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Serological evidence of vector and parasite exposure in Southern Ghana: the dynamics of malaria transmission intensity.

Badu K, Gyan B, Appawu M, Mensah D, Dodoo D, Yan G, Drakeley C, Zhou G, Owusu-Dabo E, Koram KA - Parasit Vectors (2015)

Bottom Line: Temporal variations in seroprevalence of both antigens as well as differences between the age-stratified cohorts were determined by χ (2) test with p < 0.05 statistically significant.For MSP1(19), no differences were observed in antibody levels between February and May but a significant decline was observed from May to August.Operational factors for scaling up have been discussed.

View Article: PubMed Central - PubMed

Affiliation: Department of Immunology, Noguchi Memorial Institute for Medical Research, College of Health Science University of Ghana, LG581, , Legon, Accra, Ghana. Kingsbadu@gmail.com.

ABSTRACT

Background: Seroepidemiology provides robust estimates for tracking malaria transmission when intensity is low and useful when there is no baseline entomological data. Serological evidence of exposure to malaria vectors and parasite contribute to our understanding of the risk of pathogen transmission, and facilitates implementation of targeted interventions. Ab to Anopheles gambiae salivary peptide (gSG6-P1) and merozoite surface protein one (MSP-1(19)) reflect human exposure to malaria vectors and parasites. This study estimated malaria transmission dynamics using serological evidence of vector and parasite exposure in southern Ghana.

Methods: Total IgG responses to both antigens in an age stratified cohort (<5, 5-14, >14) were measured from South-eastern Ghana. 295 randomly selected sera were analyzed from archived samples belonging to a cohort study that were followed at 3 consecutive survey months (n = 885); February, May and August 2009. Temporal variations in seroprevalence of both antigens as well as differences between the age-stratified cohorts were determined by χ (2) test with p < 0.05 statistically significant. Non-parametric repeated ANOVA - Friedman's test was used to test differences in antibody levels. Seroprevalence data were fitted to reversible catalytic model to estimate sero-conversion rates.

Results: Whereas parasite prevalence was generally low 2.4%, 2.7% and 2.4% with no apparent trends with season, seroprevalence to both gSG6-P1 and MSP1(19) were high (59%, 50.9%, 52.2%) and 57.6%, 52.3% and 43.6% in respective order from Feb. to August. Repeated measures ANOVA showed differences in median antibody levels across surveys with specific significant differences between February and May but not August by post hoc Dunn's multiple comparison tests for gSG6-P1. For MSP1(19), no differences were observed in antibody levels between February and May but a significant decline was observed from May to August. Seroconversion rates for gSG6-P1 increased by 1.5 folds from February to August and 3 folds for MSP1(19).

Conclusion: Data suggests exposure to infectious bites may be declining whereas mosquito bites remains high. Sustained malaria control efforts and surveillance are needed to drive malaria further down and to prevent catastrophic rebound. Operational factors for scaling up have been discussed.

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Correlation of antigen specific seroprevalence and parasite prevalence with age.
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Fig1: Correlation of antigen specific seroprevalence and parasite prevalence with age.

Mentions: The spearman correlation analysis revealed an inverse relationship between P. falciparum prevalence and age for all three survey months although this was not strong to achieve statistical significance; Feb (r = −0.30; p =0.46), May (r = −0.05; p =0.93) and August (r = −0.39; p =0.32). High exposures to the salivary gland peptide corresponded to strong association with age observed in the first and second survey months (Figure 1), however these exposures gradually declined with a non significant correlation with age in the third survey (r = 0.16; p = 0.11). gSG6-P1 responses had very similar trends compared with that observed in MSP119 which also had a strong correlation in the first survey with a gradual decline in the second and third surveys (Figure 1).Figure 1


Serological evidence of vector and parasite exposure in Southern Ghana: the dynamics of malaria transmission intensity.

Badu K, Gyan B, Appawu M, Mensah D, Dodoo D, Yan G, Drakeley C, Zhou G, Owusu-Dabo E, Koram KA - Parasit Vectors (2015)

Correlation of antigen specific seroprevalence and parasite prevalence with age.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4418069&req=5

Fig1: Correlation of antigen specific seroprevalence and parasite prevalence with age.
Mentions: The spearman correlation analysis revealed an inverse relationship between P. falciparum prevalence and age for all three survey months although this was not strong to achieve statistical significance; Feb (r = −0.30; p =0.46), May (r = −0.05; p =0.93) and August (r = −0.39; p =0.32). High exposures to the salivary gland peptide corresponded to strong association with age observed in the first and second survey months (Figure 1), however these exposures gradually declined with a non significant correlation with age in the third survey (r = 0.16; p = 0.11). gSG6-P1 responses had very similar trends compared with that observed in MSP119 which also had a strong correlation in the first survey with a gradual decline in the second and third surveys (Figure 1).Figure 1

Bottom Line: Temporal variations in seroprevalence of both antigens as well as differences between the age-stratified cohorts were determined by χ (2) test with p < 0.05 statistically significant.For MSP1(19), no differences were observed in antibody levels between February and May but a significant decline was observed from May to August.Operational factors for scaling up have been discussed.

View Article: PubMed Central - PubMed

Affiliation: Department of Immunology, Noguchi Memorial Institute for Medical Research, College of Health Science University of Ghana, LG581, , Legon, Accra, Ghana. Kingsbadu@gmail.com.

ABSTRACT

Background: Seroepidemiology provides robust estimates for tracking malaria transmission when intensity is low and useful when there is no baseline entomological data. Serological evidence of exposure to malaria vectors and parasite contribute to our understanding of the risk of pathogen transmission, and facilitates implementation of targeted interventions. Ab to Anopheles gambiae salivary peptide (gSG6-P1) and merozoite surface protein one (MSP-1(19)) reflect human exposure to malaria vectors and parasites. This study estimated malaria transmission dynamics using serological evidence of vector and parasite exposure in southern Ghana.

Methods: Total IgG responses to both antigens in an age stratified cohort (<5, 5-14, >14) were measured from South-eastern Ghana. 295 randomly selected sera were analyzed from archived samples belonging to a cohort study that were followed at 3 consecutive survey months (n = 885); February, May and August 2009. Temporal variations in seroprevalence of both antigens as well as differences between the age-stratified cohorts were determined by χ (2) test with p < 0.05 statistically significant. Non-parametric repeated ANOVA - Friedman's test was used to test differences in antibody levels. Seroprevalence data were fitted to reversible catalytic model to estimate sero-conversion rates.

Results: Whereas parasite prevalence was generally low 2.4%, 2.7% and 2.4% with no apparent trends with season, seroprevalence to both gSG6-P1 and MSP1(19) were high (59%, 50.9%, 52.2%) and 57.6%, 52.3% and 43.6% in respective order from Feb. to August. Repeated measures ANOVA showed differences in median antibody levels across surveys with specific significant differences between February and May but not August by post hoc Dunn's multiple comparison tests for gSG6-P1. For MSP1(19), no differences were observed in antibody levels between February and May but a significant decline was observed from May to August. Seroconversion rates for gSG6-P1 increased by 1.5 folds from February to August and 3 folds for MSP1(19).

Conclusion: Data suggests exposure to infectious bites may be declining whereas mosquito bites remains high. Sustained malaria control efforts and surveillance are needed to drive malaria further down and to prevent catastrophic rebound. Operational factors for scaling up have been discussed.

Show MeSH
Related in: MedlinePlus