Aesculus species: Horse Chestnut

Family

Hippocastanaceae

Common Name

Horse chestnut, buckeye, fish poison, marronnier. California buckeye (A. californica), Ohio buckeye (A. glabra), red buckeye (A. pavia), horsechestnut (A. hippocastanu).

Plant Description

A genus of some 20 species of trees and shrubs, Aesculus are frequently planted as ornamental trees for their attractive flowers, leaves, and fruits. At least half of the 20 known species grow in North America. Extensive hybridization has occurred amongst the species. These deciduous trees generally prefer moist soil conditions and can develop into large specimen trees. Trunks have gray to brown smooth or rough bark, the characteristic large palmate leaves have 5 - 11 leaflets. Inflorescences are produced terminally on branches, either before or after leads are produced. Flower color is typically white, creamy-yellow, or red (Fig. 21 and Fig. 22). Fruits are smooth or warty capsules that break open in the fall to release one to three dark brown shiny seeds that have a characteristic lighter scar on one side (Fig. 23 and Fig. 24).

Figure 21. Aesculus carnea.

Figure 22. Aesculus carnea.

Figure 23. Horse chestnuts.

Figure 24. Aesculus hippocastanum.

Toxic Principle and Mechanism of Action

Aesulus species contain a variety of toxins in the buds, leaves, and seeds including esculin (a coumarin glycoside), escin (complex saponin) and frangula (an anthraquinone) [1,2]. These compounds, once hydrolyzed, become toxic and through their irritant effects on the gastrointestinal tract can induce colic and diarrhea. Esculin is known to be cytotoxic and may account for the neurologic signs seen in some cases of poisoning.

Risk Assessment

Horse chestnuts or buckeyes (conkers) are produced in large numbers in the fall and the attractive brown seeds are commonly collected and brought into households, where they become accessible to pets. The seeds are a potential source of poisoning to animals that eat them. Most poisoning reported in animals has occurred in livestock [3,4]. The edible chestnut (Castanea species) is not related to the Aesculus species.

Clinical Signs

Gastrointestinal signs generally predominate, and consist of vomiting and diarrhea shortly after ingestion of the leaves or seeds. Colic is the principal clinical sign seen in horses. Depending on the quantity and frequency of Aesculus consumed, neurologic signs, including excitement and ataxia, muscle twitching, a stiff gait, seizures, recumbency, and death may occur in severe cases.

Treatment

Symptomatic treatment is indicated as there is no specific antidote. Inducing vomiting, if the animal is known to have eaten the seeds within the past two hours, is beneficial. Activated charcoal given via stomach tube with a laxative may help to inactivate the toxins and remove them from the gastrointestinal tract.

Intravenous fluid therapy may be indicated in cases of severe dehydration. Animals showing neurologic signs and seizures may be treated with diazepam.