Research Articles
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A research article reports the results of original research, assesses its contribution to the body of knowledge in a given area, and is published in a peer-reviewed scholarly journal. The faculty publications through published and on-going articles/researches are captured in this community
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Item Assessing the Presence of Wuchereria bancrofti Infections in Vectors Using Xenomonitoring in Lymphatic Filariasis Endemic Districts in Ghana(Tropical Medicine and Infectious Disease, 2019-03-13) Dadzie, S.K.; Pi-Bansa, S.; Osei, J.H.N.; Kartey-Attipoe, W.D.; Elhassan, E.; Agyemang, D.; Otoo, S.; Appawu, M.A.; Wilson, M.D.; Koudou, B.G.; De Souza, D.K.; Utzinger, J.; Boakye, D.A.Mass drug administration (MDA) is the current mainstay to interrupt the transmission of lymphatic filariasis. To monitor whether MDA is effective and transmission of lymphatic filariasis indeed has been interrupted, rigorous surveillance is required. Assessment of transmission by programme managers is usually done via serology. New research suggests that xenomonitoring holds promise for determining the success of lymphatic filariasis interventions. The objective of this study was to assess Wuchereria bancrofti infection in mosquitoes as a post-MDA surveillance tool using xenomonitoring. The study was carried out in four districts of Ghana; Ahanta West, Mpohor, Kassena Nankana West and Bongo. A suite of mosquito sampling methods was employed, including human landing collections, pyrethrum spray catches and window exit traps. Infection of W. bancrofti in mosquitoes was determined using dissection, conventional and real-time polymerase chain reaction and loop mediated isothermal amplification assays. Aedes, Anopheles coustani, An. gambiae, An. pharoensis, Culex and Mansonia mosquitoes were sampled in each of the four study districts. The dissected mosquitoes were positive for filarial infection using molecular assays. Dissected An. melas mosquitoes from Ahanta West district were the only species found positive for filarial parasites. We conclude that whilst samples extracted with Trizol reagent did not show any positives, molecular methods should still be considered for monitoring and surveillance of lymphatic filariasis transmission.Item Progress towards lymphatic filariasis elimination in Ghana from 2000-2016: Analysis of microfilaria prevalence data from 430 communities(PLoS Neglected Tropical Diseases, 2019-06-05) Frempong, K.K.; Biritwum, N.K.; Verver, S.; Odoom, S.; Alomatu, B.; Asiedu, O.; Kontoroupis, P.; Yeboah, A.; Hervie, E.T.; Marfo, B.; Boakye, D.A.; De Vlas, S.J.; Gyapong, J.O.; Stolk, W.A.BACKGROUND: Ghana started its national programme to eliminate lymphatic filariasis (LF) in 2000, with mass drug administration (MDA) with ivermectin and albendazole as main strategy. We review the progress towards elimination that was made by 2016 for all endemic districts of Ghana and analyze microfilaria (mf) prevalence from sentinel and spot-check sites in endemic districts. METHODS: We reviewed district level data on the history of MDA and outcomes of transmission assessment surveys (TAS). We further collated and analyzed mf prevalence data from sentinel and spot-check sites. RESULTS: MDA was initiated in 2001-2006 in all 98 endemic districts; by the end of 2016, 81 had stopped MDA after passing TAS and after an average of 11 rounds of treatment (range 8-14 rounds). The median reported coverage for the communities was 77-80%. Mf prevalence survey data were available for 430 communities from 78/98 endemic districts. Baseline mf prevalence data were available for 53 communities, with an average mf prevalence of 8.7% (0-45.7%). Repeated measurements were available for 78 communities, showing a steep decrease in mean mf prevalence in the first few years of MDA, followed by a gradual further decline. In the 2013 and 2014 surveys, 7 and 10 communities respectively were identified with mf prevalence still above 1% (maximum 5.6%). Fifteen of the communities above threshold are all within districts where MDA was still ongoing by 2016. CONCLUSIONS: The MDA programme of the Ghana Health Services has reduced mf prevalence in sentinel sites below the 1% threshold in 81/98 endemic districts in Ghana, yet 15 communities within 13 districts (MDA ongoing by 2016) had higher prevalence than this threshold during the surveys in 2013 and 2014. These districts may need to intensify interventions to achieve the WHO 2020 target.Item Notes on distribution of Simulium damnosum s. l. along Atbara River in Galabat sub-focus, eastern Sudan(BMC Infectious Diseases, 2019-05-20) Boakye, D.A.; Zarroug, I.M.A.; Elaagip, A.; Gumaa, S.G.; Ali, A.K.; Ahmed, A.; Siam, H.A.M.; Abdelgadir, D.M.Background: Onchocerciasis is caused by a nematode worm Onchocerca volvulus, which is transmitted in Sudan by black fly vectors of the Simulium damnosum sensu lato species complex. In Sudan, the disease is found in four foci where fast flowing rivers provide suitable breeding sites for the Simulium vector flies. The construction of dams and irrigation schemes for agricultural purposes has affected black fly breeding and distribution, such as in Merowe Dam in Abu-Hamed focus, where the perennially flowing water downstream of the Dam created new vector breeding sites, thereby, changing the pattern of disease transmission and creating public health problems. Based on this situation, this study was carried out to measure the effect of the Upper Atbara and Setit Dam complex on the distribution of Simulium damnosum s.l. breeding sites and on disease elimination in the Galabat sub-focus in eastern Sudan. Methods: Aquatic stages of Simulium were collected between October and November 2009, prior to the construction of the dam complex, and again in 2013 and 2015 while the dam complex construction was ongoing. Results: A total of 40 breeding sites were identified at the beginning of the study. After the construction of the dam complex in 2015, seventeen previously mapped breeding sites were inaccessible as they had been flooded by the dam complex’s lake when reach its maximum size. Three species were obtained from different locations: S. damnosum s.l., S. griseicolle, and S. adersi. Conclusions: This study has shown a link between the construction of the dam complex and a reduction in the breeding sites of black fly vectors. This reduction has limited the Galabat sub-focus to a small area at the upper Atbara River which become the end of the focus. To sustain the success achieved in onchocerciasis control in the Galabat sub-focus, disease control and its vector control should be strengthened in the area cross-boarding Sudan and Ethiopia.Item An Evaluation of Wb123 Antibody Elisa in Individuals Treated With Ivermectin and Albendazole, and Implementation Challenges in Africa(Pan African Medical Journal, 2017-05) de Souza, D.K.; Owusu, I.O.; Otchere, J.; Adimazoya, M.; Frempong, K.; Ahorlu, C.S.; Boakye, D.A.; Wilson, M.D.The development of antibody testing for the diagnosis of lymphatic filariasis (LF) is intended to enhance the monitoring and evaluation activities of the Global Program for the Elimination of LF. This is due to the fact that antibody tests are expected to be the most sensitive at detecting exposure to LF compared to antigen that takes longer to develop. To this end a new antibody-based enzyme linked immunosorbent assay (ELISA) to Wuchereria bancrofti antigen Wb123 has been developed and further designed into a point of care rapid diagnostic test, under evaluation. In pre-treatment surveys, individuals were tested for antigen using the immuno-chromatographic test (ICT) card, and night blood microfilariae, after which all positives were treated using Ivermectin and Albendazole. The Wb123 ELISA was tested in antigen positive individuals, three months after they were treated. Samples were also tested for ICT and night blood microfilariae. The results revealed a reduction in microfilariae and ICT prevalence after treatment. Antigen and antibody prevalence increased with age. However, there was no correlation with the antibody responses observed. The mean WB123 antibody titers were higher among ICT positives, but not significantly different from ICT negative persons. While the Wb123 is targeted for use in untreated populations, further evaluations and guidelines will be required to define its use in populations that have undergone treatment for the control of LF.Item Genome-wide analysis of ivermectin response by Onchocerca volvulus reveals that genetic drift and soft selective sweeps contribute to loss of drug sensitivity(PLoS Neglected Tropical Diseases, 2017) Doyle, S. R.; Bourguinat, C; Nana-Djeunga, H. C.; Kengne-Ouafo, J. A.; Bopda, J.; Kamgno, J.; Wanji, S.; Kuesel, A. C.; Walker, M.; Boakye, D.A.; Osei-Atweneboana, M.Y.; Boussinesq, M.; Prichard, R.K.; Grant, W.N.Background: Treatment of onchocerciasis using mass ivermectin administration has reduced morbidity and transmission throughout Africa and Central/South America. Mass drug administration is likely to exert selection pressure on parasites, and phenotypic and genetic changes in several Onchocerca volvulus populations from Cameroon and Ghana—exposed to more than a decade of regular ivermectin treatment—have raised concern that sub-optimal responses to ivermectin's anti-fecundity effect are becoming more frequent and may spread. Methodology/Principal findings: Pooled next generation sequencing (Pool-seq) was used to characterise genetic diversity within and between 108 adult female worms differing in ivermectin treatment history and response. Genome-wide analyses revealed genetic variation that significantly differentiated good responder (GR) and sub-optimal responder (SOR) parasites. These variants were not randomly distributed but clustered in ~31 quantitative trait loci (QTLs), with little overlap in putative QTL position and gene content between the two countries. Published candidate ivermectin SOR genes were largely absent in these regions; QTLs differentiating GR and SOR worms were enriched for genes in molecular pathways associated with neurotransmission, development, and stress responses. Finally, single worm genotyping demonstrated that geographic isolation and genetic change over time (in the presence of drug exposure) had a significantly greater role in shaping genetic diversity than the evolution of SOR. Conclusions/Significance: This study is one of the first genome-wide association analyses in a parasitic nematode, and provides insight into the genomics of ivermectin response and population structure of O. volvulus. We argue that ivermectin response is a polygenically-determined quantitative trait (QT) whereby identical or related molecular pathways but not necessarily individual genes are likely to determine the extent of ivermectin response in different parasite populations. Furthermore, we propose that genetic drift rather than genetic selection of SOR is the underlying driver of population differentiation, which has significant implications for the emergence and potential spread of SOR within and between these parasite populations. © 2017 Doyle et al.Item Evaluation of piperonyl butoxide in enhancing the efficacy of pyrethroid insecticides against resistant Anopheles gambiae s.l. in Ghana(Malaria Journal, 2017) Dadzie, S.K.; Chabi, J.; Asafu-Adjaye, A.; Owusu-Akrofi, O.; Baffoe-Wilmot, A.; Malm, K.; Bart-Plange, C.; Coleman, S.; Appawu, M.A.; Boakye, D.A.Background: Malaria vector control methods involving the use of pyrethroids remain the strategies being used against malaria vectors in Ghana. These methods include the use of long-lasting insecticidal nets and indoor residual spraying in many areas in Ghana. However, there is evidence that pyrethroid resistance is widespread in many areas in Ghana. Synergists have been shown to be useful in inhibiting the enzymes that are responsible for the development of resistance and hence enhance the insecticide susceptibility of Anopheles gambiae sensu lato (s.l.) in many areas. The present study investigated the effect of piperonyl butoxide (PBO) on the susceptibility status of An. gambiae s.l. across some sentinel sites in Ghana. Methods: Three to five day old An. gambiae s.l. reared from larvae were used in WHO susceptibility tube assays. Batches of 20-25 female adult An. gambiae s.l. were exposed simultaneously to the insecticide alone and to the PBO + insecticide. The knock down rate after 60 min and mortality at 24 h were recorded. Results: Deltamethrin and permethrin resistance of An. gambiae s.l. was observed in all the sites in 2015 and 2016. The mortality after 24 h post exposure for deltamethrin ranged from 16.3% in Weija to 82.3% in Kade, whereas that for permethrin ranged from 3.8% in Gomoa Obuasi to 91.3% in Prestea. A significant increase in susceptibility to deltamethrin and less to permethrin was observed during both 2015 and 2016 years in most of the sites when An. gambiae s.l. mosquitoes were pre-exposed to PBO. Conclusion: Findings from this study showed that the use of PBO significantly enhanced the susceptibility of An. gambiae s.l. mosquitoes in most of the sentinel sites. It is recommended that vector control strategies incorporating PBO as a synergist can be effective in killing mosquitoes in the presence of deltamethrin and permethrin resistance. © 2017 The Author(s).Item Molecular xenomonitoring for post-validation surveillance of lymphatic filariasis in Togo: no evidence for active transmission(Parasites and Vectors, 2018-01) Dorkenoo, M.A.; De Souza, D.K.; Apetogbo, Y.; Oboussoumi, K.; Yehadji, D.; Tchalim, M.; Etassoli, S.; Koudou, B.; Ketoh, G.K.; Sodahlon, Y.; Bockarie, M.J.; Boakye, D.A.Background Lymphatic filariasis (LF) is a mosquito-borne filarial disease targeted for elimination by the year 2020. The Republic of Togo undertook mass treatment of entire endemic communities from 2000 to 2009 to eliminate the transmission of the disease and is currently the first sub-Saharan African country to be validated by WHO for the elimination of LF as a public health problem. However, post-validation surveillance activities are required to ensure the gains achieved are sustained. This survey assessed the mosquito vectors of the disease and determined the presence of infection in these vectors, testing the hypothesis that transmission has already been interrupted in Togo. Method Mosquitoes were collected from 37 villages located in three districts in one of four evaluation units in the country. In each district, 30 villages were selected based on probability proportionate to size; eight villages (including one of the 30 villages already selected) where microfilaremia-positive cases had been identified during post-treatment surveillance activities were intentionally sampled. Mosquitoes were collected using pyrethrum spray collections (PSC) in households randomly selected in all villages for five months. In the purposefully selected communities, mosquitoes were also collected using human landing collections (HLC) and exit traps (ET). Collected mosquitoes were identified morphologically, and the identification of Wuchereria bancrofti DNA in the mosquitoes was based on the pool screening method, using the LAMP assay. Results A total of 15,539 mosquitoes were collected during the study. Anopheles gambiae (72.6%) was the predominant LF vector collected using PSC. Pool screen analysis of 9191 An. gambiae in 629 pools revealed no mosquitoes infected with W. bancrofti (0%; CI: 0–0.021). Conclusions These results confirm the findings of epidemiological transmission assessment surveys conducted in 2012 and 2015, which demonstrated the absence of LF transmission in Togo. The challenges of implementing molecular xenomonitoring are further discussed.Item Effects of lyophilization and storage temperature on Wuchereria bancrofti antigen sensitivity and stability(BMC Research Notes, 2018-07) Agbozo, E.Y.; Dumashie, E.; Boakye, D.A.; de Souza, D.K.Objective Antigen-based rapid diagnostic tests for Lymphatic filariasis (LF) do not come with external quality control (QC) materials, and research and disease control programmes rely on stored positive samples. This study was undertaken to evaluate the use of lyophilized Wuchereria bancrofti antigen positive plasma samples to serve as QC materials for LF diagnostic tests. 10 well characterized W. bancrofti positive samples were lyophilized and stored at 4, 28 and 40 °C. The samples were evaluated using the Alere Filariasis Test Strips before lyophilization, and after 1 and 3 months of storage. The sensitivity and stability of the lyophilized samples were evaluated. Results The results revealed a loss of sensitivity and stability with increasing temperature and duration of storage. The results are further discussed in terms of the use of dried blood spot (DBS) in diagnostic studies on LF, and the need for thoughtful DBS preparation and storage.Item Ivermectin treatment in humans for reducing malaria transmission(Cochrane Database of Systematic Reviews, 2018-09) de Souza, D.K.; Larbi, I.; Boakye, D.A.; Okebe, J.This is a protocol for a Cochrane Review (Intervention). The objectives are as follows: To assess the effects of ivermectin on malaria transmission and mosquito survival. © 2018 The Cochrane Collaboration.Item Soluble FcɛRI: A biomarker for IgE‐mediated diseases(Allergy: European Journal of Allergy and Clinical Immunology, 2019-02) Moñino-Romero, S.; Lexmond, W.S.; Singer, J.; Bannert, C.; Amoah, A.S.; Yazdanbakhsh, M.; Boakye, D.A.; Jensen-Jarolim, E.; Fiebiger, E.; Szépfalusi, Z.Soluble IgE receptors interact with IgE in the extracellular matrix andare important in the regulation of immune diseases.1-5Soluble FcεRII(sCD23) and galectin‐3(εBP) are currently used as biomarkers,1though correlation data on serum titers and severity of allergies arecontroversial.1,6FcεRI, the high‐affinity IgE Fc receptor, is expressed on severalinnate cell types,2and a truncated version of the IgE‐binding alphasubunit is found as a soluble isoform (sFcεRI) in human serum. In cir-culation, sFcεRI is mostly detected as a complex with IgE.7Thisobservation raises the question of how sFcεRI affects detection ofserum IgE titers.In order to assign clinical implications of sFcεRI, we assessedserum titers in its total and IgE‐bound forms in different IgE‐mediated diseases in 312 individuals. We compared pediatric popula-tions with primary food allergies (n = 59), insect venom allergies(n = 9), allergic asthma (n = 24), atopic dermatitis (n = 25), food‐sen-sitized nonallergic children (n = 31), and nonallergic controls (n = 17).Additionally, other sensitized groups and controls (n = 147) wereincluded in the study (Table S1-S4).