By Peter Apps

LONDON, Jan 23 (Reuters) - Using a cocktail of drugs may help doctors more effectively treat three of the world's most common parasitic diseases, researchers working in Zanzibar reported on Wednesday.

The drugs treat elephantiasis -- also known as lymphatic filariasis -- soil-transmitted worms and schistomiasis. All the treatments are known to be effective but the impact of delivering them all at once was not known.

"Nearly all sub-Saharan African countries are affected by one or more of these diseases," said Albis Gabrielli, a medical officer specialising in neglected diseases at the World Health Organisation (WHO).

"An important characteristic of these diseases is that they often co-exist in the same person. That is why this research is so important," Gabrielli said in a telephone interview.

The WHO has long recommended the coordinated delivery of drugs to tackle neglected tropical diseases, but the number of treatments has so far been limited to two because of safety concerns over potential side-effects.

But the study published in the Public Library of Science journal "PLoS Neglected Tropical Diseases" showed that the drugs ivermectin, albendazole and praziquantel could safely be used together.

The findings spurred the researchers to urge WHO to quickly recommend all three as a simultaneous treatment for the diseases, which affect tens of million of people across the developing world, notably in sub-Saharan Africa.

The three diseases are rarely fatal but can scar and disable people. The drugs can kill some or all of the parasites, providing at least a partial recovery.

The study began with 5,055 children and adults in Zanzibar, which lies in the Indian Ocean off the coast of east Africa's Tanzania.

Researchers made the study country-wide after determining there were no severe side effects from administering the three drugs simultaneously.

The researchers said the results brought a change in the WHO guidelines much closer, though the body was cautious.

"We are not yet in a position to make a clear recommendation," said WHO medical officer Francesco Rio. "The results of the study -- if they are confirmed by other studies -- mean that three drugs can be given together."

Merck & Co <MRK.N> developed ivermectin, or Mectizan, also used to treat river blindness. Merck also sells praziquental as Cesol. GlaxoSmithKline Plc <GSK.L> makes Albendazole, used to treat elphantiasis. (Editing by Michael Kahn and Jon Boyle) (For more information on humanitarian crises and issues visit www.alertnet.org)

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