Zamia species: Coontie

Family

Zamiaceae

Common Names

Sago palm, coontie, chamal, coyolillo, cycad

Plant Description

Comprising about 60 species, Zamia is a diverse genus of the cycad family found in Florida, Caribbean area and tropical South America. There is one species that is native to the states of Florida and Georgia, Zamia integrifolia (Z. floridana) that is commonly known as coontie, Florida arrow root, Seminole bread or guayiga.

Similar genera are Ceratozamia, Cycas, Dioon, and Macrozamia (Fig. 406).

Figure 406. Cycas revoluta.

Zamia integrifolia is a perennial herb growing from an underground, branching stem, with 4 - 10 erect leaves up to 4 feet (1.5 m) in length, with up to 80 dark green, glossy, stiff, linear leaflets. The male pollen cones are narrowly cylindrical, while the female seed cones are ovoid, both being a rusty brown color. The seeds are bright orange to red in color and are exposed when the fruit is ripe (Fig. 407, Fig. 408 and Fig. 409).

Figure 407. Zamia integrifloia.

Figure 408. Zamia species fruit cone.

Figure 409. Zamia floridiana fruits.

Toxic Principle and Mechanism of Action

The primary toxins in the Zamia species are the glycosides cycasin and macrozamin, found in all parts of the plant but especially in the seeds. The glycosides are hydrolyzed by bacterial enzymes in the digestive tract of animals consuming the plant or its seeds to produce the toxic aglycone methylazoxymethanol (MAM), which alkylates DNA and RNA causing severe hepatic necrosis [1,2]. It also has carcinogenic, mutagenic, and teratogenic properties [2,3]. Similar toxins are found in the fruits of the Cycas and Macrozamia species [4].

A second toxin, an amino acid beta-N-methylamino-L-alanine (BMAA), is found predominantly in the seeds and causes neurologic lesions similar to other neurolathyrogens involving neuroreceptors [5]. Prolonged consumption of the Cycas seeds or flour made from the seeds is necessary to induce neurologic signs and lesions.

Risk Assessment

Dogs and humans are most likely to be affected after eating the attractive fruits that are toxic. Zamia species are commonly grown as garden plants, in tropical areas, and occasionally as house plants in temperate areas.

Clinical Signs

Humans, dogs, cattle, and sheep that eat the seeds of Zamia species typically develop signs of poisoning within an hour of consuming the seeds, and exhibited signs of digestive disturbance, liver failure, and in some instances neurological signs [6-10].

Dogs typically vomit and may continue doing so for several hours. Excessive salivation and increased thirst are often noticeable. During the next few days anorexia, depression, diarrhea or constipation, and icterus develop. Serum bilirubin, liver enzymes, blood urea nitrogen, and creatinine levels become elevated. The prognosis is guarded to poor once evidence of hepatic necrosis develops. Neurological signs are more common in people and livestock who have consumed the plants or seeds over a prolonged period. Neurologic signs include weakness, loss of proprioception, staggering gait, and incoordination. Treatment should be directed to support the liver and neurological signs.

At post mortem examination, the characteristic findings include an enlarged, congested liver, with a "nutmeg" appearance. Focal and centrilobular necrosis of the liver is seen in acute cases, while fibrosis and biliary hyperplasia is seen in more chronic cases. In cattle showing neurologic signs, bilateral, symmetrical degeneration of the cervical spinal cord is evident [9].