Autor/a:
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Waltmann, Andreea; Darcy, Andrew W.; Harris, Ivor; Koepfli, Cristian; Lodo, John; Vahi, Ventis; Piziki, David; Shanks, G. Dennis; Barry, Alyssa E.; Whittaker, Maxine; Kazura, James W.; Mueller, Ivo
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Abstract:
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INTRODUCTION: Solomon Islands is intensifying national efforts
to achieve malaria elimination. A long history of indoor
spraying with residual insecticides, combined recently with
distribution of long lasting insecticidal nets and
artemether-lumefantrine therapy, has been implemented in Solomon
Islands. The impact of these interventions on local endemicity
of Plasmodium spp. is unknown. METHODS: In 2012, a
cross-sectional survey of 3501 residents of all ages was
conducted in Ngella, Central Islands Province, Solomon Islands.
Prevalence of Plasmodium falciparum, P. vivax, P. ovale and P.
malariae was assessed by quantitative PCR (qPCR) and light
microscopy (LM). Presence of gametocytes was determined by
reverse transcription quantitative PCR (RT-qPCR). RESULTS: By
qPCR, 468 Plasmodium spp. infections were detected (prevalence =
13.4%; 463 P. vivax, five mixed P. falciparum/P. vivax, no P.
ovale or P. malariae) versus 130 by LM (prevalence = 3.7%; 126
P. vivax, three P. falciparum and one P. falciparum/P. vivax).
The prevalence of P. vivax infection varied significantly among
villages (range 3.0-38.5%, p<0.001) and across age groups
(5.3-25.9%, p<0.001). Of 468 P. vivax infections, 72.9% were
sub-microscopic, 84.5% afebrile and 60.0% were both
sub-microscopic and afebrile. Local residency, low education
level of the household head and living in a household with at
least one other P. vivax infected individual increased the risk
of P. vivax infection. Overall, 23.5% of P. vivax infections had
concurrent gametocytaemia. Of all P. vivax positive samples,
29.2% were polyclonal by MS16 and msp1F3 genotyping. All five P.
falciparum infections were detected in residents of the same
village, carried the same msp2 allele and four were positive for
P. falciparum gametocytes. CONCLUSION: P. vivax infection
remains endemic in Ngella, with the majority of cases afebrile
and below the detection limit of LM. P. falciparum has nearly
disappeared, but the risk of re-introductions and outbreaks due
to travel to nearby islands with higher malaria endemicity
remains. |