The epidemiology of malaria in Rondonia (Western Amazon region, Brazil): study of a riverine population

Camargo, Luís Marcelo Aranha; Noronha, Elza Ferreira; Salcêdo, Juan Miguel Villalobos; Dutra, Araripe Pacheco; Krieger, Henrique; Silva, Luis Hildebrando Pereira da; Camargo, E.

doi:10.1016/s0001-706x(98)00082-5

Cited by 52 publications

(41 citation statements)

References 14 publications

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“…Subpatent and asymptomatic parasitemias persist interseasonally in places with seasonal transmission 3 ; such patients likely represent a major mechanism for over-seasoning of malaria parasites. Similar findings have been reported regarding P. vivax infections in other regions, for example western Thailand , Sri Lanka , and in Brazilian western Amazonia as shown in previous studies by the group of Alves et al 6,7 Using both cross-sectional and prospective approaches, Alves et al examined the proportion of both P. falciparum and P. vivax parasitemic inhabitants of riverine communities in the Rondonia region of the Brazilian Amazon. Of substantial interest, in one community, they determined whether such parasitemic individuals were truly asymptomatic by following up microscopy or PCR-positive individuals for 60 days to ascertain whether they developed malaria parasite-related symptoms.…”

supporting

confidence: 68%

Asymptomatic Plasmodium parasitemia and the ecology of malaria transmission.

Vinetz

Gilman

2002

The American Journal of Tropical Medicine and Hygiene

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Tip O'Neill, former speaker of the United States House of Representatives, famously pointed out that all politics is local. The same is true of malaria. Malaria transmission is not homogeneous through an endemic area but spotty, and depends on two primary factors: location of mosquito breeding sites, and clustering of human habitations where people serving as reservoirs of parasites for mosquito infection live.1 Whether malaria transmission in focal areas of a malaria-endemic region is stable or unstable is an important determinant of morbidity and mortality. Stable malaria implies that prevalence of infection is sufficiently high to engender a substantial level of clinical immunity within a population, i.e. the presence of parasitemia in the absence of malaria-related symptoms. In contrast, unstable malaria, characterized by spatial and temporal variability, is associated with lower levels of clinical immunity within a population, the propensity for epidemics, and a higher rate of severe disease in adults. Clinical immunity to malaria within a population occurs in the context of premunition, defined as the presence of an immune response that produces control of but not complete elimination of parasitemia and pathological sequelae.In the following pages of this issue of the Journal, Alves et al. describe a relatively high proportion of both asymptomatic Plasmodium vivax and P. falciparum infections among parasitemic individuals within populations of indigenous AmerIndians in the western Brazilian Amazon region. A high rate of asymptomatic P. falciparum prevalence has been well known to occur in areas of high malaria transmission in Africa and other parts of the world. This has been well demonstrated by work in Senegal and other malaria endemic areas.2 Using sensitive molecular techniques, these investigators have shown that while in places such as Dielmo, Senegal, many individuals in particular communities are parasitemic at any one point, only a small fraction of these individuals have malaria-related illness. Subpatent and asymptomatic parasitemias persist interseasonally in places with seasonal transmission 3 ; such patients likely represent a major mechanism for over-seasoning of malaria parasites. Similar findings have been reported regarding P. vivax infections in other regions, for example western Thailand , Sri Lanka , and in Brazilian western Amazonia as shown in previous studies by the group of Alves et al. 6,7 Using both cross-sectional and prospective approaches, Alves et al. examined the proportion of both P. falciparum and P. vivax parasitemic inhabitants of riverine communities in the Rondonia region of the Brazilian Amazon. Of substantial interest, in one community, they determined whether such parasitemic individuals were truly asymptomatic by following up microscopy or PCR-positive individuals for 60 days to ascertain whether they developed malaria parasite-related symptoms. The authors note, quite appropriately, that "the absence of symptoms in cross-sectional studies is not tantamount to asym...

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supporting

confidence: 68%

Asymptomatic Plasmodium parasitemia and the ecology of malaria transmission.

Vinetz

Gilman

2002

The American Journal of Tropical Medicine and Hygiene

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“…The annual parasite index (API) in this settlement was 385 per 1,000 inhabitants in 1999, a much higher value than the API estimated for the whole state of Rondônia in the same year (49.6 per 1,000 inhabitants). Detailed information on the malarial epidemiological data, that included prevalence of P. falciparum and P. vivax infections in the cross-sectional surveys, is presented elsewhere (Camargo et al 1999.…”

Section: Methodsmentioning

confidence: 99%

“…The present study is part of a large scientific project aimed to investigate the biological characteristics of some infectious diseases in the Western Amazon region of Brazil (Camargo et al 1994(Camargo et al , 1996(Camargo et al , 1999 in which the association of some blood polymorphisms with two traits involved with the malaria infection is tested. Exception made to haptoglobin, which has an important role as hemoglobin carrier, the investigated genetic markers are red blood cell polymorphisms, since erythrocytes are the ultimate target cells of the malarial parasite.…”

mentioning

confidence: 99%

The association of genetic markers and malaria infection in the Brazilian Western Amazonian region

Beiguelman

Alves

Moura

et al. 2003

Mem. Inst. Oswaldo Cruz

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“…Clyde (1989) discussed the potential impact of that this has on transmission. In our previous cross-sectional surveys (Camargo et al 1994) in Urupá we did not detect asymptomatic carriers, but in the nearby locality of Portuchuelo we have had some indirect evidence of P. vivax premunition in adults who have lived for many years in the endemic area (Camargo et al 1999).…”

Section: Discussionmentioning

confidence: 61%