Chagas Disease - Transmission, Symptoms and Treatment
Chagas disease is an infection caused by the protozoan Trypanosoma cruzi, acquired through contact with the feces of the insect barber. Chagas disease is also known by the names: Chagas disease, chagas disease or American trypanosomiasis.
Most cases of Chagas disease are transmitted by the bite of a group of insects from the stink bug family known as a barber. The main barber species that transmit Chagas disease in Brazil are: T.brasiliensis , Panstrongylus megistus, T.pseudomaculata and T.sordida. The T.infestans was another important species, but control measures of the Ministry of Health were able to stop the transmission of Chagas disease by this type of barber.
The barber is a type of bedbug that feeds on blood, and can transmit Chagas disease through the bite. During or immediately after a person stings, a barber defecates on his or her skin, eliminating large quantities of the protozoan Trypanosoma cruzi , allowing it to penetrate the body through the bite wound. Scratching the site that has been stung increases the chance of contamination. Barbers tend to feed at night, being able to bite their victims without waking them up.
Not every barber is infected with the parasite of Chagas disease. The barber is contaminated by stinging animals that are infected with Trypanosoma cruzi . Therefore, the barber acquires the parasite by stinging an infected person, stays with him in his intestine for the rest of his life, and transmits it when a new victim is bitten. It is important to note that the parasite is also capable of infecting animals other than humans, including dogs, cats, pigs, rodents, opossums, bats, etc., being these important reservoirs for the transmission of Chagas disease to humans.
Barbers often live on palm fronds or in rudimentary construction houses, such as those made from stick-a-pike. Chickens, pigstones and bird nests are also places that can house the insect. People living in barber-infested areas are those most at risk of being contaminated with Trypanosoma cruzi.
Other forms of transmission
Transmission through the bite of the barber is the main route, but Trypanosoma cruzi can also be acquired in other ways, such as:
Blood transfusion
Transplantation of organs from infected donors
Food contaminated by barbers, such as cane juice
Vertical transmission from mother to fetus during pregnancy
Contact of injured skin, mucous membranes or eyes with blood from infected patients
After contamination by Trypanosoma cruzi, the incubation period is usually 1 to 2 weeks. However, if contamination has been caused by blood transfusion, the symptoms may take more than 40 days to emerge.
The symptoms of Chagas disease are divided into acute stage and chronic stage. Let's talk a little bit about both.
1. Acute phase
The acute phase of T.cruzi infection lasts 8 to 12 weeks and is characterized by the circulation of large amounts of the parasite into the bloodstream. At this stage, most patients have no symptoms. When they do, they are mild and nonspecific symptoms, such as fever and malaise. The fever is usually not very high, being around 37.5 and 38.5ºC. Increased liver and spleen size may also occur.
In a minority of patients, an inflamed nodule may appear at the site of the barbed bite, known as a chagoma. If the bite is around one eye, it is common to see a swelling of the upper and lower eyelid, known as the Romagna sign.
The severe form of acute Chagas disease, with high mortality, occurs in less than 1% of patients; the manifestations may include acute myocarditis (inflammation of the heart muscle), pericarditis (inflammation of the pericardium, membrane surrounding the heart), or meningitis. Transmission of the parasite by contaminated food appears to be associated with an increased risk of severe acute disease.
It is worth mentioning, however, that in the majority of cases, the acute phase is mild and patients do not realize they have been infected by T.cruzi . The acute phase ends when the parasites disappear from the bloodstream.
2. Chronic phase
There are three distinct presentations of the chronic form of Chagas disease:
I. Undetermined form: it is the patients who remain infected by Trypanosoma cruzi, but they remain without symptoms. Many of these patients do not even know they are infected.
About 20 to 30% of patients with an indeterminate form of chronic Chagas disease develop into symptomatic, cardiac or gastrointestinal disease after years or decades of silent disease. The remaining 70% remain asymptomatic for the rest of their lives.
II. Cardiac form: approximately 30% of the patients who are contaminated with Trypanosoma cruzi present cardiac involvement due to the disease. Infection by the parasite causes destruction of the heart's muscle fibers, leading to severe heart failure. Cardiac involvement is the main cause of death in patients with Chagas disease. Sudden death, arrhythmias, and terminal heart failure are the leading causes.
III. Gastrointestinal tract: gastrointestinal tract involvement occurs in 10% of patients with Chagas disease. Exaggerated dilation of the colon (megacolon) or esophagus (megaesophagus) are the main manifestations of this form of chronic Chagas.
Megaesophagus causes difficulty in swallowing food and frequent regurgitation. Megacolon is characterized by constipation and abdominal pain.
It is possible for the same patient to have cardiac and gastrointestinal involvement concomitantly.
During the acute phase of Chagas disease, as there is a large amount of the parasite circulating in the blood, it can be easily identified by analyzing a drop of blood under a microscope. In the chronic phase the diagnosis is made through the serology (search for antibodies in the blood).
The earlier treatment is instituted against Chagas disease, the better the clinical results. Preferably, every patient should be treated in the acute phase, whether or not he has symptoms. The problem is that as not all patients at this stage are aware of being infected with Trypanosoma cruzi, most end up looking for medical care early.
Early treatment aims to cure T.cruzi infection, prevent organ damage, such as heart and intestines, and reduce the possibility of protozoal transmission. The patient who already presents the chronic form, with severe organ damage presents little or no benefit with the treatment.
Therefore, people living in areas where there are cases of Chagas disease or who have recently had vacations in one of them, should pay close attention to fever and malaise, even if these be gentle. Sometimes it is necessary to have a very high degree of suspicion to detect Chagas disease early.
Benznidazole is the drug of choice in the treatment of acute Chagas disease. Treatment should be done for 60 days and the dose varies according to the patient's weight. Nifurtimox is an alternative for cases of Benznidazole intolerance. Treatment with Nifurtimox is done for 90 days.
