currently exist and the development of effective vaccination strategies as part of improved management of pigs will greatly reduce the impact and spread of S. suis, decrease the volume of antibiotics used for infection and prophylactic treatment, and reduce associated human infection risks.
This project is being implemented in collaboration with the University of Nottingham and Vietnam’s National Institute for Veterinary Research of the Ministry of Agriculture and Rural Development. It focuses on the identification of genes that encode factors essential for the pathogenesis of S. suis in pigs from strains currently circulating in Vietnam and assesses their suitability as vaccine candidates in a passive immunization model using pregnant sows. The research aims at identifying virulence factors produced by S. suis to evade immune response using a combination of random bacterial mutagenesis and high throughput sequencing. The vaccine strategy is to induce immune response to these factors in sows, who will transfer maternal antibodies via colostrum (first milk consumed by newborns) to protect piglets from infection. The weaned period is the most critical and stressful phase for piglets and often coincides with increased S. suis-related mortality. The development of such a product will offset the economic impact of this disease and reduce the requirement for antimicrobials (thus reducing pressure on the development of resistance) and reduce the risk of animal-to-human transmission of the infection during food production.