Horse Beans Poisoning in Dogs

The scientific name for the plant that produces the horse bean is called Vicia Faba. It is an erect plant with a unique grey-green coloration and flowers with five petals. They develop a broad leathery pod in which the legume itself develops. It is most commonly known in the United States as a fava bean. When cooked these beans are nontoxic, and fava bean flour, made with the cooked legumes, is sometimes added to gluten free treats. Uncooked or undercooked horse beans, like other legumes, are noxious rather than healthy as they contain the toxic lectin known as phytohemagglutinin (PHA).

Horse beans, more commonly known as fava beans, contain a toxic lectin known as phytohemagglutinin (PHA). Although rarely fatal, it can cause gastrointestinal distress, including severe vomiting and diarrhea.

The signs of toxicity with this plant usually occur within just a few hours and recovery is often rapid once the toxin has been cleared from the system. Other raw or improperly cooked legumes can also cause the same symptoms, particularly kidney beans and cannoli beans.  

• Abdominal pain
• Depression
• Diarrhea
• Drooling
• Lethargy
• Loss of appetite
• Vomiting 

Types

Other legumes also contain the toxic lectin phytohemagglutinin (PHA), and can be dangerous if consumed raw or when improperly cooked. These include beans with the scientific name of phaseolus vulgaris, such as kidney beans, black beans, cannellini beans, and navy beans. Insufficient cooking of any of these beans may actually increase the danger of the toxin, so care should be taken to ensure that any dried beans are boiled thoroughly for at least thirty minutes. PHA is also present in beans of this family such as green beans and wax beans but the concentrations are usually too low to be of any concern.

The chemical responsible for the toxicity in the fava bean is lectin called phytohemagglutinin (PHA). Any monogastric (single stomach) animal is susceptible to this noxious compound, which can cause the red blood cells to stick together, possibly causing clumps or clots. The body’s response to this sort of toxin is to remove it as quickly as possible and severe vomiting and diarrhea are the most likely result.

Witnessing the consumption of the raw or undercooked bean, either directly off the plant or during food preparation, is often enough to generate a preliminary diagnosis when combined with the symptoms and signs of Vicia Faba poisoning. If the consumption of the plant was not witnessed your veterinarian may recommend a visit to the office based on the symptoms described. As the symptoms are general and could describe a number of disorders or toxins, your veterinarian will want as thorough a history as you can provide, including any information about opportunities for inappropriate eating and prescriptions or supplements your dog may be taking. They will also order a biochemistry profile, complete blood count, and urinalysis to uncover any toxins or imbalances. The expelled stomach contents will also be analyzed in order to confirm the preliminary diagnosis. Material from the horse bean plant may be observed in these contents, further confirming the diagnosis.

In most cases, treatment for consumption of any part of the vicia faba plant can be handled at home with relative ease. It is always wise to contact your veterinarian before starting treatments to get specific instructions for your pet and to determine if either the amount eaten or the reaction to the toxin warrants a visit to the veterinarian’s office. Early therapy for dogs showing gastric distress often includes the withholding food until the vomiting and diarrhea have ceased for at least 12 hours, and this may be what your veterinarian recommends. This technique is designed to give the dog’s stomach muscles time to recover from the gastric spasms caused by the vomiting. Water and crushed ice should be offered often to combat dehydration, but only in small amounts. After the initial withholding period only soft, bland foods should be offered for at least a day or two. The ideal recovery diet would include one easily-digestible carbohydrate, such as rice or potatoes, and a mild protein source like unseasoned boiled chicken or cottage cheese. When excessive vomiting or diarrhea become a concern your veterinarian is likely to recommend bringing your pet into their office for supportive treatment. IV fluid treatment will be administered at the veterinarian’s office to prevent dehydration and medications such as Imodium or Pepcid AC may also be recommended for their gastroprotective properties.

In most cases, the effects will dissipate within a few hours. If particularly large quantities of the horse bean plant are eaten or if your dog is sensitivity to the chemical in the plant, it may cause excessive nausea and vomiting. One of the biggest dangers with such copious vomiting and diarrhea is the danger of dehydration. While your companion is affected by the toxin you should monitor them carefully for signs of dehydration such as exhaustion, excessive panting, sunken eyes, loss of elasticity in the skin and unsteadiness when standing. These symptoms may signal that the dog is in distress, and your veterinarian should be contacted for further instructions.