Alfalfa dodder (Cuscuta campestris) toxicity in horses: clinical, haematological and serum biochemical findings.
Authors: Abutarbush S M
Journal: The Veterinary record
Summary
Alfalfa dodder (*Cuscuta campestris*), a parasitic weed that can contaminate forage, presents a significant but underrecognised toxicity risk in horses, with clinical signs emerging rapidly—typically within 36 hours of ingestion. This observational study examined 20 horses naturally exposed to contaminated alfalfa, documenting clinical presentations, haematological changes and serum biochemistry across affected animals. Gastrointestinal disturbances dominated the clinical picture, with diarrhoea occurring in 8 horses and reduced appetite in 7, whilst 4 animals exhibited neurological signs; laboratory findings revealed leukocytopenia, neutropenia and thrombocytopenia alongside decreased alkaline phosphatase, aspartate aminotransferase and creatine phosphokinase activity, with elevated direct bilirubin—indicating hepatic and muscle involvement. Critically, all clinical abnormalities resolved within three days of removing the contaminated forage, with no specific treatment required, emphasising the importance of forage source verification and quality control during hay and haylage procurement. Given the scarcity of published information on *Cuscuta* toxicity in equine veterinary literature, this work provides essential reference data for practitioners to recognise this syndrome and implement rapid preventative measures rather than reactive therapeutic intervention.
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Practical Takeaways
- •Inspect alfalfa hay carefully for dodder contamination before feeding; even small amounts can cause clinical signs within 36 hours
- •Watch for sudden onset of diarrhoea, inappetence, and neurological signs in multiple horses on the same premises, and investigate feed quality immediately
- •Removing contaminated feed is the primary treatment; horses typically recover fully within 3 days without additional intervention
Key Findings
- •Clinical signs of alfalfa dodder toxicity appeared within 36 hours of ingestion, affecting 11 of 20 exposed horses
- •Gastrointestinal signs (diarrhoea in 8 horses, decreased appetite in 7) were most common, with neurological signs occurring in 4 horses
- •Haematological abnormalities included leukocytopenia, neutropenia, and thrombocytopenia
- •All abnormal clinical signs resolved within 3 days of removing contaminated feed without specific treatment