Vinca species: Periwinkle

Family

Apocynaceae

Common Names

Common periwinkle, old maid, running myrtle - Vinca minor

Blue or greater periwinkle - Vinca major

Plant Description

A genus of 8 species native to Europe and North Africa, Vinca species are perennials with trailing stems containing a milky sap. Leaves are simple, opposite, 2 - 3 cm long, dark green, glossy surfaced, round-ovate, and pinnately veined. The flowers are showy, produced in alternate leaf axils, and have a short tube opening to 5 flat petals that range from a rosy purple to blue in color. (Fig. 398) Fruits are short follicles with numerous seeds.

Closely related to Vinca is the genus Catharanthus (Madagascar periwinkle). Some taxonomists consider these two plant genera one and the same! Originating in Madagascar, and now cosmopolitan, it is a popular garden plant. It has a compact habit and is a profuse bloomer in white, pink, rosy red, magenta or purple, some with a red center.

Figure 398. Vinca minor.

Toxic Principle and Mechanism of Action

Numerous alkaloids including alstronine, reserpine, vinblastine, vincristine, and yohimbine are present in all parts of the plant and have hypotensive, digestive and neurotoxic effects if consumed in large doses [1,2]. Some alkaloids such as reserpine reduce blood pressure, while vinblastine and vincristine affect bone marrow cells and have been used effectively for the treatment of leukemias [3]. These alkaloids inhibit mitosis through binding of tubulin and arresting microtubule formation. They also have neurotoxic and teratogenic effects in mice [4]. Cattle and sheep have reportedly developed neurotoxicity from grazing the plant [5].

Risk Assessment

Vinca or periwinkle is commonly grown as a garden plant for its attractive flowers and as a ground cover. It also does well as a potted plant. Because of its high alkaloid content there is potential for poisoning of household pets that might eat the plant.

Clinical Signs

Animals eating the leaves in quantity develop anorexia, anemia, hypotension, incoordination, muscle tremors, lateral flexion of the neck, and convulsions. Coma and death follow [5,6].

There is no specific treatment and animals should be given symptomatic supportive treatment including activated charcoal orally and intravenous fluid therapy.