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Home arrow Economics arrow American Trypanosomiasis Chagas Disease, Second Edition: One Hundred Years of Research


The medical burden of HCD in endemic and nonendemic areas

According to recent PAHO data, 21 countries must be considered endemic for HCD in the Americas, with a general prevalence rate of 1.448 by 100,000 inhabitants, meaning at least 7,694,500 infected individuals. Between 60 and 80 million susceptible individuals remain under the risk of T. cruzi transmission, in endemic countries.21

The annual incidence rate was calculated as 0.008 cases by 100,000 inhabitants, meaning a number of 41,200 cases of vectorial transmission and 14,385 cases of congenital transmission yearly.21 Since the morbidity of HCD is different according to different geographical regions and age groups, general data have been restricted to estimate the impact of HCD in terms of cardiac involvement and premature deaths, both in the acute and in the chronic phase of the infection. For the acute disease, it is accepted that the mortality of nontreated individuals will depend on the intensity and the virulence of the infection, producing an acute myo- cardiopathy associated or not with a meningo-encephalic compromise. Deaths in acute HCD occur basically in children up to 3 years of age, a fact that means a very high pressure of transmission, chiefly of “domiciliated” infected triatomines.4,8,22

The general rate in nontreated individuals comprises between 2% and 12% of mortality in the acute phase, being higher in low age groups. A correlated consequence of severe acute HCD has been demonstrated in longitudinal studies, in which the worst evolution of HCD at long term (50 years of follow-up) corresponds exactly to those cases with severe acute onset detected in ages below 3 years.18 On the other hand, acute HCD has shown to be curable with the current available drugs (nifurtimox and benznidazole).14,15

The adequate treatment reaches the betterment of the clinical picture and the parasitological cure in about 80—90% of the cases. Nevertheless, three major constraints involve acute treatment: (1) the great shortage of medical expertise in endemic areas, making the correct diagnosis difficult and rare; (2) the problem of correct and early diagnosis, because of the laboratory difficulties and of the clinical picture, which is often not apparent or too similar to other several febrile diseases; and (3) the difficulties of medical access for the poor and rural populations of endemic countries.18 An additional problem remains in the progressive loss of interest and visibility of this disease, which is occurring in endemic areas following the control implementation.16

The chronic phase constitutes nowadays the major problem of HCD in all endemic and nonendemic countries. Among the millions of infected individuals, at least 20% will develop a chronic heart disease and/or a digestive form. All of them are potential transmitters of the parasite by means of blood and organ transplantation. And those patients suffering from Chagas heart disease will certainly have severe working limitations, high costs concerning medical attention, and reduction of life expectation according to several studies.10,13,14,22

Another aspect concern the superposition of coinfections and/or chronic degenerative diseases in individuals primo-infected with T. cruzi. Both these situations are related to social and demographic factors involving the migration to urban centers and the survival of “chagasic” people.2,13 At the present, the possibilities for chronic infected individuals have been considered much more optimistic, in comparison with the medical and social situation 30 years ago. Not only the specific treatment, but also the supportive management for chronic cardiopathy and digestive “megas” have been considerably improved in recent decades.1314 Following the evolution of disease management, according to the recent consensus of several scientific working groups, it is possible to improve the quality and quantity of life of the infected individuals, regarding chiefly the prevention of severe arrhythmias, the progression of cardiac failure, and the occurrence of sudden death. The same is valid for the “mega” syndromes, since a precocious intervention at the beginning of the symptoms can be used to delay or even to prevent late severe complications. At this point, the social and political aspects can be crucial for the prognosis and the follow-up of thousands of patients: We must consider, above all, that the “chagasic” people are generally very poor, illiterate, and politically weak, a context extremely traditional among the “neglected diseases.”2,8,22

The correct management of HCD presupposes continuity for several years, with regular medical supervision, including for indeterminate chronic patients. In this context, three main elements must be considered for an effective sector management policy: access, expertise, and drug availability. On the other hand, the social security is deeply involved with the evolution of the chronic HCD, mainly for those patients who demonstrate initial and severe degrees of cardiac failure and complex arrhythmias. When adequately managed and detected early, these classical heart disturbances of HCD can be effectively controlled by means of modern drugs and other medical interventions such as pace-makers, defibrillators, and (of course) rest and physical adequacy. , , , Obviously, social security is strictly involved with social, administrative, and economic aspects.

For instance, in Brazil, with about 2.5 chronic infected individuals, it can be calculated that 20% of them will develop a cardiac disease (500,000 individuals) and, among these, 5—10% (25,000—50,000) of individuals will develop severe degrees of “chagasic” cardiopathy.9,23 All of them will require not only permanent medical but also social attention, involving the traditional problems of medical access and expertise, as well as the budgetary constraints of social security in poor countries. In such a context, probably the half of Brazilian individuals who deserve the benefit will never receive it, a fact clearly linked with the reduction of their survival. In our framework, the social consequences of HCD are mainly due to chronic cardiopathy, involving work limitation and quality and quantity of life, thus generating severe social consequences at the individual and group level. Besides the T. cruzi infection and some biological characteristics, some social factors are recognized as determinants of Chagas heart disease, such as physical effort, undernourishment, alcoholism, and the lacking of medical attention.3,23

The more severe “chagasic” cardiopathy used to kill very early the affected patients, generally of the male gender, of age 35—50 years. The immediate social and group consequences involve a significant population of orphans, widows, and children who must prematurely leave school to help the family survive.3,9,10 On the other hand, the majority of infected individuals remain several years in the chronic indeterminate clinical form. Most of them never will be diagnosed since neither symptoms nor physical signs are present. Some of them will be diagnosed by means of blood banks serological screening, others by population serology, presurgical procedures, or special public health programs (e.g., pregnant women screening).15,17,22

The conspicuous consequence will be the lost opportunity to treat precociously such individuals and to interview clinically at the beginning of a cardiac or digestive disturbance. Nowadays, especially in low age groups, specific treatment is being considered as a very promising procedure, able to achieve the delay of severe chronic forms or even the parasitological cure of the infection.1,22 In the case of nonendemic areas, the social and macropolitical aspects involving globalization, underemployment, and immigration of people from endemic countries have been the main causes for the detection of thousands of infected individuals in several countries of Europe, Oceania, Asia, and North America (mainly the United States). This relatively new situation involves serial problems concerning medical attention, labor affairs, and concrete possibilities of disease transmission, chiefly by blood transfusion, congenital, and organ transplantation mechanisms. Two correlated and crucial problems involved are medical expertise to diagnose and treat the disease, and the clandestine situation

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of thousands of individuals who are socially unprotected. , , ,

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