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School-based countrywide seroprevalence survey reveals spatial heterogeneity in malaria transmission in the Gambia.

Okebe J, Affara M, Correa S, Muhammad AK, Nwakanma D, Drakeley C, D'Alessandro U - PLoS ONE (2014)

Bottom Line: Factors associated with a positive serological status were identified in a univariate model and then combined in a multilevel mixed-effects logistic regression model, simultaneously adjusting for variations between individuals and school.Age (OR 1.12, 95% CI 1.07-1.16,) and parasite carriage (OR 3.36, 95% CI 1.95-5.79) were strongly associated with seropositivity.Field-adapted antibody tests able to guide mass screening and treatment campaigns would be extremely useful.

View Article: PubMed Central - PubMed

Affiliation: Disease Control & Elimination Theme, Medical Research Council Unit, Fajara, The Gambia.

ABSTRACT

Background: As the geographical distribution of malaria transmission becomes progressively clustered, identifying residual pockets of transmission is important for research and for targeting interventions. Malarial antibody-based surveillance is increasingly recognised as a valuable complement to classic methods for the detection of infection foci especially at low transmission levels. The study presents serological evidence for transmission heterogeneity among school children in The Gambia measured during the dry, non-transmission season.

Methods: Healthy primary school children were randomly selected from 30 schools across the country and screened for malaria infection (microscopy) and antimalarial antibodies (MSP119). Antibody distribution was modelled using 2-component finite mixture model with cut-off for positivity from pooled sera set at 2-standard deviation from the mean of the first component. Factors associated with a positive serological status were identified in a univariate model and then combined in a multilevel mixed-effects logistic regression model, simultaneously adjusting for variations between individuals and school.

Results: A total of 4140 children, 1897 (46%) boys, were enrolled with mean age of 10.2 years (SD 2.6, range 4-20 years). Microscopy results available for 3640 (87.9%) children showed that 1.9% (69) were positive for Plasmodium falciparum infections, most of them (97.1%, 67/69) asymptomatic. The overall seroprevalence was 12.7% (527/4140) with values for the schools ranging from 0.6% to 43.8%. Age (OR 1.12, 95% CI 1.07-1.16,) and parasite carriage (OR 3.36, 95% CI 1.95-5.79) were strongly associated with seropositivity.

Conclusion: Serological responses to malaria parasites could identify individuals who were or had been infected, and clusters of residual transmission. Field-adapted antibody tests able to guide mass screening and treatment campaigns would be extremely useful.

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Related in: MedlinePlus

Slide positivity and seroprevalence rates for sampled schools.Circles represent schools location and colour graded according to the inset showing the prevalence of individuals with a positive blood slide for P. falciparum (A) and positive for antibodies to MSP119 (B).
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pone-0110926-g002: Slide positivity and seroprevalence rates for sampled schools.Circles represent schools location and colour graded according to the inset showing the prevalence of individuals with a positive blood slide for P. falciparum (A) and positive for antibodies to MSP119 (B).

Mentions: The prevalence of malaria infection, measured by microscopy, was spatially variable with the highest prevalence seen in schools in the eastern part of the country. In 27 of the 30 schools, malaria prevalence was less than 5% (in 13 of these schools, the prevalence was 0%) while in the three remaining schools, the prevalence ranged between 9% and 15% (Figure 2a). Infected children had lower haemoglobin levels compared to the uninfected (OR 0.78, 95% CI 0.67–0.90).


School-based countrywide seroprevalence survey reveals spatial heterogeneity in malaria transmission in the Gambia.

Okebe J, Affara M, Correa S, Muhammad AK, Nwakanma D, Drakeley C, D'Alessandro U - PLoS ONE (2014)

Slide positivity and seroprevalence rates for sampled schools.Circles represent schools location and colour graded according to the inset showing the prevalence of individuals with a positive blood slide for P. falciparum (A) and positive for antibodies to MSP119 (B).
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4206471&req=5

pone-0110926-g002: Slide positivity and seroprevalence rates for sampled schools.Circles represent schools location and colour graded according to the inset showing the prevalence of individuals with a positive blood slide for P. falciparum (A) and positive for antibodies to MSP119 (B).
Mentions: The prevalence of malaria infection, measured by microscopy, was spatially variable with the highest prevalence seen in schools in the eastern part of the country. In 27 of the 30 schools, malaria prevalence was less than 5% (in 13 of these schools, the prevalence was 0%) while in the three remaining schools, the prevalence ranged between 9% and 15% (Figure 2a). Infected children had lower haemoglobin levels compared to the uninfected (OR 0.78, 95% CI 0.67–0.90).

Bottom Line: Factors associated with a positive serological status were identified in a univariate model and then combined in a multilevel mixed-effects logistic regression model, simultaneously adjusting for variations between individuals and school.Age (OR 1.12, 95% CI 1.07-1.16,) and parasite carriage (OR 3.36, 95% CI 1.95-5.79) were strongly associated with seropositivity.Field-adapted antibody tests able to guide mass screening and treatment campaigns would be extremely useful.

View Article: PubMed Central - PubMed

Affiliation: Disease Control & Elimination Theme, Medical Research Council Unit, Fajara, The Gambia.

ABSTRACT

Background: As the geographical distribution of malaria transmission becomes progressively clustered, identifying residual pockets of transmission is important for research and for targeting interventions. Malarial antibody-based surveillance is increasingly recognised as a valuable complement to classic methods for the detection of infection foci especially at low transmission levels. The study presents serological evidence for transmission heterogeneity among school children in The Gambia measured during the dry, non-transmission season.

Methods: Healthy primary school children were randomly selected from 30 schools across the country and screened for malaria infection (microscopy) and antimalarial antibodies (MSP119). Antibody distribution was modelled using 2-component finite mixture model with cut-off for positivity from pooled sera set at 2-standard deviation from the mean of the first component. Factors associated with a positive serological status were identified in a univariate model and then combined in a multilevel mixed-effects logistic regression model, simultaneously adjusting for variations between individuals and school.

Results: A total of 4140 children, 1897 (46%) boys, were enrolled with mean age of 10.2 years (SD 2.6, range 4-20 years). Microscopy results available for 3640 (87.9%) children showed that 1.9% (69) were positive for Plasmodium falciparum infections, most of them (97.1%, 67/69) asymptomatic. The overall seroprevalence was 12.7% (527/4140) with values for the schools ranging from 0.6% to 43.8%. Age (OR 1.12, 95% CI 1.07-1.16,) and parasite carriage (OR 3.36, 95% CI 1.95-5.79) were strongly associated with seropositivity.

Conclusion: Serological responses to malaria parasites could identify individuals who were or had been infected, and clusters of residual transmission. Field-adapted antibody tests able to guide mass screening and treatment campaigns would be extremely useful.

Show MeSH
Related in: MedlinePlus