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Falling Through the Cracks: Working to Fight Chagas Disease with Limited Tools

© Juan Carlos Tomasi

Chagas disease is caused by an insect that lives in the cracks of the mud hut homes of many of South America's poorest people. It affects an estimated 16 - 18 million people, and claims up to 50,000 lives a year.

Dr. José Luis Dvorzak and Dr. Victor Condé work in six different MSF primary health clinics near Cochabamba, Bolivia, where among other tasks, they struggle to diagnose and treat Chagas patients with the inadequate tools at their disposal. Their wish list for new drugs and diagnostics is long.

 Who are the people who come to your clinic?
Mainly poor people. Our patients suffer from a wide range of diseases: tuberculosis, diarrhoea, acute respiratory infections... and Chagas. The poor are at greater risk from Chagas, because the bug that transmits the infection lives in the wall cracks of their houses, as they're often made of mud or earth. When a family member is affected with Chagas, it becomes a major problem for the entire family, especially when the affected person is the main breadwinner.
At public health facilities in Bolivia, testing and treatment for Chagas is free in theory, but it's not actually available in most clinics. Plus, there's no free treatment for adults. The only alternative for most people is expensive private medicine. So they come to us.

What are some of the difficulties associated with diagnosing Chagas disease?
The first major difficulty is that Chagas is often asymptomatic, which means that during the first acute stage of the disease, immediately after a person is infected, there are often no apparent symptoms. Children may show some symptoms, but these can be confused with those of other common childhood illnesses. At later stages of the disease, people do not show symptoms at all. So this means they are never diagnosed. Millions of people are in fact carrying this infection, and have never been diagnosed.

About 20-30% of those infected will go on to develop the chronic form of the disease, as much as ten or twenty years later. Most people we see were infected years ago, or even when they were children. By the time the chronic disease activates, patients may have developed lesions that cause irreversible damage to the heart and digestive system. At that point, treatment with the current anti-Chagas drugs is no longer effective.

The second problem is that the diagnostic tools we have to deal with this situation are far from ideal. The tests that give the most precise results are complex ones that require multiple blood tests. And this means you run the risk of losing the patient, because they won't come back, which is a big risk especially when someone isn't showing any symptoms. So what we use is a rapid test, which is far from perfect, but is the best screening tool. If the test is positive, the patient gets the blood tests to confirm the result.

There is also a major issue around diagnosis of cure, because we don't have a tool that tells us whether someone is cured or not.

Dr. Víctor Condé:
“I got to know a 17-year-old teenager who suffered from a Chagas-related advanced cardiopathy that needed to have a permanent pacemaker implanted. His heart problems meant that it was too late for him to benefit from specific Chagas treatment, but we managed to get a free pacemaker for him. But, just as we were about to go ahead and operate, the patient changed his mind, wrongly advised by those closer to him.”

What about treatments: are they available and how effective are they?
Oral benznidazol is the first choice treatment. If the patient suffers too much from the side effects, we replace it with nifurtimox, but that causes very frequent side effects, too. The side effects include allergic skin reactions that can be very severe in rare cases, and even fatal. There is also the risk of nerve damage and gastro-intestinal problems.

Both treatments take a considerable amount of time – 60 days – and must be taken under medical supervision. None of this makes treating Chagas an easy affair.

What's worse, neither of these drugs is sufficiently effective to eliminate the parasite during the chronic phase of the disease. So the success of the treatment depends on how advanced the disease is and how it evolves. Patients who have recently been infected, usually children, show cure rates higher and faster than patients who have had the disease for a long time. We can say that cure rates may be around 60-80% of cases at an early stage of the disease, although this seems to vary widely in different contexts, and we cannot really be sure because there hasn't been enough research. In chronic cases, that cure rate falls to below 50%.

Dr. José Luis Dvorzak:
“I especially remember a 24-year-old young man suffering from a Chagas-related severe cardiopathy with symptoms such as syncope and palpitations. He came to the clinic asking for benznidazol, believing that this would solve his heart problem, when in fact what he really needed was a pacemaker.”

Another issue is that there are still no paediatric versions of these drugs available. Instead, what we have to do is crumble adult tablets to give to children. But this is not an accurate or satisfactory way to treat our patients.

Basically, we're making do: the treatment is effective enough in both children and adults to make it worth using. But it's not nearly effective or safe enough to accept as the only option… that's why we need more research. The problem is, there isn't enough commercial incentive to ensure that happens.

What would you like to see happen to improve the situation?
There have to be much higher budgets allocated to the research of drugs that could help our patients in more effective and less risky ways. We have a long list of needs. We need a shorter treatment course, drugs with fewer side-effects, and drugs that don't require as much close medical supervision. These drugs need to be affordable immediately when they come onto the market.

Of course we also need paediatric versions of the drugs. We need better diagnostic tests that are effective at all stages of the disease, so that we can catch the disease at a stage when it can most effectively be cured.

And we need tests that can tell us whether someone has been cured or not, without having to wait 10-20 years to find out. This last one is very much a vicious circle, because it is very hard to test new treatments when you have to wait so long to find out if they work or not.