Gametocyte carriage after seasonal malaria chemoprevention in Plasmodium falciparum infected asymptomatic children

Ahmad, Abdullahi; Prom, Aurelia; Bradley, John; Ndiath, Mamadou Ousmane; Etoketim, Blessed; Bah, Mamadou; Geertruyden, Jean-Pierre Van; Drakeley, Chris; Bousema, Teun; Achan, Jane; D’Alessandro, Umberto

doi:10.1186/s12936-021-03706-1

Cited by 10 publications

(8 citation statements)

References 34 publications

(57 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…With the observed higher odds of carriage in older children, coupled with the relatively higher exposure of this age group to mosquito bites (30), they probably contribute the most to the initiation of the yearly seasonal malaria epidemic.. The proportion of infections with microscopically patent gametocytes, the transmissible form of the parasites, detected in June by microscopy was similar to that reported amongst clinical cases during the transmission season (31). A much higher proportion of gametocyte positive asymptomatic infections during the dry season has been reported by studies that used sensitive molecular diagnostic methods (9,32).…”

Section: Discussionsupporting

confidence: 67%

Asymptomatic Plasmodium falciparum carriage and clinical disease: a five-year community-based longitudinal study in The Gambia.

Ahmad

Mohammed

Joof

et al. 2022

Preprint

Self Cite

View full text Add to dashboard Cite

Background Carriers of persistent asymptomatic Plasmodium falciparum infections constitute an infectious reservoir that maintains malaria transmission. Understanding the extent of carriage and characteristics of carriers specific to endemic areas could guide use of interventions to reduce infectious reservoir. Methods In eastern Gambia, an all-age cohort from four villages was followed up from 2012 to 2016. Each year, cross-sectional surveys were conducted at the start and end of the malaria transmission season to determine asymptomatic P. falciparum carriage by microscopy while passive case detection was conducted during the transmission to determine incidence of clinical malaria. Association between carriage at the end of a season and at the start of the next and risk factors for this were assessed. Effect of carriage at the start of the season on risk of clinical malaria during the season was also examined. Results A total of 1403 individuals − 1154 from a semi-urban village and 249 from three rural villages were enrolled; median age was 12 years (IQR 6, 30) and 12 years (IQR 7, 27) respectively. In adjusted analysis, asymptomatic P. falciparum carriage at the end of a transmission season and at the start of the next were strongly associated (OR = 19.99; 95% CI 12.57–31.77, P < 0.001). The odds of carriage across seasons (i.e carriage at the end of a season and at the start of the next) were higher in rural villages (OR = 13.0; 95% CI 6.33–26.88, P < 0.001) and amongst children aged 5–15 years (OR = 5.03; 95% CI 2.47–10.23, P = < 0.001). In the rural villages, carriage at the start of the transmission season was associated with a lower risk of clinical malaria (IRR 0.48, 95% CI 0.27–0.81, P = 0.007). Conclusions Asymptomatic P. falciparum carriage at the end of a transmission season strongly predicts carriage at the start the next season. Odds of carriage across seasons was higher in villages with relatively higher transmission and in older children. Interventions that reduce persistent asymptomatic infections can be applied in a targeted manner and may supress the initiation of yearly seasonal malaria transmission.

show abstract

Section: Discussionsupporting

confidence: 67%

Asymptomatic Plasmodium falciparum carriage and clinical disease: a five-year community-based longitudinal study in The Gambia.

Ahmad

Mohammed

Joof

et al. 2022

Preprint

Self Cite

View full text Add to dashboard Cite

show abstract

“…Consistent with previous studies in The Gambia [6,13,20], the prevalence of infection was lower in children under 5 years of age than in older children and adults, possibly due to the seasonal malaria chemoprophylaxis programme (monthly antimalarial treatment during the transmission season) [28,29]. The higher prevalence of infection and high parasite densities in older children than in adults may be the result of acquired immunity that makes adults better protected and able to better control parasite growth when infected [30].…”

Section: Discussionsupporting

confidence: 89%

AsymptomaticPlasmodium falciparumCarriage at the End of the Dry Season is Associated with Subsequent Infection and Clinical Malaria in Eastern Gambia

Fogang,

Lellouche,

Ceesay

et al. 2023

Preprint

Self Cite

View full text Add to dashboard Cite

BackgroundChronic carriage of asymptomatic low-densityPlasmodium falciparumparasitaemia in the dry season may support maintenance of acquired immunity that protects against clinical malaria. However, the relationship between chronic low-density infections and subsequent risk of clinical malaria episodes remains unclear.MethodsIn a 2-years study (December 2014 to December 2016) in eastern Gambia, nine cross-sectional surveys using molecular parasite detection were performed in the dry and wet season. During the 2016 malaria transmission season, passive case detection identified episodes of clinical malaria.ResultsAmong the 5,256 samples collected, 444 (8.4%) were positive forP. falciparum. A multivariate model identified village of residence, male sex, age ≥5 years old, anaemia, and fever as independent factors associated withP. falciparumparasite carriage. Infections did not cluster over time within the same households or recurred among neighbouring households. Asymptomatic parasite carriage at the end of dry season was associated with a higher risk of infection (Hazard Ratio, HR= 3.0, p< 0.0001) and clinical malaria (HR= 1.561, p= 0.057) during the following transmission season. Age and village of residence were additional predictors of infection and clinical malaria during the transmission season.ConclusionChronic parasite carriage during the dry season is associated with an increased risk of malaria infection and clinical malaria. It is unclear whether this is due to environmental exposure or to other factors.

show abstract

“…We observed no clear relationship between subject age and duration of parasite carriage, although all persistent infections were found in those above 5 years of age. In general, the number of children under 5 infected at the end of the wet season was low compared to the other age groups, possibly reflecting the levels of protective immunity, with younger children being more likely to develop symptoms when infected [7], or the impact of seasonal malaria chemoprevention [29].…”

Section: Discussionmentioning

confidence: 99%

A cohort study on the duration of Plasmodium falciparum infections during the dry season in The Gambia

Collins¹,

Ceesay

Drammeh

et al. 2021

Preprint

Self Cite

View full text Add to dashboard Cite

BackgroundIn areas where Plasmodium falciparum malaria is highly seasonal, a dry season reservoir of blood-stage infection is essential for initiating transmission during the following wet season, bridging transmission seasons several months apart. Understanding infections during the dry season could thus inform approaches for malaria control.MethodsIn The Gambia, a cohort of 42 individuals with qPCR positive P. falciparum infections at the end of the transmission season (December) were followed monthly until the end of the dry season (May) to evaluate the duration of detectable infections. The influence of human host (age, sex, haemoglobin concentration and genotype, and P. falciparum-specific antibodies), and parasitological (parasite density, gametocyte density and genotypic multiplicity of infection) factors was investigated.ResultsA large proportion of individuals infected at the end of the wet season had detectable infections until the end of the dry season (40.0%; 16/40), with the majority of these infections also harbouring gametocytes (81.3%; 13/16). 22 infections were classified as persistent (detectable for at least 3 months), 17 were classified as short-lived (undetectable within 2 months), and 3 were treated (due to symptoms). At the start of the dry season, the majority of persistent infections (82%; 18/22) had parasite densities >10 p/µL compared to only 5.9% (1/17) of short-lived infections. Persistent infections (59%; 13/22) were also more likely to be multi-clonal than short-lived infections (5.9%; 1/17), they were most common in 5 to 15 year old children (63%; 12/19), and were associated with individuals having higher levels of P. falciparum-specific antibodies (p = 0.058).ConclusionsAsymptomatic persistent dry season infections in The Gambia were multiclonal with higher parasite densities at the beginning of the dry season, mostly occurring in school age children and adults with higher P. falciparum-specific antibodies. Screening and treating asymptomatic, malaria-infected individuals during the dry season may reduce the human reservoir of malaria responsible initiating transmission in the wet-season.

show abstract

Gametocyte carriage after seasonal malaria chemoprevention in Plasmodium falciparum infected asymptomatic children

Cited by 10 publications

References 34 publications

Asymptomatic Plasmodium falciparum carriage and clinical disease: a five-year community-based longitudinal study in The Gambia.

Asymptomatic Plasmodium falciparum carriage and clinical disease: a five-year community-based longitudinal study in The Gambia.

AsymptomaticPlasmodium falciparumCarriage at the End of the Dry Season is Associated with Subsequent Infection and Clinical Malaria in Eastern Gambia

A cohort study on the duration of Plasmodium falciparum infections during the dry season in The Gambia

Contact Info

Product

Resources

About