Dieffenbachia species: Dumb cane

Family

Araceae

Common Name

Dumb cane, camilichigui, American arum, poison arum.

Plant Description

Dieffenbachia species (25 - 30) originate in tropical regions of the Americas, and are universally used as ornamental plants in gardens and households. Dieffenbachias are one of the most popular houseplants in North America. The evergreen, erect perennials can grow up to 10 feet in height on thick stems that have prominent leaf scars. The leaves are simple, oblongovate, and are typically mottled or variegated in various shades of white, cream, yellow, green, or red, the lighter colors occupying the space between the leaf veins (Fig. 143 and Fig. 144). The petioles are long and sheath the stem. The inflorescence consists of a solitary spathe, whose margins overlap forming a tube. The fruits consist of red-yellow berries.

The two most commonly encountered species of Dieffenbachia, and the ones from which most hybrids have been developed are Dieffenbachia maculata, and D. seguine.

Figure 143. Dieffenbachia sequine.

Figure 144. Dieffenbachia sequine "Tropic Makianne".

Toxic Principle and Mechanism of Action

Like other members of the Arum family, Dieffenbachia species contain calcium oxalate crystals in the stems and leaves [1]. The calcium oxalate crystals (raphides) are contained in specialized cells referred to as idioblasts [1,2]. Raphides are long needle-like crystals that are bunched together in these specialized cells. When the plant tissue is chewed by an animal, the crystals are extruded into the mouth and mucous membranes of the unfortunate animal.

The raphides once embedded in the mucous membranes of the mouth cause an intense irritation and inflammation. In addition, there is evidence that the oxalate crystals act as a means for introducing other toxic compounds from the plant such as prostaglandins, histamine, and proteolytic enzymes that mediate the inflammatory response [3]. Unlike other members of the Arum family, Dieffenbachias are more toxic, because they have raphides in both the epidermal and mesophyll layers of the stems and leaves [1].

The name "dumb cane" given to Dieffenbachia originated from the fact that people who chewed and ate the stems and leaves of the plant were unable to speak because they developed severe swelling of the mucous membranes of the mouth and pharynx. Similarly, dogs that chew on the plant may develop a severe stomatitis that has led to asphyxiation and death [4].

Risk Assessment

Of all the Arum family, Dieffenbachia species are the most likely to cause problems in household pets, because the plants are common ornamentals in gardens and households. Dieffenbachia species make up one of the most frequent reports of plant poisoning exposures in people and animals reported to poison control centers [5,6]. Cattle and sheep may also be poisoned if they consume the plants [7]. In North America, this is most likely to occur when plant prunnings are inadvertently fed to livestock. Dieffenbachias should not be put into aviaries as birds are susceptible to poisoning from chewing on the leaves and stems [8].

Clinical Signs

Dogs and cats that chew repeatedly on the leaves and stems of the Dieffenbachia develop edema of the oral mucous membranes shortly after chewing on the plants. Excessive salivation, difficulty in eating and swallowing, and vomiting are common signs of poisoning [9,10]. The edema, inflammation, and pain in the mouth of affected animals can resemble the lesions that would occur if the animal had consumed a caustic chemical. Humans who have chewed on Dieffenbachia stems and leaves also develop a severe stomatitis, leading to difficulty in eating and speaking [11]. If swelling in the pharynx is severe, animals will have difficulty in breathing, and in severe cases may die from asphyxiation [9,12,13]. Fortunately, in most cases, animals do not persist in chewing Dieffenbachia because of the rapid onset of inflammation and pain induced by the embedded oxalate crystals. Severe conjunctivitis and keratitis may result, if plant juices are rubbed into the eyes [14].

Treatment

Unless salivation and vomiting are excessive, treatment is seldom necessary. Swelling of the lips and gums may persist for several days. Anti-inflammatory therapy may be necessary in cases where stomatitis is severe. The plant should be removed from the animal’s environment.