scholarly journals Assessment of submicroscopic infections and gametocyte carriage of Plasmodium falciparum during peak malaria transmission season in a community-based cross-sectional survey in western Kenya, 2012

2016 ◽  
Vol 15 (1) ◽  
Author(s):  
Zhiyong Zhou ◽  
Rebecca M. Mitchell ◽  
Simon Kariuki ◽  
Christopher Odero ◽  
Peter Otieno ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Malaria Transmission ◽  
Cross Sectional Survey ◽  
Community Based ◽  
Cross Sectional ◽  
Western Kenya ◽  
Transmission Season ◽  
Gametocyte Carriage ◽  
Malaria Transmission Season

scholarly journals Gametocyte clearance in children, from western Kenya, with uncomplicated Plasmodium falciparum malaria after artemether–lumefantrine or dihydroartemisinin–piperaquine treatment

2019 ◽  
Vol 18 (1) ◽  
Author(s):  
Protus Omondi ◽  
Marion Burugu ◽  
Damaris Matoke-Muhia ◽  
Edwin Too ◽  
Eva A. Nambati ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Malaria Transmission ◽  
Plasmodium Falciparum Malaria ◽  
Western Kenya ◽  
Transmission Season ◽  
Gametocyte Carriage ◽  
Qrt Pcr ◽  
Malaria Transmission Season ◽  
Significant Difference ◽  
Blocking Malaria Transmission

Abstract Background The efficacy and safety of artemether–lumefantrine (AL) and dihydroartemisinin–piperaquine (DP) against asexual parasites population has been documented. However, the effect of these anti-malarials on sexual parasites is still less clear. Gametocyte clearance following treatment is essential for malaria control and elimination efforts; therefore, the study sought to determine trends in gametocyte clearance after AL or DP treatment in children from a malaria-endemic site in Kenya. Methods Children aged between 0.5 and 12 years from Busia, western Kenya with uncomplicated Plasmodium falciparum malaria were assigned randomly to AL or DP treatment. A total of 334 children were enrolled, and dried blood spot samples were collected for up to 6 weeks after treatment during the peak malaria transmission season in 2016 and preserved. Plasmodium falciparum gametocytes were detected by qRT-PCR and gametocyte prevalence, density and mean duration of gametocyte carriage were determined. Results At baseline, all the 334 children had positive asexual parasites by microscopy, 12% (40/334) had detectable gametocyte by microscopy, and 83.7% (253/302) children had gametocytes by RT-qPCR. Gametocyte prevalence by RT-qPCR decreased from 85.1% (126/148) at day 0 to 7.04% (5/71) at day 42 in AL group and from 82.4% (127/154) at day 0 to 14.5% (11/74) at day 42 in DP group. The average duration of gametocyte carriage as estimated by qRT-PCR was slightly shorter in the AL group (4.5 days) than in the DP group (5.1 days) but not significantly different (p = 0.301). Conclusion The study identifies no significant difference between AL and DP in gametocyte clearance. Gametocytes persisted up to 42 days post treatment in minority of individuals in both treatment arms. A gametocytocidal drug, in combination with artemisinin-based combination therapy, will be useful in blocking malaria transmission more efficiently.

scholarly journals Effect of 4 years of seasonal malaria chemoprevention on the acquisition of antibodies to Plasmodium falciparum antigens in Ouelessebougou, Mali

2021 ◽  
Vol 20 (1) ◽  
Author(s):  
Almahamoudou Mahamar ◽  
Djibrilla Issiaka ◽  
Ahamadou Youssouf ◽  
Sidi M. Niambele ◽  
Harouna M. Soumare ◽  
...  
Keyword(s):  
At Risk ◽  
Plasmodium Falciparum ◽  
Malaria Transmission ◽  
Confidence Intervals ◽  
Cross Sectional Survey ◽  
Cross Sectional ◽  
Transmission Season ◽  
Malaria Transmission Season ◽  
Seasonal Malaria Chemoprevention ◽  
Antibody Levels

Abstract Background More than 200 million people live in areas of highly seasonal malaria transmission where Seasonal Malaria Chemoprevention (SMC) with sulfadoxine-pyrimethamine (SP) and amodiaquine (AQ) was recommended in 2012 by WHO. This strategy is now implemented widely and protected more than 19 million children in 2018. It was previously reported that exposure to SMC reduced antibody levels to AMA1, MSP-142 and CSP, but the duration of exposure to SMC up to three 3 years, had no effect on antibody levels to MSP-142 and CSP. Methods In 2017, a cross-sectional survey was carried out 1 month after the last dose of SMC had been given to children aged 4–5 years randomly selected from areas where SMC had been given for 2 or 4 years during the malaria transmission season. A total of 461 children were enrolled, 242 children in areas where SMC had been implemented for 4 years and 219 children in areas where SMC had been implemented for 2 years. Antibody extracted from dry blood spots was used to measure IgG levels to the malaria antigens CSP, MSP-142 and AMA1 by ELISA. Results The prevalence of antibodies to MSP-142 was similar in children who had received SMC for 4 years compared to those who had received SMC for only 2 years (85.1 vs 86.0%, ajusted odd ratio (aOR) = 1.06, 95% confidence intervals (CI 0.62–1.80), p = 0.80). The prevalence of antibodies to AMA-1 and to CSP was not lower in children who received SMC for 4 years compared to those who had received SMC for only 2 years (95.3 vs 88.8%, aOR = 3.16, 95% CI 1.44–6.95, p = 0.004 for AMA-1; and 91.2 vs 81.9%, aOR = 3.14, 95% CI 1.70–5.76, p < 0.001 for CSP). Median antibody levels for anti-MSP-142 IgG were not significatively inferior in children who had received SMC for four rather than 2 years (0.88 (IQR: 0.64–1.15) and 0.95 ((0.68–1.15), respectively), anti-CSP (1.30 (1.00–1.56) and 1.17 (0.87–1.47)), and anti-AMA-1 (1.45 (1.24–1.68) and 1.41 (1.17–1.64)). Conclusion In an area of high seasonal malaria transmission, children who had received SMC for 4 years did not had lower seropositivity or antibody levels to AMA1, MSP-142 and CSP compared to children who had received SMC for only 2 years suggesting that children who have received SMC for 4 years may not be more at risk of malaria after the cessation of SMC than children who have received SMC for a shorter period.

scholarly journals The prevalence and density of asymptomatic Plasmodium falciparum infections among children and adults in three communities of western Kenya

2021 ◽  
Vol 20 (1) ◽  
Author(s):  
Christina Salgado ◽  
George Ayodo ◽  
Michael D. Macklin ◽  
Meetha P. Gould ◽  
Srinivas Nallandhighal ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Malaria Transmission ◽  
Malaria Incidence ◽  
Experimental Studies ◽  
Low Density ◽  
Healthy Children ◽  
Cross Sectional Survey ◽  
Western Kenya ◽  
Transcriptional Pattern ◽  
Asymptomatic Infections

Abstract Background Further reductions in malaria incidence as more countries approach malaria elimination require the identification and treatment of asymptomatic individuals who carry mosquito-infective Plasmodium gametocytes that are responsible for furthering malaria transmission. Assessing the relationship between total parasitaemia and gametocytaemia in field surveys can provide insight as to whether detection of low-density, asymptomatic Plasmodium falciparum infections with sensitive molecular methods can adequately detect the majority of infected individuals who are potentially capable of onward transmission. Methods In a cross-sectional survey of 1354 healthy children and adults in three communities in western Kenya across a gradient of malaria transmission (Ajigo, Webuye, and Kapsisywa–Kipsamoite), asymptomatic P. falciparum infections were screened by rapid diagnostic tests, blood smear, and quantitative PCR of dried blood spots targeting the varATS gene in genomic DNA. A multiplex quantitative reverse-transcriptase PCR assay targeting female and male gametocyte genes (pfs25, pfs230p), a gene with a transcriptional pattern restricted to asexual blood stages (piesp2), and human GAPDH was also developed to determine total parasite and gametocyte densities among parasitaemic individuals. Results The prevalence of varATS-detectable asymptomatic infections was greatest in Ajigo (42%), followed by Webuye (10%). Only two infections were detected in Kapsisywa. No infections were detected in Kipsamoite. Across all communities, children aged 11–15 years account for the greatest proportion total and sub-microscopic asymptomatic infections. In younger age groups, the majority of infections were detectable by microscopy, while 68% of asymptomatically infected adults (> 21 years old) had sub-microscopic parasitaemia. Piesp2-derived parasite densities correlated poorly with microscopy-determined parasite densities in patent infections relative to varATS-based detection. In general, both male and female gametocytaemia increased with increasing varATS-derived total parasitaemia. A substantial proportion (41.7%) of individuals with potential for onward transmission had qPCR-estimated parasite densities below the limit of microscopic detection, but above the detectable limit of varATS qPCR. Conclusions This assessment of parasitaemia and gametocytaemia in three communities with different transmission intensities revealed evidence of a substantial sub-patent infectious reservoir among asymptomatic carriers of P. falciparum. Experimental studies are needed to definitively determine whether the low-density infections in communities such as Ajigo and Webuye contribute significantly to malaria transmission.

scholarly journals Iodine status in western Kenya: a community-based cross-sectional survey of urinary and drinking water iodine concentrations

2019 ◽  
Vol 42 (4) ◽  
pp. 1141-1151 ◽  
Author(s):  
Michael J. Watts ◽  
Daniel R. S. Middleton ◽  
Andrew Marriott ◽  
Olivier S. Humphrey ◽  
Elliott Hamilton ◽  
...  
Keyword(s):  
Drinking Water ◽  
Cross Sectional Survey ◽  
Community Based ◽  
Cross Sectional ◽  
Western Kenya ◽  
Iodine Status

scholarly journals Plasmodium falciparum increases its investment in gametocytes in the wet season in asymptomatic individuals

2020 ◽  
Author(s):  
Colins O. Oduma ◽  
Sidney Ogolla ◽  
Harrysone Atieli ◽  
Bartholomew N. Ondigo ◽  
Ming-Chieh Lee ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Malaria Transmission ◽  
Parasite Prevalence ◽  
Dry Season ◽  
Wet Season ◽  
Western Kenya ◽  
Gametocyte Carriage ◽  
Vector Abundance ◽  
Asymptomatic Individuals

AbstractIn many regions, malaria transmission is seasonal, but it is not well understood whether P. falciparum modulates its investment in transmission in response to seasonal vector abundance. In two sites in western Kenya (Chulaimbo and Homa Bay), we sampled 1116 asymptomatic individuals in the wet season, when vectors are abundant, and 1743 in the dry season. We screened for P. falciparum by qPCR, and gametocytes by pfs25 RT-qPCR. Parasite prevalence in Chulaimbo and Homa Bay was 27.1% and 9.4% in the dry season, and 48.2% and 7.8% in the wet season respectively. Mean parasite densities did not differ between seasons (P=0.562). A contrasting pattern of gametocyte carriage was observed. In the wet season, fewer infections harbored gametocytes (22.3% vs. 33.8%, P=0.009), but densities were 3-fold higher (P<0.001). Thus, in the wet season, among gametocyte positive individuals, higher proportion of all parasites were gametocytes, reflecting an increased investment in transmission.

scholarly journals Long-distance transmission patterns modelled from SNP barcodes of Plasmodium falciparum infections in The Gambia

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Alfred Amambua-Ngwa ◽  
David Jeffries ◽  
Julia Mwesigwa ◽  
Aminata Seedy-Jawara ◽  
Joseph Okebe ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Malaria Transmission ◽  
Genetic Relatedness ◽  
Malaria Prevalence ◽  
The Gambia ◽  
Long Distance ◽  
Travel History ◽  
Transmission Season ◽  
Malaria Transmission Season ◽  
Likelihood Model

Abstract Malaria has declined significantly in The Gambia and determining transmission dynamics of Plasmodium falciparum can help targeting control interventions towards elimination. This can be inferred from genetic similarity between parasite isolates from different sites and timepoints. Here, we imposed a P. falciparum life cycle time on a genetic distance likelihood model to determine transmission paths from a 54 SNP barcode of 355 isolates. Samples were collected monthly during the 2013 malaria season from six pairs of villages spanning 300 km from western to eastern Gambia. There was spatial and temporal hierarchy in pairwise genetic relatedness, with the most similar barcodes from isolates within the same households and village. Constrained by travel data, the model detected 60 directional transmission events, with 27% paths linking persons from different regions. We identified 13 infected individuals (4.2% of those genotyped) responsible for 2 to 8 subsequent infections within their communities. These super-infectors were mostly from high transmission villages. When considering paths between isolates from the most distant regions (west vs east) and travel history, there were 3 transmission paths from eastern to western Gambia, all at the peak (October) of the malaria transmission season. No paths with known travel originated from the extreme west to east. Although more than half of all paths were within-village, parasite flow from east to west may contribute to maintain transmission in western Gambia, where malaria transmission is already low. Therefore, interrupting malaria transmission in western Gambia would require targeting eastern Gambia, where malaria prevalence is substantially higher, with intensified malaria interventions.

scholarly journals The prevalence and density of asymptomatic Plasmodium falciparum infections among children and adults in three communities of western Kenya

2021 ◽  
Author(s):  
Christina Salgado ◽  
George Ayodo ◽  
Michael D. Macklin ◽  
Meetha P. Gould ◽  
Srinivas Nallandhighal ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
Malaria Transmission ◽  
Malaria Incidence ◽  
Experimental Studies ◽  
Low Density ◽  
Healthy Children ◽  
Cross Sectional Survey ◽  
Western Kenya ◽  
Transcriptional Pattern ◽  
Asymptomatic Infections

Background: Further reductions in malaria incidence as more countries approach malaria elimination require the identification and treatment of asymptomatic individuals who carry mosquito-infective Plasmodium gametocytes that are responsible for furthering malaria transmission. Assessing the relationship between total parasitemia and gametocytemia in field surveys can provide insight as to whether detection of low-density, asymptomatic Plasmodium falciparum infections using sensitive molecular methods can sufficiently detect the majority of infected individuals who are potentially capable of onward transmission. Methods: In a cross-sectional survey of 1,354 healthy children and adults in three communities in western Kenya across a gradient of malaria transmission (Ajigo, Webuye, and Kapsisywa-Kipsamoite), we screened for asymptomatic P. falciparum infections by rapid diagnostic tests, blood smear, and quantitative PCR of dried blood spots targeting the varATS gene in genomic DNA. A multiplex quantitative reverse-transcriptase PCR assay targeting female and male gametocyte genes (pfs25, pfs230p), a gene with a transcriptional pattern restricted to asexual blood-stages (piesp2), and human GAPDH was also developed to determine total parasite and gametocyte densities among parasitemic individuals. Results: The prevalence of varATS-detectable asymptomatic infections was greatest in Ajigo (42%), followed by Webuye (10%). Only two infections were detected in Kapsisywa. No infections were detected in Kipsamoite. Across all communities, children aged 11-15 years account for the greatest proportion total and sub-microscopic asymptomatic infections. In younger age groups, the majority of infections were detectable by microscopy, while 68% of asymptomatically infected adults (>21 years old) had sub-microscopic parasitemia. Piesp2-derived parasite densities correlated poorly with microscopy-determined parasite densities in patent infections relative to varATS-based detection. In general, both male and female gametocytemia increased with increasing varATS-derived total parasitemia. A substantial proportion (41.7%) of individuals with potential for onward transmission had qPCR-estimated parasite densities below the limit of microscopic detection but above the detectable limit of varATS qPCR. Conclusions: This assessment of parasitemia and gametocytemia in three communities with different transmission intensities revealed evidence of a substantial sub-patent infectious reservoir among asymptomatic carriers of P. falciparum. Experimental studies are needed to definitively determine whether the low-density infections in communities such as Ajigo and Webuye contribute significantly to malaria transmission.

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