What is Cowbane Poisoning?
Cowbane (also called northern water hemlock or McKenzie’s water hemlock) is the common name for Cicuta virosa, one of four species of cicuta plants that are highly toxic. It is found in parts of Europe and northern Asia, as well as northwestern North America. The cicuta species are considered the most poisonous plants in North America. Reportedly, Native Americans used to dip their arrows in poison extracted from the root to make them more deadly. The main toxin in cowbane and other cicuta species is cicutoxin, a yellow colored retinoid found in strongest concentration in the root. Toxic root juices are said to smell like parsnip when cut, accounting for one of the plants many common names, poison parsnip. The root is toxic all year long. The early shoots in spring are also highly toxic, however during summer and fall the woody stem and larger leaves contain much less cicutoxin. Cowbane is the type species for other cicuta; it grows from 3-7 feet (1 to 2 meters) tall with leaves that are about 15 inches (38 cm) long placed alternately on each side of the stem. Three pairs of pointed oval leaflets branch on either side of the leaf stem (in botanical language this is described as tri-pinnately compound). The tiny white flowers are arranged in umbrella shaped clusters that are 1-4 inches (2.5-10 cm) across. Each flower has 5 petals and 5 stamen.
Cowbane and other cicuta species grow wild in wetlands, fields or along the banks of streams. They are a hazard for livestock if they get into a field, but they are also dangerous for dogs out for a walk or anyone else who doesn’t recognize the plant. The lethal dose is extremely low. As little as a single bite of root, root stem, or early spring leaves could be enough to kill an animal, depending on weight. Cicutoxin is a neurotoxin which stimulates the central nervous system almost immediately. Excessive salivation, vomiting and seizures can occur from 15 minutes to 6 hours after ingestion. Death often takes place within a few hours, so treatment may be difficult. Immediate treatment can reduce absorption and control the severity of symptoms, but cowbane poisoning doesn’t have a high rate of recovery.
Cowbane, also called water hemlock, is one of the most dangerously toxic plants in North America. It has been known to cause fatal poisoning in humans, dogs, and livestock animals. Symptoms appear quickly and can cause death in only a few hours.
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Symptoms of Cowbane Poisoning in Dogs
These are the symptoms you may see if your dog eats cowbane. Call a veterinarian or a poison helpline immediately.
- Foaming at the mouth
- Muscle twitches
- High Pulse
- Dilated pupils
- Wheezing or difficulty breathing
- Death from respiratory failure
There are four species of Cicuta which are currently classified in the Apiaceae family.
- Cicuta virosa – Cowbane, Mackenzie’s water hemlock, northern water hemlock
- Cicuta maculata or Cicuta occidentalis – Beaver poison, spotted water hemlock, spotted cowbane, spotted parsley, musquash root
- Cicuta douglasii – Western water hemlock, Douglas water hemlock
- Cicuta bulbifera – Bulblet-bearing water hemlock, bulbous water hemlock
Causes of Cowbane Poisoning in Dogs
These factors could put your dog at risk for cowbane poisoning.
- Dogs that like to eat shoots or leaves when out for a walk
- Dog digging up a root and biting off the root stem (this is where the strongest concentration of toxin is located)
- Frequent walks in areas where cowbane grows
- Dogs running free in the fields
- More likely in springtime when leaves are most toxic
Diagnosis of Cowbane Poisoning in Dogs
Cowbane poisoning will be diagnosed based on symptoms and a history of ingestion. Specialized blood tests can determine the presence of cicutoxin in the blood, but given the swift onset of symptoms, this is not usually used as a diagnostic method. Retaining a sample of the plant for identification is the best way to ensure a swift diagnosis, but care should be taken to avoid exposure. Wash your hands after handling and don’t touch your mouth or face. Use gloves if possible. If you think your dog may have eaten cowbane or another cicuta species, you should call a veterinarian or a poison helpline immediately. Be prepared to describe the plant exactly as well as give your dog’s breed and weight and an estimate of how much you think was ingested.
Treatment of Cowbane Poisoning in Dogs
If poisoning took place within the last hour, the veterinarian will induce vomiting and may also perform gastric lavage under anesthesia. Your dog may need an oxygen tube inserted down the throat during this process to ensure breathing remains constant. Activated charcoal will be given to help reduce absorption in the gastrointestinal tract.
There is no antidote to cicutoxin, so treatment will be symptomatic. Various types of anti-seizure medication will be given to control seizures, either a benzodiazepine like diazepam, or a barbiturate such as phenobarbital. Several types of medication may need to be tried since seizures often recur even with treatment. Metabolic and blood pressure abnormalities will be maintained through intravenous fluid and electrolyte treatment, or with medication like dopamine or norepinephrine if low blood pressure persists. Kidney failure is often a problem with cicutoxin toxicity, so medications may be given to support kidney function. Humans with cicutoxin poisoning are often treated with dialysis. If your dog survives, symptoms will usually taper off in 24-48 hours, but seizures have been known to persist as long as 96 hours.
Recovery of Cowbane Poisoning in Dogs
Dogs with cowbane poisoning have a low chance of recovery. Symptoms are often fatal before treatment is possible, and severe cases will likely not respond to treatment. Humans that have recovered from cicutoxin poisoning have experienced negative long-term side effects including amnesia, restlessness, muscle weakness, twitching and anxiety, so physical and behavioral changes may be possible even if your dog recovers. In some cases, symptoms have been known to persist for days or even months after poisoning.
It’s almost impossible to keep dogs from digging and investigating unknown plants, but there are several things you can do to help reduce the risk of exposure. Learn to recognize cowbane and other types of cicuta species found in your area. Keep your dog enclosed in the yard unless you can accompany him on a walk. Use a leash in areas where cowbane is known to grow. Have a plan in place for emergency veterinary treatment, so if your dog is exposed you will be able to get professional treatment as soon as possible.