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Levamisole stimulates systemic and intestinal cellular immunity and improves gut health in weaned pigs

Considerable efforts have been focused to understanding of porcine enteric infectious diseases, their diagnosis, including biology of pathogens, host resistance and therapy. Conversely, little is known on prevention of such diseases through immunomodulatory and dietary strategies because these problems have been overcome thus far by adding sub-therapeutic doses of antibiotic growth promoters (AGP) in-feed to enhance production efficiency in the intensive production of food animals, such as pigs. The AGP were used not only to improve growth but also to control enteric infections during critical periods, such as weaning. Concerns about potential risks for human health due to use/misuse of AGP in animal feeds have led to their ban throughout the EU since 2006. To accommodate to withdrawal of AGP it now becomes urgent to provide relevant gut health criteria and scientifically founded recommendations for alternatives to in-feed AGP. With the growing knowledge of porcine immune system and its endogenous modulation, it has been clearly stated that exogenous specific/nonspecific immunomodulation represents an important prophylactic/therapeutic approach in prevention/treatment of both stress- and enterotoxigenic E. coli (ETEC)-indued infections accompanied weaning. We have demonstrated that levamisole (LEVA) acts as a potent adjuvant when applied with the experimental non-ETEC vaccines against porcine postweaning colidiarrhea /colienterotoxemia (CD/CE). The aim of this study was to evaluate Uie effectiveness of LEVA applied perorally {; ; ; 2.5 mg/kg) to weaned (4-week-old) pigs in: (1) stimulation of systemic and intestinal cellular immunity, (2) enhancement of nonspecific resistance to ETEC strains, and (3) maintenance of their gut health based on follow-up on-farm trial during 5 weeks after the treatment. Pigs treated with LEVA had increased proportions of CD45+ lymphoid cells, CD4+ and CD8+T cells (p<0.01), but not of CD21+ peripheral blood B cells at Day 35 following the treatment. The later subset of cells was found to be increased (p < 0.01}; ; ; between Days 14 and 21 of the experiment. Also, we have found that LEVA stimulated stronger proliferation of CD45RA+ naive lymphoid cells in ileal intrafollicular areas (p <0.01 ; index of increase vs. control values = 1, 86) but not with in Payer's patches (1.20). The sum of diarrhea severity score (DSS) observed in pigs treated with LEVA was 10 or 81 % lower than that in the controls (DSS = 54). Pigs that received LEVA had much lower average diarrhea severity (ADS) (0.29 or 81%) during 35 days of the experiment than control pigs (ADS = 1.54). Substantially lower mortality rate was recorded in LEVA-treated pigs (10%) as compared to the controls {; ; ; 25%). Accordingly, we have concluded that LEVA exhibited strong stimulation of both systemic and intestinal cellular immunity in weaned pigs, which resulted in establishing of nonspecific resistance to CD/CE, and hence, the maintenance or their gut health.

levamisole stimulates systemic and intestinal cellular immunity and improves gut health in weaned pigs

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