The parasite causing Chagas disease is carried by an arthropod vector known as Triatoma dimidiata, chinche, or the kissing bug.

Chagas is a parasitic disease found on the American continent, where it affects an estimated 16 to 18 million people and claims up to 50,000 lives every year. Dr Carlos Chagas, a Brazilian physician, first described in 1909 the often fatal condition that damages the victim's cardiovascular, nervous and digestive systems. Some 100 million people in Latin America are at risk of contracting Chagas today. As a result of increased global travel, cases have also been reported in the US and Europe. Treatments and diagnostic tests for Chagas are inadequate and ill-suited for resource-poor settings, a fact that continues to frustrate medical staff caring for people living with the disease.

Transmission

Chagas is caused by Trypanosoma cruzi, a parasite transmitted to humans by blood-sucking insects known as triatomines. As it bites, the insect carrying the parasite deposits feces on the person's skin, and when the person rubs their eyes, mouth or the bite wound, the feces containing the parasite enters the bloodstream. Chagas can also be transmitted through blood transfusion, from mother to child during pregnancy, or less commonly, via organ transplants or contaminated food. There is no vaccine against Chagas, and a person can be reinfected after treatment.

Though asymptomatic, these children were found to have Chagas. Treatment with appropriate medicine will prevent them from developing serious complications in the years to come. © Serge Sibert/Cosmos

Symptoms: a silent killer

Chagas infection progresses in stages. During the first, acute stage of the disease, which occurs in the immediate aftermath of infection, there are often no apparent symptoms. Children may show some symptoms such as fever, swollen lymph glands, enlarged liver and spleen, or an inflamed bite wound. These non-specific symptoms may often be confused with those of other common childhood illnesses. The indeterminate stage begins between eight to ten weeks after the initial infection and may last for many years. In this stage people do not have symptoms and can carry the parasite for years without knowing it. About 20-30% of those infected will go on to develop the chronic form of the disease up to ten or twenty years after they first contracted it. By this time, patients will have developed lesions causing irreversible damage to the heart, esophagus and colon. Heart failure is a common cause of death among young adults - people who should be in the most productive phase of their lives.

A disease of poverty

The beetles that transmit Chagas live in cracks in the walls and roofs of mud and straw housing, which are common in rural areas and poor urban slums in Latin America. Population movements from rural to urban areas in the 1970s and 80s brought Chagas into cities, and it became an urban infection transmitted through blood transfusions. Blood banks reported T. cruzi infection rates ranging from 1.7% in Sao Paulo, Brazil, to 53% in Santa Cruz, Bolivia, where Chagas infection rates far exceeded those of HIV and hepatitis. Chagas is most common among the poorest and most vulnerable populations. Often unaware of how the disease is caught or what their chances of being cured are, those infected by T. cruzi are unlikely to be in a position to fight for their right to be treated. Treatment of the disease has been systematically sidelined by national and regional health authorities.

An MSF clinician obtains a blood sample for testing at a rural Honduran school. Photo © Serge Sibert/Cosmos

The access problem: lack of appropriate diagnostic tests and medicines

Chagas is one of the most neglected diseases in the world. Millions of people who were infected decades ago still go undetected and untreated because diagnosis is complicated by several issues. Doctors usually need to perform several blood tests to determine whether a patient is infected. In adults, the disease is often not actively diagnosed in early stages because carriers tend to be asymptomatic. Unfortunately, by the time a patient has developed chronic Chagas, treatment with current drugs is no longer effective. Efforts should therefore be stepped up to develop methods of actively identifying the acute phase of the disease, when patients can truly benefit from available treatment.

There are two medicines that can be used to treat Chagas. The first, nifurtimox, is commercially available for US$48 per treatment course-- the equivalent of a Bolivian miner's monthly salary. Following an agreement negotiated by WHO, a one-off donation of five million tablets of nifurtimox was made available to Latin America's Ministries of Health through the Pan American Health Organization (PAHO) in 2004. The other medication, benznidazol, is available with delays of up to four months due to limited supply of the drug's active pharmaceutical ingredient. The necessary technology to manufacture benznidazol is being transferred from Roche to a small public laboratory in Brazil. Once functional, this facility will be the sole producer of a drug needed in 21 countries across Latin America.

But the long-term availability of the existing medications is not guaranteed, and neither of the two drugs are ideal. First, cure rates are only 60- 70%, and in chronic cases, they remain under 50%. Second, the treatment can have severe side-effects and must be taken under medical supervision. This is a challenge because the treatment regimen lasts 30 to 60 days. The drugs cannot be used in adults due to frequency and severity of side-effects, and there is no formulation adapted for young children. At present, medical staff have to cut tablets to achieve the appropriate dosage, and mothers have to mix the crushed pills in juice or breast milk for babies. Third, neither treatment can be prescribed to pregnant women who risk passing the disease to newborns.

The market represented by Chagas patients is insufficient to motivate the private sector to invest in drug development and therapeutic innovations, or even to register existing medicines. Indeed, more research and development (R&D) into new molecules is badly needed. An ideal drug candidate would be effective for patients in the acute, undetermined and chronic phases of the disease.

In Olopa, Guatemala, a local health official fumigates a house in an effort to eliminate the Chagas vector. Photo © MSF

Linking treatment and prevention

Prevention programs, such as vector control and blood transfusion testing, are in place in most Latin American countries, even if they are not always implemented or effective. It has been argued that treatment should be available to patients regardless of whether or not vector control activities exist or are functioning. While MSF began with this notion, it is becoming clear that a treatment-only strategy without complementary could backfire. In Bolivia, for example, where vector control is patchy at best, there is a considerable risk of re-infection. Since treatment is toxic and resource-intensive, treatment efforts are undermined by ineffective vector control.

As a result of its experiences, MSF now only treats patients when infestation rate is below 3%. However, this position raises moral and practical dilemmas. Vector control is not always delivering beneficial results, and often it is not even possible. Should people living in inaccesible regions such as the Amazon Baisin then not be treated at all? What about areas where vector control is possible, but is not carried out or not completed? Patients might end up seeing their chances of being cured vanish while waiting for the goverment to institute effective control programs.

MSF and Chagas disease

MSF has been working with patients suffering from Chagas since 1999. MSF currently provides medical care to patients suffering from Chagas in two Bolivian projects, Tarija and Sucre. In Tarija, 20.5% of the population between nine months and 15 years is infected with Chagas. Between February 2003 and June 2005, MSF tested 4750 children, and 935 of these have already received treatment and are being followed up for two years. In Guatemala, MSF expects to complete treatment of 200 patients until the end of 2006. MSF has also finished two other Chagas projects in Honduras and Nicaragua. In Honduras, MSF successfully treated over 200 patients under 14 years of age and followed them up over two years. In Nicaragua, out of 3500 patients tested, 66 received treatment and follow up. In Mexico, MSF conducted a study that showed a 2.3% prevalence of Chagas in children under 14, and subsequently urged the government to address the problem.

While there have been efforts to understand Chagas and to control the spread of the vector, too little attention has been paid to treating those who have been infected. Through its programs in Latin America, MSF aims to show that treatment is not only possible, but that it is imperative. While certainly not optimal, MSF's clinical results demonstrate that the existing drugs can be used more widely than previously understood, with manageable side-effects. Governments of endemic countries will have to recognize their responsibility for public health and commit to taking care of their high-risk population. There is clear momentum for integrated national Chagas programs in Latin America, but significant funding is needed from the international community to support the battle against Chagas.

MSF is urging that:

• The production and availability of nifurtimox and benznidazol, the two existing drugs, be secured.
• Pediatric versions of the existing drugs be developed.
• Diagnostic tests for all stages of the disease be improved.
• R&D efforts into affordable, more efficient, and less toxic treatments for Chagas be increased.