Individual and combined effects of subclinical doses of mycotoxins deoxynivalenol and fumonisins on the vaccinal and intestinal responses of piglets

Mycotoxins are a group of structurally diverse secondary metabolites of fungi that can result in health problems in animals and severe economic losses. Pigs are naturally exposed to mycotoxins due to the high inclusion of cereals and by-products in their diets. Based on recent surveys, 70% of worldwide feed and feed raw materials are positive for at least one mycotoxin and 40% are found to be co-contaminated. Co-occurrence of mycotoxins is thus the norm and not the exception, and until now not much is known about the risk in pigs of exposure to multi-contaminated feed.

Therefore, we investigated the interaction between deoxynivalenol (DON) and fumonisins (FB), two major mycotoxins from Fusarium species co-occurring very often in finished feed. Piglets received separate diets for five weeks: a control diet; a diet contaminated with either DON (3 mg/kg) or FB (6 mg/kg); or both toxins. The levels of contamination were considered representative of field conditions. Given the mode of action of both mycotoxins, the effects on the vaccinal response were investigated following immunization of pigs with ovalbumin (OVA), as well as the effects on the intestinal response.

Pigs fed DON and/or FB were not able to mount an appropriate immune response following vaccination, especially in pigs fed the co-contaminated diet, as seen with the reduced concentration of specific anti-OVA IgG, the low proliferation of lymphocytes upon OVA stimulation, and the decreased expression of cytokines in the spleen (IL-1β, IL-8, IL-6, IL-12p40). Our findings in the small intestine (jejunum and ileum) also suggested that ingestion of DON and/or FB affected the gut integrity and induced intestinal alterations that are similar to those observed during low-grade inflammation and chronic disease (up-regulation of pro-inflammatory cytokines, reduced expression of tight junction proteins, and infiltration of immune cells). The type of interaction between DON and FB was determined by analyzing the data with a two-way factorial ANOVA on each endpoint assessed. The interaction of DON and FB was very dependent on the endpoint, with ten endpoints reporting antagonism, eighteen additivity, and three synergism.

In conclusion, ingestion of subclinical doses of mycotoxins does not induce visible clinical signs but result in immunological disturbances and may act as predisposing factors and impair the response of animals to antigenic challenges, such as vaccination or infection. In addition, further work is needed to characterize the type of interaction between mycotoxins and evaluate the risk in animals since current legislations in feed only set limits for one single mycotoxin.

Disclosure of Interest: None Declared.