7 research outputs found
Defining the next generation of Plasmodium vivax diagnostic tests for control and elimination: Target product profiles.
The global prevalence of malaria has decreased over the past fifteen years, but similar gains have not been realized against Plasmodium vivax because this species is less responsive to conventional malaria control interventions aimed principally at P. falciparum. Approximately half of all malaria cases outside of Africa are caused by P. vivax. This species places dormant forms in human liver that cause repeated clinical attacks without involving another mosquito bite. The diagnosis of acute patent P. vivax malaria relies primarily on light microscopy. Specific rapid diagnostic tests exist but typically perform relatively poorly compared to those for P. falciparum. Better diagnostic tests are needed for P. vivax. To guide their development, FIND, in collaboration with P. vivax experts, identified the specific diagnostic needs associated with this species and defined a series of three distinct target product profiles, each aimed at a particular diagnostic application: (i) point-of-care of acutely ill patients for clinical care purposes; (ii) point-of-care asymptomatic and otherwise sub-patent residents for public health purposes, e.g., mass screen and treat campaigns; and (iii) ultra-sensitive not point-of-care diagnosis for epidemiological research/surveillance purposes. This report presents and discusses the rationale for these P. vivax-specific diagnostic target product profiles. These contribute to the rational development of fit-for-purpose diagnostic tests suitable for the clinical management, control and elimination of P. vivax malaria
Defining the next generation of Plasmodium vivax diagnostic tests for control and elimination: Target product profiles
The global prevalence of malaria has decreased over the past
fifteen years, but similar gains have not been realized against
Plasmodium vivax because this species is less responsive to
conventional malaria control interventions aimed principally at
P. falciparum. Approximately half of all malaria cases outside
of Africa are caused by P. vivax. This species places dormant
forms in human liver that cause repeated clinical attacks
without involving another mosquito bite. The diagnosis of acute
patent P. vivax malaria relies primarily on light microscopy.
Specific rapid diagnostic tests exist but typically perform
relatively poorly compared to those for P. falciparum. Better
diagnostic tests are needed for P. vivax. To guide their
development, FIND, in collaboration with P. vivax experts,
identified the specific diagnostic needs associated with this
species and defined a series of three distinct target product
profiles, each aimed at a particular diagnostic application: (i)
point-of-care of acutely ill patients for clinical care
purposes; (ii) point-of-care asymptomatic and otherwise
sub-patent residents for public health purposes, e.g., mass
screen and treat campaigns; and (iii) ultra-sensitive not
point-of-care diagnosis for epidemiological
research/surveillance purposes. This report presents and
discusses the rationale for these P. vivax-specific diagnostic
target product profiles. These contribute to the rational
development of fit-for-purpose diagnostic tests suitable for the
clinical management, control and elimination of P. vivax
malaria
Plasmodium vivax Diversity and Population Structure across Four Continents
Plasmodium vivax is the geographically most widespread human
malaria parasite. To analyze patterns of microsatellite
diversity and population structure across countries of different
transmission intensity, genotyping data from 11 microsatellite
markers was either generated or compiled from 841 isolates from
four continents collected in 1999-2008. Diversity was highest in
South-East Asia (mean allelic richness 10.0-12.8), intermediate
in the South Pacific (8.1-9.9) Madagascar and Sudan (7.9-8.4),
and lowest in South America and Central Asia (5.5-7.2). A
reduced panel of only 3 markers was sufficient to identify
approx. 90% of all haplotypes in South Pacific, African and
SE-Asian populations, but only 60-80% in Latin American
populations, suggesting that typing of 2-6 markers, depending on
the level of endemicity, is sufficient for epidemiological
studies. Clustering analysis showed distinct clusters in Peru
and Brazil, but little sub-structuring was observed within
Africa, SE-Asia or the South Pacific. Isolates from Uzbekistan
were exceptional, as a near-clonal parasite population was
observed that was clearly separated from all other populations
(FST>0.2). Outside Central Asia FST values were highest
(0.11-0.16) between South American and all other populations,
and lowest (0.04-0.07) between populations from South-East Asia
and the South Pacific. These comparisons between P. vivax
populations from four continents indicated that not only
transmission intensity, but also geographical isolation affect
diversity and population structure. However, the high effective
population size results in slow changes of these parameters.
This persistency must be taken into account when assessing the
impact of control programs on the genetic structure of parasite
populations
Summary of key distinguishing features of TPP PvA, PvB1, and PvB2
<p>Summary of key distinguishing features of TPP PvA, PvB1, and PvB2</p
Malaria testing strategies and TPP coverage.
<p>Testing strategies are typically classified as passive and active detection where passive detection concerns symptomatic cases and active detection all infections, symptomatic or not. Passive detection is used for the confirmation of symptomatic suspected cases presenting to the healthcare system where treatment is based on a positive parasitological test (PCD: passive case detection). Active detection is typically divided as reactive and proactive detection where reactive detection consists of the active screening of a set of individuals linked geographically or sociologically to an index case for infection detection and treatment. Proactive detection can either be linked with treatment in focal screen-and-treat (FSAT) or mass screen-and-treat (MSAT) interventions or in location-based testing (<i>e</i>.<i>g</i>. boarder screening) or be independent of treatment in epidemiological surveys. The coverage of each of the three TPPs for <i>P</i>. <i>vivax</i> diagnostic tests, PvA, PvB1 and PvB2, is indicated in relation to these testing strategies. The classification of intervention types is adapted from [<a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0005516#pntd.0005516.ref036" target="_blank">36</a>].</p
Average panel detection scores of quality-controlled RDTs from WHO-FIND Product Testing Programme (n = 126).
<p>Average panel detection scores of quality-controlled RDTs from WHO-FIND Product Testing Programme (n = 126).</p