Sustained malaria control over an eight-year period in Papua New Guinea: the challenge of low-density asymptomatic infections
Background: The scale-up of effective malaria control in the last decade has resulted in a substantial decline in the incidence of clinical malaria in many countries. The effects on the proportions of asymptomatic and submicroscopic infections, and on transmission potential are yet poorly understood...
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Published in | The Journal of infectious diseases |
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Main Authors | , , , , , , , , , , , , , , , |
Format | Journal Article |
Language | English |
Published |
Oxford University Press
19.09.2017
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Subjects | |
Online Access | Get full text |
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Summary: | Background: The scale-up of effective malaria control in the
last decade has resulted in a substantial decline in the
incidence of clinical malaria in many countries. The effects on
the proportions of asymptomatic and submicroscopic infections,
and on transmission potential are yet poorly understood.
Methods: In Papua New Guinea, vector control has been
intensified since 2008, and improved diagnosis and treatment
introduced in 2012. Cross-sectional surveys were conducted in
Madang Province in 2006 (n=1280), 2010 (n=2117) and 2014
(n=2516). Infections were quantified by highly sensitive qPCR
and gametocytes by RT-qPCR. Results: P. falciparum prevalence by
qPCR decreased from 42% in 2006 to 9% in 2014. P. vivax
prevalence decreased from 42% in 2006 to 13% in 2010, but then
increased to 20% in 2014. Parasite densities decreased 5-fold
from 2006 to 2010; 72% of P. falciparum and 87% of P. vivax
infections were submicroscopic in 2014. Gametocyte density and
positivity correlated closely with parasitemia, and population
gametocyte prevalence decreased 3-fold for P. falciparum and 29%
for P. vivax from 2010 to 2014. Conclusions: Sustained control
has resulted in reduced transmission potential but an increasing
proportion of gametocyte carriers are asymptomatic and
submicroscopic and represent a challenge to malaria control. |
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ISSN: | 0022-1899 |