Toxigenic strains of Stachybotrys atra associated with poisonous straw in Morocco.

This research paper investigates the relationship between toxic strains of Stachybotrys atra found in straw samples and an outbreak of equine illness in Morocco. The study found significant variations in toxicity among the isolated samples, thereby linking the outbreak to the presence of these toxins.

Research Context

• The research was carried out following an outbreak of equine stachybotryotoxicosis – a horse disease caused by the toxin-producing fungi Stachybotrys atra – in a region of Morocco in November 1991.
• The researchers sought to explore whether there was a connection between this outbreak and the presence of Stachybotrys atra in moldy straw samples from the affected area.

Study Methodology

• 10 moldy straw samples were collected from the location of the outbreak, from which 8 isolates of Stachybotrys atra were ultimately obtained.
• These isolates were tested to determine their toxigenicity, with a particular focus on identifying variability in the toxins they produced and in their potency.
• The toxicity of each isolate was tested in various ways, including feeding mice with moldy barley and exposing Artemia Salina larvae and rat skin to the toxins, and observing the effects.

Key Findings

• Interestingly, all the isolates demonstrated toxigenicity, i.e., they all produced toxins. However, the intensity and nature of the toxins varied from one isolate to another.
• One isolate showed only mild toxicity when fed to mice as moldy barley. However, another isolate was found to be highly toxic, causing significant harm to Artemia saline larvae, rat skin, and mice.
• The other six isolates exhibited toxicity levels that fell between these two extremes, suggesting a wide range of toxicity within these strains of Stachybotrys atra.

Conclusion

• The results of this study affirm that the equine stachybotryotoxicosis outbreak observed in November 1991 was indeed caused by the toxigenic strains of Stachybotrys atra present in the straw from the affected region in Morocco.
• This research enhances the scientific community’s understanding of the health risks associated with moldy straw and provides important insights for the prevention and mitigation of similar outbreaks in the future.