Fumonisins have been found worldwide, primarily in maize. More than 10 compounds have been isolated and characterised. Of these, fumonisins B1, B2 and B3 are the major fumonisins produced. The most prevalent in contaminated maize is fumonisin B1, which is believed to be the most toxic.

Fumonisin toxicosis in swine has been related to porcine pulmonary oedema (PPE) since 1981, when it was caused by the experimental exposure of pigs to corn which was contaminated with F. verticillioides. This was confirmed by outbreaks of porcine pulmonary oedema in the midwestern and southeastern parts of the United States due to ingestion of corn contaminated with fumonisins. Nevertheless, before causing such typical clinical symptoms, mycotoxins often act as immunosuppressive agents. Chronic exposure to fumonisin B1 can decrease the proliferation of undifferentiated porcine epithelial intestinal cells, altering the integrity of intestinal epithelium and consequently facilitating the entrance of pathogens into the body (Bouhet and Oswald, 2005).

In fact, 1mg of fumonisin B1/kg body weight for 10 days in weaned piglets can predispose to a longer shedding of F4+ enterotoxigenic E. coli following infection, which deepens intestinal damage (Devriendt et al., 2009). Step by step, fumonisin B1 deteriorates the host’s immune system, affecting recognition and processing of pathogens by the antigen–presenting cells, avoiding signaling (lower cytokine production) the attraction of effector cells for pathogen elimination, which finally leads to prolonged intestinal infection.

Fumonisins can decrease the clearance of Pseudomonas aeruginosa (Haschek et al., 2001).

Also, the phagocytosis of Salmonella typhimurium is decreased in alveolar macrophages from pigs fed fumonisin B1 (Liu et al., 2002). Consequently, pigs’ susceptibility to diseases caused by those pathogens is increased.

Feeding weaning piglets with 8mg fumonisin B1/kg for 28 days leads to a significant decrease in antibody titre after vaccination against Mycoplasma agalactiae (Taranu et al., 2005). Feeding pigs fumonisin–contaminated feed could lead to an inappropriate vaccination response, reducing the level of specific antibodies and reducing the period of vaccine protection, or just leaving animals unprotected against this specific disease.

The aforementioned studies describe some of the immunosuppressive effects of fumonisins and their role as a predisposing factor to disease in pigs. Still, more information is needed about its mechanisms of action to induce these and other effects. One thing is certain: fumonisins represent a risk to animal health and performance, and that is why proper mycotoxin risk management is indispensable.