Black Walnut Poisoning in Dogs

Poisoning of canines and horses by the black walnut is well documented. Though it is most commonly thought that the nut, when subjected to mold, is the toxic component of the tree, studies have shown that eating wood from the black walnut tree can cause poisoning in dogs as well. Horses exposed to black walnut shavings may develop laminitis (an inflammatory condition in the hoof wall) which causes lameness and pain in as little as 8 hours of exposure. Ponies may suffer from respiratory difficulties when exposed.

Canines who ingest moldy husks and nuts from the black walnut tree are in particular danger because the mold is a potent fungal neurotoxin. Tremors and seizures are seen at the height of the poisoning. Aggressive treatment is required with black walnut poisoning in dogs.

The black walnut tree is known for the beautiful quality wood it produces, and the tree is grown and harvested for its premium hardwood. The black walnut tree is native in many areas of North America and also produces an edible nut. Pet owners need to be aware of the dangers of this tree; ingestion of the wood or of the nuts and shells can result in a lethal toxicity to canines.

The black walnut tree is thought to be one of the top 5 trees poisonous to large animals. Horses can experience sweating, fever, colic, and lameness when black walnut shavings are used in their stalls. Dogs may show the following symptoms after ingestion of the black walnut wood or nut:

• Panting
• Restlessness
• Excess salivation
• Vomiting
• Incoordination
• Tremors in the muscles
• Fever
• Hyperresponsiveness to stimuli
• Seizures
• Liver damage (signs could be jaundice, abdominal pain, and fatigue)
• Death

Types

Toxicity can result from ingestion of the wood, nut, husks, and shells. Typically it is thought that the main source of poison is the mold that develops after a rainy period. The walnuts may appear to be in a state of decomposition and are black or brown in color.

The black walnut tree is of the scientific family Juglandaceae and is also known as Juglans nigra

• The husks of the walnuts found on the ground and consumed by dogs contain the mycotoxin Penitrem A 
• This toxin is produced by the mold penicillium
• Bread and cheese also produce this mold
• Neurologic and musculoskeletal signs may be seen
• Buried walnuts can become available for consumption by dogs at any time of year but spring is thought to be the most problematic time
• Black walnut mold is common in shady, wet areas

Raking up the area under the tree is a good way to avoid the ingestion of the walnut by your dog. However, the tree is common in many areas all over North America, including parks where you and your canine companion may take walks. If you see that your dog has ingested wood  from the black walnut tree, or are aware that he has eaten the walnuts that have fallen from the tree, be sure to bring a specimen to the veterinary clinic. Having a plant or nut to identify is helpful to the veterinarian as symptoms of other poisonings (such as chocolate or pesticides) can be similar in presentation. Do not wait for symptoms to appear as a lethal toxicity is highly possible, particularly if the nuts and husks are brown or black in color.

The veterinarian may confirm the diagnosis based on clinical signs and plant identification. If your pet is vomiting, analysis of the vomitus and stomach contents will aid in the diagnosis. A urinalysis may indicate if the liver or kidneys have been affected; blood tests will not add to the diagnosis but can provide baseline markers for the treatment.

Treatment of black walnut poisoning in your pet will depend on how much of the wood or moldy nut was consumed, and how much time lapsed between the exposure and the clinical appointment. Early intervention is key to a timely recovery. Elimination of the toxin as soon as possible is essential. Your dog will be admitted to the hospital in order to facilitate removal of the poison from the body, and to give supportive treatment.

Vomit induction

An injection will usually be administered to ensure your dog vomits all of the stomach contents. This should be given within 4 hours of ingestion; the sooner the better.

Gastric Lavage

This is a procedure whereby the stomach is flushed with fluids in order to remove any remaining nuts or plant material from the body, Activated charcoal is administered after the procedure to bind any remaining toxins.

Intravenous Fluids

Giving fluids by the intravenous route will also help the organs of the body to flush the poison from the system. With the aid of extra liquids provided by the intravenous route, the kidneys and liver are supported. Medications needed to control seizures, and drugs to help pass the plant material through the body will be prescribed if indicated. 

Bothe fatality and recovery are recorded in black walnut poisoning in dogs. Recovery may take two to five days, and once home your dog will require additional care. Rest, a quiet place to recover, and support from all family members will be needed. Do not place expectations on your pet as he may need time to get back to normal. The poisoning by black walnut may leave him fatigued and depressed; patience and care on your part will help him in the recovery process. If at any time you are concerned about the rate of recovery, contact your veterinarian. A follow-up appointment will most likely be necessary so the veterinarian can assess the health of your dog. 

If you have the black walnut on your property, strict adherence to a raking protocol should be followed on a daily basis. Block access to the area where the black walnut tree is located. If the black walnut is located in the area where you usually walk your dog, a change of exercise venue is a must.