A study by Lankan researchers shows hookworm treatment is safe during pregnancy

Off the hook

By Feizal Samath

A team of Sri Lankan medical researchers has concluded that drugs used to treat worm infection are safe for pregnant women and, contrary to previous international belief, won't harm the foetus.

The study has put to rest global fears that worm treatment may affect the foetus, and based on this evidence, the WHO has recommended the drug, Mebendazole, for millions of pregnant women infected with hookworm Mebendazole is the generic name for Vermox, a drug used by millions of people against worm infection.

The researchers said that the results of the study were likely to revolutionize the control of anaemia in pregnancy, which is a major public health problem in developing countries.

Though the study was completed two years ago, it was made known to the international medical community only this year through publication of the study in The Lancet, one of Britain's best medical journals, in its 1999 April issue.

"We finished collecting the data in 1997 and sent the results to the WHO last year. The WHO was very pleased with the results of the study and has now recommended the drug, across the world, for use by pregnant women after the first three months," said Dr Nilanthi de Silva, who led the five-member research team.

According to WHO estimates, as many as 44 million pregnant women throughout the world, at any given time, are infected with hookworms.

Estimates indicate that over 50 per cent of pregnant women in developing countries have iron-deficiency anaemia.

"Although iron-deficiency has many contributing causes, hookworm infection is an important contributory factor in endemic areas, especially among women of the reproductive age group," a WHO document said.

Medical experts say that hookworm, which is endemic in tropical countries, affects at least 800 million people in the world annually.

The routine use of anthelmintic (a medical term for control) treatment amongst pregnant women was not a widely accepted strategy across the world.

In Sri Lanka, the use of Mebendazole by pregnant women became almost common in the 1980s when hookworm became endemic and the proportion of pregnant women affected rose to 60 percent.

Hookworm has been largely controlled due to the use of control treatment. It is normally prevalent in tea plantation areas in the south and south-western regions due to lack of proper sanitation.

While for many years, Sri Lankan doctors have been prescribing Mebendazole for pregnant women, their colleagues in the rest of the world did not do so fearing the drug would harm the unborn child.

"For some reason, Sri Lankan doctors had been prescribing this drug for pregnant women as a precautionary measure," said Prof. Carlo Fonseka, former head of the Faculty of Medicine University of Kelaniya under whose purview the research team worked.

He said the drug was not used on a worldwide scale since "its toxicity to the foetus had not been clearly excluded." "One of the problems (outside Sri Lanka) was that there was lack of data on the safety of this drug," research leader De Silva, who is head of the Department of Parasitology at the same university, told The Sunday Times.

Anthelmintic drugs like Levamisole, Mebendazole and Albendazole are all highly effective against intestinal hookworm and used across the world.

"Mebendazole is probably the most widely used of these anthelmintics, especially in control strategies, because of its efficacy, lack of side effects and low-cost," the study published in Lancet said.

In 1994, the Ministry of Health formally recommended that Mebendazole be given to all pregnant women in their first trimester through government clinics.

De Silva said that it was on the basis of the Sri Lankan experiment, that the WHO asked Colombo to undertake a research study on this issue to obtain a clearer picture of how successful the country has been in this field.

"It was Professor Mahroof Ismail, then dean of the faculty of medicine at the Colombo University, who discussed the Colombo experiment at a WHO meeting in December 1994 and got the WHO interested in a research project," said De Silva.

Prof. Ismail was a senior partner in De Silva's research team.

With 85 per cent of births taking place in government hospitals in Sri Lanka, the research team studied the pregnancies of 7,087 women at the hospitals at Ragama and Peradeniya. The women were interviewed from May 1996 to March 1997.

The study showed that 74 per cent of the women had taken a course of Mebendazole at least once during their current pregnancy while 24.5 percent had not taken any kind of anthelmintic treatment at all.

It found that the rate of stillbirth and perinatal deaths was significantly lower at 1.9 per cent amongst Mebendazole users, compared to 3.3 percent amongst non-users.

"The incidence of major congenital deaths was slightly higher (1.8 per cent) in women who took Mebendazole in the first trimester compared to the non-user group (1.5 percent) but these differences were not significant," the study revealed.

It said the proportion of mothers who had babies with very low birthweights was significantly lower in the Mebendazole group than the other group, at both hospitals.

De Silva said that their data indicated no significant association between the use of Mebendazole in pregnancy and an increase in major congenital defects.

"The findings were also consistent with the views of medical practitioners that Mebendazole therapy is safe during pregnancy," she said.

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