Títol:
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Declining malaria transmission in rural Amazon: changing
epidemiology and challenges to achieve elimination
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Autor/a:
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Vitor Silva, Sheila; Siqueira, André Machado; Souza Sampaio, Vanderson de; Guinovart, Caterina; Reyes-Lecca, Roberto Carlos; Melo, Gisely Cardoso de; Monteiro, Wuelton Marcelo; Portillo Obando, Hernando A. del; Alonso, Pedro; Bassat Orellana, Quique; Lacerda, Marcus Vinícius Guimarães
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Abstract:
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BACKGROUND: In recent years, considerable success in reducing
its incidence has been achieved in Brazil, leading to a relative
increase in the proportion of cases caused by Plasmodium vivax,
considered a harder-to-eliminate parasite. This study aim is to
describe the transmission dynamics and associated risk factors
in a rural settlement area in the Western Brazilian Amazon.
METHODS: A prospective cohort was established in a rural
settlement area for 3 years. Follow-up included continuous
passive case detection and monthly active case detection for a
period of 6 months. Demographic, clinical and transmission
control practices data were collected. Malaria diagnosis was
performed through thick blood smear. Univariable and
multivariable analyses of factors associated with malaria
incidence were performed using negative binomial regression
models. Factors associated with recurrence of P. vivax and
Plasmodium falciparum malaria within 90 days of a previous
episode were analysed using univariable and multivariable
Cox-Proportional Hazard models. RESULTS: Malaria prevalence
decreased from 7 % at the study beginning to 0.6 % at month 24,
with P. vivax predominating and P. falciparum disappearing after
1 year of follow-up. Malaria incidence was significantly higher
in the dry season [IRR (95 % CI) 1.4 (1.1-1.6); p < 0.001)].
Use of ITN was associated to malaria protection in the
localities [IRR (95 % CI) 0.7 (0.6-0.8); p = 0.001)]. A
recurrent P. vivax episode within 90 days was observed in 29.4 %
of individuals after an initial diagnosis. A previous P. vivax
[IRR (95 % CI) 2.3 (1.3-4.0); p = 0.006)] or mixed P. vivax + P.
falciparum [IRR (95 % CI) 2.9 (1.5-5.7); p = 0.002)] infections
were significantly associated to a vivax malaria episode within
90 days of follow-up. CONCLUSIONS: In an area of P. falciparum
and P. vivax co-endemicity, a virtual disappearance of P.
falciparum was observed with P. vivax increasing its relative
contribution, with a large proportion of recurring episodes.
This finding reinforces the perception of P. falciparum being
more responsive to early diagnosis and treatment and ITN use and
the contribution of relapsing P. vivax to maintain this species'
transmission. In areas of P. vivax endemicity, antihypnozoite
treatment effectiveness assessment in different transmission
intensity may be a fundamental activity for malaria control and
elimination. |
Matèries:
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-Malària -Amazònia -Malaria -Amazon River Region |
Drets:
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cc by (c) Vitor-Silva et al., 2016
http://creativecommons.org/licenses/by/3.0/es/ |
Tipus de document:
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Article Article - Versió publicada |
Publicat per:
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BioMed Central
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