Antônio Carlos Silveira

Current epidemiological trends for Chagas disease in Latin America and future challenges in epidemiology, surveillance and health policy

Chagas disease, named after Carlos Chagas, who first described it in 1909, exists only on the American Continent. It is caused by a parasite, Trypanosoma cruzi, which is transmitted to humans by blood-sucking triatomine bugs and via blood transfusion. Chagas disease has two successive phases: acute and chronic. The acute phase lasts six-eight weeks. Several years after entering the chronic phase, 20-35% of infected individuals, depending on the geographical area, will develop irreversible lesions of the autonomous nervous system in the heart, oesophagus and colon, and of the peripheral nervous system. Data on the prevalence and distribution of Chagas disease improved in quality during the 1980s as a result of the demographically representative cross-sectional studies in countries where accurate information was not previously available. A group of experts met in Brasilia in 1979 and devised standard protocols to carry out countrywide prevalence studies on human T. cruzi infection and triatomine house infestation. Thanks to a coordinated multi-country programme in the Southern Cone countries, the transmission of Chagas disease by vectors and via blood transfusion was interrupted in Uruguay in 1997, in Chile in 1999 and in Brazil in 2006; thus, the incidence of new infections by T. cruzi across the South American continent has decreased by 70%. Similar multi-country initiatives have been launched in the Andean countries and in Central America and rapid progress has been reported towards the goal of interrupting the transmission of Chagas disease, as requested by a 1998 Resolution of the World Health Assembly. The cost-benefit analysis of investment in the vector control programme in Brazil indicates that there are savings of US

O controle da transmissão vetorial

17 in medical care and disabilities for each dollar spent on prevention, showing that the programme is a health investment with very high return. Many well-known research institutions in Latin America were key elements of a worldwide network of laboratories that carried out basic and applied research supporting the planning and evaluation of national Chagas disease control programmes. The present article reviews the current epidemiological trends for Chagas disease in Latin America and the future challenges in terms of epidemiology, surveillance and health policy.

Monitoring the domiciliary and peridomiciliary invasion process of Triatoma rubrovaria in the State of Rio Grande do Sul, Brazil

Between 1950 and 1951, the first Prophylactic campaign against Chagas Diseases was carried on in Brazil by the so existing Servico Nacional de Malaria. The actions involving chemical vector control comprehended 74 municipalities along the Rio Grande Valley, between the States of Sao Paulo and Minas Gerais. Ever since, until 1975, the activities were performed according the availability of resources, being executed with more or less regularity and coverage. At that time, Chagas disease did no represent priority, in comparison with other endemic diseases prevalent in the Country. Even so, taking into account the accumulated data along those 25 years, the volume of work realized cannot be considered despicable. Nevertheless, it was few consistent, in terms of its impact on disease transmission. In 1975, with an additional injection of resources surpassed from the malaria program, plus the methodological systematization of the activities, and with the results of two extensive national inquiries (entomologic and serologic), the activities for vector control could be performed regularly, following two basic principles: interventions in always contiguous areas, progressively enlarged, and sustainability (continuity) of the activities, until being attained determined requirements and purpose previously established. Such actions and strategies lead into the exhaustion of the populations of the principal vector species, Triatoma infestans, no autochthonous and exclusively domiciliary, as well as the control of the domiciliary colonization of autochthonous species important to disease transmission. Vector transmission today is being considered residual, by means of some few native and peridomestic species, such as Triatoma brasiliensis and Triatoma pseudomaculata. There is, also, the risk of progressive domiciliation of some species before considered sylvatic, such as Panstrongylus lutzi and Triatoma rubrovaria. Finally, there is the possibility of the occurrence of cases of human infection directly related to the enzootic cycle of the parasite. By all these reasons, it is still indispensable the maintenance of a strict epidemiological surveillance against Chagas Disease in Brazil.

II Consenso Brasileiro em Doença de Chagas, 2015

The presence of Triatoma rubrovaria in Brazil has only been confirmed in the States of Paraná and Rio Grande do Sul (RS), where it is found naturally infected with Trypanosoma cruzi. In the wild environment it occurs in rocky habitats and has an eclectic diet, feeding from cockroaches, reptiles and mammals. Data from the Chagas Disease Control Program obtained by the Fundação Nacional de Saúde, between 1975 and 1997, indicate a growing domiciliary and peridomiciliary invasion of T. rubrovaria in RS, where it has become the most frequently Triatominae species captured in this state since the control of Triatoma infestans. In order to monitor this process, we analyzed collection data derived from 22 years of control campaigns against T. infestans. Collection data for triatomines from domestic habitats show an inverse relationship, with high numbers of T. infestans and low numbers of T. rubrovaria during 1976-1987, compared to the following ten years, 1986-1997, when the number of T. infestans dropped drastically and that of T. rubrovaria increased. There are no consistent indications of intradomiciliary colonization by T. rubrovaria, since only low numbers of nymphs have been captured in the intradomiciliary ecotopes. Nevertheless, this species appears to have preadaptive characteristics for anthropic ecotopes, and should be kept under constant epidemiological surveillance.

2 nd Brazilian Consensus on Chagas Disease, 2015

Chagas disease is a neglected chronic condition that presents high morbidity and mortality burden, with considerable psychological, social, and economic impact. The disease represents a significant public health issue in Brazil, with different regional patterns. This document presents the evidence that resulted in the Brazilian Consensus on Chagas Disease. The objective was to review and standardize strategies for diagnosis, treatment, prevention, and control of Chagas disease in the country, based on the available scientific evidence. The consensus is based on collaboration and contribution of renowned Brazilian experts with vast knowledge and experience on various aspects of the disease. It is the result of close collaboration between the Brazilian Society of Tropical Medicine and the Ministry of Health. This document shall strengthen the development of integrated control measures against Chagas disease in the country, focusing on epidemiology, management, comprehensive care (including families and communities), communication, information, education, and research.

O Inquérito triatomínico (1975-1983)

Chagas disease is a neglected chronic condition with a high burden of morbidity and mortality. It has considerable psychological, social, and economic impacts. The disease represents a significant public health issue in Brazil, with different regional patterns. This document presents the evidence that resulted in the Brazilian Consensus on Chagas Disease. The objective was to review and standardize strategies for diagnosis, treatment, prevention, and control of Chagas disease in the country, based on the available scientific evidence. The consensus is based on the articulation and strategic contribution of renowned Brazilian experts with knowledge and experience on various aspects of the disease. It is the result of a close collaboration between the Brazilian Society of Tropical Medicine and the Ministry of Health. It is hoped that this document will strengthen the development of integrated actions against Chagas disease in the country, focusing on epidemiology, management, comprehensive care (including families and communities), communication, information, education, and research .

O Inquérito de soroprevalência da infecção chagásica humana (1975-1980)

After the systematization and re-dimension of the vectorial control in all the Country by 1975, it was considered necessary to have an up-to-date information on the distribution of vectors in Brazil, and differentiate precisely the role of each of the different species on the intra-domiciliary transmission of Chagas disease. For this purpose, sampling regional surveys for regions with non reliable information were performed, as well as, a house by house search for vectors on those areas considered at risk. For this last, 1,942 municipalities from 19 states were searched, as by the political division of the country by 1980, that was taken as a reference in this paper. These activities, that were implemented as part of the routine for intervention, were completed by 1983. Immediately after, this work was also extended for other areas considered targets for infected bugs. Results obtained, allowed to map the endemic area and the area under risk of vectorial transmission all over the country. Even more, with the results obtained it was possible to recognize those five species proved as vectors of the infection, among thirty already identified. These species, in order of importance, were: Triatoma infestans, Panstrongylus megistus, T. brasiliensis, T pseudomaculata and T. sordida. It was possible also to verify the increase in the dispersion of T. infestans, an aloctonous vector captured now in states of the North-east region, where it was not recognized previously. In relation with native species, a clear division of territories among them was found. Furthermore, P. megistus was found with a diffuse distribution, but T. brasiliensis and T. pseudomaculata were restricted to the semi-arid North-east. The most often captured bug was T. sordida, (mostly around houses) limited to the cerrado area, which is its origin.

The control of Chagas' disease transmission in Mambaí, Goiás-Brazil (1980-1981)

The results of the Serological survey for the prevalence of chagasic infection in Brazil, 1975/1980, were published before (Camargo et al, 1984) but the detailed geographical distribution is described in this paper. This was an initiative of two governmental bodies: the Superintendencia de Campanhas de Saúde Pública a Ministry of Health Division in charge of all public health policies, and, the Research National Council of the Ministry of Science and Technology through a program called Integrated Program for Endemic Diseases. Results obtained were extremely useful for a precise delimitation of the area with endemic transmission of Chagas disease, and hence, to direct the activities for vector control, which were implemented from 1975 onwards. This survey showed an estimated seroprevalence of 4.2% of T. cruzi infection in the rural population in the country. Only two federal units were not included, São Paulo and the Federal District (Brasilia) for which enough recent information was available. This survey included all the other federal units of Brazil, with the examination of 1,626,745 blood samples by indirect immunofluorescence. From them, 1,352,197 were validated for processing and statistical analysis, which were from 3,026 municipalities of 24 states, as by the political division of the country by this time. Overall results obtained, confirmed data that were well known, but some were non expected. These last were subject of further investigations, until confirmation, based also on entomological data and a better interpretation of the results obtained.

Group discussion: epidemiological and social determinants of Chagas disease and its control in the Amazon countries

BHC application in Mambai in 1980 resulted in a significant decline but not elimination of domiciliated T. infestans. T. sordida peridomestic populations persist and could pose a threat to interupting human transmission of T. cruzi The results of one massive attack spray application alone was compared with this application plus one selective application as regards the presence of T. infestans in houses oneyear later. No significance difference could be detected. It is likely that for interruption of T. infestans transmission cheaper procedures can be devised than those currently in use. A further pilot study of a virgin community afflicted by T. infestans transmission is indicated since Mambai cannot be regarded as a representative areafor those still awaiting insecticide application.

Síntese dos resultados dos inquéritos nacionais

The emergence of Chagas disease transmission in theAmazon region is a new challenge for controlling thedisease. It takes on special importance, considering that:(i) vector transmission in homes in many other areas hasnow been brought under control, or at least that the tech-nology available for control presents proven efficiency;(ii) the transmission patterns are different; (iii) some ofits epidemiological and social determinants or risk con-ditions are unknown.The enzootic transmission cycle of Trypanosomacruzi has long been known in the Amazon region. CarlosChagas himself already recognized flagellates isolated frommonkeys of the species Saimiri scirius as T. cruzi, in theyear 1924 (Chagas 1924). Following this, many other ani-mal reservoirs were identified (Deane 1961, 1964). Thetriatomine fauna is also very diversified and natural infec-tion has been observed in several of the species present(Barret 1988, Coura et al. 1994, Schofield 2002).However, the domestic transmission cycle has notbecome established in an evident manner or on a largescale. With the progressive human occupation of the re-gion, introduction of non-autochthonous species or colo-nization by native species as a result of human predatoryaction on the natural environment were considered likely(Silveira et al. 1984, Barret 1988, Silveira 1997). So far, ithas not been possible to confirm this. Nonetheless, au-tochthonous cases started to be recognized in the Ama-zon region, including in countries without a history ofoccurrences of this disease (Shaw 1969, Rambajan 1984,Beauder 1985). Moreover, increasing numbers of suchcases have been found over recent years (Valente 2005).On the one hand, this may be ascribed to possible newevents or environmental changes. On the other hand, thisis certainly due to the greater attention that has been givento studying the disease and performing disease surveil-lance in this region, even if done non-systematically.The means of transmission in the Amazon region donot correspond to those that are recognized as charac-teristic of the endemic disease, with “installation andpermanence” of the vector in the home. The known au-tochthonous cases are produced by the following meansof transmission: (i) oral transmission, which indirectlyor passively may be understood as vectorial, providedthat it only occurs by means of contamination of foodsby the feces of infected triatomines; (ii) vectorial trans-mission in the home, without colonization, by meansof periodic or regular incursions by specimens that in-vade the home; (iii) vectorial transmission outside ofthe home, by means of frequent human entry into for-ests and contact with wild triatomines, as occurs withRhodnius brethesi in the case of extraction activitiesrelating to the piacaba palm tree.The peculiarities of Chagas disease in the Amazonregion require the adoption of a surveillance model dif-fering from what has been followed in historically en-demic areas, in which it is fundamentally centered onentomological surveillance.Likewise, in conceptualizing a surveillance and con-trol model for the disease in this region, the followingmust be considered: (i) the extent of the Amazon terri-tory and the operational difficulties implied; (ii) the factthat it is not recognized as a public health problem inthat region; (iii) the resources already installed in the re-gion that mat serve for preventing endemic Chagas disease.