17 results on '"Estelle Essangui"'
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2. Chemical composition and repellent activity of essential oils of Tithonia diversifolia (Asteraceae) leaves against the bites of Anopheles coluzzii
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Cédric Akeumbiwo Tchumkam, Loick Pradel Kojom Foko, Cyrille Ndo, Estelle Essangui Same, Glwadys Cheteug Nguetsa, François Eya’Ane Meva, Lawrence Ayong, and Carole Else Eboumbou Moukoko
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Medicine ,Science - Abstract
Abstract Tithonia diversifolia is widely used in African traditional medicine for the treatment of a large number of ailments and disorders, including malaria. In the present study, we evaluated the repellent activity of essential oils (EO) of this plant against Anopheles coluzzii, a major vector of malaria in Africa. Fresh leaves of T. diversifolia were used to extract EO, which were used to perform repellency assays in the laboratory and in the field using commercially available N,N-Diethyl-meta-toluamide (DEET) and Cymbopogon (C.) citratus EO as positive controls and vaseline as negative control. The repellency rates and durations of protection of the human volunteers involved were used as measures of repellent activity. Chemical composition of the T. diversifolia EO was established further by gas chromatography coupled with mass spectrometry. The moisture content and oil yield were 81% and 0.02% respectively. A total of 29 compounds in the T. diversifolia EO was identified, with d-limonene (20.1%), α-Copaene (10.3%) and o-Cymene (10.0%) as the most represented. In field studies, the mean time of protection against mosquito bites was significantly lower in T. diversifolia EO-treated volunteers compared to treatments with C. citratus EO (71 min versus 125 min, p = 0.04), but significantly higher when compared with the non-treated volunteers (71 min vs 0.5 min, p = 0.03). The same pattern was found in laboratory repellency assays against A. coluzzii. In contrast, repulsion rates were statistically similar between T. diversifolia EO and positive controls. In conclusion, the study suggests promising repellent potential of leaves of T. diversifolia EO against A. coluzzii.
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- 2023
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3. Diagnosis of malaria in pregnancy: accuracy of CareStart™ malaria Pf/PAN against light microscopy among symptomatic pregnant women at the Central Hospital in Yaoundé, Cameroon
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Cliford Ebontane Ebong, Innocent Mbulli Ali, Hortence Jeanne Fouedjio, Estelle Essangui, Dorothy Fosah Achu, Ayong Lawrence, and Dohbit Sama
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Malaria ,Pregnancy ,CareStart pf/PAN RDT ,Sensitivity ,Yaoundé ,Plasmodium falciparum ,Arctic medicine. Tropical medicine ,RC955-962 ,Infectious and parasitic diseases ,RC109-216 - Abstract
Abstract Background The need to start treatment early for pregnant women who present with clinical features of malaria usually conflicts with the need to confirm diagnosis by microscopy (MP) before treatment, due to delays in obtaining results. Parasite sequestration in the placenta is also a problem. Rapid diagnostic tests (RDT), which detect soluble antigens, are a valuable alternative. The objective of this study was to evaluate pretreatment parasite prevalence by microscopy and by RDT and to assess the accuracy of RDT with MP as reference. Methods A prospective cross-sectional study was carried out at the obstetrical unit of the Central Hospital in Yaoundé, during the period January-August 2015. Consenting patients with symptoms of suspected malaria in pregnancy were recruited and a blood sample taken for MP and RDT before treatment was started. The estimates of diagnostic performance (with 95% confidence interval) were calculated in OpenEpi online software using the Wilson’s score. The agreement, as reflected by the Cohen’s kappa, was calculated and interpreted using known intervals. Results The results showed that, out of the 104 patients recruited, 69.2% (95%CI: 59.1–77.5) were MP positive while 77.94% (95%CI: 63.1–80.9) were RDT positive. The sensitivity of the malaria RDT was 91.67% (95%CI: 83.69–96.77) while the specificity was 53.13% (95%CI: 31.39–65.57). The diagnostic accuracy of the RDT with MP as reference was 79.81% (95%CI: 70.0–86.1). All cases were due to Plasmodium falciparum. A Cohen’s kappa of 0.45 (95%CI: 0.26–0.64) was obtained, consistent with a moderate agreement between the tests. Conclusions The diagnostic accuracy of the CareStart™ malaria Pf/PAN compared to microscopy was high, but not as desirable, with a false negative RDT at very high parasitaemia. In tertiary facilities, RDTs appear to provide a better diagnostic solution compared to microscopy. However, future studies with larger sample sizes should make this observation more generalizable; as missing a case could have serious consequences on pregnancy outcome.
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- 2022
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4. Chemokine modulation in microscopic and submicroscopic Plasmodium falciparum malaria infection in women at delivery in Yaoundé, Cameroon.
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Rosette Megnekou, Chris Marco Mbianda Nana, Jean Claude Djontu, Bernard Marie Zambo Bitye, Benderli Christine Nana, Berenice Kenfack Tekougang Zangue, Christiane Josiane Donkeu, Estelle Essangui, Rodrigue Mbea Salawiss, Reine Ndeumou Medouen Seumko'o, Lawrence Ayong, and Rose Gana Fomban Leke
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Medicine ,Science - Abstract
In pregnancy-associated malaria, chemokines such as CXCL-4, CXCL-13, CXCL-16, and CCL-24 play critical roles in leucocyte trafficking to tissue sites in the infected placenta where inflammatory reactions are active. However, how plasma levels of these chemokines associate with Plasmodium falciparum placental malaria and pregnancy outcomes remains not well understood. The present study analyzed the plasma levels of CXCL-4, CXCL-13, CXCL-16, and CCL-24 chemokines in matched peripheral, placental and cord blood in relation with placental malaria (PM), and with submicroscopic parasitaemia. This was a retrospective case-control study (1:3 ratio) involving samples from 134 women (34 PM+ and 100 PM-) enrolled at delivery at the Marie Reine Health Center in Yaoundé, Cameroon between June 2013 and October 2018. Samples were collected just after delivery and used to diagnose microscopic and submicroscopic Plasmodium falciparum infections. Submicroscopic infections were detected by reverse transcription LAMP whereas chemokine levels were determined by Magnetic Luminex Screening Assay. Overall, PM was associated with increased plasma levels of CXCL-13 and CXCL-16 and low levels of CXCL-4 and CCL-24 in both peripheral and placental blood (0.0002 ≤ p ≤ 0.042). Similarly, CCL-24 levels in peripheral and placental blood samples were significantly lower in submicroscopically infected women compared to healthy controls (p = 0.04 and 0.02, respectively). Maternal hemoglobin levels increased with peripheral plasma levels of CXCL-4 (p = 0.005), CXCL-16 (p = 0.03), and CCL-24 (p = 0.002) while birth weight was lower for babies born from women with high levels of peripheral CXCL-13 (p = 0.0006) and low levels of cord CXCL-4 and CCL-24 (p = 0.02 and 0.08, respectively). Together the data suggest that low levels of CXCL-4 and CCL-24 coupled with high plasma levels of CXCL-13 and for a lesser extend CXCL-16 represent signatures of PM in the study population. These findings are relevant for understanding the immunopathogenesis of PM and developing new therapeutic or preventive strategies against severe PM outcomes.
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- 2023
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5. High Prevalence of Polyclonal Plasmodium falciparum Infections and Association with Poor IgG Antibody Responses in a Hyper-Endemic Area in Cameroon
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Marie Florence A Bite Biabi, Balotin Fogang, Estelle Essangui, Franklin Maloba, Christiane Donkeu, Rodrigue Keumoe, Glwadys Cheteug, Nina Magoudjou, Celine Slam, Sylvie Kemleu, Noella Efange, Ronald Perraut, Sandrine Eveline Nsango, Carole Else Eboumbou Moukoko, Jean Paul Assam Assam, François-Xavier Etoa, Tracey Lamb, and Lawrence Ayong
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Plasmodium falciparum ,polyclonal infection ,adaptive immune responses ,Medicine - Abstract
Malaria remains a major public health problem worldwide, with eradication efforts thwarted by drug and insecticide resistance and the lack of a broadly effective malaria vaccine. In continuously exposed communities, polyclonal infections are thought to reduce the risk of severe disease and promote the establishment of asymptomatic infections. We sought to investigate the relationship between the complexity of P. falciparum infection and underlying host adaptive immune responses in an area with a high prevalence of asymptomatic parasitaemia in Cameroon. A cross-sectional study of 353 individuals aged 2 to 86 years (median age = 16 years) was conducted in five villages in the Centre Region of Cameroon. Plasmodium falciparum infection was detected by multiplex nested PCR in 316 samples, of which 278 were successfully genotyped. Of these, 60.1% (167/278) were polyclonal infections, the majority (80.2%) of which were from asymptomatic carriers. Host-parasite factors associated with polyclonal infection in the study population included peripheral blood parasite density, participant age and village of residence. The number of parasite clones per infected sample increased significantly with parasite density (r = 0.3912, p < 0.0001) but decreased with participant age (r = −0.4860, p < 0.0001). Parasitaemia and the number of clones per sample correlated negatively with total plasma levels of IgG antibodies to three highly reactive P. falciparum antigens (MSP-1p19, MSP-3 and EBA175) and two soluble antigen extracts (merozoite and mixed stage antigens). Surprisingly, we observed no association between the frequency of polyclonal infection and susceptibility to clinical disease as assessed by the recent occurrence of malarial symptoms or duration since the previous fever episode. Overall, the data indicate that in areas with the high perennial transmission of P. falciparum, parasite polyclonality is dependent on underlying host antibody responses, with the majority of polyclonal infections occurring in persons with low levels of protective anti-plasmodial antibodies.
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- 2023
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6. Diagnostic performance of a rapid whole blood-based RT-LAMP method for malaria diagnosis among apparently healthy blood donors and febrile neonates in Cameroon.
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Sylvie Georgette Zebaze Temgoua Kemleu, Laure Ngando, Elvige Nguekeng, Balotin Fogang, Marie Mafo Kapen, Styve Iruch Fopa, Marie Florence Biabi, Estelle Essangui, Jules Clement Assob Nguedia, and Lawrence Ayong
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Medicine ,Science - Abstract
Light microscopy and rapid diagnostic tests are the two commonly used methods for malaria diagnosis that rely on the direct use of unprocessed blood samples. However, both methods do not have the level of sensitivity required for malaria diagnosis in cases of low density parasitaemia. We report here the diagnostic performance of a whole blood-based reverse transcription loop-mediated isothermal amplification method for Plasmodium falciparum malaria diagnosis in apparently healthy blood donors and febrile neonates in Cameroon. The presence of malaria parasites in whole blood samples was determined by light microscopy, antigen-based rapid diagnostic test (RDT), and by RT-LAMP using a "lyse and amplify" experimental protocol. Of the 256 blood donors tested, 36 (14.1%) were positive for malaria parasites by light microscopy, 38 (14.8%) were positive by RDT whereas 78 (30.5%) were positive by RT-LAMP. Only light microscopy and RT-LAMP detected infection among the febrile neonates (279 neonates, median age: 2 days, range: 1-9 days), with positivity rates of 8.6% and 12.2%, respectively. The overall concordance between the three methods were 75.9% for RT-LAMP and light microscopy, 75.1% for RT-LAMP and RDT, and 83.9% for light microscopy and RDT. Blood parasite densities were significantly lower in the neonates (mean: 97.6, range: 61-192 parasites/μL) compared to the blood donors (mean: 447.8, range: 63-11 000 parasites/μL). Together, the study demonstrates the usefulness of whole blood RT-LAMP for use in rapid pre-screening of blood donors and suspected neonates to avert severe consequences of P. falciparum infections.
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- 2021
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7. Preliminary validation of the use of IgG antibody response to Anopheles gSG6-p1 salivary peptide to assess human exposure to malaria vector bites in two endemic areas of Cameroon in Central Africa.
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Glwadys Cheteug, Emmanuel Elanga-Ndille, Christiane Donkeu, Wolfgang Ekoko, Martine Oloume, Estelle Essangui, Philippe Nwane, Sandrine Eveline NSango, Josiane Etang, Samuel Wanji, Lawrence Ayong, and Carole Else Eboumbou Moukoko
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Medicine ,Science - Abstract
The specific immune response to the Anopheles salivary peptide could be a pertinent and complementary tool to assess the risk of malaria transmission and the effectiveness of vector control strategies. This study aimed to obtain first reliable data on the current state of the Anopheles gSG6-P1 biomarker for assess the level of exposure to Anopheles bites in high malaria endemic areas in Cameroon. Blood smears were collected from people living in the neighborhoods of Youpwe (suburban area, continental) and Manoka (rural area, Island), both areas in the coastal region of Cameroon. Malaria infection was determined using thick blood smear microscopy, whereas the level of specific IgG response to gSG-P1 peptide was assessed by enzyme-linked immunosorbent assay from the dried blood spots. Of 266 (153 from Youpwe, 113 from Manoka) malaria endemic residents (mean age: 22.8±19.8 years, age range: 6 months-94 years, male/female sex ratio: 1/1.2, with Manoka mean age: 23.71±20.53, male/female sex ratio:1/1.13 and Youpwe mean age: 22.12±19.22, male/female sex ratio 1/0.67) randomly included in the study, Plasmodium infection prevalence was significantly higher in Manoka than in Youpwe (64.6% vs 12,4%, p = 0.0001). The anti-gSG6-P1 IgG response showed a high inter-individual heterogeneity and was significantly higher among individuals from Manoka than those from Youpwe (p = 0.023). Malaria infected individuals presented a higher anti-gSG6-P1 IgG antibody response than non-infected (p = 0.0004). No significant difference in the level of specific IgG response to gSG-P1 was observed according to long lasting insecticidal nets use. Taken together, the data revealed that human IgG antibody response to Anopheles gSG-P1 salivary peptide could be also used to assess human exposure to malaria vectors in Central African region. This finding strengthens the relevance of this candidate biomarker to be used for measuring human exposure to malaria vectors worldwide.
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- 2020
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8. Demographical, hematological and serological risk factors for Plasmodium falciparum gametocyte carriage in a high stable transmission zone in Cameroon.
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Estelle Essangui, Carole Else Eboumbou Moukoko, Niels Nguedia, Michele Tchokwansi, Umaru Banlanjo, Franklin Maloba, Balotin Fogang, Christiane Donkeu, Marie Biabi, Glwadys Cheteug, Sylvie Kemleu, Emmanuel Elanga-Ndille, Léopold Lehman, and Lawrence Ayong
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Medicine ,Science - Abstract
Presence of mature gametocyte forms of malaria parasites in peripheral blood is a key requirement for malaria transmission. Yet, studies conducted in most malaria transmission zones report the absence of gametocyte in the majority of patients. We therefore sought to determine the risk factors of both all-stage and mature gametocyte carriage in an area with high stable transmission of Plasmodium falciparum in Cameroon. Gametocyte positivity was determined using three complementary methods: thick blood smear microscopy, RT-PCR and RT-LAMP, whereas exposure to the infection was assessed by enzyme-linked immunosorbent assay. Of 361 malaria endemic residents randomly included in the study (mean age: 28±23 years, age range: 2-100 years, male/female sex ratio: 1.1), 87.8% were diagnosed with P. falciparum infection, of whom 45.7% presented with fever (axillary body temperature ≥37.5°C). Mature gametocyte positivity was 1.9% by thick blood smear microscopy and 8.9% by RT-PCR targeting the mature gametocyte transcript, Pfs25. The gametocyte positivity rate was 24.1% and 36.3% by RT-PCR or RT-LAMP, respectively, when targeting the sexual stage marker, Pfs16. Multivariate analyses revealed anemia as a common independent risk factor for both mature and all-stage gametocyte carriage, whereas fever and low anti-gametocyte antibody levels were independently associated with all-stage gametocyte carriage only. Taken together, the data suggest important differences in risk factors of gametocyte carriage depending on stage analyzed, with anemia, fever and low antiplasmodial plasma antibody levels representing the major contributing risk factors.
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- 2019
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9. A Field-Tailored Reverse Transcription Loop-Mediated Isothermal Assay for High Sensitivity Detection of Plasmodium falciparum Infections.
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Sylvie Kemleu, Dylan Guelig, Carole Eboumbou Moukoko, Estelle Essangui, Steven Diesburg, Abas Mouliom, Bernard Melingui, Jeanne Manga, Christiane Donkeu, Annie Epote, Gaëtan Texier, Paul LaBarre, Robert Burton, and Lawrence Ayong
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Medicine ,Science - Abstract
Highly sensitive and field deployable molecular diagnostic tools are critically needed for detecting submicroscopic, yet transmissible levels of malaria parasites prevalent in malaria endemic countries worldwide. A reverse transcription loop-mediated isothermal amplification (RT-LAMP) assay was developed and evaluated in comparison with thick blood smear microscopy, an antigen-based rapid diagnostic test (RDT), and an in-house RT-PCR targeting the same RT-LAMP transcript. The optimized assay detected Plasmodium falciparum infections in as little as 0.25ng of total parasite RNA, and exhibited a detection limit of 0.08 parasites/ μL when tested directly on infected whole blood lysates, or ~0.0008 parasites/ μL when using RNA extracts. Assay positivity was observed as early as eight minutes from initiation of the RT-LAMP and in most cases the reaction was complete before twenty minutes. Clinical evaluation of the assay on 132 suspected malaria cases resulted in a positivity rate of 90% for RT-LAMP using extracted RNA, and 85% when using whole blood lysates. The positivity rates were 70% for P. falciparum-specific RDT, 83% for RT-PCR, and 74% for thick blood smear microscopy (Mean parasite density = 36,986 parasites/ μL). Concordance rates between the developed RT-LAMP and comparator tests were greater than 75%, the lowest being with light microscopy (78%, McNemar's test: P = 0.0002), and the highest was with RT-PCR (87%, McNemar's test: P = 0.0523). Compared to reference RT-PCR, assay sensitivity was 90% for RT-LAMP on whole blood, and 96% for RT-LAMP using corresponding RNA extracts. Electricity-free heaters were further developed and evaluated in comparison with a battery-operated isothermal amplification machine for use with the developed test in resource-limited settings. Taken together, the data highlight the benefits of targeting high abundant RNA transcripts in molecular diagnosis, as well as the potential usefulness of the developed RT-LAMP-assay in malaria diagnosis in low to high parasite density settings.
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- 2016
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10. Enteric Parasitosis of HIV-positive Patients in Cameroon: A Case of the Regional Hospital of Bafoussam (Western Region)
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Léopold Gustave Lehman, Alex Kevin Tako Djimefo, Estelle Essangui, Michel Lontsi-Demano, Désiré Leonard Keptcheu Tchankwé, Christian Mbohou Nchetnkou, Jacques Nack, and Roméo Tankoua-Tchounda
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General Medicine - Abstract
Objectives: The Human Immunodeficiency Virus (HIV) causes a progressive alteration of the immune system leading to increased susceptibility to infectious agents. A few studies have been done on gastrointestinal parasites in HIV-infected persons in Cameroon. However, these studies need to be updated. The objective of this study was to identify and determine the prevalence of gastrointestinal parasites in relation to associated factors in HIV+ patients at the Bafoussam Regional Hospital. Methods: The study was conducted from May to December 2021 on 240 patients aged from 3 to 73 years. Stool samples were tested for parasites and HIV viral loads were assessed in blood samples. Results: The analyses revealed that 58 (24.2%) patients were carriers of at least one parasite species. A total of 7 parasite species were identified, the most predominant being Entameba histolytica (12.62%) followed by Cryptosporidium spp (4.54%). A high majority, 91.3% had undetectable viral loads with the presence of intestinal parasitosis. However, the most infested patients were those with viral loads above 50 copies/ml. Concerning the duration of antiretroviral treatment, the rate of infestation was higher in patients with less than 12 months on treatment (OR=2.8; p=0.04). The prevalence of infestation was significantly higher in those under 20 years of age (OR = 5.13; p = 0.03). The distribution of gastrointestinal parasite species according to viral loads varied significantly for Blastocystis hominis and Dicrocoelum dendriticum with p
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- 2022
11. High Prevalence of Polyclonal Plasmodium falciparum Infections and Association with Low Adaptive Immune Responses in a Hyper-Endemic Area in Cameroon
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Marie Florence A Bite Biabi, Balotin Fogang, Estelle Essangui, Franklin Maloba, Christiane Donkeu, Rodrigue Keumoe, Glwadys Cheteug, Nina Magoudjou, Celine Slam, Sylvie Kemleu, Noella Efange, Ronald Perraut, Sandrine Eveline Nsango, Carole Else Eboumbou Moukoko, Assam A. Jean-Paul, Xavier François ETOA, Tracey J Lamb, and Lawrence Ayong
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Malaria remains a major public health problem worldwide, with eradication efforts thwarted by drug and insecticide resistance and the lack of a broadly effective malaria vaccine. In continuously exposed communities, polyclonal infections are thought to reduce the risk of severe disease and promote the establishment of asymptomatic infections. We sought to investigate the relationship between the complexity of P. falciparum infection and underlying host adaptive immune responses in an area with high prevalence of asymptomatic parasitaemia in Cameroon. A cross-sectional study of 353 individuals aged 2 to 86 years (median age = 16 years) was conducted in five villages in the Centre Region of Cameroon. Plasmodium falciparum infection was detected by multiplex nested PCR in 316 samples, of which 278 were successfully genotyped. Of these, 60.1% (167/278) were polyclonal infections, the majority (80.2%) of which were from asymptomatic carriers. Host-parasite factors associated with polyclonal infection in the study population included peripheral blood parasite density, participant age and village of residence. The number of parasite clones per infected sample increased significantly with parasite density (r = 0.3912, p
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- 2023
12. High Prevalence of Asymptomatic Malarial Anemia and Association with Early Conversion from Asymptomatic to Symptomatic Infection in a Plasmodium falciparum Hyperendemic Setting in Cameroon
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Estelle Essangui, Rodrigue Keumoe, Glwadys Cheteug, Carole Eboumbou, Christiane Donkeu, Tracey J. Lamb, Rosette Megnekou, Sylvie Kemleu, Franklin M Maloba, Balotin Fogang, Sandrine E. Nsango, Marie Mafo Kapen, Lawrence Ayong, and Marie Fslorence Biabi
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Male ,medicine.medical_specialty ,Adolescent ,Endemic Diseases ,Anemia ,Population ,Parasitemia ,Asymptomatic ,Article ,Virology ,Internal medicine ,parasitic diseases ,Prevalence ,Humans ,Medicine ,Cameroon ,Malaria, Falciparum ,Child ,education ,education.field_of_study ,biology ,business.industry ,Plasmodium falciparum ,medicine.disease ,biology.organism_classification ,Infectious Diseases ,Child, Preschool ,Asymptomatic Diseases ,Population study ,Female ,Parasitology ,medicine.symptom ,business ,Asymptomatic carrier ,Malaria - Abstract
Asymptomatic malarial parasitemia is highly prevalent in Plasmodium falciparum endemic areas and often associated with increased prevalence of mild to moderate anemia. The aim of this study was to assess the prevalence of anemia during asymptomatic malaria parasitemia and its interplay with persistent infection in highly exposed individuals. A household-based longitudinal survey was undertaken in a malaria hyperendemic area in Cameroon using multiplex nested polymerase chain reaction to detect plasmodial infections. Residents with P. falciparum asymptomatic parasitemia were monitored over a 3-week period with the aid of structured questionnaires and weekly measurements of axillary temperatures. Of the 353 individuals included (median age: 26 years, range 2–86 years, male/female sex ratio 0.9), 328 (92.9%) were positive for malaria parasitemia of whom 266 (81.1%) were asymptomatic carriers. The prevalence of anemia in the study population was 38.6%, of which 69.2% were asymptomatic. Multivariate analyses identified high parasitemia (> 327 parasites/µL) and female gender as associated risk factors of asymptomatic malarial anemia in the population. Furthermore, risk analyses revealed female gender and anemia at the time of enrolment as key predictors of early development of febrile illness (< 3 weeks post enrolment) among the asymptomatic individuals. Together, the data reveal an extremely high prevalence of asymptomatic malaria parasitemia and anemia in the study area, unveiling for the first time the association of asymptomatic malarial anemia with early clinical conversion from asymptomatic to symptomatic infection. Furthermore, these findings underscore the negative impact of asymptomatic malaria parasitemia on individual health, necessitating the development of appropriate control and preventive measures.
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- 2022
13. Asymptomatic carriage of Plasmodium falciparum in children living a hyperendemic area occurs independently of IgG responses but is associated with induction of IL-10
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Balotin Fogang, Mathieu Schoenhals, Franklin Maloba, Marie Florence Abite, Estelle Essangui, Christiane Donkeu, Glwadys Cheteug, Marie Kapen, Rodrigue Keumoe, Sylvie Kemleu, Ronald Perraut, Rosette Megnekou, Tracey Lamb, and Lawrence Ayong
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BackgroundMalaria immuno-epidemiological data suggest that two key immunological processes, including anti-parasite and anti-disease immunity, may be implicated in the maintenance of asymptomatic infections. However, in highly exposed persons where the duration of chronic malaria infection could range from a few weeks to several years, the host immunological factors that determine the persistence of asymptomatic parasitemia remain poorly understood. This study therefore aimed to define the association between antibody or cytokine responses with asymptomatic malarial parasitemia amongst highly exposed individuals in Cameroon.MethodsAn initial cross-sectional study was carried out (week 1) and individuals were classified as having asymptomatic Plasmodium parasitemia with no fever (AS), symptomatic Plasmodium parasitemia with an axillary temperature ≥37.5°C (SY) and non-infected (NI) (no Plasmodium parasitemhia and a normal body temperature). Asymptomatic individuals were followed for 10 weeks before being treated with artemisinin-based combination treatment (ACT) and a final sample taken at week 16, 5 weeks after treatment. Those who continued to carry Plasmodium parasites with no measureable fever were defined as having chronic asymptomatic malaria. Antibody levels to P. falciparum schizont extract (SE), merozoite extract (ME), erythrocyte binding antigen-175 (EBA-175) and merozoite surface protein-1 (MSP-1) were quantified by ELISA. The growth inhibitory activities of circulating anti-parasite antibodies were quantified using the 3D7 laboratory strain of P. falciparum and a Sybr Green-I based parasite growth inhibition assay. Plasma levels of 38 cytokines were measured by Luminex technology.ResultsAmongst infected individuals, parasitemia significantly decreased with increased age although this decrease in parasitemia with age was only observed until age 20. Individuals older than 20 years of age had low parasitemia and this remained constant between the ages of 20 and 80. Although there was no difference in the magnitude of the antibody response between AS, SY and NI groups to any of the antigens tested, median levels of antibody against P. falciparum crude extracts and recombinant proteins EBA-175 and MSP-1 were significantly higher in those older than 20 years of age compared with the younger age group as might be expected from lower parasite levels. Parasite densities and P. falciparum clones fluctuated widely over the 10-week follow-up period in individuals with persistent asymptomatic parasitemia but collectively there was no change in the antibody levels over time within this group. Similar to antibody levels, many levels of the cytokines measured were stable over time. However, IL-10 levels decreased after treatment indicating that this cytokine was associated with parasite carriage in asymptomatic individuals. The ratio of IL-10 to pro-inflammatory cytokines, tumor necrosis factor-α (TNF-α) and lymphotoxin-α (LT-α) ratios were higher in the symptomatic group compared to the asymptomatic individuals but only in the younger (ConclusionTaken together, the above findings indicate that asymptomatic carriage of Plasmodium falciparum in children living in a hyperendemic area occurs independently of antibody responses, but is associated with induction of IL-10.
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- 2022
14. Diagnosis of malaria in pregnancy: accuracy of CareStart™ malaria Pf/PAN against light microscopy among symptomatic pregnant women at the Central Hospital in Yaoundé, Cameroon
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Cliford Ebontane Ebong, Innocent Mbulli Ali, Hortence Jeanne Fouedjio, Estelle Essangui, Dorothy Fosah Achu, Ayong Lawrence, and Dohbit Sama
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Microscopy ,Diagnostic Tests, Routine ,Plasmodium falciparum ,Sensitivity and Specificity ,Hospitals ,Malaria ,Infectious Diseases ,Cross-Sectional Studies ,Pregnancy ,parasitic diseases ,Humans ,Parasitology ,Female ,Cameroon ,Pregnant Women ,Prospective Studies ,Malaria, Falciparum - Abstract
Background The need to start treatment early for pregnant women who present with clinical features of malaria usually conflicts with the need to confirm diagnosis by microscopy (MP) before treatment, due to delays in obtaining results. Parasite sequestration in the placenta is also a problem. Rapid diagnostic tests (RDT), which detect soluble antigens, are a valuable alternative. The objective of this study was to evaluate pretreatment parasite prevalence by microscopy and by RDT and to assess the accuracy of RDT with MP as reference. Methods A prospective cross-sectional study was carried out at the obstetrical unit of the Central Hospital in Yaoundé, during the period January-August 2015. Consenting patients with symptoms of suspected malaria in pregnancy were recruited and a blood sample taken for MP and RDT before treatment was started. The estimates of diagnostic performance (with 95% confidence interval) were calculated in OpenEpi online software using the Wilson’s score. The agreement, as reflected by the Cohen’s kappa, was calculated and interpreted using known intervals. Results The results showed that, out of the 104 patients recruited, 69.2% (95%CI: 59.1–77.5) were MP positive while 77.94% (95%CI: 63.1–80.9) were RDT positive. The sensitivity of the malaria RDT was 91.67% (95%CI: 83.69–96.77) while the specificity was 53.13% (95%CI: 31.39–65.57). The diagnostic accuracy of the RDT with MP as reference was 79.81% (95%CI: 70.0–86.1). All cases were due to Plasmodium falciparum. A Cohen’s kappa of 0.45 (95%CI: 0.26–0.64) was obtained, consistent with a moderate agreement between the tests. Conclusions The diagnostic accuracy of the CareStart™ malaria Pf/PAN compared to microscopy was high, but not as desirable, with a false negative RDT at very high parasitaemia. In tertiary facilities, RDTs appear to provide a better diagnostic solution compared to microscopy. However, future studies with larger sample sizes should make this observation more generalizable; as missing a case could have serious consequences on pregnancy outcome.
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- 2021
15. Diagnostic performance of a rapid whole blood-based RT-LAMP method for malaria diagnosis among apparently healthy blood donors and febrile neonates in Cameroon
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Marie Florence Biabi, Elvige Nguekeng, Marie Mafo Kapen, Styve Iruch Fopa, Sylvie Kemleu, Laure Ngando, Balotin Fogang, Lawrence Ayong, Jules Clement Assob Nguedia, and Estelle Essangui
- Subjects
Male ,Plasmodium ,Physiology ,Blood Donors ,Gastroenterology ,Medical Conditions ,Medicine and Health Sciences ,Medicine ,Cameroon ,Malaria, Falciparum ,Whole blood ,Protozoans ,Microscopy ,Rapid diagnostic test ,Multidisciplinary ,biology ,Malarial Parasites ,Eukaryota ,Light Microscopy ,Hematology ,Clinical Laboratory Sciences ,Body Fluids ,Blood ,Molecular Diagnostic Techniques ,Female ,Anatomy ,Nucleic Acid Amplification Techniques ,Research Article ,Adult ,medicine.medical_specialty ,Science ,Concordance ,Plasmodium falciparum ,Loop-mediated isothermal amplification ,Research and Analysis Methods ,Antigen ,Diagnostic Medicine ,Internal medicine ,Parasite Groups ,parasitic diseases ,Parasitic Diseases ,Humans ,Blood Transfusion ,Transfusion Medicine ,business.industry ,Organisms ,Infant, Newborn ,Biology and Life Sciences ,Nucleic acid amplification technique ,Tropical Diseases ,medicine.disease ,biology.organism_classification ,Parasitic Protozoans ,Malaria ,Health Care ,Cross-Sectional Studies ,Parasitology ,business ,Apicomplexa - Abstract
Light microscopy and rapid diagnostic tests are the two commonly used methods for malaria diagnosis that rely on the direct use of unprocessed blood samples. However, both methods do not have the level of sensitivity required for malaria diagnosis in cases of low density parasitaemia. We report here the diagnostic performance of a whole blood-based reverse transcription loop-mediated isothermal amplification method for Plasmodium falciparum malaria diagnosis in apparently healthy blood donors and febrile neonates in Cameroon. The presence of malaria parasites in whole blood samples was determined by light microscopy, antigen-based rapid diagnostic test (RDT), and by RT-LAMP using a “lyse and amplify” experimental protocol. Of the 256 blood donors tested, 36 (14.1%) were positive for malaria parasites by light microscopy, 38 (14.8%) were positive by RDT whereas 78 (30.5%) were positive by RT-LAMP. Only light microscopy and RT-LAMP detected infection among the febrile neonates (279 neonates, median age: 2 days, range: 1–9 days), with positivity rates of 8.6% and 12.2%, respectively. The overall concordance between the three methods were 75.9% for RT-LAMP and light microscopy, 75.1% for RT-LAMP and RDT, and 83.9% for light microscopy and RDT. Blood parasite densities were significantly lower in the neonates (mean: 97.6, range: 61–192 parasites/μL) compared to the blood donors (mean: 447.8, range: 63–11 000 parasites/μL). Together, the study demonstrates the usefulness of whole blood RT-LAMP for use in rapid pre-screening of blood donors and suspected neonates to avert severe consequences of P. falciparum infections.
- Published
- 2021
16. Demographical, hematological and serological risk factors for Plasmodium falciparum gametocyte carriage in a high stable transmission zone in Cameroon
- Author
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Marie Fslorence Biabi, Emmanuel Elanga-Ndille, Sylvie Kemleu, Niels Nguedia, Franklin Maloba, Glwadys Cheteug, Balotin Fogang, Leopold Gustave Lehman, Christiane Donkeu, Carole Else Eboumbou Moukoko, Estelle Essangui, Lawrence Ayong, Umaru Banlanjo, and Michele Tchokwansi
- Subjects
Male ,0301 basic medicine ,Plasmodium ,Epidemiology ,Physiology ,Artificial Gene Amplification and Extension ,Gametocytes ,Polymerase Chain Reaction ,law.invention ,Serology ,0302 clinical medicine ,Animal Cells ,Risk Factors ,law ,Medicine and Health Sciences ,Prevalence ,Cameroon ,Malaria, Falciparum ,Protozoans ,Multidisciplinary ,Malarial Parasites ,Eukaryota ,Anemia ,Hematology ,Transmission (mechanics) ,Carrier State ,Medicine ,Female ,Cellular Types ,Research Article ,Adult ,Adolescent ,Science ,Plasmodium falciparum ,030231 tropical medicine ,Biology ,Research and Analysis Methods ,Young Adult ,03 medical and health sciences ,Parasite Groups ,parasitic diseases ,Parasitic Diseases ,medicine ,Gametocyte ,Humans ,Risk factor ,Molecular Biology Techniques ,Molecular Biology ,Demography ,Organisms ,Biology and Life Sciences ,Cell Biology ,Reverse Transcriptase-Polymerase Chain Reaction ,Tropical Diseases ,medicine.disease ,biology.organism_classification ,Parasitic Protozoans ,Malaria ,Germ Cells ,030104 developmental biology ,Carriage ,Medical Risk Factors ,Multivariate Analysis ,Parasitology ,Apicomplexa - Abstract
Presence of mature gametocyte forms of malaria parasites in peripheral blood is a key requirement for malaria transmission. Yet, studies conducted in most malaria transmission zones report the absence of gametocyte in the majority of patients. We therefore sought to determine the risk factors of both all-stage and mature gametocyte carriage in an area with high stable transmission of Plasmodium falciparum in Cameroon. Gametocyte positivity was determined using three complementary methods: thick blood smear microscopy, RT-PCR and RT-LAMP, whereas exposure to the infection was assessed by enzyme-linked immunosorbent assay. Of 361 malaria endemic residents randomly included in the study (mean age: 28±23 years, age range: 2-100 years, male/female sex ratio: 1.1), 87.8% were diagnosed with P. falciparum infection, of whom 45.7% presented with fever (axillary body temperature ≥37.5°C). Mature gametocyte positivity was 1.9% by thick blood smear microscopy and 8.9% by RT-PCR targeting the mature gametocyte transcript, Pfs25. The gametocyte positivity rate was 24.1% and 36.3% by RT-PCR or RT-LAMP, respectively, when targeting the sexual stage marker, Pfs16. Multivariate analyses revealed anemia as a common independent risk factor for both mature and all-stage gametocyte carriage, whereas fever and low anti-gametocyte antibody levels were independently associated with all-stage gametocyte carriage only. Taken together, the data suggest important differences in risk factors of gametocyte carriage depending on stage analyzed, with anemia, fever and low antiplasmodial plasma antibody levels representing the major contributing risk factors.
- Published
- 2019
17. A Field-Tailored Reverse Transcription Loop-Mediated Isothermal Assay for High Sensitivity Detection of Plasmodium falciparum Infections
- Author
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Abas Mouliom, Paul LaBarre, Lawrence Ayong, Sylvie Kemleu, Dylan Guelig, Carole Else Eboumbou Moukoko, Gaëtan Texier, Christiane Donkeu, Annie Epote, Estelle Essangui, Steven Diesburg, Robert A. Burton, Jeanne Manga, and Bernard Melingui
- Subjects
0301 basic medicine ,Plasmodium ,Physiology ,lcsh:Medicine ,Artificial Gene Amplification and Extension ,Polymerase Chain Reaction ,0302 clinical medicine ,Limit of Detection ,Medicine and Health Sciences ,Malaria, Falciparum ,lcsh:Science ,Whole blood ,Protozoans ,Rapid diagnostic test ,Multidisciplinary ,biology ,Malarial Parasites ,Hematology ,Body Fluids ,3. Good health ,Blood ,Molecular Diagnostic Techniques ,RNA extraction ,Anatomy ,Nucleic Acid Amplification Techniques ,Research Article ,Plasmodium falciparum ,030106 microbiology ,030231 tropical medicine ,Loop-mediated isothermal amplification ,Sensitivity and Specificity ,03 medical and health sciences ,Extraction techniques ,Parasite Groups ,Parasitic Diseases ,Genetics ,medicine ,Humans ,Molecular Biology Techniques ,Molecular Biology ,Gene amplification ,Base Sequence ,lcsh:R ,Organisms ,Biology and Life Sciences ,Reverse Transcriptase-Polymerase Chain Reaction ,Reverse Transcription ,Nucleic acid amplification technique ,Assay sensitivity ,Tropical Diseases ,medicine.disease ,biology.organism_classification ,Virology ,Molecular biology ,Parasitic Protozoans ,Malaria ,Research and analysis methods ,RNA amplification ,Parasitology ,lcsh:Q ,Apicomplexa ,Sequence Alignment - Abstract
Highly sensitive and field deployable molecular diagnostic tools are critically needed for detecting submicroscopic, yet transmissible levels of malaria parasites prevalent in malaria endemic countries worldwide. A reverse transcription loop-mediated isothermal amplification (RT-LAMP) assay was developed and evaluated in comparison with thick blood smear microscopy, an antigen-based rapid diagnostic test (RDT), and an in-house RT-PCR targeting the same RT-LAMP transcript. The optimized assay detected Plasmodium falciparum infections in as little as 0.25ng of total parasite RNA, and exhibited a detection limit of 0.08 parasites/ μL when tested directly on infected whole blood lysates, or ~0.0008 parasites/ μL when using RNA extracts. Assay positivity was observed as early as eight minutes from initiation of the RT-LAMP and in most cases the reaction was complete before twenty minutes. Clinical evaluation of the assay on 132 suspected malaria cases resulted in a positivity rate of 90% for RT-LAMP using extracted RNA, and 85% when using whole blood lysates. The positivity rates were 70% for P. falciparum-specific RDT, 83% for RT-PCR, and 74% for thick blood smear microscopy (Mean parasite density = 36,986 parasites/ μL). Concordance rates between the developed RT-LAMP and comparator tests were greater than 75%, the lowest being with light microscopy (78%, McNemar's test: P = 0.0002), and the highest was with RT-PCR (87%, McNemar's test: P = 0.0523). Compared to reference RT-PCR, assay sensitivity was 90% for RT-LAMP on whole blood, and 96% for RT-LAMP using corresponding RNA extracts. Electricity-free heaters were further developed and evaluated in comparison with a battery-operated isothermal amplification machine for use with the developed test in resource-limited settings. Taken together, the data highlight the benefits of targeting high abundant RNA transcripts in molecular diagnosis, as well as the potential usefulness of the developed RT-LAMP-assay in malaria diagnosis in low to high parasite density settings.
- Published
- 2016
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