A dry summer brings with it an increased risk of plant poisonings and we have seen bracken poisoning cases at our centres across Scotland in recent weeks.
We suggest you keep bracken toxicity in mind when considering differential diagnoses for cattle with extensive or unexplained haemorrhage especially where alimentary or upper respiratory mucosal ulceration/necrosis is present.
Clinical cases may display intermittent haematuria and signs of anaemia – weakness, weight loss, pyrexia and haemorrhages, which can range from mucosal petechiae to effusive bleeding. We recently have seen a few cases where the visceral histopathology demonstrated haemorrhage and extensive fungal and/or bacterial colonisation but very few neutrophils which would be consistent with bone marrow suppression associated with bracken toxicity. Bracken poisoning is a potential food safety concern; animals must have been free from exposure to the plant for at least 15 days prior to entering the food chain.
Some points to note are as follows:
- Bracken is most commonly found in semi-shaded, well-drained, open woodlands
- Cattle are more often affected than sheep
- Poisoning most often occurs in late summer when other feed is scarce
- Poisoning requires prolonged exposure
- Poisoning is usually fatal
- Initial poisoning causes bone marrow damage
- Chronic exposure causes carcinogenic conditions, namely urinary tract neoplasia in ruminants
- Fixed bone marrow (sternum or rib) can be examined to confirm the diagnosis