Triatomine Infestation and Vector-Borne Transmission of Chagas Disease in Northwest and Central Paraná, Brazil
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ARTIGO ARTICLE 1191 Triatomine infestation and vector-borne transmission of Chagas disease in northwest and central Paraná, Brazil Infestação triatomínica e transmissão vetorial da doença de Chagas no noroeste e centro do Paraná, Brasil Ana Lucia Falavigna-Guilherme 1 Rosângela Santana 2 Gilberto Cezar Pavanelli 4 Elias Seixas Lorosa 4 Silvana Marques de Araújo 1 Abstract Introduction 1 Departamento de Análises Triatomine infestation, prevalence of T. cruzi Over the last thirty years, Chagas disease trans- Clínicas, Universidade antibodies in humans and domestic animals, mission has declined significantly both in Estadual de Maringá, Maringá, Brazil. and variables potentially associated with the Brazil and in a large part of Latin America as a 2 Departamento presence of triatomines in a rural domiciliary whole, as a result of vector control through the de Estatística, Universidade unit (DU) were investigated in nine municipali- use of insecticides and improvements in rural Estadual de Maringá, 1 Maringá, Brazil. ties and one district of Paraná, Brazil, from June housing, living standards, and education . In 3 Programa de Pós-graduação 1996 to February 2000. DUs were defined as all Brazil, rural exodus in the 1970s and ’80s re- em Ecologia de Ambientes houses and annexes on a given piece of proper- duced the use of manual labor in rural areas, Aquáticos Continentais, Universidade Estadual ty. Blood samples from human volunteers, dogs, thereby increasing the number of inhabited de Maringá, Maringá, Brazil. and cats were submitted to indirect immunoflu- houses, which provide ideal shelter for Tri- 4 Departamento orescence. An epidemiological form was com- atoma infestans Klug, 1834 2. de Entomologia, Instituto Oswaldo Cruz, pleted for each DU. A logistic model was adopt- In Brazil, the elimination of triatomines Rio de Janeiro, Brazil. ed in order to identify associations. Seven out of from domestic environments does not avoid Correspondence nine municipalities were positive for triato- the persistence of residual foci, particularly in A. L. Falavigna-Guilherme mines. T. infestans was not captured, but T. sor- the peridomicile 3, due to the invasion and col- Departamento de Análises dida, P. megistus, and R. neglectus were. Differ- onization of artificial ecotopes by triatomines Clínicas, Universidade Estadual de Maringá. ent variables were considered decisive for the whose natural habitat is the sylvatic ecotope. Av. Colombo 5790, presence of triatomines across the municipali- Such triatomes include Panstrongylus megistus Bloco I-90/13, Maringá, PR ties: proximity to residual wooded areas, i.e. ei- (Burmeister, 1835), Triatoma sordida (Stal, 1859), 87020-900, Brasil. [email protected] ther scrub forest (capoeira) or islands of resid- Triatoma braziliensis (Neiva, 1911), Rhodnius ual forest (slightly dense vegetation), longer prolixus (Stal, 1859), and others 4. time of residence, existence of inhabited houses, Camargo et al. 5 reported that the state of Pa- and past DU infestation. In order to ensure prop- raná, Brazil, had an elevated number of seropos- er continuation of the recommended Chagas itive individuals for Chagas disease, placing it disease control program, entomo-epidemiologi- fourth among all Brazilian States in a serologi- cal surveillance measures need to be maintained. cal survey to determine Chagas infection. Until 1995, current data were scarce in the literature Triatoma; Epidemiologic Factors; Chagas Dis- in relation to secondary triatomine species in ease Paraná 6,7,8,9. Toledo et al. 10 found that 98.7% of the triatomines collected in rural areas of Cad. Saúde Pública, Rio de Janeiro, 20(5):1191-1200, set-out, 2004 1192 Falavigna-Guilherme AL et al. municipalities in northwest Paraná belonged mately 90% of the existing houses are built of to the Tr. sordida species. However, Silveira & wood with ceramic tile roofs and have electricity. Vinhaes 11 did not report any triatomines in In the north-central Paraná meso-region this State during an investigation carried out (or second plateau), only the municipality of by the National Health Foundation (FUNASA) Cândido de Abreu was studied. Despite vast from 1995 to 1997. Furthermore, Falavigna-Gui- wastelands, the region has small areas of mixed lherme et al. 12 analyzed the majority of munic- vegetation including Brazilian pine and broad- ipalities from the present study and found that leafed tropical woodlands 13. The municipality uninhabited houses were the most frequently of Cândido de Abreu has an altitude of 600m infested ecotopes, followed by chicken coops and is situated at 51º19’ longitude West and and inhabited houses. 24º36’ latitude South. The climate is mesother- The lack of current information on Trypa- mal, humid, and subtropical with hot sum- nosoma cruzi infection and triatomine behav- mers, concentrated rainfall, average tempera- ior in the domiciliary and peridomiciliary envi- tures over 22ºC in the hottest month and 26 to ronments motivated the present investigation 27ºC average annual highs 14. Freezing temper- on triatomine infestation, prevalence of T. cruzi atures in the winter are infrequent. Minimum antibodies in humans and domestic animals, temperatures are around 12.7ºC, with 14 and and variables possibly associated with the fre- 15ºC as the average annual lows. There is no quency of triatomines in such environments in well-defined dry season 15. Economic produc- Paraná State. tion is centered on range-fed livestock produc- tion. However, there is also crop cultivation, mainly beans, tobacco, corn, potatoes, and soy- Material and methods beans 13. The municipality has extensive pover- ty, and mud-and-wattle houses are not uncom- Study area mon in the rural area 13. Its territory is approxi- mately equivalent to the total of the other mu- Fieldwork was carried out in the rural areas of nicipalities studied here (Figure 1). nine municipalities in Paraná that are located Due to intense deforestation in the State of mainly in the northwestern region of the State. Paraná, what remains is a predominance of The northwest Paraná meso-region is situated primitive, seasonal, latifoliate forest that ap- between 52º20’ and 52º50’ longitude West and pears in the considerably modified form of thin- 23º20’ and 23º60’ latitude South. The region is ly-spread forest and scrub, characterized by part of the geomorphological unit called the open spaces with only sparse vegetation, punc- Paraná Basin Central Plateau 13, which is part tuated by small trees and shrubs/bushes that of the Third Paraná or Sandstone-Basaltic are highly exposed to solar radiation. This de- Plateau. The terrain consists of low, flat-topped scription agrees with that of Forattini 17, who plateaus with convex slopes that reach alti- portrays Paraná as an originally umbrageous tudes of 250 to 600m. The climate is classified area, currently reduced to mainly open spaces as warm, super-humid tropical 14. Average an- due to anthropic action and presenting an ugly nual rainfall is 1,700mm. In the dry winter sea- landscape dotted with islands of residual vege- son, average temperatures are below 18ºC, tation. while the average yearly low is 16ºC and the av- erage annual highs range from 26 to 28ºC 15. Municipalities studied The overall annual temperature is 21.9ºC. Nearly 95% of the original vegetation in the Figure 1 shows the study area of eight munici- northwestern region of the State, consisting of palities and one district in northwest Paraná, latifoliate subtropical forest, was destroyed to and one municipality located in the central make way for cropland 16. The region’s current part of the State. economy is dominated by production from The selection of municipalities was based small and medium-sized farms. The farming on work by FUNASA, guided by frequent find- industry consists mainly of feedlot production ings of triatomines by inhabitants of these mu- and crops including soybeans, corn, sugarcane, nicipalities and by entomo-epidemiological manioc, wheat, and grapes 15. The rural exodus data from each municipality obtained in the from northwest Paraná has been intense since 1980s, classifying them as levels I, II, or III in the 1970s 16. Many dwellings from earlier terms of priority. According to FUNASA techni- decades that had been linked to coffee growing cal standards 18, priority I municipalities are were torn down, while most of the remaining those where it is still possible to find Tr. infes- structures were abandoned. Today, approxi- tans (the main Chagas disease vector) in the Cad. Saúde Pública, Rio de Janeiro, 20(5):1191-1200, set-out, 2004 TRIATOMINE INFESTATION AND VECTOR-BORNE TRANSMISSION OF CHAGAS DISEASE 1193 Figure 1 Location of municipalities in the State of Paraná, Brazil, where study was performed from June 1996 to February 2000. Mato Grosso do Sul State 54oW 50oW 23oS A 23oS B São Paulo State C Paraná State Paraguay Argentina Atlantic Ocean Paraná 26oS 26oS 54oW Santa Catarina State 50oW 0 66 132 198 264km A B C Maringá zona ri u andu O iç Pa Porto Rico o rg Mandaguari Cândido de Abreu ama Marialva Dr. C Floresta 0 10 20km 0 10 20km 0 10 20km domiciliary or peridomiciliary environments. palities of Paiçandu, Dr. Camargo, and Marial- In these areas, research is conducted annually va are considered “priority III”, while Cândido to identify triatomines. Priority II municipali- de Abreu is “priority I”. The Municipality of ties are those where FUNASA has verified the Porto Rico has not been classified by FUNASA. colonization of an inhabited domicile within In these municipalities, work by FUNASA the last three years, or where reports have been was conducted four days a week. To obtain the made of the presence of secondary species present data, the team from the State Universi- such as Tr. sordida and P.megistus. This classifi- ty of Maringá (UEM) accompanied FUNASA cation requires that farms within the munici- one day a week. This procedure meant that da- palities be surveyed every two years for tri- ta collection had to occur at homogeneously atomines.