Bracken fern toxicity and its associated clinicopathological effects in humans and animals: a review

Bracken fern is a delicacy consumed by humans and serves as animal forage around the world. It is said to be the 5th most common plant, an important toxic plant and the only higher plant known to cause cancer in animals. Occurrence of urinary bladder neoplasia is extremely high in cattle and it is associated with the continuous consumption of bracken fern. Animals are affected by bracken toxic active components, leading to huge economic losses. Bracken fern toxicity in cattle presents the following clinical signs of pyrexia, epistaxis, melena, chronic weight loss, dysphagia, incoordination and haemorrhagic lesions on the udder. The thiaminase content in bracken fern causes anorexia and incoordination in horses while the signs of bracken fern toxicity in ovines generally lead to retinal neuroepithelium degeneration. In bovines, bracken fern toxicity is a known aetiology in the depression of bone marrow haematopoietic activity characterised by anaemia, leucopenia, thrombocytopenia and haematuria which are cardinal haematopathology associated with bracken poisoning. Significant elevations in serum enzymes like aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), urea and creatinine levels were seen in animals exposed to bracken fern. Diagnosis of bracken toxicity is based on evidence of ingestion with appropriate clinical and postmortem findings, histopathological examination, polymerase chain reaction and immunohistochemistry are also very important tools in diagnosis. In conclusion, special attention should be given to this plant by toxicologists, botanists, veterinarians, toxicopathologists, oncologists and public health specialists. The human populace, farmers inclusive, should be educated about the public health significance of this plant.