Pollution could be the cause of a distressing disease that is killing African elephants by paralysing their trunks. Experts from the uk have been called to investigate the disease, known as flaccid trunk paralysis, that leaves animals unable to feed.

The origin of the disease is yet not known. However, Nancy Kock, who is leading the research at the University of Zimbabwe, thinks toxic chemicals could be to blame. "We believe pollutants or the ingestion of toxic plants such as thistles could be responsible,' she says.

It is believed that chemicals such as nitrates and petroleum products interfere with the absorption of selenium, resulting in a deficiency of this trace element in the elephants' diet. This could be causing the paralysis that is spreading across southern Africa. If this theory is correct, elephants in zoos could also be at risk.

So far a cure has proved elusive and the number of live animals with the disease is rising current estimates are between several hundreds and 2,000. The disease appears to work by destroying the nerves that control trunk movement. These nerves do not regenerate making the disease fatal.

Elephants rely on their trunks to pull vegetation into their mouths and death can take months as the elephants gradually lose the ability to feed.

Drinking also becomes a problem with the elephants having to wade deep into lakes and rivers to put their mouths directly into the water. Some animals already weakened by the disease have been swept away by rivers, or died after sinking into the muddy beds of lakes.