Spatial and genetic clustering of Plasmodium falciparum and Plasmodium vivax infections in a low-transmission area of Ethiopia

AbstractThe distribution of malaria infections is heterogeneous in space and time, especially in low transmission settings. Understanding this clustering may allow identification and targeting of pockets of transmission. In Adama district, Ethiopia, Plasmodium falciparum and P. vivax malaria patients and controls were examined, together with household members and immediate neighbors. Rapid diagnostic test and quantitative PCR (qPCR) were used for the detection of infections that were genetically characterized by a panel of microsatellite loci for P. falciparum (26) and P. vivax (11), respectively. Individuals living in households of clinical P. falciparum patients were more likely to have qPCR detected P. falciparum infections (22.0%, 9/41) compared to individuals in control households (8.7%, 37/426; odds ratio, 2.9; 95% confidence interval, 1.3–6.4; P = .007). Genetically related P. falciparum, but not P. vivax infections showed strong clustering within households. Genotyping revealed a marked temporal cluster of P. falciparum infections, almost exclusively comprised of clinical cases. These findings uncover previously unappreciated transmission dynamics and support a rational approach to reactive case detection strategies for P. falciparum in Ethiopia.

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Adapting Reactive Case Detection Strategies for falciparum Malaria in a Low-Transmission Area in Cambodia

Clinical Infectious Diseases ◽

10.1093/cid/cix781 ◽

2017 ◽

Vol 66 (2) ◽

pp. 296-298 ◽

Cited By ~ 7

Author(s):

Gabriele Rossi ◽

Rafael Van den Bergh ◽

Chea Nguon ◽

Mark Debackere ◽

Lieven Vernaeve ◽

...

Keyword(s):

Falciparum Malaria ◽

Case Detection ◽

Reactive Case Detection ◽

Low Transmission ◽

Transmission Area ◽

Detection Strategies

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Evaluation of the operational challenges in implementing reactive screen-and-treat and implications of reactive case detection strategies for malaria elimination in a region of low transmission in southern Zambia

Malaria Journal ◽

10.1186/s12936-016-1460-x ◽

2016 ◽

Vol 15 (1) ◽

Cited By ~ 22

Author(s):

Kelly M. Searle ◽

◽

Harry Hamapumbu ◽

Jailos Lubinda ◽

Timothy M. Shields ◽

...

Keyword(s):

Malaria Elimination ◽

Case Detection ◽

Reactive Case Detection ◽

Low Transmission ◽

Detection Strategies

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Modelling reactive case detection strategies for interrupting transmission of Plasmodium falciparum malaria

Malaria Journal ◽

10.1186/s12936-019-2893-9 ◽

2019 ◽

Vol 18 (1) ◽

Cited By ~ 6

Author(s):

Theresa Reiker ◽

Nakul Chitnis ◽

Thomas Smith

Keyword(s):

Plasmodium Falciparum ◽

Falciparum Malaria ◽

Plasmodium Falciparum Malaria ◽

Case Detection ◽

Reactive Case Detection ◽

Detection Strategies

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Seroprevalence of SARS-CoV-2, Symptom Profiles and Sero-Neutralization in a Suburban Area, France

Viruses ◽

10.3390/v13061076 ◽

2021 ◽

Vol 13 (6) ◽

pp. 1076

Author(s):

Anne Gégout Petit ◽

Hélène Jeulin ◽

Karine Legrand ◽

Nicolas Jay ◽

Agathe Bochnakian ◽

...

Keyword(s):

Odds Ratio ◽

World Health Organisation ◽

World Health ◽

Preventive Effect ◽

Neutralization Activity ◽

Symptom Profiles ◽

The World ◽

Household Members ◽

Total Immunoglobulin

The World Health Organisation recommends monitoring the circulation of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We investigated anti–SARS-CoV-2 total immunoglobulin (IgT) antibody seroprevalence and in vitro sero-neutralization in Nancy, France, in spring 2020. Individuals were randomly sampled from electoral lists and invited with household members over 5 years old to be tested for anti–SARS-CoV-2 (IgT, i.e., IgA/IgG/IgM) antibodies by ELISA (Bio-rad); the sero-neutralization activity was evaluated on Vero CCL-81 cells. Among 2006 individuals, the raw seroprevalence was 2.1% (95% confidence interval 1.5 to 2.9), was highest for 20- to 34-year-old participants (4.7% (2.3 to 8.4)), within than out of socially deprived area (2.5% vs. 1%, p = 0.02) and with than without intra-family infection (p < 10−6). Moreover, 25% of participants presented at least one COVID-19 symptom associated with SARS-CoV-2 positivity (p < 10−13), with highly discriminant anosmia or ageusia (odds ratio 27.8 [13.9 to 54.5]); 16.3% (6.8 to 30.7) of seropositive individuals were asymptomatic. Positive sero-neutralization was demonstrated in vitro for 31/43 seropositive subjects. Regarding the very low seroprevalence, a preventive effect of the lockdown in March 2020 can be assumed for the summer, but a second COVID-19 wave, as expected, could be subsequently observed in this poorly immunized population.

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Genotyping cognate Plasmodium falciparum in humans and mosquitoes to estimate onward transmission of asymptomatic infections

Nature Communications ◽

10.1038/s41467-021-21269-2 ◽

2021 ◽

Vol 12 (1) ◽

Cited By ~ 2

Author(s):

Kelsey M. Sumner ◽

Elizabeth Freedman ◽

Lucy Abel ◽

Andrew Obala ◽

Brian W. Pence ◽

...

Keyword(s):

Plasmodium Falciparum ◽

Odds Ratio ◽

Asymptomatic Malaria ◽

Major Contributor ◽

Western Kenya ◽

High Transmission ◽

Transmission Reduction ◽

Asymptomatic Infections ◽

Infection Types ◽

Natural Settings

AbstractMalaria control may be enhanced by targeting reservoirs of Plasmodium falciparum transmission. One putative reservoir is asymptomatic malaria infections and the scale of their contribution to transmission in natural settings is not known. We assess the contribution of asymptomatic malaria to onward transmission using a 14-month longitudinal cohort of 239 participants in a high transmission site in Western Kenya. We identify P. falciparum in asymptomatically- and symptomatically-infected participants and naturally-fed mosquitoes from their households, genotype all parasites using deep sequencing of the parasite genes pfama1 and pfcsp, and use haplotypes to infer participant-to-mosquito transmission through a probabilistic model. In 1,242 infections (1,039 in people and 203 in mosquitoes), we observe 229 (pfcsp) and 348 (pfama1) unique parasite haplotypes. Using these to link human and mosquito infections, compared with symptomatic infections, asymptomatic infections more than double the odds of transmission to a mosquito among people with both infection types (Odds Ratio: 2.56; 95% Confidence Interval (CI): 1.36–4.81) and among all participants (OR 2.66; 95% CI: 2.05–3.47). Overall, 94.6% (95% CI: 93.1–95.8%) of mosquito infections likely resulted from asymptomatic infections. In high transmission areas, asymptomatic infections are the major contributor to mosquito infections and may be targeted as a component of transmission reduction.

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The epidemiology and detectability of asymptomatic Plasmodium vivax and Plasmodium falciparum infections in low, moderate and high transmission settings in Ethiopia

Malaria Journal ◽

10.1186/s12936-021-03587-4 ◽

2021 ◽

Vol 20 (1) ◽

Author(s):

Elifaged Hailemeskel ◽

Surafel K Tebeje ◽

Sinknesh W. Behaksra ◽

Girma Shumie ◽

Getasew Shitaye ◽

...

Keyword(s):

Plasmodium Falciparum ◽

Plasmodium Vivax ◽

Age Groups ◽

Diagnostic Tools ◽

Asymptomatic Malaria ◽

Rapid Diagnostics ◽

Cross Sectional ◽

Low Transmission ◽

High Transmission ◽

Study Sites

Abstract Background As countries move to malaria elimination, detecting and targeting asymptomatic malaria infections might be needed. Here, the epidemiology and detectability of asymptomatic Plasmodium falciparum and Plasmodium vivax infections were investigated in different transmission settings in Ethiopia. Method: A total of 1093 dried blood spot (DBS) samples were collected from afebrile and apparently healthy individuals across ten study sites in Ethiopia from 2016 to 2020. Of these, 862 were from community and 231 from school based cross-sectional surveys. Malaria infection status was determined by microscopy or rapid diagnostics tests (RDT) and 18S rRNA-based nested PCR (nPCR). The annual parasite index (API) was used to classify endemicity as low (API > 0 and < 5), moderate (API ≥ 5 and < 100) and high transmission (API ≥ 100) and detectability of infections was assessed in these settings. Results In community surveys, the overall prevalence of asymptomatic Plasmodium infections by microscopy/RDT, nPCR and all methods combined was 12.2% (105/860), 21.6% (183/846) and 24.1% (208/862), respectively. The proportion of nPCR positive infections that was detectable by microscopy/RDT was 48.7% (73/150) for P. falciparum and 4.6% (2/44) for P. vivax. Compared to low transmission settings, the likelihood of detecting infections by microscopy/RDT was increased in moderate (Adjusted odds ratio [AOR]: 3.4; 95% confidence interval [95% CI] 1.6–7.2, P = 0.002) and high endemic settings (AOR = 5.1; 95% CI 2.6–9.9, P < 0.001). After adjustment for site and correlation between observations from the same survey, the likelihood of detecting asymptomatic infections by microscopy/RDT (AOR per year increase = 0.95, 95% CI 0.9–1.0, P = 0.013) declined with age. Conclusions Conventional diagnostics missed nearly half of the asymptomatic Plasmodium reservoir detected by nPCR. The detectability of infections was particularly low in older age groups and low transmission settings. These findings highlight the need for sensitive diagnostic tools to detect the entire parasite reservoir and potential infection transmitters.

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