Peer-reviewed veterinary case report
Horses getting skin problems from eating a toxic plant in Brazil?
By Riquelme, Lourdes Fernández et al.·Published in Toxicon : official journal of the International Society on Toxinology·2026·Graduate Program in Animal Science, Brazil·View original on PubMed →
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Original publication title: Primary photosensitization in horses associated with ingestion of Malachra fasciata Jacq. (Malvaceae) in the Northeast of Brazil.
- Species:
- horse
Plain-English summary
Four Quarter Horses in Brazil developed severe skin problems after grazing on a pasture filled with a toxic plant called Malachra fasciata. The horses showed signs of distress, with hair loss, red and crusty lesions on their skin, and intense itching. After being moved to a shaded area away from the plant, their condition improved, but the skin issues returned when they were exposed to the plant again. This case highlights the importance of managing pastures to prevent horses from coming into contact with harmful plants.
People also search for: horse skin problems · photosensitization in horses · toxic plants for horses · horse itching treatment · Quarter Horse skin lesions
Abstract
Malachra fasciata Jacq. (Malvaceae) is an invasive plant widely found in Northeastern Brazil and has been experimentally demonstrated to cause severe dermatitis in sheep. However, its toxic effects in horses have not previously been documented. This report describes primary photosensitization in four Quarter Horses grazing on a pasture heavily infested with M. fasciata in Paraíba, Brazil. Affected animals developed alopecic, erythematous, crusted, and ulcerated lesions on sun-exposed areas, accompanied by severe pruritus and behavioral signs of distress. Histopathology revealed epidermal ulceration with serocellular crusts, marked hyperkeratosis, keratinocyte necrosis, spongiosis, and an eosinophil-rich dermal infiltrate. All horses improved after removal from the infested pasture and were housed in a shaded environment, but lesions recurred upon re-exposure. This case represents the first confirmed report of primary photosensitization caused by M. fasciata in horses and highlights the clinical significance of this emerging toxic plant in equine management.
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Search related cases →Original publication on PubMed: https://pubmed.ncbi.nlm.nih.gov/41490913/