NOVEL APPROACHES TO IDENTIFY OPTIMAL ANTIVIRAL PROBIOTICS FOR SWINE INDUSTRY IN LOW-INCOME COUNTRIES

Effective prevention and control of enteric viral diseases of livestock are critical for food security and public health. However, it remains challenging, due to the lack of efficacious vaccines and antivirals. Increased environmental contamination and higher exposure to enteric pathogens associated with poor biosecurity practices represent an additional challenge in developing countries. Porcine rotavirus (RV) is a major enteric pathogen causing substantial economic losses to farmers.

Antibiotics are important in human and animal health but prolonged use as growth-promoters in food animals leads to increased antimicrobial resistance (AMR) which is a public health concern. In order to be compliant with the global efforts of controlling AMR, the swine producers with other livestock industries are ceasing from the use of antibiotics as growth promoters. However, electrolytes and antibiotics are frequently prescribed to treat gastroenteritis of viral or bacterial origin as a result of enteric viral infections that increase secondary bacterial infections. Thus, unselective or improper antibiotic use due to misdiagnosis or lack of such is another antibiotic-related practice that needs to be changed. Therefore, reduced use of antibiotics could help addressing this issue.

Probiotics are the best substitute to antimicrobials. Historically, various probiotics were used as feed additives and were shown to improve growth and health of livestock animals. However, the results were mostly inconsistent due to variable dosages and types of probiotics used, animal diet, and age. Additionally, while most studies did not evaluate probiotic effects on enteric viruses; some studies demonstrated contrasting results of the effects of some probiotics on post-weaning diarrhea in pigs. This can partially result from the lack of mechanistic understanding of how probiotic bacteria interact with enteric viruses and certain host-related factors. Therefore, a stronger rationale for selection of optimal in-feed alternatives is gaining higher priority to support a sustainable swine industry.

Noroviruses, RVs and Coronaviruses (CoVs) recognize Histo-Blood Group Antigens (HBGAs) as attachment factors that determines their pathogenesis, host and age range and infectivity. Further, certain lactobacilli were shown to bind HBGAs, while some enteric bacteria produce HBGA-like substance suggesting that such bacteria (HBGA+) can directly bind some enteric viruses. Thus, besides immunomodulatory properties, probiotic and commensal bacteria can either block HBGA attachment sites on intestinal epithelial cells or directly bind enteric viruses. These underappreciated mechanisms of their action should be systematically evaluated in vitro and in vivo {in gnotobiotic (Gn) and conventional pigs models} to formulate optimal probiotic treatments to combat enteric viruses and to compensate for the loss of antibiotic-related benefits.