Toxicity of field samples and Fusarium moniliforme from feed associated with equine-leucoencephalomalacia.

The research focuses on the link between a specific type of fungus found in horse feed and a disease affecting horses called equine leucoencephalomalacia (ELEM). The fungus, Fusarium moniliforme, is prevalent in feed samples associated with incidents of the disease, and toxicity tests show that it can be lethal to animals — implicating it as a possible cause of ELEM.

Collection and Analysis of Feed Samples

• Feed samples, including corn, pelleted feed, and oats, were obtained from North Carolina, Illinois, Indiana, and Oklahoma. These were all sites of equine leucoencephalomalacia cases.
• The collected samples had a high colony density of Fusarium moniliforme, a fungus known to be toxic to animals. It made up 64 to 87% of all fungi found in the samples.
• 59 strains of F. moniliforme were isolated for further testing.

Fungus Culturing and Toxicity Testing

• The F. moniliforme strains were cultured on corn, which were fed to one-day-old ducklings. This resulted in a high average mortality rate of 55%, suggesting that the fungus could be potentially dangerous.
• Methanol extracts from the corn fermented with the F. moniliforme strains were also tested on mice and rabbits. Some of the extracts caused deaths in mice and skin necrosis in rabbits, further underlining the fungus’ toxicity.

Toxin Analysis

• In analyzing the feed samples and the fermented corn, known toxins — vomitoxin, T-2 toxin, zearalenone, and moniliformin — were not found. This indicates that the toxicity of the F. moniliforme doesn’t come from these poisons.
• Instead, small amounts of aflatoxin B1, a potent carcinogen, were found in the North Carolina samples.
• Bikaverin, a red pigment associated with the Fusarium genus of fungi, was detected. While it’s commonly found in this kind of fungi, this is the first instance of its discovery in feed samples associated with ELEM.

The research concludes that F. moniliforme Sheldon could likely be a contributing factor to the outbreak of equine leucoencephalomalacia (ELEM) in the observed locations. The toxins found in the F. moniliforme strains show a capacity to be lethal to animals, providing evidence of the fungus’s role in the disease. The detection of Bikaverin is also a significant discovery, opening further paths for future study.