Nerve poison leaves telltale evidence

Hundreds of sheep farmers believe they have suffered OP poisoning

By environment correspondent Alex Kirby

A US team has found changes in the blood of a child with organophosphate (OP) poisoning, which could make it easier for other patients to prove exposure to similar poisons.

The changes, a series of antibodies, provide physical evidence of the neurological damage caused by the poison.

This is thought to be the first physical evidence discovered of the neurological damage many believe is caused by OP exposure and related conditions, like Gulf War Syndrome.

The researchers say the antibodies' discovery "may provide a useful marker for diagnosis of chemically-induced neurological disorders, and may help in the development of appropriate treatment".

The research team, whose work is reported in the journal Environmental Epidemiology and Toxicology, was led by Professor Mohamed Abou-Donia, of Duke University Medical Center, Durham, North Carolina.

Not imaginary

Professor Abou-Donia told BBC News Online: "This is a potentially very significant discovery.

"Until now, doctors have told people suffering from similar conditions that their symptoms were all in their heads.

Professor Abou-Donia

"We've shown that a bio-marker exists, and it could help a range of patients to persuade their doctors of the reality of what they're suffering."

The patient he and his team examined was a five-year-old boy who had been exposed to tar and to an OP insecticide, chlorpyrifos, when he was a year old.

The tar had been shallowly buried in earth where the boy played, and the insecticide had been used several times inside his home.

By the time he was 14 months old, two months after his exposure, his family thought he was unsteady on his feet, and his speech, which had been normal, was deteriorating.

He was also irritable. At 17 months he was unable to walk without falling. By 26 months, however, there was some improvement in his speech, and his irritability had lessened.

His neurological problems were judged to be consistent with OP ester-induced delayed neurotoxicity (OPIDN).

Blood samples

Five years after his exposure, when he was seven years old, the boy's intellect was defined as lower than his family's, and he was placed in a special school because of "a mild degree of mental retardation".

The researchers tested his blood for the presence of antibodies against three proteins characteristic of neurodegenerative disorders.

They used blood samples from the boy's 6- and 9-year-old brothers, his 32-year-old father and 34-year-old mother as controls.

Gulf War Syndrome remains unproven

Antibodies against two of the proteins were found in the boy's blood, and in that of several of the controls. No antibodies against the third were found in any of the samples.

The researchers say: "In healthy individuals, the presence of autoantibodies against [these] proteins is age-dependent: they increase with age. In the present study, more of the antibodies were detected in the mother's serum than in any of the other controls."

But it was the boy himself who showed by far the highest levels.

Elizabeth Sigmund, of the OP Information Network, told BBC News Online: "This is a wonderful breakthrough.

"We have 800 people on our database, mainly sheep farmers who have been exposed to OPs while dipping their animals.

"This news is vitally important for them, and for veterans from the Gulf.

"They're chronically ill, and for years they've been struggling to prove the cause of their condition to their doctors.

"Now it looks as though they'll be able to do that."