Field outbreaks of leukoencephalomalacia in horses consuming maize infected by Fusarium verticillioides (= F. moniliforme) in South Africa.

This research article details four outbreaks of leukoencephalomalacia, a brain disease, in horses across South Africa, which were linked to the horses consuming mouldy home-grown maize infected with the fungus Fusarium verticillioides. The disease symptoms and lesions observed in these outbreaks align with previous cases caused by this fungus.

Multiple Outbreaks in South Africa

• The study begins with reporting on four distinct outbreaks of leukoencephalomalacia in horses that occurred across various areas in South Africa. Leukoencephalomalacia is a fatal brain disease that affects horses, showing symptoms like depression, impaired vision, difficulties in chewing and swallowing, and incoherent behaviour.
• These outbreaks were widely separated geographically, implying different sources of infection but with a common feature being the infection from the Fusarium verticillioides fungus.

Evidence of Mouldy Maize Involvement

• The researchers found a common factor among these outbreaks: the horses consumed mouldy home-grown maize which was infected with Fusarium verticillioides, also known as F. moniliforme. The fungus was isolated in every instance, highlighting its involvement in the series of outbreaks.
• The presence of mouldy maize points towards a possible negligence in the storage and maintenance of the feed, leading to fungal infestation and resultant infection once consumed by the horses.

Similar Symptoms to Experimental Cases

• Interestingly, the clinical signs and pathological lesions that were observed in the affected horses during these outbreaks were found to be identical to those seen in cases where horses were experimentally poisoned with F. verticillioides. This further solidified the role of this specific fungus in causing the disease outbreaks.
• The results from the field aligned with previous laboratory findings, providing more weight to the theory that the fungus Fusarium verticillioides, when present in mouldy maize, is a direct contributing factor in causing outbreaks of leukoencephalomalacia in horses.