Dramatic declines in seropositivity as determined with crude extracts of Plasmodium falciparum schizonts between 2000 and 2010 in Dielmo and Ndiop, Senegal

Diop, Fatou; Richard, Vincent; Diouf, Babacar; Sokhna, Cheikh; Diagne, Nafissatou; Trape, Jean‐François; Faye, Michel Matar; Tall, Adama; Diop, Gora; Balde, Aissatou Toure

doi:10.1186/1475-2875-13-83

Cited by 30 publications

(66 citation statements)

References 25 publications

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“…Temporal variation in seroprevalence/levels against these conserved antigens is thus unlikely due to temporal genetic variation of the parasites circulating in the villages. Data regarding anti-SE responses are consistent with the observed decrease from 2000 to 2010 in the 5–19 year old villagers from Dielmo and Ndiop[5]. We show here that by 2013 the decay had occurred in all previously immune groups, including adults and importantly, that the children under 6 years were essentially seronegative against SE indicating quite limited exposure to parasites in this age group.…”

Section: Discussionsupporting

confidence: 89%

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Serological signatures of declining exposure following intensification of integrated malaria control in two rural Senegalese communities

et al. 2017

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Recent control scale-up has reduced malaria in many areas but new tools are needed to monitor further progress, including indicators of decreasing exposure to parasite infection. Although serology is considered a promising approach in this regard, the serological impact of control interventions has been so far studied using indirect quantification of exposure. Cohort surveys concomitantly recording entomological and malariometric indices have been conducted in two Senegalese settings where supervised control intensification implemented in 2006 shifted malaria from historically holoendemic in Dielmo and mesoendemic in Ndiop to hypoendemic in both settings by 2013. We analyse here serological signatures of declining transmission using archived blood samples. Responses against ten pre-erythrocytic and erythrocytic antigens from Plasmodium falciparum and P. malariae alongside an Anopheles gambiae salivary gland antigen were analysed. Cross-sectional surveys conducted before (2002) and after (2013) control intensification showed a major impact of control intensification in both settings. The age-associated prevalence, magnitude and breadth of the IgG responses to all antigens were village-specific in 2002. In 2013, remarkably similar patterns were observed in both villages, with marginal responses against all parasite antigens in the 0-5y children and reduced responses in all previously seropositive age groups. Waning of humoral responses of individuals who were immune at the time of control intensification was studied from 2006 to 2013 using yearly samplings. Longitudinal data were analysed using the Cochran-Armittage trend test and an age-related reversible catalytic conversion model. This showed that the antigen-specific antibody declines were more rapid in older children than adults. There was a strong association of antibody decline with the declining entomological inoculation rate. We thus identified serological markers of declining exposure to malaria parasites that should help future monitoring of progress towards malaria elimination.

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Section: Discussionsupporting

confidence: 89%

“…Procedures were performed using sera diluted 1/200 as described [5, 15, 16]. A pool of sera from immune adults from Dielmo and a pool of European and African non-immune sera were included in each assay as positive and negative controls, respectively.…”

Section: Methodsmentioning

confidence: 99%

Serological signatures of declining exposure following intensification of integrated malaria control in two rural Senegalese communities

et al. 2017

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“…These observations are in agreement with previous studies [13]. A high level of antibody recognition of strains PA, F15, and F16 was also obtained in samples from both Dielmo and Ndiop villages.…”

Section: Discussionsupporting

confidence: 93%

“…Three field strains of P. falciparum isolated from clinical or asymptomatic malaria-infected Senegalese patients and adapted for in vitro culture as described elsewhere [13, 18]. The 0703 strain was isolated from an inhabitant of Dielmo on November 1991 and successfully adapted to continuous in vitro culture thereafter [19].…”

Section: Methodsmentioning

confidence: 99%

The value of local malaria strains for serological studies: local strains versus Palo Alto reference strain

Diop

Niang

et al. 2015

Malar J

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BackgroundThe standardization of the type of crude Plasmodium falciparum extracts for assays to evaluate the overall anti-blood-stage immune response in humans may be beneficial to malaria pre-elimination programmes. However, there is no consensus on which strain is appropriate for routine analyses. This study aimed to compare the responses of malaria IgG antibodies in serum collections from Dielmo and Ndiop to crude extracts of merozoites and schizonts of local and reference strains of P. falciparum.MethodsMalaria antibodies were evaluated using serological tests for exposure to three local strains (0703, F15 and F16) and the P. falciparum reference Palo Alto strain (PA). A total of 218 sera collected in 2000 from inhabitants of the villages of Dielmo and Ndiop were used: 142 from Dielmo and 76 from Ndiop. The biological collection was used to evaluate by ELISA the prevalence of IgG antibodies against crude merozoite and schizont extracts. The genetics of the local and reference strains were compared.ResultsThere was genetic divergence between strains 0703, F15, F16 and PA. IgG responses against local and reference strains correlated well (0.6 to 0.8; p < 0.01). Ig G responses were highest to schizont and merozoite extracts from the field strain of P. falciparum 0703 adapted to in vitro culture. Extracts of P. falciparum strain 0703 isolated from a subject in Dielmo was the most widely recognized [91.3 % (199/218) and 81.2 % (177/218) for schizonts and merozoites, respectively], although the responses were high for merozoites from PA [85.3 % (186/218)] the reference strain, and the two strains isolated from subjects living in Dakar: F15 [90.4 % (197/218)] and F16 [72.5 % (158/218)].ConclusionsFor serological studies, the local strain provided the most complete picture of exposure to transmission and malaria prevalence in the local context. However, for the standardization of this method by different laboratories, the reference strain appeared to perform sufficiently well to be used for the evaluation of malaria control programmes.

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“…5 Two years after the implementation of LLINs, an increase of malaria morbidity was unfortunately observed in 2010 and 2011, which was explained by the non-use of the LLINs (Wotodjo AN, personal communication), the resistance of Anopheles against pyrethroid insecticide, and the loss of immunity. 8,9 After this recrudescence of malaria morbidity, all LLINs were replaced in July of 2011, which resulted in a significant decrease of the disease from January of 2012 to September of 2013. 5 However, between October and November of 2013, an unexplained slight increase of malaria clinical attacks occurred again.…”

Section: Introductionmentioning

confidence: 99%

Malaria Risk Factors in Dielmo, A Senegalese Malaria-Endemic Village, Between October and November of 2013: A Case-Control Study

Wotodjo¹,

Diagne²,

Gaudart³

et al. 2015

The American Society of Tropical Medicine and Hygiene

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Abstract. The incidence of malaria has decreased recently in parts of Africa, coinciding with the widespread use of long-lasting insecticide-treated nets (LLINs) and artemisinin-based combination therapy (ACT). This reduction was also observed in Dielmo, our study area, and it was associated with the use of ACT as the first-line treatment against malaria beginning in 2006 and the implementation of LLINs in 2008. However, an unexplained slight increase in malaria incidence was observed in October and November of 2013. The aim of this study was to identify individual and environmental risk factors for malaria using a case-control study approach. Thirty cases and sixty controls were investigated. The use of LLINs was protective against malaria (adjusted odds ratio [AOR] = 0.10; 95% confidence interval [95% CI] = 0.02-0.45; P = 0.003). The risk of malaria transmission was high among villagers who watched television outside the house or the bedroom during the night (AOR = 8.83; 95% CI = 1.39-56.22; P = 0.021). The use of LLINs should be reinforced by the use of individual protection measures to avoid malaria transmission outside of the home. BACKGROUND

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Dramatic declines in seropositivity as determined with crude extracts of Plasmodium falciparum schizonts between 2000 and 2010 in Dielmo and Ndiop, Senegal

Cited by 30 publications

References 25 publications

Serological signatures of declining exposure following intensification of integrated malaria control in two rural Senegalese communities

Serological signatures of declining exposure following intensification of integrated malaria control in two rural Senegalese communities

The value of local malaria strains for serological studies: local strains versus Palo Alto reference strain

Malaria Risk Factors in Dielmo, A Senegalese Malaria-Endemic Village, Between October and November of 2013: A Case-Control Study

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