Browsing by Author "De Souza, D.K."

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Assessing the presence of Wuchereria bancrofti in vector and human populations from urban communities in Conakry, Guinea
(Parasites & Vectors, 2015-09) Kouassi, B.L.; De Souza, D.K.; Goepogui, A.; Narh, C.A.; King, S.A.; Mamadou, B.S.; Diakité, L.; Dadzie, S.K.; Boakye, D.A.; Utzinger, J.; Bockarie, M.J.; Koudou, B.G.
Background The Global Programme to Eliminate Lymphatic Filariasis was launched in 2000 with the goal of interrupting transmission of lymphatic filariasis (LF) through multiple rounds of mass drug administration (MDA). In Guinea, there is evidence of ongoing LF transmission, but little is known about the most densely populated parts of the country, including the capital Conakry. In order to guide the LF control and elimination efforts, serological and entomological surveys were carried out to determine whether or not LF transmission occurs in Conakry. Methods The prevalence of circulating filarial antigen (CFA) of Wuchereria bancrofti was assessed by an immuno-chromatography test (ICT) in people recruited from all five districts of Conakry. Mosquitoes were collected over a 1-year period, in 195 households in 15 communities. A proportion of mosquitoes were analysed for W. bancrofti, using dissection, loop-mediated isothermal amplification (LAMP) assay and conventional polymerase chain reaction (PCR). Results CFA test revealed no infection in the 611 individuals examined. A total of 14,334 mosquitoes were collected; 14,135 Culex (98.6 %), 161 Anopheles (1.1 %) and a few other species. Out of 1,312 Culex spp. (9.3 %) and 51 An. gambiae (31.7 %) dissected, none was infected with any stage of the W. bancrofti parasite. However, the LAMP assay revealed that 1.8 % of An. gambiae and 0.31 % of Culex spp. were positive, while PCR determined respective prevalences of 0 % and 0.19 %. Conclusions This study revealed the presence of W. bancrofti DNA in mosquitoes, despite the apparent absence of infection in the human population. Although MDA interventions are not recommended where the prevalence of ICT is below 1 %, the entomological results are suggestive of the circulation of the parasite in the population of Conakry. Therefore, rigorous surveillance is still warranted so that LF transmission in Conakry would be identified rapidly and adequate responses being implemented.
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.
Community perspectives on persistent transmission of lymphatic filariasis in three hotspot districts in Ghana after 15 rounds of mass drug administration: a qualitative assessment
(BMC Public Health, 2018-02) Ahorlu, C.S.K.; Koka, E.; Adu-Amankwah, S.; Otchere, J.; De Souza, D.K.
Background The Global Program for the Elimination of Lymphatic Filariasis (GPELF) started operation in 2000 and aimed at eliminating the disease by the year 2020, following 5–6 rounds of effective annual Mass Drug Administration (MDA). The MDA programme took off in Ghana in 2001 and has interrupted transmission in many areas while it has persisted in some areas after 10 or more rounds of MDA. This study was to appreciate community members’ perspectives on MDA after over 15 years of implementation. Findings will inform strategies to mobilise community members to participate fully in MDA to enhance the disease elimination process. Methods This was a qualitative study, employing key-informant in-depth-interviews. Respondents were selected based on their recognition by community members as opinion leaders and persons who were knowledgeable about the topic of interest in the community. A snowball sampling technique was used to select respondents. Results Respondents were well informed about the MDA with most of them saying, it has been implemented for over 12 years. They were aware that the MDA was for the treatment/control of LF (elephantiasis). It came to light that MDA compliance was affected by five related barriers. These are; Medication, Personal, Health system, Disease and Social structure related barriers. Adverse effects of the drugs and the fact that many people perceived that they were not susceptibility to the infection have grossly affected the ingestion of the drugs. Conclusion There is a need for community mobilization and promotional activities to explain the expected adverse reactions associated with the drugs to the people. Also the importance of why every qualified person in the community must comply with MDA must be emphasized.
Filling the Gap 115 Years after Ronald Ross: The Distribution of the Anopheles coluzzii and Anopheles gambiae s.s from Freetown and Monrovia, West Africa
(Public Library of Science, 2013) De Souza, D.K.; Koudou, B.G.; Bolay, F.K.; Boakye, D.A.; Bockarie, M.J.
It was in Freetown, Sierra Leone, that the malaria mosquito Anopheles coastalis, now known as Anopheles gambiae, was first discovered as the vector of malaria, in 1899. That discovery led to a pioneering vector research in Sierra Leone and neighbouring Liberia, where mosquito species were extensively characterized. Unfortunately, the decade long civil conflicts of the 1990s, in both countries, resulted in a stagnation of the once vibrant research on disease vectors. This paper attempts to fill in some of the gaps on what is now known of the distribution of the sibling species of the An. gambiae complex, and especially the An. coluzzii and An. gambiae s.s, formerly known as the An. gambiae molecular M and S forms respectively, in the cities of Freetown and Monrovia.
The impact of residual infections on Anopheles-transmitted Wuchereria bancrofti after multiple rounds of mass drug administration
(Parasites & Vectors, 2015-09) De Souza, D.K.; Ansumana, R.; Sessay, S.; Conteh, A.; Koudou, B.; Rebollo, M.P.; Koroma, J.; Boakye, D.A.; Bockarie, M.J.
Background Many countries have made significant progress in the implementation of World Health Organization recommended preventive chemotherapy strategy, to eliminate lymphatic filariasis (LF). However, pertinent challenges such as the existence of areas of residual infections in disease endemic districts pose potential threats to the achievements made. Thus, this study was undertaken to assess the importance of these areas in implementation units (districts) where microfilaria (MF) positive individuals could not be found during the mid-term assessment after three rounds of mass drug administration. Methods This study was undertaken in Bo and Pujehun, two LF endemic districts of Sierra Leone, with baseline MF prevalence of 2 % and 0 % respectively in sentinel sites for monitoring impact of the national programme. Study communities in the districts were purposefully selected and an assessment of LF infection prevalence was conducted together with entomological investigations undertaken to determine the existence of areas with residual MF that could enable transmission by local vectors. The transmission Assessment Survey (TAS) protocol described by WHO was applied in the two districts to determine infection of LF in 6–7 year old children who were born before MDA against LF started. Results The results indicated the presence of MF infected children in Pujehun district. An. gambiae collected in the district were also positive for W. bancrofti, even though the prevalence of infection was below the threshold associated with active transmission. Conclusions Residual infection was detected after three rounds of MDA in Pujehun – a district of 0 % Mf prevalence at the sentinel site. Nevertheless, our results showed that the transmission was contained in a small area. With the scale up of vector control in Anopheles transmission zones, some areas of residual infection may not pose a serious threat for the resurgence of LF if the prevalence of infections observed during TAS are below the threshold required for active transmission of the parasite. However, robust surveillance strategies capable of detecting residual infections must be implemented, together with entomological assessments to determine if ongoing vector control activities, biting rates and infection rates of the vectors can support the transmission of the disease. Furthermore, in areas where mid-term assessments reveal MF prevalence below 1 % or 2 % antigen level, in Anopheles transmission areas with active and effective malaria vector control efforts, the minimum 5 rounds of MDA may not be required before implementing TAS. Thus, we propose a modification of the WHO recommendation for the timing of sentinel and spot-check site assessments in national programs.
Increased pfmdr1 gene copy number and the decline in pfcrt and pfmdr1 resistance alleles in Ghanaian Plasmodium falciparum isolates after the change of anti-malarial drug treatment policy
(2013-10-30) Duah, N.O.; Matrevi, S.A.; De Souza, D.K.; Binnah, D.D.; Tamakloe, M.M.; Opoku, V.S.; Onwona, C.O.; Narh, C.A.; Quashie, N.B.; Abuaku, B.; Duplessis, C.; Kronmann, K.C.; Koram, K.A.
Abstract Background With the introduction of artemisinin-based combination therapy (ACT) in 2005, monitoring of anti-malarial drug efficacy, which includes the use of molecular tools to detect known genetic markers of parasite resistance, is important for first-hand information on the changes in parasite susceptibility to drugs in Ghana. This study investigated the Plasmodium falciparum multidrug resistance gene (pfmdr1) copy number, mutations and the chloroquine resistance transporter gene (pfcrt) mutations in Ghanaian isolates collected in seven years to detect the trends in prevalence of mutations. Methods Archived filter paper blood blots collected from children aged below five years with uncomplicated malaria in 2003–2010 at sentinel sites were used. Using quantitative real-time polymerase chain reaction (qRT-PCR), 756 samples were assessed for pfmdr1 gene copy number. PCR and restriction fragment length polymorphism (RFLP) were used to detect alleles of pfmdr1 86 in 1,102 samples, pfmdr1 184, 1034, 1042 and 1246 in 832 samples and pfcrt 76 in 1,063 samples. Merozoite surface protein 2 (msp2) genotyping was done to select monoclonal infections for copy number analysis. Results The percentage of isolates with increased pfmdr1 copy number were 4, 27, 9, and 18% for 2003–04, 2005–06, 2007–08 and 2010, respectively. Significant increasing trends for prevalence of pfmdr1 N86 (×2 = 96.31, p <0.001) and pfcrt K76 (×2 = 64.50, p <0.001) and decreasing trends in pfmdr1 Y86 (×2 = 38.52, p <0.001) and pfcrt T76 (×2 = 43.49, p <0.001) were observed from 2003–2010. The pfmdr1 F184 and Y184 prevalence showed an increasing and decreasing trends respectively but were not significant (×2 = 7.39,p=0.060; ×2 = 7.49, p = 0.057 respectively). The pfmdr1 N86-F184-D1246 haplotype, which is alleged to be selected by artemether-lumefantrine showed a significant increasing trend (×2 = 20.75, p < 0.001). Conclusion Increased pfmdr1 gene copy number was observed in the isolates analysed and this finding has implications for the use of ACT in the country although no resistance has been reported. The decreasing trend in the prevalence of chloroquine resistance markers after change of treatment policy presents the possibility for future introduction of chloroquine as prophylaxis for malaria risk groups such as children and pregnant women in Ghana.
Low prevalence of Plasmodium and absence of malaria transmission in Conakry, Guinea: Prospects for elimination
(BioMed Central Ltd, 2016) Kouassi, B.L.; De Souza, D.K.; Goepogui, A.; Balde, S.M.; Diakité, L.; Sagno, A.; Djameh, G.I.; Chammartin, F.; Vounatsou, P.; Bockarie, M.J.; Utzinger, J.; Koudou, B.G.
Background: Over the past 15 years, mortality and morbidity due to malaria have been reduced substantially in sub-Saharan Africa and local elimination has been achieved in some settings. This study addresses the bio-ecology of larval and adult stages of malaria vectors, Plasmodium infection in Anopheles gambiae s.l. in the city of Conakry, Guinea, and discusses the prospect for malaria elimination. Methods: Water bodies were prospected to identify potential mosquito breeding sites for 6 days each in the dry season (January 2013) and in the rainy season (August 2013), using the dipping method. Adult mosquitoes were collected in 15 communities in the five districts of Conakry using exit traps and indoor spraying catches over a 1-year period (November 2012 to October 2013). Molecular approaches were employed for identification of Anopheles species, including An. coluzzii and An. gambiae s.s. Individual An. gambiae mosquitoes were tested for Plasmodium falciparum and P. vivax sporozoites using the VecTest™ malaria panel assay and an enzyme-linked immunosorbent assay. A systematic research of Ministry of Health statistical yearbooks was performed to determine malaria prevalence in children below the age of 5 years. Results: Culex larval breeding sites were observed in large numbers throughout Conakry in both seasons. While Anopheles larval breeding sites were less frequent than Culex breeding sites, there was a high odds of finding An. gambiae mosquito larvae in agricultural sites during the rainy season. Over the 1-year study period, a total of 14,334 adult mosquitoes were collected; 14,135 Culex (98.6 %) and 161 (1.1 %) from the An. gambiae complex. One-hundred and twelve Anopheles mosquitoes, mainly collected from rice fields and gardens, were subjected to molecular analysis. Most of the mosquitoes were An. gambiae s.s. (n = 102; 91.1 %) while the remaining 10 (8.9 %) were An. melas. The molecular M form of An. gambiae s.s. was predominant (n = 89; 79.5 %). The proportions of kdr genotype in the An. gambiae s.s. M and S form were 65.2 and 81.8 % (n = 9), respectively. No sporozoite infection were detected in any of the mosquitoes tested. The prevalence of Plasmodium recorded in children aged below 5 years was relatively low and varied between 2.2 and 7.6 % from 2009 to 2012. Conclusions: The low density of larval and adult stages of Anopheles mosquitoes, the absence of infected An. gambiae species and the low prevalence of Plasmodium in under 5-year-old children are important features that might facilitate malaria elimination in Conakry. The heterogeneity in species composition and resistance profiles call for vector control interventions that are tailored to the local bio-ecological setting. © 2016 Ijaopo et al.
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.
Potential factors influencing lymphatic filariasis transmission in “hotspot” and “control” areas in Ghana: the importance of vectors
(Infectious Diseases of Poverty, 2019-02) Pi-Bansa, S.; Osei, J.H.N.; Frempong, K.K.; Elhassan, E.; Akuoko, O.K.; Agyemang, D.; Ahorlu, C.; Appawu, M.A.; Koudou, B.G.; Wilson, M.D.; De Souza, D.K.; Dadzie, S.K.et.al
Background Mass drug administration (MDA) programmes for the control of lymphatic filariasis in Ghana, have been ongoing in some endemic districts for 16 years. The current study aimed to assess factors that govern the success of MDA programmes for breaking transmission of lymphatic filariasis in Ghana. Methods The study was undertaken in two “hotspot” districts (Ahanta West and Kassena Nankana West) and two control districts (Mpohor and Bongo) in Ghana. Mosquitoes were collected and identified using morphological and molecular tools. A proportion of the cibarial armatures of each species was examined. Dissections were performed on Anopheles gambiae for filarial worm detection. A questionnaire was administered to obtain information on MDA compliance and vector control activities. Data were compared between districts to determine factors that might explain persistent transmission of lymphatic filariasis. Results High numbers of mosquitoes were sampled in Ahanta West district compared to Mpohor district (F = 16.09, P = 0.002). There was no significant difference between the numbers of mosquitoes collected in Kassena Nankana West and Bongo districts (F = 2.16, P = 0.185). Mansonia species were predominant in Ahanta West district. An. coluzzii mosquitoes were prevalent in all districts. An. melas with infected and infective filarial worms was found only in Ahanta West district. No differences were found in cibarial teeth numbers and shape for mosquito species in the surveyed districts. Reported MDA coverage was high in all districts. The average use of bednet and indoor residual spraying was 82.4 and 66.2%, respectively. There was high compliance in the five preceding MDA rounds in Ahanta West and Kassena Nankana West districts, both considered hotspots of lymphatic filariasis transmission. Conclusions The study on persistent transmission of lymphatic filariasis in the two areas in Ghana present information that shows the importance of local understanding of factors affecting control and elimination of lymphatic filariasis. Unlike Kassena Nankana West district where transmission dynamics could be explained by initial infection prevalence and low vector densities, ongoing lymphatic filariasis transmission in Ahanta West district might be explained by high biting rates of An. gambiae and initial infection prevalence, coupled with high densities of An. melas and Mansonia vector species that have low or no teeth and exhibiting limitation. Electronic supplementary material The online version of this article (10.1186/s40249-019-0520-1) contains supplementary material, which is available to authorized users.
Rapid high throughput SYBR green assay for identifying the malaria vectors Anopheles arabiensis, Anopheles coluzzii and Anopheles gambiae s.s. Giles
(PLoS ONE, 2019-04) Chabi, J.; Van’t Hof, A.; N’dri, L.K.; Datsomor, A.; Okyere, D.; Njoroge, H.; Pipini, D.; Hadi, M.P.; De Souza, D.K.; Suzuki, T.; Dadzie, S.K.; Jamet, H.P.
The Anopheles gambiae sensu lato species complex consists of a number of cryptic species with different habitats and behaviours. These morphologically indistinct species are identified by chromosome banding. Several molecular diagnostic techniques for distinguishing between An. coluzzii and An. gambiae are still under improvement. Although, the current SINE method for identification between An. coluzzii and An. gambiae works reliably, this study describes a refinement of the SINE method to increase sensitivity for identification of An. coluzzii, An. gambiae and An. arabiensis based on amplicon dissociation curve characteristics. Field-collected samples, laboratory-reared colonies and crossed specimens of the two species were used for the design of the protocol. An. gambiae, An. coluzzii, and hybrids of the two species were sampled from Ghana and An. arabiensis from Kenya. Samples were first characterised using conventional SINE PCR method, and further assayed using SYBR green, an intercalating fluorescent dye. The three species and hybrids were clearly differentiated using the melting temperature of the dissociation curves, with derivative peaks at 72˚C for An. arabiensis, 75˚C for An. gambiae and 86˚C for An. coluzzii. The hybrids (An. gambiae / An. coluzzii) showed both peaks. This work is the first to describe a SYBR green real time PCR method for the characterization of An. arabiensis, An. gambiae and An. coluz-zii and was purposely designed for basic melt-curve analysis (rather than high-resolution melt-curve) to allow it to be used on a wide range of real-time PCR machines.