Bracken Fern Toxicosis

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Key Points

Bracken fern toxicosis results from ingestion of bracken fern (Pteridium spp.) by grazing animals or via contaminated forage
The main toxin is ptaquiloside (a carcinogen) but the plant also contains thiaminases
In ruminants, chronic exposure is associated with enzootic haematuria and urinary bladder neoplasia and excessive intake can cause bone marrow suppression
Monogastric species (e.g. horses, pigs) are more likely to present with thiamine deficiency
Clinical signs include haematuria, anaemia, petechiae and neurological signs
Diagnosis is usually presumptive based on clinical presentation
Humane euthanasia is usually recommended in chronic cases as the condition is progressive, severe and incurable once clinically apparent
- Thiamine deficiency has a good prognosis if treated promptly
Prevention focuses on good pasture management and preventing access to high-risk areas

Differential Diagnoses

Pyelonephritis
Cystitis
Listeriosis (L. monocytogenes)
Sweet clover toxicosis

Educational content only. This factsheet is for general veterinary education and is not a substitute for professional veterinary advice, diagnosis, or treatment. Not for use in an emergency — contact a veterinarian or emergency service. Full disclaimer →