Parasites linked to allergy therapy

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Ancient parasites that have plagued the human race throughout its history are being sought by scientists so they can be used to treat allergies.

The intestinal worms and amoeba-like organisms have been our companions since humans and apes separated on the evolutionary path five million years ago.

Experts think the "heirloom" parasites are so wedded to humans that their removal through clean food and hygiene can upset the immune system.

This may result in an untargeted immune response that can trigger allergy conditions such as asthma and eczema, according to the theory.

Scientists hope treatment with harmless parasites, or proteins derived from them, may combat allergies by bringing the immune system back under control.

But first they must know which organisms fall into the heirloom category that infected our most distant ancestors and their ape relatives.

Other parasites known as "souvenirs", acquired more recently as humans spread around the world, are not expected to offer effective therapies.

A study based on archaeological evidence and data from non-human primates such chimpanzees, gorillas and baboons, has singled out 10 heirloom parasites believed to have originated in Africa.

They include malaria - one of the greatest scourges of the developing world - as well the toxoplasmosis parasite spread by cats, and several flukes and worms.

An immune system antibody called immunoglobin E (IgE) that is linked to allergies has evolved specifically to target parasites.