ISSN 2398-2993      

Bracken fern poisoning


Synonym(s): Pteridium species

Podcast: Bracken fern poisoning


  • Cause: ingestion of bracken (Pteridium species).
  • Signs: hemorrhage, pyrexia, loss of condition, intermittent hematuria. 
  • Diagnosis: based on clinical signs, history of exposure and post-mortem findings.
  • Treatment: supportive, but generally ineffective.
  • Prognosis: poor.



Acute hemorrhagic syndrome 
  • Poisoning only occurs after ingestion of bracken for several weeks or months and can occur weeks after cessation of exposure. 
Enzootic bovine hematuria
  • Associated with chronic low-level ingestion of bracken over months or years.
  • Signs are intermittent and can occur weeks after cessation of exposure. 
  • More common in cattle aged > 4 years. 
  • Episodes can be precipitated by stress (eg parturition, transport).

Predisposing factors


Acute hemorrhagic syndrome ​
  • Young age.


Enzootic bovine hematuria


Acute hemorrhagic syndrome
  • The mechanism of bone marrow suppression is unknown but is attributed to radiomimetic damage to proliferating bone marrow stem cells by the compound ptaquiloside. 
  • There is depletion of bone marrow megakaryocytes followed by panhypoplasia. 
  • Affected animals have both an increased susceptibility to infection and a tendency to bleed.
 Enzootic bovine hematuria
  • The toxin ptaquiloside is a direct-acting carcinogen. 
  • It is converted in alkaline conditions to a highly reactive dianone intermediate which reacts with DNA to produce chromosomal damage which can lead to the formation of neoplasms. 
  • Ptaquiloside and bracken-induced chromosomal aberrations have been demonstrated experimentally.


Acute hemorrhagic syndrome 
  • This form of bracken toxicosis is rapidly progressive; death is common and generally occurs 1-6 days after onset of signs. 
Enzootic bovine hematuria
  • Poisoning only occurs after ingestion of bracken for months or years. 
  • Episodes of hematuria may last for weeks or months.


  • Bracken is a very common plant, throughout most of the world.
  • The concentration of ptaquiloside varies in bracken populations; where it is low the incidence of poisoning is also low. 


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Further Reading


Refereed Papers

  • Recent references from PubMed and VetMedResource.
  • Faccin T C, Masuda E K, Piazer J V M, Melo S M P & Kommers G D (2017) Annular stenotic oesophageal squamous cell carcinoma in cattle exposed naturally to bracken fern (Pteridium arachnoideum). J Comp Pathol 157 (2-3), 174-180.
  • Plessers E, Pardon B, Deprez P, De Backer P & Croubels S (2013) Acute hemorrhagic syndrome by bracken poisoning in cattle in Belgium. Vlaams Diergeneeskundig Tijdschrift 82, 31-37.
  • Di Loria A, Piantedosi D, Cortese L, Roperto S et al (2012) Clotting profile in cattle showing chronic enzootic hematuria (CEH) and bladder neoplasms. Res Vet Sci 93 (1), 331-5.
  • Fletcher M T, Reichmann K G, Brock I J, McKenzie R A & Blaney B J (2011) Residue potential of norsesquiterpene glycosides in tissues of cattle fed Austral bracken (Pteridium esculentum). J Agric Food Chem 59 (15), 8518-23.
  • Masuda E K, Kommers G D, Martins T B, Barros C S & Piazer J V (2011) Morphological factors as indicators of malignancy of squamous cell carcinomas in cattle exposed naturally to bracken fern (Pteridium aquilinum). J Comp Pathol 144 (1), 48-54. 
  • Anjos B L, Irigoyen L F, Fighera R A, Gomes A D et al (2008) [Acute poisoning by bracken fern (Pteridium aquilinum) in cattle in central Rio Grande do Sul, Brazil.] Intoxicação aguda por samambaia (Pteridium aquilinum) em bovinos na Região Central do Rio Grande do Sul. Pesquisa Veterinária Brasileira 28 (10), 501-507.
  • Borzacchiello G & Roperto F (2008) Bovine papillomaviruses, papillomas and cancer in cattle. Vet Res 39 (5), 45. 
  • Carvalho T, Pinto C & Peleteiro M C (2006) Urinary bladder lesions in bovine enzootic hematuria. J Comp Pathol 134 (4), 336-346. 
  • Perez-Alenza M D, Blanco J, Sardon D, Sanchez Moreiro M A &Rodriguez-Bertos A (2006) Clinico-pathological findings in cattle exposed to chronic bracken fern toxicity. N Z Vet J 54 (4), 185-92. 
  • Souto M A M, Kommers G D, Barros C S L, Piazer J V M et al (2006) [Neoplasias do rato alimentar superior de bovinos associadas ao consumo espontâneo e samambaia (Pteridium aquilinum)]. Pesq Vet Bras 26 (2), 112-122.
  • Gava A, da Silva Neves D, Gava D, de Moura S T et al (2002) Bracken fern (Pteridium aquilinum) poisoning in cattle in southern Brazil. Vet Hum Toxicol 44 (6), 362-5.
  • Hoque M, Somvanshi R, Singh G R & Mogha I V (2002) Ultrasonographic evaluation of urinary bladder in normal, fern fed and enzootic bovine hematuria-affected cattle. J Vet Med A Physiol Pathol Clin Med 49 (8), 403-7.
  • Sandoval J M, Sánchez A V, Pino D R, Villarroel R N et al (2002) Estudio ultrasonográfico de la vejiga urinaria En la hematuria enzoótica bovina (Ultrasonographic study of the urinary bladder in bovine enzootic hematuria). Revista Científica, FCV-LUZ 12 (5), 346-350.
  • Alonso-Amelot M E & Avendaño M (2001) Possible association between gastric cancer and bracken fern in Venezuela: an epidemiologic study. Int J Cancer 91 (2), 252-9.
  • Marrero E, Bulnes C, Sánchez L M, Palenzuela I et al (2001) Pteridium aquilinum (bracken fern) toxicity in cattle in the humid Chaco of Tarija, Bolivia. Vet Hum Toxicol 43 (3), 56-8.
  • Wilson D, Donaldson L J & Sepai O (1998) Should we be frightened of bracken? A review of the evidence. J Epidemiol Community Health 52 (12), 812-7.
  • Alonso-Amelot M E, Castillo U, Smith B L & Lauren D R (1996) Bracken ptaquiloside in milk. Nature 382, 587.
  • Smith B L & Seawright A A (1995) Bracken fern (Pteridium spp.) carcinogenicity and human health - a brief review. Nat Toxins 3 (1), 1-5.
  • Smith B L, Seawright A A, Ng J C, Hertle A T et al (1994) Concentration of ptaquiloside, a major carcinogen in bracken fern (Pteridium spp.), from eastern Australia and from a cultivated worldwide collection held in Sydney, Australia. Nat Toxins 2 (6), 347-53.
  • Evans I A, Jones R S & Mainwaring-Burton R (1972) Passage of bracken fern toxicity in milk. Nature 237, 107–8.
  • Jarrett W F H, McNeill P E, Grimshaw W T R, Selman I E & McIntyre W I (1978) High incidence area of cattle cancer with a possible interaction between an environmental carcinogen and a papilloma virus. Nature 274, 215–17.
  • Pamukcu A M, Price J M & Bryan G T (1976) Naturally occurring and bracken-fern-induced bovine urinary bladder tumors. Clinical and morphological characteristics. Vet Pathol 13 (2), 110-22.
  • Evans I A (1968) The radiomimetic nature of bracken toxin. Cancer Res 28, 2252-2261.
  • Evans I A & Mason J (1965) Carcinogenic activity of bracken. Nature 208, 913–14.
  • Tustin R C, Adelaar T F & Meldal-Johnsen C M (1968) Bracken poisoning in cattle in the Natal Midlands. J S Afr Vet Med Assoc 39 (3), 91-99.

Other sources of information

  • Waine K, Busin V & Strugnell B (2019) Getting the Most out of On-Farm Post-Mortems: A Guide for Veterinary Surgeons. AHDB, UK. Website:
  • Burrows G E & Tyrl R J (2013) Toxic Plants of North America, 2nd edn. Wiley Blackwell, Ames, Iowa.
  • Ramwell C T, van Beinum W, Rowbotham A, Parry H et al (2010) Ptaquiloside and other bracken toxins: a preliminary risk assessment. The Food and Environment Research Agency, York. Available at:
  • Evans W C (1989) The acute diseases caused by bracken in animals. In: Bracken Toxicity and Carcinogenicity as Related to Animal and Human Health. Institute of Earth Studies. University College of Wales: Aberystwyth, 22-34.


  • ASPCA Animal Poison Control Center:, telephone number (888) 426-4435.
  • Veterinary Poisons Information Service (VPIS);, telephone + 44 (0) 2073 055 055.

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