Sodium fluoroacetate

Sodium fluoroacetate (also known as sodium monofluoroacetate, compound 1080 or 1080) is a potent metabolic poison that occurs naturally as an anti-herbivore metabolite in various plants. It works by interfering with the citric acid cycle, and is used primarily to control mammalian pests, including invasive species. The existence of this chemical was first noted in the Second World War.

Natural occurrence
Sodium fluoroacetate occurs naturally in at least 40 plants in Australia, Brazil and Africa. It was first identified as the poison of poison leaf Dichapentalum cymosum by Marais in 1944, although it had been reported as early as 1904 that colonists in Sierra Leone used extracts of Chailletia toxicaria which also contains fluoroacetic acid or its salts to poison rats. It is believed that the compound is even present in tea leaves in tiny amounts. The Australian pea family Gastrolobium ("poison peas"), have sodium fluoroacetate in the leaf tips and seeds. This forces livestock farmers in Western Australia to hand-weed out all the plants from their paddocks. It also means that some Western Australian herbivores have, by natural selection, developed partial immunity to the effects of fluoroacetate, this has been used for an advantage in DEC's wildlife conservation project named Western Shield.

Mechanism of action
Sodium fluoroacetate is believed to disrupt the citric acid cycle (also known as the Krebs cycle). In the body the fluoroacetate is converted to fluorocitrate, a compound which prevents citrate from being used in the cycle. This results in an accumulation of citrate in the blood and deprives cells of energy, leading to a slow and painful death as the body "suffocates from within".

History
Sodium fluoroacetate was discovered by German military chemists in World War II. The chemical was highly potent — theoretically, one tenth of a gram could kill a grown man — but it was difficult to deliver, requiring ingestion or injection for optimal effect. As such, it was largely overlooked until it was independently rediscovered by American chemists researching pesticides. The name "1080" refers to the catalogue number of the poison, which became its brand name.

Symptoms and treatment
The symptoms of poisoning normally appear between 30 minutes and four hours after exposure. They include vomiting, involuntary hyper-extension of the limbs, convulsions, and finally cardiac and respiratory collapse. There is no known effective antidote. In humans, sodium fluoroacetate poisoning has somewhat similar symptoms to an acute heart attack. Symptoms in domestic animals vary: dogs tend to show nervous system signs such as convulsions and uncontrollable running, whilst large herbivores such as cattle and sheep more predominantly show cardiac signs.

Sub-lethal doses of sodium fluoroacetate may cause damage to tissues with high energy needs &mdash; in particular, the brain, gonads, heart, lungs and fetus. Sub-lethal doses are typically completely metabolised and excreted within four days.

Because of the biochemical interference in the TCA or Krebs Cycle, sodium fluoroacetate poisoning is very difficult to treat, as once clinical symptoms are shown, the Krebs Cycle has shut down. Research in monkeys has shown that the use of glyceryl monoacetate can prevent problems if given after ingestion of sodium fluoroacetate, and this has been done in domestic animals with some positive results. The theory of using glyceryl monoacetate is that it will supply acetate ions to allow continuation of the cellular respiration process which the sodium fluoroacetate has disrupted.

In clinical cases, use of muscle relaxants, anti-convulsants, mechanical ventilation and other supportive measures may all be required. Few animals or people have been treated successfully after significant sodium fluoroacetate ingestions.

Uses
Farmers and graziers use the poison to protect pastures and crops from various herbivorous mammals.

Sodium fluoroacetate is used in New Zealand to control the Common Brushtail Possum an animal pest introduced from Australia. As the Possum is from the eastern states of Australia and is a mainly arboreal forager, it has never developed a resistance to sodium fluoroacetate.

Western Shield is a recent project to boost populations of endangered mammals in south-west Australia. The project is to drop Sodium fluoroacetate baited meat from helicopters or light aircraft to kill predators. Wild dogs and foxes will readily eat the baited meat. Cats pose a greater difficulty as cats aren't interested in already dead animals. However, recently a pilot tried putting small sound generators inside the baits with significant positive results.

Sodium fluoroacetate is used to protect tree plantations from browsing animals that may damage seedlings.

New Zealand aerial 1080 application
1080 baits have been used through ground based and aerial application to control possums and other non-native predators in New Zealand. New Zealand's unique fauna and flora is endangered by the rapid spread of possums, introduced into the country last century to create an industry for possum fur.

While New Zealand's Department of Conservation Doc favors the effectiveness of aerial 1080 application, vocal critics of the application of 1080 claim: "government agencies increasingly use large scale indiscriminate aerial applications to cut costs. Large number of non-target species are destroyed as a result, including deer and native birds. Southern Boobook, a species of owl, is particularly vulnerable through secondary poisoning. A positive side effect of blanket aerial poisoning is a temporary drop in rat numbers, but they quickly recover due to the niche created by low possum numbers. The effectiveness of aerial drops is being questioned due to pockets of possum population either resistant to the compound or not taking the bait with the overall numbers bouncing back rapidly. Ground operations using bait stations with sodium fluoroacetate are not as effective as other modern target poisons such as cyanide baits."

New Zealand's Environment Risk Management Authority ERMA released in August 2007 its latest review of the matter. The review gives new guidelines for the use of 1080 in New Zealand and concludes that the beneficial effects of pest eradication outweigh the risks.