Atropa Belladonna Intoxication in Horses

There are a whole host of wild plants that have been found to be poisonous to horses. One of the more common and especially toxic types is the deadly nightshade, or atropa belladonna.

Nightshade is naturally distasteful to horses, and as a rule they do not prefer the taste of this plant over other grazing foods. More often, it is eaten unintentionally when parts of the plant make it into the horse's food supply, perhaps the fallen leaves from the nightshade bush were razed along with the grass, or when there is a lack of grazing material for the horse to choose from. The most toxic parts of the plant are the leaves and stems, which may be found in the grazing grass. The degree of toxicity decreases in the berries of the plant, but they do continue to be toxic and can accrue in the system over time, resulting in chronic toxicity.

This can affect horses of any age, and the plants can be found in a number of environments, most often in wooded areas, along roadsides, amongst wild growth on farmland, and on open pastures and fields.

Symptoms and Types

• Dry mouth
• Dilated pupils (mydriasis)
• Change in heart beat (i.e., irregular in pace or increased pace - tachycardia)
• Sensitivity to light, or blindness
• Nervousness
• Muscle tremors
• Muscle convulsions
• Constipation
• Diarrhea
• Disorientation
• Loss of coordination (ataxia)
• Recumbence (lying down excessively)
• Loss of consciousness, coma
• Death (severe cases)

Causes

Ultimately the poisoning will occur when the horse ingests deadly nightshade (atropa belladonna). This may occur while the horse is grazing or unintentionally if the plant is accidentally mixed with horse's feed.

Diagnosis

Along with a full examination, a complete blood profile will be conducted, including a chemical blood profile, a complete blood count, and a urinalysis. In some cases, the toxic properties of the plant can be isolated and verified. Atropine, the main toxic component of atropa belladonna, may be detected in the samples.

If your horse is showing definitive symptoms of toxicity, bring a sample of your horse's feed as well as fecal sample. Your veterinarian will use them to determine its material makeup.