Inadequate management of natural ecosystem in the Brazilian Amazon region results in the emergence and reemergence of arboviruses

Um total de 187 diferentes espécies de arbovírus, além de outros vírus de vertebrados, foram identificados pelo Instituto Evandro Chagas (IEC) no período de 1954 a 1998, entre as mais de 10.000 cepas de vírus isoladas de seres humanos, insetos hematófagos e vertebrados-sentinela e silvestres. Apesar dos estudos intensivos realizados na Amazônia brasileira, sobretudo no Estado do Pará, pouco se sabe a respeito da maioria desses vírus, com exceçäo de dados a respeito de data, hora, fonte e método de isolamento, assim como a capacidade de infectar animais laboratoriais. Fazem uma revisäo dos dados ecológicose epidemiológicos e procuram associar o impacto, sobre os diversos vírus, das mudanças populacionais dos vetores e hospedeiros induzidas por profundas alteraçöes no meio ambiente. O desmatamento, o uso do subsolo, a construçäo de represas e de rodovias, a colonizaçäo humana e a urbanizaçäo foram as principais modificaçöes ambientais introduzidas pelo homem e associadas à emergência ou reermegência de importantes arbovírus, inclusive alguns com atividade patogênica em seres humanos.

Inquérito soro-epidemiológico na Ilha de Säo Luis durante epidemia de dengue no Maranhäo / Seroepidemiologic survey in Säo Luis Island, State of Maranhäo, Brazil, during a dengue fever epidemies

Nos anos de 1995 e 1996, ocorreu em Säo Luis uma epidemia de dengue (DEN), causada pelo sorotipo DEN1. Objetivando avaliar o impacto da mesma na populaçäo da grande Säo Luis (municípios de Paço do Lumiar - PL, Säo José de Ribamar - SJR e Säo Luis SL), realizamos um inquérito soro epidemiológico aleatório, onde aplicamos um questionário. Os soros foram testados por inibiçäo da hemaglutinaçäo (IH) e os resultados negativo e positivo (resposta primária - RP e resposta secundária RS), foram analisados utilizando os "software's" Lotus 123, Epi-info 6.0. Excel 5.0 e STATA. Coletaram-se 1277 amostras, (101 de PL, 100 de SJR e 1016 de SL). A positividade foi: 55,4 por cento em PL, 28 por cento em SJR e 41,4 por cento em SL. Destes, 505(4.1,2 por cento) amostras foram positivas sendo 96 RP (7,9 por cento) e 405 RS (33,3 por cento). Da amostra obtida, 508 soros (227 positivos) foram do sexo masculino e 709 (278 positivos) do feminino, näo havendo diferença estatística significativa. Houve significância (p < 0,003) na estratificaçäo de acordo com a renda, sendo mais freqüente nas populaçöes com melhor nível sócio econômico. Estimou-se em 401.933 infecçöes causadas pelo vírus dengue. Os pacientes referiram febre, cefaléia, calafrios, tonturas, astenia, dor retro ocular, mialgia, artralgia, náuseas, anorexia, prurido e exantema. Há uma grande populaçäo sensibilizada pelo DEN-1, suscetível a outro sorotipos o que aumenta o risco de dengue hemorrágico

Involvement of the central nervous system in dengue fever: three serologically confirmed cases from Fortaleza, Ceara, Brazil

Neste trabalho säo descritos tres casos de dengue com manifestaçöes neurológicas incomuns durante a epidemia de dengue em Fortaleza, Estado do Ceará, em 1994. Todos os pacientes eram do sexo feminino. A paciente do primeiro caso tinha 17 anos e apresentou além da sindrome febril, sinais de comprometimento meningeo com rigidez de nuca, e sangramento genital. No segundo caso a paciente de 86 anos apresentou quadro febril, intensa dor muscular e articular, alteraçöes da consciencia, desmaio, rigidez de nuca e meningismo. A terceira, de 67 anos, teve um quadro inicial de sindrome febril, seguido de comportamento anormal, tremores de extremidades, trombocitopenia, hematocrito aumentado, leucopenia, hipotensäo arterial e choque, evoluindo para obito...

Clinical and ecoepidemiological situation of human arboviruses in Brazilian Amazonia

The main aspects of clinic manifestations and epidemiological data about human arboviruses in the Brazilian Amazonian region is reviewed. Thirty four types of arboviruses from 183 types isolated in the Amazonia have been associated with human diseases. Four of them are important in public health and are involved with epidemics; they are namely, Dengue (DEN), Mayaro (MAY), Oropouche (ORO) and Yellow Fever (YF) viruses. ORO and DEN are associated with human epidemic diseases in urban areas while MAY and YF in rural areas. Basically, ORO causes a febrile disease, sometimes accompanied with aseptic meningitis. MAY and DEN are associated with rash febrile disease, while YF determines hemorrhagic fever. Thirty other arboviruses are involved with febrile illnesses in a few and sporadic cases. All arboviruses (apart from DEN) are maintained within a sylvatic cycle in the forest, where several species of hemathophagous insects act as vectors and wild vertebrates are involved as hosts. DEN has a cycle where the Aedes aegypti mosquito is the vector and man is the host. With the exception of the four viruses associated with epidemics which determine great economical and social impacts, including death (as in the case of YF), the real involvement of these viruses as systematic agents of human disease is unknown. Further studies are needed to clarify unclear aspects of the epidemiological cycles of these viruses.

Modifications of arbovirus transmission in relation to construction of dams in Brazilian Amazonia

The Amazonian region of Brazil seems to be the world's richest reservoir of arboviruses. To date, 183 different types of arboviruses have been detected in the Amazonian region, accounting for more than one third of the 535 arboviruses reported in the world. Of these, 136 (74.3 per cent) are endemic. The main objective of this paper was to evaluate what the effects of the construction and flooding of dams would be on the transmission and epidemiology of sylvatic arboviruses, in order to define the potential health hazards to which the human population would be subjected. Five areas were surveyed but only one could be thoroughly studied. Comparisons were made between surveys: i) inside the dam region, before, during and after the flooding period; ii) outside the dam region, in an area with a similar climate, landscape and vegetation, during the total time of the studies. The two chosen areas, namely Altamira and Tucuruí, were studied since 1974, and since September, 1982, respectively. The former, and the latter before the outset of flooding (September 6, 1984) were considered as a control or reference for comparisons with data obtained in Tucuruí during flooding and thereafter. The surveys consisted of sampling as many wild vertebrates and haematophagous Diptera as possible. Human sera were collected from febrile cases and random serological surveys. Very few variations seem to have occurred among the three phases of the study, with a maximum of positive serologies during the flooding period, but the differences were not statistically significant. Similarly, in the reference region, the prevalence of antibodies against the four more important arbovirus groups did not vary significantly. The arboviruses were classified under two categories: i) those which showed enhanced transmission and ii) those which showed no apparent modifications in their transmission patterns (referring to the control area). Three new and three already known types in the Anopheles A group of Bunyavirus were favoured by the great proliferation of Anopheles nuneztovari and An. triannulatus which accompanied the flooding of the dam. An epizootic of the Gamboa virus (Bunyavirus, Gamboa serogroup), newly reported in Brazil, was observed one year after the outset of flooding, when the mosquito Aedeomyia squamipennis showed very large populations. Guaroa (Bunyavirus, California group), an endemic arbovirus, showed an epizootic probably as a consequence of the proliferation of anopheline mosquitoes. A temporary proliferation of Culex spp. mosquitoes and the presence of a rich avifauna in the dam area during flooding are probable causes of the enhanced circulation of Turlock (Bunyavirus, Turlock group) and Kwatta-like (Rhabdoviridae, Kwatta group) viruses...

New entomological and virological data on the vectors of sylvatic fever in Brazil

The present report focuses on recent ecoepidemiological data on yellow fever, obtained recently in two very distinct ecoepidemiological contexts: the Barcarena (PA) area, situated in the dense Amazonian rain forest, and the Campo Grande (MS) region, situated in the cerrado with gallery forest in central Brazil. In the first region, one strain was isolated from a pool of 6 Haemagogus janthinomys. In the other region, 2,480 anthropophilous mosquitoes were collected, of which near 40 per cent were potential YF vectors. These species, classified by decreasing relative abundance, were: Aedes scapularis, Sabethes chloropterus, Hg.janthinomys, Hg. leucocelaenus, Hg. spegazinii, and Sa. soperi. Four strains of YF virus were isolated from Hg. janthinomys, one from Sa. cheoropterus (first report for South America) and one from Sa. soperi (first report). The minimal infection rates varied among the three localities of collection but were all high, compared with previous data. The mean daily survival rate was O.9635 for the populations of Hg. janthinomys, allowing extrapolation of the value of the infection rate when people were infected most recently. It was deduced that the epizootics were intense and more or less concomitant in the three areas. The main problem that remained to be solved concerns the mode(s) of reintroduction or survival of YF virus in each of the two regions under study.

A comparative study of yellow fever in Africa and South America

In order to look for an ecoepidemiological model of sylvatic yellow fever (YF) transmission in South America, differences from and similarities to available African YF data are considered. Strains from both areas, representing various topotypes, are distinct serologically, genetically and biochemically. In Africa, all vector mosquitoes are Aedes species, some related to the forest cycle and others responsible for the transmission in dryer areas. In South America, and particularly in Brazil, the main vector is Haemagogus janthinomys. Hg. albomaculatus has been incriminated in human peridomestic transmission in Central Amazonia. In the two continents, monkeys are the only regular vertebrate hosts of YF but the indigenous neotropical monkeys, show higher mortality rates. The South American and African vectors are diurnal and crespuscular/nocturnal in habit, respectively. The urban vector (Ae. aegypti) has the same habits in both continents, but its competence in transmitting the virus is very variable, and no urban epidemic has been notified in South America since the 4Os. A general ecoepidemiological model was elaborated to explain the maintenance and circulation of YF virus in West and Central Africa, which are related to the phytoclimatical regions. Because no such hypothesis has yet been presented in the case of YF in South America, we tested this with the available data from Brazil. All occurrences (of which 386 were lab-confirmed) were distributed in five phytogeographical zones: dense rain forest (l89), open rain forest (30), savannah with gallery forest (l47), ecotones (lO) and decidual seasonal forest (7). For each of these zones mean intervals between years with occurrences of YF were estimated. They were all found to be lower than 3 years, and lower than 5 years when standard deviation was added. Despite the close values obtained for the means, the distribution of the years as a function of number of occurrences of YF showed two groups: a) gallery forest and dense forest and b) open forest and ecotones. However, more data are necessary to enable the study of such variations which are thought to be related to ecological differences in YF transmission.

Arboviruses in Serra Norte, Carajás region, Pará, Brazil

mhis report outlines studies carried out from 1982 to 1987 in Serra Norte, Carajás region, Pará State, to ascertain the existence of known or new arbovirus types in the area, especially those of medical interest, and to gather information about their natural patterns of activity. These studies have included both serological tests and attempts to isolate viruses from haematophagous insects, wild animals and man. A total of 184,884 haematophagous insects were collected and blood and tissue samples were obtained from 1,726 wild vertebrates caught in the area. Attempts to isolate viruses in suckling mice yielded 21 strains, including 15 different serological types, of which 7 have been shown to constitute new types, so far found only in the Brazilian Amazonian region, and two of them have already been confirmed to be new types to the world. Serological studies performed on 2,680 sera (1,380 humans and 1,300 wild animals) against selected arboviruses pointed out the circulation of several of these agents in the investigated area. The Carajás region therefore, maintains established ecosystems which are rich in arbovirus fauna, and exploration of these natural niches must be done carefully and rationally to avoid breaking out the current foci of infestation maintained in the forest. Further studies are necessary to obtain a better understanding of these agents in this region and of the threats that they may pose to the health of humans and livestock.