In the medical world, ‘complications’ is a term that stimulates high anxiety in patients.  A post-surgical patient in recovery who picks up an infection in the hospital goes suddenly from a few days of routine convalescence to a potentially life-threatening struggle.  That may not be the best example of an “interaction” but it comes close.  In the scientific world, interactions amongst factors in an experiment or on a farm range from additive, in which the outcome of multiple factors can be predicted as a simple sum of their individual effects to either antagonism or synergism.  Antagonism occurs when the effect of one factor negates or lessens the effect of another.  Synergism, or potentiation, is when the combined factors produce a result significantly worse than could be predicted from the individual factor effects.  Unfortunately mycotoxins don’t seem to interact antagonistically, and while additive effects are sometimes the result, generally we can expect a synergistic response.  There are two ways of looking at this phenomenon in toxicology.   First, given acute doses of two toxins, we expect the animal to have a much worse result than the two individual activities would suggest.  But, second, and what is often seen in the field, is that an animal exhibits a toxicity syndrome even though the doses of the two or more toxins are in the ‘low’ range that generally is not expected to produce an ill effect.  Pigs consuming some dose of vomitoxin (DON) might show some minor reduction of performance variables, but when some other mycotoxins are present, that tested dose of DON appears to have been responsible for more extensive pathology, even though such results are not within the conventional wisdom surrounding that particular level of DON.

Mycotoxins have been shown in numerous reports to interact with other mycotoxins.  In some cases the result observed is actually a ‘new’ disease that may lack the specific toxicological markers of any of the contributing poisons.  But mycotoxins also interact with other stressors that occur in commercial animal operations.  These can include social stresses, such as those experienced by animals moved into a new grouping or new facility, or environmental stresses, such as heat, cold, etc.  Mycotoxins also interact with other biologically active compounds, such as phytoestrogens.   Most swine producers are familiar with risks and signs of zearalenone in their pigs.  But coupled with a feed-borne phytoestrogen, these effects can be magnified greatly.  Mycotoxins also are well known to interact with infectious agents, e.g., bacteria, protozoa, viruses, whether they are high virulence pathogens or opportunistic pathogens.  One of the classic examples of a mycotoxin interaction in pigs was reported three decades ago.  In a research trial, young pigs were given either an acute dose of aflatoxin, an infective dose of a dysentery-producing organism (Treponema hyodysentariae) or the combination of both (Joens, L.A., Pier, A.C., and Cutlip, R.C. ,1981. Effects of aflatoxin consumption on the clinical course of swine dysentery. Amer. J. Vet. Res. 42: 1170-1172).  The table below summarizes the results of the trial.