ARTIGO ARTICLE 1325 The Acre Project: the epidemiology of malaria and arthropod-borne virus infections in a rural Amazonian population Projeto Acre: epidemiologia da malária e das arboviroses em uma população rural amazônica Mônica da Silva-Nunes 1,2 Rosely dos Santos Malafronte 2,3 Bruna de Almeida Luz 1 Estéfano Alves de Souza 1 Lívia Carício Martins 4 Sueli Guerreiro Rodrigues 4 Jannifer Oliveira Chiang 4 Pedro Fernando da Costa Vasconcelos 4 Pascoal Torres Muniz 2,5 Marcelo Urbano Ferreira 1,2 Abstract Introduction 1 Instituto de Ciências The authors describe the baseline malaria preva- Since early 2003, the county (municipality) of Biomédicas, Universidade de lence and arbovirus seroprevalence among 467 Acrelândia in the easternmost area of the State São Paulo, São Paulo, Brasil. 2 Centro de Saúde de subjects in an ongoing cohort study in rural of Acre, Brazil, has been the site of a collabora- Acrelândia, Acrelândia, Brasil. Amazonia. Most subjects (72.2%) reported one tive research project involving the Universida- 3 Laboratório de or more previous episodes of malaria, and 15.6% de Federal do Acre (Federal University of Acre – Protozoologia, Instituto de Medicina Tropical de had been hospitalized for malaria, but only 3.6% UFAC), the Instituto Evandro Chagas (Evandro São Paulo, São Paulo, Brasil. of individuals five years or older had malaria Chagas Institute – IEC), and the Universidade 4 Seção de Arbovirologia parasites detected by microscopy (10 with Plas- de São Paulo (University of São Paulo – USP), e Febres Hemorrágicas, Instituto Evandro Chagas, modium vivax and 4 with P. falciparum). Anti- aimed at investigating the population’s health Belém, Brasil. bodies to Alphavirus, Orthobunyavirus, and/or conditions and proposing possible targets for 5 Departamento de Ciências Flavivirus were detected by hemagglutination public health interventions. Acrelândia is lo- da Saúde, Universidade Federal do Acre, inhibition (HI) in 42.6% of subjects aged five cated in an area with high malaria transmis- Rio Branco, Brasil. years or older, with a higher seropositivity rate sion, with an annual parasite index (number of Correspondence among males (49.2%) than females (36.2%). malaria cases per year per thousand inhabi- M. U. Ferreira Since 98.9% of subjects had been immunized for tants) of 104.3 in 2002 1. It is also one of the pri- Departamento de yellow fever, the presence of cross-reactive anti- ority counties in the Amazon Basin for dengue Parasitologia, Instituto 2 de Ciências Biomédicas, bodies to dengue and other Flaviviruses cannot control activities . The follow-up of a cohort of Universidade de São Paulo. be ruled out, but at least 12 subjects (3.3%) with 467 individuals began in March 2004 (includ- Av. Prof. Lineu Prestes 1374, IgM antibodies to dengue virus detected by ing all age brackets) in an agricultural settle- São Paulo, SP 05508-900, Brasil. ELISA had a putative recent exposure to this virus. ment in rural Acrelândia. The principal objec- [email protected] tive of this prospective study is to identify risk Malaria; Dengue; Arboviruses; Arbovirus Infec- and protective factors associated with acute tions; Amazonian Ecosystem febrile diseases, particularly malaria and ar- bovirus infections. The current article de- scribes the baseline malaria prevalence and ar- bovirus seroprevalence in March-April 2004. Cad. Saúde Pública, Rio de Janeiro, 22(6):1325-1334, jun, 2006 1326 Da Silva-Nunes M et al. Methodology (with the aid of maps provided by the local teams from the Coordinating Body for the Con- Study area and population trol of Endemics under SESACRE) and visited by our team. The household census identified Acrelândia, a county (municipality) founded in 473 inhabitants (226 males, 247 females), rang- January 1993 through repartitioning of the coun- ing in age from one day to 90 years (mean 23.5 ties of Plácido de Castro and Senador Guio- years), distributed in 114 households. All mem- mard, has a population of 8,697 (estimated for bers of these households were considered eli- 2003 by the IBGE, Instituto Brasileiro de Geo- gible for entry into our cohort and were invited grafia e Estatística, or National Census Bureau, to participate in the study. 2000 Census; unpublished data). The county has a territory of 1,607.5km2 and is located be- Field study tween the Abunã and Iquiri Rivers (the latter also known as the Ituxi) in the Acre River Valley During the cross-sectional survey from March (Figure 1). The estimated human development 16 to April 29, 2004, all households in the study index (HDI) in 2000 for the total population area were visited by the field team (two physi- was 0.680 3, with an infant mortality rate of cians, a biologist, and a research assistant). The 70.75 per thousand live births (IBGE estimate project objectives were explained to each fami- for 1998; unpublished data). The overall illiter- ly in order to obtain written informed consent. acy rate is 26.7%, reaching 31.9% in the rural The following procedures were also performed: area 3, which includes 57% of the population. (a) application of an extensive questionnaire to Acrelândia is located 112km east of Rio Branco, obtain demographic, socioeconomic, and pri- capital of the State of Acre, and borders on the or disease history data and a detailed descrip- counties of Senador Guiomard and Plácido de tion of the households, (b) clinical examination Castro in Acre as well as the Brazilian States of of all household members by a field team physi- Amazonas and Rondônia and the country Bo- cian, (c) collection of venous blood samples livia (Figure 1). from all household members aged five years or The study area encompasses rural localities older, and (d) determination of the household’s known as Linha 14 Gleba Q and Reserva da Lin- exact location using portable navigation equip- ha 14 (9o41’-9o49’S, 67o05’-67o07’W), demar- ment (eTrex®, Garmin International, Olathe, cated by the Coordinating Body for the Control USA), with an accuracy of 15 meters. Data ob- of Endemics under the Acre State Secretariat of tained during this cross-sectional survey pro- Health and Sanitation (SESACRE). Linha 14 vide the baseline for the prospective cohort, main- Gleba Q includes both sides of the last 16 kilo- tained since then under clinical and epidemio- meters of Linha 14, an unpaved road that be- logical surveillance for acute febrile diseases. gins at the highway connecting Rio Branco to Porto Velho (BR-364); Reserva da Linha 14 in- Microscopic diagnosis of malaria cludes the edges of an unpaved road that be- gins at the end (km 30) of Linha 14 and is per- Microscopic diagnosis of malaria used thick pendicular to it, running parallel to the Iquiri blood smears stained with Giemsa according to River. In this article, these sites will be referred the Walker technique and thin smears fixed with to collectively as Ramal do Granada, the name methanol and stained with Giemsa 4. At least used by the local population to refer to Linha 14. 200 high-magnification (700x) microscopic fields Ramal do Granada is located in the largest were examined by two experienced microscopy farming settlement in the State of Acre, the Pe- technicians before defining the result for each dro Peixoto Organized Agricultural Settlement slide 5. Individuals with a malaria diagnosis re- (Figure 1), implemented by the National Insti- ceived free medication provided by the SESACRE tute for Colonization and Agrarian Reform in based on Ministry of Health treatment protocols the mid-1970s. The main economic activities 4. The drugs used were: (a) chloroquine and pri- are coffee and banana growing and beef and maquine for Plasmodium vivax and (b) meflo- dairy cattle-raising. There are three malaria di- quine or a quinine-doxycycline combination (in agnostic outposts maintained by the SESSACRE addition to primaquine in cases with patent ga- at kilometers 16, 24, and 30 of Ramal do Grana- metocytemia) for P.falciparum. da; the largest, at km 16, also has nursing tech- nicians trained in primary health care. Investigation of arbovirus antibodies During the census conducted by our field- work team, all buildings (both inhabited and All serological assays were performed at the Di- uninhabited) in the study area were located vision of Arbovirology and Hemorrhagic Fevers Cad. Saúde Pública, Rio de Janeiro, 22(6):1325-1334, jun, 2006 EPIDEMIOLOGY OF MALARIA AND ARTHROPOD-BORNE VIRUS INFECTIONS 1327 Figure 1 Location of the County (Municipality) of Acrelândia, Acre State, Brazil, and the Pedro Peixoto Organized Settlement Project where the study area is located. AMAZONAS STATE ACRE STATE SOUTH AMERICA Rio RONDÔNIA PERU Branco STATE AMAZONIA BOLIVIA Brasília BRAZIL r ve i uxi R t I 64 PAD - 3 Pedro BR Rio Branco Peixoto Acrelândia ã River Abun BR Senador - 36 Guiomard 4 Plácido de Castro at IEC in Belém, Pará. Serum samples were ob- samples were also tested by ELISA for IgM anti- tained by centrifuging the venous blood in the bodies to the dengue and yellow fever viruses. field laboratory and storing at -20oC in dry ice until shipping by airplane to Belém. The samples Statistical analysis were initially submitted to microplate hemag- glutination inhibition (HI) 6 against standard- Two or more proportions were compared using ized antigens from 19 types of arbovirus, in- the χ2 or linear trend χ2 tests. Odds ratios and cluding four from genus Alphavirus (Eastern respective 95% confidence intervals (95%CI) equine encephalomyelitis [EEE], Western equine were calculated for the target associations us- encephalomyelitis [WEE], Mayaro, and Mucam- ing 2x2 tables. The 95% confidence intervals bo), nine from genus Flavivirus (two samples were obtained for proportions. These analyses of yellow fever virus [wild and vaccinal], Ilhéus, used the open-access software Epidat (http:// São Luís, Rocio, dengue [DEN] 1, DEN-2, DEN-3, www.paho.org/spanish/sha/epidat.htm; Pan- and DEN-4), and six from genus Orthobunya- American Health Organization).