New hope for a neglected disease


Mamma always said you can do anything you put your mind to. But that's both a blessing and a curse. Science has made some amazing strides in medicine, but where minds—and money—aren't applied, progress sputters.

Chagas is a parasitic disease spread by a bug. Somewhere between 8 and 20 million people—mostly in the Americas—are infected. No one knows for sure. Most of the victims are poor.

A little over 100 years after the parasite that causes Chagas was first discovered, this disease is still difficult to diagnose, treatment regimens are complicated and fraught with side-effects and 20,000 people die from Chagas each year. The best hopes are prevention campaigns, and a new generation of drugs that researchers hope will be easier to take.

In the blood

In urban areas, blood banking is also an issue, because Chagas can be passed through transfusions. Unfortunately, there's not a lot of attention on this. Even the United States only introduced blood-donor screening for the disease in 2007, and that's still a voluntary measure that not all blood centers practice, said Dr. Susan Montgomery, veterinary medical officer and epidemiologist with the Centers for Disease Control and Prevention. Since screening began, it's identified more than 1000 infections, mostly in new immigrants who picked up the parasite in their home countries. Only seven cases of US-acquired Chagas have been reported in scientific literature, Montgomery said, but she and other experts suspect there are more that have gone unnoticed.

Chagas is caused by a parasite, called Trypanosoma cruzi. Just as the malaria parasite hitches a ride on mosquitoes, T. cruzi also travels by blood-sucking pest—in this case triatomine bugs, also called "kissing bugs" because of their tendency to bite people on the face at night. Unlike mosquitoes, kissing bugs don't pass their parasites to humans via saliva. Instead, they further the indignity by relieving themselves on people they've just bitten. When the victim tries to swat the bug away, or even just rolls over in their sleep, they can smear bug waste&and T. cruzi parasites along with it—into their eyes, nose or mouth.

Some of these people will never know that they've been infected. Up to 70% of those who carry T. cruzi parasites never have any serious symptoms. Others won't know they're infected for years. They'll live with no sign of disease, sometimes passing the parasites on to their children in utero, until it's too late.

When you die of Chagas disease, you aren't killed directly by parasites. Instead, Chagas victims suffer years of chronic organ damage—usually to the heart, digestive or nervous systems.

"We don't know why some patients end up with severe damage and others don't," said Rick Tarleton, Ph.D., president of the Chagas Disease Foundation and professor of cellular biology at the University of Georgia. "My personal hypothesis is that the human immune system actually does a fantastic job of battling this parasite. But decades of killing parasites and their infected host cells produces tissue damage. Individual results depend on a lot of factors: Host genetics, the efficiency of the immune system, their living situation, their nutritional level, their level of stress, their gender, the parasite strain they picked up and how long they've been infected," he said.

There are drugs to treat Chagas disease, but they can only go after the parasites, not heal the tissue damage. And poverty plays a big role in both spreading the disease and complicating treatment. In rural areas of Central and South America, where Chagas is endemic, people live in thatch and adobe houses that are perfect nesting ground for kissing bugs. Inevitably, they get bit, but they also don't have much access to health care, so it's rare to be tested for the disease until symptoms appear.

"The available drugs are expensive. You have to take two pills a day for 60 days and there's a lot of serious side effects, nausea, skin disease problems. Treatment has to be monitored closely by a doctor. None of that's feasible for rural areas. And the side-effects also make it difficult to treat patients in the chronic phase, those most likely to be diagnosed, because of their organ damage," said Eric Stobbaerts, policy & advocacy coordinator for the not-for-profit product development partnership Drugs for Neglected Diseases Initiative.

Right now, prevention is the most effective protection against Chagas. And, basically, that boils down to bug spray.

With most of the funding for Chagas focused on killing kissing bugs before they bite, the Drugs for Neglected Diseases Initiative has focused its work on making it easier to treat the infected. They're going about that two ways. First, they're trying to make it easier to treat children. Chagas can be passed from mother to baby, but none of the available drugs are produced in child-size doses, Stobbaerts said. That often leaves rural doctors trying to hand-cut adult pills into eight or 12 pieces. Within a year, the Drugs for Neglected Diseases Initiative hopes to release a real pediatric formulation.

The organization is also working on a new drug treatment that could be less of a pain to take. Called ravuconazole, it's related to a common family of anti-fungal drugs. In vitro tests, and trials in lab animals have shown that ravuconazole can kill T. cruzi parasites. The tests also suggest that it stays in the body longer than current Chagas drugs, meaning fewer pills could do the same job. It also seems likely to produce fewer side effects. Clinical trials in humans are set to begin later this year.