João Carlos Pinto Dias

Epidemiology, control and surveillance of Chagas disease: 100 years after its discovery

Chagas disease originated millions of years ago as an enzootic infection of wild animals and began to be transmitted to humans as an anthropozoonosis when man invaded wild ecotopes. While evidence of human infection has been found in mummies up to 9,000 years old, endemic Chagas disease became established as a zoonosis only in the last 200-300 years, as triatomines adapted to domestic environments. It is estimated that 15-16 million people are infected with Trypanosoma cruzi in Latin America, and 75-90 million are exposed to infection. Control of Chagas disease must be undertaken by interrupting its transmission by vectors and blood transfusions, improving housing and areas surrounding dwellings, providing sanitation education for exposed populations and treating acute and recently infected chronic cases. These measures should be complemented by surveillance and primary, secondary and tertiary care.

Southern Cone Initiative for the elimination of domestic populations of Triatoma infestans and the interruption of transfusion Chagas disease: historical aspects, present situation, and perspectives

Created in 1991 by the governments of Argentina, Bolivia, Brazil, Chile, Paraguay, and Uruguay, the Southern Cone Initiative (SCI) has been extremely important for Chagas disease control in this region. Its basic objective was to reach the interruption of this disease, chiefly by means of the elimination of the principal vector Triatoma infestans and by the selection of safe donors in the regional blood banks. After a summarized historic of SCI, the text shows the advance of technical and operative activities, emphasizing some factors for the initiative success, as well as some difficulties and constraints. The future of SCI will depend of the continuity of the actions and of political priority. Scientific community has been highly responsible for this initiative and its maintenance. At the side of this, national and international efforts must be involved and reinforced to assure the accomplishment of the final targets of SCI. Very specially, the Pan American Health Organization has cooperated with the Initiative in all its moments and activities,being the most important catalytic and technical factor for SCI success.

The evolution of Chagas disease (American Trypanosomiasis) control after 90 years since Carlos Chagas discovery

SUMMARY OF THE PRINCIPAL EVENTS RELATEDTO HUMAN CHAGAS DISEASE CONTROL FROM1909 TO 1999 In order to have a general and chronologic com-prehension of the facts appointed above, the fol-lowing picture was prepared, showing the consid-ered most relevant facts concerning to the controlof human Chagas disease, since its discovery andaccording to the consensus of the majority of theauthors (Dias 1988, Coura 1997, Schofield & Dias1999): YEARS SUBJECT/OBSERVATION 1909 Carlos Chagas discovers the disease1911 Chagas proposes vector control andhousing improvement and describes thecongenital transmission of Trypanono-ma cruzi1913 Brumpt describes xenodiagnosis;Guerreiro and Machado develop comple-ment fixation test1916 Chagas emphasizes chronic heart disease1918 Souza Araujo promotes a law con-cern ing house improvement in endemicareas1919-22 N Larrier and S Campos study congenit-al transmission at experimental level1926 Mazza begins the MEPRA project inJujuy, Argentina1930-34 C Chagas and E Chagas employ EKG inchronic Chagas heart disease1932-36 Mazza claims for housing improvementand tries some classical drugs in Chagasdisease1935 IX MEPRA meeting; Romana describeshis eye portal of entry sign1935-44 Many acute cases are described in Ar-gentina, Brazil, Uruguay and Venezuela.Mazza warns about the risk of transfu-sion and oral (mother milk) transmission1943 Foundation of the Bambui center inMinas Gerais, Brazil, by EmmanuelDias, where trials are made of severalavailable insecticides (including cya-nidegas), physical methods (flame-thrower), housing improvement andcommunity participation1944-46 Still in Bambui, beginning of chronic car-diopathy systematization; failure of DDTagainst triatomines; Dias warns againstthe risk of transfusion disease1947-48 First laboratory trials against insects(Busvine & Barnes 1947) and descrip-tion of the action of HCH (gammexane)against triatomines (Dias & Pellegrino,Romana & Abalos); first large scale sur-vey employing serology and EKG innon-selected population (Bambui)1949 First regional serological survey of blooddonors (Pellegrino, in Belo Horizonte,Brazil); L Dao confirms in Venezuela thecongenital transmission of humanChagas disease; Ramos and Freitas carryon a serological and EKG inquiry inCassia dos Coqueiros, SP, Brazil1950-52 In Sao Paulo, Brazil, Nussensweig,Freitas and Amato Neto confirm trans-fusional transmitted Chagas disease. Thesame group employs successfully gen-tian violet as chemoprophylactic agentin blood banks. First large-scale trial withgammexane against triatomines inUberaba, Minas Gerais, Brazil (E Dias,Bustamante et al.)1955 First experimental trial attempting Tri-atoma infestans eradication in Bambui(E Dias)1956 Publication of the definitive systemati-zation of chronic heart Chagas diseasein Circulation by Laranja, Dias, Nobregaand Miranda1957-58 Re-description of Chagas disease diges-tive forms by Koberle and others. Im-portant serological and EKG survey inthe Cordoba region of Argentina, byRosenbaum and Cerisola. Important re-gional epidemiological surveys in Ven-ezuela, by Pifano et al.1959 Neghme and Schenone confirm in Chilethe results obtained in Bambui againstT. infestans . E Dias emphasises the con-cept of T. infestans eradication1960-70 Beginning of vector control in Sao Paulo,Brazil, and in Venezuela (NationalProgramme: using insecticide plus hous-

Chagas disease in the Amazon Region

The risk that Chagas disease becomes established as a major endemic threat in Amazonia (the worlds largest tropical biome, today inhabited by over 30 million people) relates to a complex set of interacting biological and social determinants. These include intense immigration from endemic areas (possibly introducing parasites and vectors), extensive landscape transformation with uncontrolled deforestation, and the great diversity of wild Trypanosoma cruzi reservoir hosts and vectors (25 species in nine genera), which maintain intense sylvatic transmission cycles. Invasion of houses by adventitious vectors (with infection rates > 60%) is common, and focal adaptation of native triatomines to artificial structures has been reported. Both acute (approximately 500) and chronic cases of autochthonous human Chagas disease have been documented beyond doubt in the region. Continuous, low-intensity transmission seems to occur throughout the Amazon, and generates a hypoendemic pattern with seropositivity rates of approximately 1-3%. Discrete foci also exist in which transmission is more intense (e.g., in localized outbreaks probably linked to oral transmission) and prevalence rates higher. Early detection-treatment of acute cases is crucial for avoiding further dispersion of endemic transmission of Chagas disease in Amazonia, and will require the involvement of malaria control and primary health care systems. Comprehensive eco-epidemiological research, including prevalence surveys or the characterization of transmission dynamics in different ecological settings, is still needed. The International Initiative for Chagas Disease Surveillance and Prevention in the Amazon provides the framework for building up the political and scientific cooperation networks required to confront the challenge of preventing Chagas disease in Amazonia.

Control of chagas disease in Brazil

Chagas disease (South American trypanosomiasis) is a chronic but often fatal disease endemic throughout much of Latin America. Serological surveys suggest around 24 million people seropositive for the causative agent, Trypanosoma cruzi (Fig. 1), with over 65 million living in the endemic areas and at risk to infection. In Brazil, over 25 million people are considered at risk, and control of the disease constitutes one of Brazils public health priorities. Treatment or vaccination against T. cruzi is impossible at the public health level because suitable drugs or vaccines are not available. But it is well recognized that transmission can be interrupted by eliminating the domestic vectors - blood-sucking reduviid bugs of the subfamily Triatominae. In Brazil, eradication of Triatoma infestans - the major domestic vector of T. cruzi - is now seen as a feasible target by the Ministry of Health. However, although other domestic vectors can also be controlled, they will retain their sylvatic ecotopes from which they can reinvade houses. In this article, Joao Carlos Pinto Dias explains the current Brazilian policy, high-lighting the successful elimination of T. infestans from much of the southern part of the country.

Doença de Chagas no Brasil

This article presents the current situation for Chagas disease vectors in Brazil, based on data from the Brazilian National Health Foundation (FNS). Over the course of the last 20 years, continuous chemical control has resulted in a clear reduction of triatomine densities and Trypanosoma cruzi in Brazilian dwellings. Results have been particularly promising in relation to Triatoma infestans and Panstrongylus megistus, considered the most important species in the past. In parallel, data from school serological surveys, hospitalized patients, and mortality records show an important decrease in the disease. Nevertheless, some areas of the Brazilian Northeast and some residual foci of Triatoma infestans and Panstrongylus megistus remain as major challenges for public health authorities, requiring effective epidemiological surveillance. States and municipalities are required to assume this task at present, as the traditional Brazilian National Health Foundation is undergoing decentralization.

Problems and perspectives for Chagas disease control: in search of a realistic analysis

Chagas disease was an important medical and social problem in almost all of Latin America throughout the twentieth century. It has been combated over a broad swath of this continent over recent decades, with very satisfactory results in terms of vector and transfusional transmission. Today, a surveillance stage still remains to be consolidated, in parallel with appropriate care required for some millions of infected individuals who are today living in endemic and non-endemic areas. Contradictorily, the good results attained have generated excessive optimism and even disregard among health authorities, in relation to this disease and its control. The loss of visibility and priority may be a logical consequence, particularly in Latin American healthcare systems that are still disorganized and overburdened due to insufficiencies of financial and human resources. Consolidation of the victories against Chagas disease is attainable but depends on political will and continual attention from the most consequential protagonists in this struggle, especially the Latin American scientific community.

Challenges and opportunities for primary, secondary, and tertiary prevention of Chagas’ disease

A century after its discovery, Chagas’ disease still represents a major public health challenge in Latin America. Moreover, because of growing population movements, an increasing number of cases of imported Chagas’ disease have now been detected in non-endemic areas, such as North America and some European countries. This parasitic zoonosis, caused by Trypanosoma cruzi, is transmitted to humans by infected Triatominae insects, or occasionally by non-vectorial mechanisms, such as blood transfusion, mother to fetus, or oral ingestion of materials contaminated with parasites. Following the acute phase of the infection, untreated individuals enter a chronic phase that is initially asymptomatic or clinically unapparent. Usually, a few decades later, 40–50% of patients develop progressive cardiomyopathy and/or motility disturbances of the oesophagus and colon. In the last decades several interventions targeting primary, secondary and tertiary prevention of Chagas’ disease have been attempted. While control of both vectorial and blood transfusion transmission of T cruzi (primary prevention) has been successful in many regions of Latin America, early detection and aetiological treatment of asymptomatic subjects with Chagas’ disease (secondary prevention) have been largely underutilised. At the same time, in patients with established chronic disease, several pharmacological and non-pharmacological interventions are currently available and have been increasingly used with the intention of preventing or delaying complications of the disease (tertiary prevention). In this review we discuss in detail each of these issues.

Elimination of Chagas disease transmission: perspectives

One hundred years after its discovery by Carlos Chagas, American trypanosomiasis, or Chagas disease, remains an epidemiologic challenge. Neither a vaccine nor an ideal specific treatment is available for most chronic cases. Therefore, the current strategy for countering Chagas disease consists of preventive actions against the vector and transfusion-transmitted disease. Here, the present challenges, including congenital and oral transmission of Trypanosoma cruzi infections, as well as the future potential for Chagas disease elimination are discussed in light of the current epidemiological picture. Finally, a list of challenging open questions is presented about Chagas disease control, patient management, programme planning and priority definitions faced by researchers and politicians.

General situation and perspectives of Chagas disease in Northeastern Region, Brazil

Primary and secondary data show the importance and distribution of human Chagas disease (HCD) in Northeast Brazil. Among the 27 detected vector species, Triatoma infestans, Panstrongylus megistus, Triatoma brasiliensis and Triatoma pseudomaculata are epidemiologically important. Major medical impact is attributed to T. infestans and P. megistus, the most domiciliated and vulnerable species, while the other two are native and more difficult to control. Regional differences in transmission and medical impact of HCD exist in the Northeast, where in general the disease appears to be less harmful than in other Brazilian regions like the Southeast and State of Goiás. There is a downward trend in HCD transmission and morbidity in the Northeast, its control in the region is a cause of concern because of the decommissioning of the National Health Foundation without a corresponding assimilation of its routine activities by regional and municipal institutions.