Autumn Crocus (Colchicum Autumnale)
The autumn crocus (Colchicum autumnale) is one of the highly toxic plants in Central Europe and poses a serious threat to our pets. This perennial plant from the Colchicaceae family is particularly insidious because it appears both in autumn with its purple flowers and in spring with its green, tulip-like leaves. All parts of the plant contain the highly effective alkaloid colchicine, with the highest concentrations found in the seeds and tubers. The toxicity of the autumn crocus is classified as +++ (very high).
Colchicine is rapidly absorbed from the gastrointestinal tract after oral ingestion and quickly distributed throughout body tissues. The substance acts as a potent cell poison by inhibiting cell division through binding to tubulin, thereby preventing the formation of the spindle apparatus during mitosis. Tissues with a high cell division rate, such as the mucous membranes of the digestive tract and the bone marrow, are particularly affected. The therapeutic window of colchicine is extremely narrow, meaning that the gap between effective and toxic doses is very small.
The most important facts at a glance
Autumn crocus poisoning represents a life-threatening emergency for dogs and cats. The alkaloid colchicine, contained in all parts of the plant, acts as a potent cell poison that primarily damages tissues with a high cell division rate, such as the gastrointestinal mucosa and bone marrow. The course of poisoning is characterized by an initial gastrointestinal phase with vomiting and diarrhea, followed by systemic effects leading to multi-organ failure.
Diagnosis is based on anamnesis, clinical picture, and laboratory changes. Since no specific antidote exists, therapy consists of decontamination, intensive symptomatic treatment, and careful monitoring. Despite optimal treatment, the prognosis is cautious, and the recovery phase can extend over weeks.
For pet owners, prevention is of utmost importance. This includes recognizing the plant in its various growth stages and avoiding areas where autumn crocus is found. Special caution is advised in autumn during its flowering season and in spring during leaf development.
Causes, development and progression
Initially, the mucous membrane of the gastrointestinal tract is primarily damaged. Later, multi-organ failure must be considered. Furthermore, inhibition of blood formation in the bone marrow, combined with coagulation disorders, occurs. This is followed by damage to the nervous system.
A small portion is excreted via the kidneys. The majority is metabolized in the liver and excreted via bile. Partial reabsorption occurs in the intestine (enterohepatic circulation).
Supplement
Poisoning in dogs and cats typically occurs from directly eating the plant. Dogs are more frequently affected than cats, as they are more prone to eating or chewing plant parts during walks. The risk of poisoning exists during two seasons: in autumn (September to November), when the characteristic purple flowers appear, and in spring (March to May), when the leaves sprout, which can easily be mistaken for wild garlic.
Even small amounts of the plant can cause severe poisoning symptoms. In cats, the LD50 (the dose at which 50% of exposed animals die) for colchicine is approximately 0.125 mg/kg body weight. For dogs, no exact data exists, but a similar sensitivity is assumed. For comparison: in humans, a single intake of 0.5 mg colchicine/kg body weight already leads to a mortality rate of about 10%.
The autumn crocus primarily grows in moist meadows, at forest edges, and in floodplains. Owners should be aware of these areas and supervise their animals particularly well there. The plant can also occur as an ornamental plant in gardens, which increases the risk for pets.
Mechanism of action
Colchicine is a cell poison. It inhibits cell division. It also accumulates in white blood cells (leukocytes).
In white blood cells, colchicine at higher concentrations induces the cleavage of proteins.
These intracellular structural changes affect the flexibility of leukocytes and thus their penetration into capillaries and tissue spaces. The result is a reduced level of inflammatory mediators in these areas and a reduction in inflammatory processes.
These mechanisms led to its use as a medication, for example, in gout diseases.
In the CNS, colchicine also causes a lowering of body temperature.
The therapeutic window is narrow and is quickly exceeded when autumn crocus is ingested.
Due to the principle of inhibiting cell division, damage first occurs in tissues and organs with a high cell division rate.
This affects the mucous membrane of the gastrointestinal tract and blood formation in the bone marrow.
In humans, a single intake of 0.5 mg colchicine/kg body weight is associated with a 10% mortality rate.
The following information applies to humans:
- Dose 0.8 mg/kg body weight – additionally hair loss, fatalities 10–50%, additional circulatory failure, fatalities 100%
The LD50 in cats for oral intake of colchicine is stated as 0.125 mg/kg body weight.
Symptoms of intoxication
First symptoms appear approximately 2–5 hours after ingestion of the plants.
Initial signs are:
- Drooling
- Vomiting, sometimes bloody
- Abdominal cramps
- Diarrhea, sometimes bloody
In the further course
- Dizziness
- Seizures
- Breathing difficulties
- Fever
- Anämie
Organ damage affects
- Leber
- Kidneys
- Bone marrow (→ anemia)
- Pancreas (insulin secretion)
In the final stage, expect
- Disturbances of consciousness
- Coma
- Death due to multi-organ failure
The clinical signs of autumn crocus poisoning develop in several phases and typically begin 2–5 hours after ingestion of the plant. The course of poisoning can be divided into three stages:
In the first phase (2–24 hours after ingestion), gastrointestinal symptoms dominate. Animals show severe salivation, violent vomiting (often with blood), intense abdominal pain, and severe, sometimes bloody diarrhea. These symptoms result from the direct damaging effect of colchicine on the mucous membranes of the digestive tract. Massive fluid loss can quickly lead to dehydration and electrolyte imbalances.
In the second phase (24–72 hours after ingestion), systemic effects come to the forefront. Animals develop fever, respiratory distress, and neurological symptoms such as lethargy, coordination disorders, and seizures. Laboratory tests at this stage already show signs of incipient bone marrow depression with decreasing blood cell counts and coagulation disorders.
The third phase (3–7 days after ingestion) is characterized by multi-organ failure. Liver and kidney damage manifest as jaundice and decreased urine production. Bone marrow damage leads to severe anemia, leukopenia, and thrombocytopenia with spontaneous bleeding. Neurological symptoms worsen to unconsciousness and coma. Without intensive treatment, death due to circulatory failure often occurs at this stage.
Diagnosis
The diagnosis of autumn crocus poisoning is based on several pillars and requires a systematic approach. First and foremost is a thorough anamnesis, in which the veterinarian asks about possible contact with the plant. Information about walks in areas where autumn crocus occurs, as well as observation of the animal eating unknown plants, is particularly important.
The clinical examination shows the characteristic picture of acute gastroenteritis with dehydration and, depending on the stage of poisoning, neurological abnormalities. In the course, signs of a coagulation disorder such as petechiae (pinpoint hemorrhages) on the mucous membranes or prolonged bleeding times may occur.
Laboratory tests are important for diagnosis and monitoring the course. A complete blood count typically shows initial leukocytosis (increased white blood cells), followed by leukopenia (decreased white blood cells) due to bone marrow damage. Blood chemistry indicates liver and kidney damage, with elevated liver enzymes (ALT, AST, AP), bilirubin, as well as urea and creatinine. Coagulation parameters such as prothrombin time and activated partial thromboplastin time are prolonged.
Direct detection of colchicine in blood or urine using chromatographic methods is possible but rarely performed in practice, as these tests are only available in specialized laboratories and the results often arrive too late for acute therapeutic decisions.
Differential diagnoses include other plant poisonings (e.g., by yew, oleander, or lily of the valley), acute gastrointestinal infections, acute pancreatitis, and heavy metal or pesticide poisonings.
Therapeutic principles
There is no specific antidote.
Decontamination by inducing vomiting and gastric lavage is of great importance in cases of recent ingestion.
Afterwards, activated charcoal is repeatedly used to counteract the effect of reabsorption of the poison after excretion via the bile (enterohepatic circulation). Bowel transit is accelerated by laxatives.
In cases of intractable vomiting, antiemetics are used.
The subsequent symptomatic therapy involves careful stabilization of water, electrolyte, and acid-base balance and prevents hypovolemic shock (volume depletion shock). Potassium supplementation prevents potassium deficiency due to losses via the intestine. Glucose infusions stabilize the energy balance.
Supplements
There is no specific antidote for autumn crocus poisoning, which is why treatment is based on three main pillars: decontamination, symptomatic therapy, and intensive medical monitoring.
Decontamination should be performed as quickly as possible after toxin ingestion. If presented within the first two hours, inducing vomiting with apomorphine (in dogs) or xylazine (in cats) may be beneficial. Gastric lavage under anesthesia may be considered for larger ingested amounts or in animals that do not vomit. Administration of activated charcoal (1–4 g/kg body weight) is particularly important and should be repeated several times at 4 to 6-hour intervals to interrupt the enterohepatic circulation of colchicine. Laxatives such as sodium sulfate accelerate intestinal transit and reduce toxin absorption.
Symptomatic therapy initially includes aggressive fluid therapy with crystalloid solutions to compensate for dehydration and promote renal excretion of the toxin. Electrolytes, especially potassium, must be regularly monitored and supplemented. For intractable vomiting, antiemetics such as maropitant or ondansetron are used. Pain relievers such as butorphanol or buprenorphine alleviate abdominal pain.
In case of signs of a coagulation disorder, a transfusion of whole blood or plasma may be necessary. Antibiotics are used prophylactically to prevent bacterial secondary infections through the damaged intestinal mucosa. Hepatoprotectants such as S-adenosylmethionine or silymarin can be administered to support liver function.
Intensive medical monitoring with regular checks of vital parameters, acid-base balance, and organ functions is required for several days. In severe cases, hemodialysis may be considered to remove the toxin, although its effectiveness in colchicine poisoning is limited.
Prognosis & follow-up care
The prognosis should be made cautiously.
Recovery with appropriate intensive symptomatic therapy is possible but takes a longer time due to high tissue absorption in intoxication. Excretion can take more than 10 days.
The prognosis for autumn crocus poisoning must generally be classified as cautious to unfavorable. The course and chances of survival depend significantly on the ingested amount, the time until therapy begins, and the intensity of treatment.
Animals that are adequately treated within the first phase and primarily show gastrointestinal symptoms have a better prognosis. Once signs of bone marrow depression or multi-organ failure appear, the prognosis significantly worsens. The mortality rate in severe poisonings can be 30–50% despite intensive therapy.
The recovery phase after surviving acute poisoning is lengthy and can take weeks to months. Complete excretion of colchicine from the body can take more than 10 days. During this time, regular follow-up examinations are necessary to detect and treat possible long-term consequences early.
In aftercare, regular blood tests should be performed to monitor bone marrow recovery and liver and kidney function. A gentle, easily digestible diet supports the regeneration of the intestinal mucosa. In cases of persistent liver dysfunction, long-term hepatoprotective therapy may be necessary.
Owners must be informed that relapses or late effects can occur even after acute poisoning has been overcome. Kidney damage, in particular, may only manifest weeks after poisoning, which is why long-term monitoring of kidney function is recommended.
Research outlook
Research into autumn crocus poisoning in small animals currently focuses on several promising areas. One key area is the development of specific antidotes that can directly interact with colchicine. Experimental studies using colchicine-specific antibodies have shown initial positive results in animal models, but are still in the preclinical stage.
Modern extracorporeal blood purification procedures, such as hemoperfusion with special adsorption materials, are being investigated for their effectiveness in removing colchicine from the bloodstream. These methods could be a valuable addition to conventional therapy, especially in severe poisoning cases.
In the field of biomarkers, researchers are looking for early indicators that can improve prognosis assessment. Recent studies are investigating the role of microRNAs and specific proteins in the blood, which could enable early identification of animals at high risk of multi-organ failure.
Supportive therapy is also being further developed. The use of growth factors to stimulate bone marrow function and newer cytoprotective substances to protect organs from colchicine-induced damage are subjects of current investigations.
Improvements in diagnostic methods, particularly faster and more sensitive detection methods for colchicine in biological samples, could lead to earlier diagnosis and thus improved treatment outcomes in the future.
Frequently asked questions (FAQs)
- How do I recognize the autumn crocus and how do I distinguish it from similar plants?
The autumn crocus blooms in autumn with purple, crocus-like flowers, while its leaves only appear in spring. Unlike the true crocus, which blooms in spring, the autumn crocus has no white stripes on its petals. The leaves can be mistaken for wild garlic but are not aromatic and do not have a garlic smell. - How quickly do I need to act if my pet has eaten parts of the autumn crocus?
You should act immediately and consult a veterinarian. The first few hours are crucial for successful decontamination and can mean the difference between life and death. - Can I induce vomiting at home as a first measure?
Self-medication is strongly discouraged. Instead, go to the vet immediately, who has the appropriate medications and methods to safely induce vomiting. - What quantities of autumn crocus are dangerous for my pet?
Even small amounts can be dangerous. In cats, the potentially fatal dose is approximately 0.125 mg of colchicine per kg of body weight, which can correspond to about 1–2 flowers or a small leaf. - How long does autumn crocus poisoning last?
The acute course of poisoning extends over 5–7 days. However, full recovery can take weeks to months, depending on the severity of the poisoning and the organ systems affected. - Are there long-term consequences after surviving poisoning?
Yes, possible long-term consequences include chronic kidney or liver damage, persistent digestive problems, and in rare cases, neurological deficits. Regular follow-up checks are important. - How can I protect my pet from autumn crocus poisoning?
Learn to recognize the plant at all growth stages. Avoid meadows and forest edges where the plant grows, especially in autumn and spring. Keep your dog on a leash when in affected areas. - Are certain dog breeds or age groups particularly at risk?
There are no breed-specific differences in sensitivity. Young, curious animals and those with pica syndrome (eating non-nutritive substances) have an increased risk. Small dogs and cats are more at risk due to their lower body weight for the same amount ingested. - Can the autumn crocus also be dangerous for humans?
Yes, the autumn crocus is also highly toxic to humans. Gloves should be worn when removing the plant, and hands should be thoroughly washed after contact. - Is autumn crocus poisoning covered by pet insurance?
Most pet insurance policies cover poisonings as emergencies. However, it is advisable to check the individual contract terms, as deductibles and maximum limits may vary.
Literature
- Anadón, A., Martínez-Larrañaga, M. R., Ares, I., & Martínez, M. A. (2018). Poisonous plants of Europe. In Veterinary Toxicology (pp. 891-909). Academic Press.
- Milewski, L. M., & Khan, S. A. (2021). Plant toxicities in small animals: herbs and flowers. Veterinary Clinics: Small Animal Practice, 51(6), 1343-1368.
- Schmid, A., Schmid, H., & Sutor, V. (2020). Poisoning in small animals: Causes, symptoms, therapy. Stuttgart: Enke Verlag.
- Wagenaar, Z., & Kooistra, H. S. (2019). Accidental colchicine poisoning in dogs: a retrospective study of 48 cases. Journal of Veterinary Emergency and Critical Care, 29(3), 319-327.
- Anadón, A., Martínez-Larrañaga, M. R., & Ares, I. (2018). Poisonous plants of Europe. In Veterinary Toxicology (pp. 891-909). Academic Press.
- Gwaltney-Brant, S. M. (2020). Colchicum autumnale intoxication: Current approaches to diagnosis and treatment in veterinary medicine. Topics in Companion Animal Medicine, 38, 100432.
- Löwe G, Löwe O. Poisoning in Dogs and Cats – A Veterinary Guide. 2nd edition. Kreuztal: Kynos-Verlag. 2021; 208 p.