Chagas disease: what it is and how it is transmitted?

This disease is transmitted mainly through the bite of certain insects: large blood-feeding bugs - known as Kissing Bugs or Vinchucas in Castilian-speaking countries or Barbeiros in Brazil - which carry a protozoan, Trypanosoma cruzi (T. cruzi), in their intestines. 

“The contagion occurs in most cases through the deposition on the skin of a small amount of feces emitted by the bedbug when it stings or immediately afterwards: especially the sting, which occurs at night mainly on the skin of the face or more rarely in other parts of the body left uncovered, causes itching. Scratching the wound as well as even touching the mouth and eyes with hands soiled with traces of feces helps spread the insect feces containing the parasite to the skin,” tropical disease expert explains.

In addition to insect bites, the other modes of infection of Chagas disease are as follows:

• transmission of infected blood between 2 individuals: through a blood transfusion or blood/mucosal contact or passing of syringes between drug users or organ transplantation;
• during pregnancy or childbirth, when blood is passed from a mother with Chagas disease to the fetus (vertical contagion);
• ingestion of contaminated food or drink.

Chagas disease is also present to a small extent in Europe and Italy; there are 2 main reasons for such presence:

• due to migration flows from Latin America to the United States and Europe, particularly Spain and Italy;
• due to the flow of tourism to Mexico, Central America, and South America. 

“Although in the vast majority of cases the episodes of infection are limited to Central and South America and are due to the mode of transmission via vector insect, a non-negligible number of cases have been diagnosed among immigrants from Latin America to Europe and North America and among those who received transfusions or organ transplants from infected individuals (who did not know they were infected) or among the children of infected women from endemic areas.

Strict hospital controls in Italy on blood donors or organ donors rule out the presence of blood contaminated with T. cruzi, which is responsible for Chagas disease, in Italy,” Dr. Gaiera explains. 

Blood donors returning from trips to Mexico, Central America, South America (T. cruzi endemic areas) will have to abstain from donation for 3 months: after observing the prescribed withdrawal period in order to rule out possible contagion, they will have to perform serological testing for anti-T. cruzi antibodies in blood.

There are rare cases of Chagas disease transmission from street food: the traveler to South America should take special care not to consume unsealed beverages (such as typical sugarcane juice drinks) and/or food exposed to air without adequate protection.

It can be an asymptomatic disease for years. Absence of symptoms can lead infected persons to neglect examinations and therapies necessary for the treatment of Chagas disease. If left untreated, this condition can also lead to patient death both in the acute phase (in the weeks after infection) and especially in the chronic phase with mainly cardiac involvement. 

As the doctor explains, “It can manifest in 3 forms also called phases, to which corresponds the presence or absence of symptoms: 

1. acute: may be symptomatic or asymptomatic: if symptomatic, it usually presents as a cardiac infection (myocarditis) or more frequently in children as an infection of the meninges and brain (meningoencephalitis);
2. indeterminate chronic (also called latency): no symptoms are present, only positive serology for T. cruzi;
3. chronic: with more frequent damage to the heart (dilated heart disease, arrhythmia/complex ventricular arrhythmias, aneurysm of the ventricular apex of the heart, thromboembolism, ventricular dysfunction with heart failure and sudden death) and less frequent to the esophagus and colon (dilatation of these tracts of the gastrointestinal tract) and even rarer to the central nervous system (dementia, paresis).”

The tests useful in diagnosing Chagas disease and verifying the function of the 3 main affected organs (heart, esophagus, colon) are:

• 2 different tests for anti-T. cruzi antibodies in blood;
• electrocardiogram and echocardiogram in case of cardiac pathology (arrhythmias and chronic cardiomyopathy);
• abdominal CT scan and esophagogastroduodenoscopy and colonoscopy in case of suspected digestive tract involvement (megaesophagus or magacolon).

It is also possible to conduct preconception/prenatal/neonatal screening in the woman and the couple of parents-to-be seeking a child. Should the condition be diagnosed, the tropical disease specialist will focus on checking the functionality of the 3 main organs affected by Chagas disease.

“While in stage 1 (acute) and stage 3 (chronic) of Chagas disease, the organ most affected is the heart, followed by frequency in the chronic stage by esophagus and colon, in stage 2 (indeterminate) the patient is asymptomatic and only tests positive in the blood for antibodies against T. cruzi,” Dr. Gaiera explains. 

Incubation period for this tropical disease may differ depending on the mode of infection. As specified by the expert: 

• Insect bite contagion: “It has an incubation period of about 1 to 2 weeks; in this case a red nodule/ponophore may appear in the area where there was the bite. After the incubation period in most cases a high fever appears, which can last for a few days, and there are usually symptoms and signs of cardiac distress, but it can also remain asymptomatic for even 10-20 years.”
• Contagion by blood and/or organ transplantation: “The incubation of Chagas disease is shorter. If present, the symptomatology is superimposed on that of the acute phase after insect bite. Once these symptoms disappear the disease can remain silent for a lifetime, in which case we speak of Chagas disease in the indeterminate or latency phase, or after decades it can become chronic: this occurs in 30-35% of infected people,” the specialist continues.

There is no vaccine against Chagas disease. While traveling in South America, the only form of prevention is to avoid getting bitten by bedbugs by avoiding sleeping in typical country houses made of mud and straw and sprinkling uncovered body parts and/or even clothes and suitcases/backpacks with insect repellents (sprays or topical lotions), periodically pest control of homes and work areas, and washing hands often (soap and water and hydroalcoholic solutions), avoiding touching the face, eyes and mouth. It is also recommended to avoid ingestion of potentially contaminated food and drinks and contact with blood/mucous membranes (personal protective equipment and condoms must be used).

As the expert points out, “Benznidazole and nifurtimox are the only 2 antiparasitic drugs that proved to be effective against T. cruzi; until 20 years ago they were used only to treat the acute or congenital (inherited from parents) phase of Chagas disease, while for the past few years they have also been used to prevent the possible evolution of the disease from the indeterminate to the chronic phase.

On the other hand, these 2 drugs have not shown any efficacy when the chronic cardiac, intestinal, or central nervous system phase has developed: in these cases, treatment is only symptomatic (i.e., it only treats the symptoms, but cannot cure or eradicate the disease). The 2 antiparasitic drugs mentioned above are not currently on the market in Italy and are difficult to find even internationally, but to date they are the ones used in the treatment of this disease.”

The doctor of Tropical Medicine warns: “Finally, one should not underestimate the important side effects of these oral pesticides, especially those of nifurtimox (a chemotherapeutic antiparasitic drug). Moreover, both of these drugs are contraindicated during pregnancy because of the drug's passage from mother to fetus.”

Some types of patients are asked to take special care in choosing their travel destination by avoiding Chagas disease endemic areas or traveling to those areas, but paying extreme attention to behavioral norms for prevention of bedbug bite: 

• women who are seeking pregnancy or are already pregnant;
• patients with kidney or liver failure;
• immunocompromised patients and those with AIDS, and in other specific cases that the physician will notify the patient before travel to tropical destinations.

“With no effective and well-tolerated therapy available to date in all stages of Chagas disease, all the preventive interventions already mentioned are even more important, both in case of infection via vector and in case of transmission through blood, organ transplants and contaminated food,” Dr. Gaiera concludes.