Authors: Shapter Frances Marie, Granados-Soler José Luis, Stewart Allison J, Bertin Francois Rene, Allavena Rachel
Journal: Animals : an open access journal from MDPI
Summary
Crofton weed (Ageratina adenophora) causes severe, irreversible pulmonary fibrosis and oedema in horses, yet remains poorly recognised outside Australia and New Zealand despite being endemic in many regions where it could be underdiagnosed. Shapter and colleagues conducted a comprehensive literature review synthesising toxicological and exposure data from equine cases alongside experimental findings from rodent, rabbit, and goat models to identify knowledge gaps in our understanding of the plant's mechanisms of harm. Critically, whilst the pathogenesis has been characterised in various laboratory species, the pulmonary-selective toxicity observed in horses differs markedly from organ-specific damage patterns in other animals, suggesting species-dependent differences in toxin biotransformation, bioactivation, and susceptibility to individual plant compounds. The authors highlight that without identifying the specific equine toxins responsible and understanding the mechanistic pathways unique to horses, development of prophylactic or therapeutic interventions remains stalled. This review underscores the need for horse-specific toxicological research to support earlier diagnosis in at-risk regions and to progress viable treatment strategies for what currently remains an irreversible condition.
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Practical Takeaways
- •Veterinarians should maintain high clinical suspicion for Crofton weed toxicity in horses presenting with respiratory disease in endemic regions, as cases may be underdiagnosed outside Australia and New Zealand
- •Understanding that Crofton weed causes irreversible pulmonary disease emphasizes the importance of pasture management and exclusion of this invasive weed from grazing areas as the primary prevention strategy
- •Current evidence does not support curative or preventive treatments once exposure occurs; management focus should be on plant identification, removal, and avoiding affected grazing areas
Key Findings
- •Crofton weed toxicity causes irreversible and untreatable pulmonary fibrosis and oedema in horses following ingestion
- •Equine pneumotoxicity from Crofton weed may be underdiagnosed in countries where the weed is endemic but poorly differentiated
- •Toxicity pathogenesis differs markedly between horses and other animal models (rodents, rabbits, goats) despite similar plant exposure, suggesting species-specific susceptibility mechanisms
- •Variation in toxic effects across species likely results from differences in species susceptibility to specific plant toxins, biotransformation mechanisms, and organ-selective toxin bioactivation