Chagas disease: The Brazilian forest bites back

Bugs that lost their natural habitat through deforestation in the Amazon region are spreading disease in human settlements

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In February, when José de Jesus Pinheiro Braga spent two weeks cutting timber for a logging company in the jungle near Atalaia do Norte, a remote corner of Brazil’s Amazonas state, he unwittingly contracted a potentially fatal illness. He was bitten by one of the Amazon’s native inhabitants, the triatomine beetle, a blood-sucking bug about the size of a cockroach, also known in Brazil as the barbeiro (barber), which carries a parasite that causes Chagas disease.

The wiry farmer soon developed a fever accompanied by severe chills, a headache and sore muscles. Alarmed health workers at the hospital in Atalaia transferred him to the Fundação de Medicina Tropical Doutor Heitor Vieira Dourado — a hospital for tropical medicine, known to locals simply as “the Tropical” — in the distant state capital of Manaus. Luckily, the municipality had the funds to fly him there; by boat, the only other means of transport, the journey would have taken seven days.

“If I had stayed in the hospital in Atalaia you would be looking at a dead man now,” Braga says from his hospital bed. “I’ve had malaria five times, I’ve had a kidney infection, but nothing compares with this.”

José Soares Ribeiro, who has the chronic form of Chagas © Raphael Alves

The Amazon basin is one of the frontlines in the battle against Chagas, also known as American trypanosomiasis, a disease caused by the Trypanosoma cruzi (T. cruzi) protozoan parasite. About 6m-7m people, mostly in Latin America, are thought to be infected with the disease, named after the Brazilian physician Carlos Ribeiro Justiniano Chagas, who discovered it in 1909.

Chagas is endemic in 21 Latin American countries, according to the World Health Organization. Increasingly, it is also found in the US, Canada and Europe as a result of increased travel and migration between Latin America and the rest of the world. “For Brazil, this is a very serious problem,” says Dr Jorge Augusto de Oliveira Guerra, a Chagas specialist at the Tropical. The disease is already present in most of the south and centre of the country, he says. “In the north, it is considered an emerging problem.”

Braga was lucky. His acute symptoms meant the infection was discovered and treated early, so his chances of being fully cured are high. Guerra prescribed a 60-day course of benznidazole, the drug that, along with nifurtimox, is commonly used to treat Chagas. But most people who contract Chagas are classed as chronic cases. They show no symptoms of the disease during the initial two-month acute phase, after which the parasite retreats into the muscles of the heart or bowels, where it may lie undetected for decades.

In a third of chronic cases, the parasite will cause severe damage to the cells of these organs over time, resulting in tissue swelling and scarring. After 10-15 years this can lead to a condition known as Chagas cardiomyopathy, which can involve heart failure, heart attack, an enlarged heart and irregular heartbeat. It can also lead to acute swelling of the bowel and the oesophagus. Such chronic cases can be treated using the same drugs but never fully cured, doctors say.

Doctor Maria das Graças Barbosa Guerra with triatomine beetle specimens © Raphael Alves

Archeological studies show that Chagas has been present in human settlements since prehistoric times in the Chihuahuan desert in what is now Texas in the US, and in parts of the central Andes and Peruaçu valley in the state of Minas Gerais in central Brazil. More than 100 wild mammals act as hosts for T. cruzi, from marsupials and bats to armadillos and monkeys. Rats, dogs and other domestic animals can bring the parasite into the home.

The principal agent of transmission for the disease from animals to humans is the barbeiro, of which 140 species have the potential to transmit the disease, according to a paper by a Brazilian researcher, Dr José Rodrigues Coura of the parasitic diseases laboratory at Instituto Oswaldo Cruz-Fiocruz in Rio de Janeiro.

The different species are highly adaptable and can live in forests or in houses. One widespread species, the Triatoma dimidiata, hides itself with dirt on floors of houses. The bugs defecate on skin near their bites and the T. cruzi in their faeces enters the body when a victim scratches the area that has been bitten. The name barbeiro is thought to originate in the 19th century, when barbers, who often doubled as doctors in Brazil’s remote villages, used blood-letting as their default treatment.

Today, the spread of Chagas in the Amazonian region is being driven by human factors such as deforestation and the growing consumption of palm products, such as the local fruit açaí, researchers say. Deprived of its habitat and the proximity to wild animals, once its main source of food, the barbeiro is increasingly invading human settlements.

“Over the past 10 years, [Manaus] has changed completely,” says Guerra’s wife, Dr Maria das Graças Barbosa Guerra, who heads a department at the Tropical. “People have built residential towers . . . and messed with [the barbeiro’s] natural habitat.”

The Tropical maintains small colonies of barbeiro for use in testing chronic patients. Uninfected bugs bite patients and the insect’s faeces is examined for signs of the parasite. Maria Guerra takes a jar filled with live bugs with a lid of fine gauze. When she puts a finger near the gauze, the barbeiros poke their proboscises through, looking for blood.

Although the disease is best known in Amazonas as coming from the barbeiro’s bite, the biggest Chagas outbreaks have arisen from consumption of homemade açaí juice sold at roadsides, into which bugs have been accidentally crushed with the fruit. “If you take the trouble to carefully wash the fruit before processing it, the risk of an infection is greatly reduced,” says Jorge Guerra.

The Brazilian government has aggressively targeted the disease in other areas of the country, using insecticides to kill the barbeiro, particularly in poorer communities, and making treatment widely available. As yet, though, there is no vaccine and the huge pool of potential host animals, especially in the wild, makes its total eradication almost impossible, scientists say.

Valdemir Alves de Nascimento has heart problems as a result of Chagas © Raphael Alves

About 20km from Manaus, in a community of small farmers called the Pau Rosa co-operative, chronic patient José Soares Ribeiro seems unaffected by the disease, despite having being diagnosed with it about 20 years ago. One of the community’s more colourful personalities (he has built an outdoor toilet out of bottles of cachaça, the throat-burning Brazilian sugarcane spirit), Ribeiro says the area is still wild and prone to barbeiros.

Even so, he takes few precautions against insects. He does not use repellent even though he has caught the sandfly-borne disease leishmaniasis five times. “I don’t know how I caught [Chagas],” he says.

Ribeiro was treated and now undergoes regular monitoring for possible complications but says he has never felt any symptoms.

But for other long-term patients, the disease can be devastating. Ribeiro’s neighbour, Valdemir Alves de Nascimento, who spends much of his time watching television on his jungle porch, describes in a near whisper how the disease has ruined his health. The 56-year-old was diagnosed nearly 10 years ago; his heart is swollen and he now suffers from acute shortness of breath and uses a pacemaker. He has had two strokes that left him temporarily paralysed on one side.

Alves de Nascimento thinks he was bitten while collecting the fruit of the buriti palm, whose oil is used for skin and hair cream. A retired driver, he used to live in Manaus with his wife and children before his condition worsened.

“I wanted to come here to the country, where it’s calmer. [My wife] didn’t want to, so we separated,” he says, his gaze drifting back to the TV. For now, he says, he prefers the quiet of his forest hut.

Additional reporting by Carina Rossi in São Paulo

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