Highly toxic, monobasic diterpenoid alkaloids including aconitine, mesaconitine, and hypaconitine form the principle toxins in monkshood. The alkaloids are similar to those found in Delphinium species. All species of monkshood including cultivated species (A. napellus) should be considered toxic to animals and humans. All parts of the plant are toxic, but the roots, seeds and preflowering leaves are especially toxic. Although there is no extensive documentation of the toxic dose of monkshood, horses have been reported to be fatally poisoned after eating 0.075% of their body weight in green plant.
Perennial herbaceous plants with tall leafy stems growing to 5 feet tall. The leaves are alternate, palmately lobed or parted and similar to Delphinium spp. Monkshood can however be differentiated from larkspur if the flowers are not present by the fact that the stems of monkshood and wild geranium are not hollow like those of larkspur. The flowers are usually deep blue-purple, but occasionally white or yellow, and are produced on simple racemes or panicles. The flowers are perfect, zygomorphic, with 5 sepals which are petal like, the upper sepal being larger and forms a characteristic helmet or hood. There are 2-5 petals usually concealed within the hooded sepal. Numerous stamens and 2-5 pistils are present in each flower. The fruits are follicles that split open at the ends to release the seeds.
Excessive salivation and bloating may be seen in cattle
Muscle weakness, staggering gait, and eventually recumbency with inability to stand due to muscle paralysis.
There is no proven treatment for monkshood poisoning. Affected animals should be stressed as little as possible, and possibly have a better chance of survival if they are herded away from the source of the plants without stressful attempts at treatment. Symptomatic treatment with intravenous fluids, and relief of rumen bloat should be undertaken as necessary.
Sudden death due to severe cardiac arrhythmias is common.
Increased respiratory rate, and difficulty in breathing
Sudden death with evidence that monkshood has been consumed. Post mortem findings are non specific.
In the Western United States, most suspected cases of Aconitum poisoning prove to be due to tall larkspur which grows more abundantly in the same areas. Human poisoning occured in the past due to the misuse of medicinal extracts of aconitine. Occassionally poisoning occurs when the root of monkshood is mistakenly eaten for root of wild horseradish or other wild plants.