It is hard to get rid of whipworms (also called roundworms).

The parasitic worms live in the large intestine. Children often catch them as a result of playing in contaminated soil. And a lack of toilets and clean water helps the worms to spread in developing countries.

Now, researchers from the Swiss Tropical and Public Health Institute in Basel may have found an effective drug, they write in "The New England Journal of Medicine." They treated schoolchildren in Pemba, Tanzania, with oxanthel pamoate - an active component of a deworming drug for dogs in several countries.

After receving one tablet, 31 percent of children infected with roundworms were cured.

"The number doesn't sound so great, but it is much better compared to what you get with the standard drug," Benjamin Speich, the lead author of the study, told DW.

Better than the drugs on the market

Albendazole and mebendazole are the standard drugs used for treating worms in schoolchildren in many African countries.

These drugs are good for getting rid of hookworms and giant roundworms, but they aren't that effective with whipworms. Speich and his team found that albendazole only cured whipworm infections in just 2.6 percent of cases. And it reduced the number of eggs in the children's faeces by 45 percent. The number of eggs went down by 96 percent when it was taken with oxanthel pamoate - the agent using in dog deworming drugs.

Giving the standard agent albendazole with oxanthel pamoate could ensure children get treated for whipworms as well as other worms, the researchers say.

No adverse effects

When it is taken as a tablet, oxanthel pamoate tends to remain in the intestine - it doesn't enter the bloodstream. And that could be the reason why the subjects who took it didn't experience many adverse effects.

"A few children complained about mild headaches and nausea, but the same was true for the standard drugs as well," Speich says.

But before the agent can be approved for treating whipworms in humans, more clinical trials with a larger test group are needed. The researchers also need to find out the best dosage.

Treating humans may not be profitable enough

For now, anyone who wants to deworm a person or be dewormed with oxanthel pamoate may need to travel to the Philippines - the only one country in the world where it is approved for humans. Researchers had already successfully tested the drug in a small number of humans in the 1970s. But that study was forgotten.

"Worm infections mostly occur in poor people. The pharmaceutical industry is simply not that interested in developing drugs against these illnesses," Speich says.

Treating animals might be more profitable. Cattle might grow less meat when they are infected with worms. In fact, a lot of drugs for treating parasitic worms originated in veterinary medicine, according to Speich. And there might not have been the need for a new drug against roundworms in the past, he notes, adding that they have noticed that the current medicamentation is not effective with this kind of worm. Roundworms could have become resistant to them.

"Very much an exception"

Rolf Hömke from the the German association of research-based pharmaceutical companies is aware of other cases in which a drug was first approved for use in animals and only later showed to be an effective drug for humans as well. One of these substances is used to treat another disease caused by worms, river blindness.

"But such cases are very much an exception," he says. Often, it is the other way around.

For years, doctors have been using telmisartan to manage hypertension. And it is only now that the agent has been approved for treating cats with renal failure.

But most of the time, companies develop an agent into a veterinary and a human medicine together.

"That is because there is big similarity between human beings and their pets or farm animals," Hömke says. They are mammals.

"Clinical trials are always very expensive", he adds. So a pharmaceutical company will not save money if it develops an animal drug first and then adjusts it for human use. Clinical trials have to start from scratch if the drug or agent is to be used in another species.