Gifblaar

''Dichapetalum cymosum'', commonly known as gifblaar from Afrikaans, or occasionally by its English translation, poison leaf, is a small prostrate shrub occurring in northern parts of Southern Africa in the family Dichapetalaceae. It is notable as a common cause of lethal cattle poisoning in this region and is considered one of the 'big 6' toxic plants of cattle in South Africa. A 1996 estimate of plant poisonings in South Africa attributes 8% of cattle mortality caused by poisonous plants to it. The majority (70%) of fatal cases are in Limpopo province, with 10% each in North West, Mpumalanga, and Gauteng. Fluoroacetate, the poison used to synthetically produce Compound 1080 used extensively in New Zealand, occurs in all parts of the plant and is responsible for the toxic effects shown.

Toxic effects include vomiting, seizures, and an irregular heartbeat, and death can occur in as little as a few hours. This poison is known as “the poison that keeps on killing” because the toxin stays in the body after the animal dies, so if a predator eats the animal, the predator gets poisoned, and so on up the food chain. It can easily kill small mammals such as rats, earning it the name "ratbane"; it was banned for commercial use in the United States in 1972 by the Environmental Protection Agency

''Dichapetalum cymosum'' was first recognised as toxic by the early Voortrekkers entering the Transvaal, who were probably alerted to its lethality by natives living in the region.

Description

Above ground, the plant is seen as a clump of small, woody shrubs about 15 cm (6 in) high. Such a clump is typically a single plant, as gifblaar has a huge underground root system - likened to an underground tree - and sends numerous shoots above ground in favourable conditions. The most obvious above ground parts are the leaves - simple, alternate with initially fine hairs later becoming glabrous. The leaves are bright green in colour on both sides. The secondary veins form loops and do not reach the margin. The flowers are small and white, and occur as dense clumps in the early spring. Fruit formation is rare; the fruits are orange and leathery, are not poisonous and known to be consumed by the San people.

Identification of gifblaar in the field is important in prevention of toxicity and also in assigning gifblaar as the cause of toxicity in an outbreak. It is a small, low-growing, nondescript shrub and thus easily confused with other species. There are four principal "confusers" in its habitat. These are '' Ochna pulchra'' (lekkerbreek) saplings, '' Parinari capensis'' (grysappel), ''Pygmaeothamnus'' spp. (goorappels) and the various gousiektebossies (various genera and species of the family Rubiaceae, such as Vangueria). The first three of these are non-toxic, but gousiektebossies are also toxic and another of the 'big 6' cattle poisons.

Of the similar species, gousiektebossies and goorappel have opposite, not alternate, leaves. Goorappel leaves also have a characteristic bulge terminally, though only when mature. Grysappel and ''Ochna pulchra'' have alternate leaves, but grysappel has pale grey undersides to its leaves (its name means grey apple). ''O. pulchra'' leaves have secondary veins that are not looped and reach the margin, and the margin itself is dentate not smooth.
File:Poison leave plant.jpg, Leaves
File:Flowering poison leaf.jpg, In flower

Distribution and habitat

Gifblaar occurs in dry, sandy areas in acidic soils, as well as the northern slopes of rocky hills in the southern parts of the African savannah biome. In South Africa, the distribution is within the so-called 'gifblaar triangle', the points of which are Mmabatho; Middelburg, Mpumalanga; and Musina. The traditional southern border of distribution is the Magaliesberg mountains. It also occurs in an isolated region in the far north of KwaZulu-Natal. Gifblaar is also found in Namibia, Zimbabwe, Botswana as well as southern Angola. Within its habitat certain indicator species are used to identify veld which potentially harbours gifblaar - this veld is called 'gifveld' by farmers of the region. These are the trees '' Burkea africana'', '' Terminalia sericea'', and ''Ochna pulchra'', and also the shrub '' Parinari capensis''. The latter two species can easily be mistaken for gifblaar.

Toxicity and biochemistry

The toxic compound isolated as the cause of gifblaar poisoning is fluoroacetate