Browsing by Author "Osei, J.H.N."

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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.
Detection of a novel putative phlebovirus and first isolation of Dugbe virus from ticks in Accra, Ghana
(Ticks and Tick-borne Diseases, 2017) Kobayashi, D.; Ohashi, M.; Osei, J.H.N.; Agbosu, E.; Opoku, M.; Agbekudzi, A.; Joannides, J.; Fujita, R.; Sasaki, T.; Bonney, J.H.K.; Dadzie, S.; Isawa, H.; Sawabe, K.; Ohta, N.
Ticks are ectoparasites that transmit various types of human and animal pathogens. In particular, emerging and re-emerging diseases caused by tick-borne viruses are public health concerns around the world. However, in many countries of the sub-Saharan African region, epidemiological information on tick-borne viral infections is limited, and their prevalence and distribution remain largely unknown. In this study, we conducted surveillance on ticks to detect medically important tick-borne bunyaviruses in three study sites in and near to Accra, the capital city of Ghana, in 2015. Domestic dogs and cattle were surveyed and were found to be infested with various tick species belonging to the genera Rhipicephalus, Amblyomma and Haemaphysalis. Importantly, we detected a novel putative phlebovirus in Rhipicephalus ticks, and successfully isolated a new strain of Dugbe virus from Am. variegatum ticks. To our knowledge, this is the first report of tick-associated viruses in Ghana other than Crimean-Congo hemorrhagic fever virus. © 2017 Elsevier GmbH
Discovery of Point Mutations in the Voltage-Gated Sodium Channel from African Aedes aegypti Populations: Potential Phylogenetic Reasons for Gene Introgression
(Public Library of Science, 2016) Kawada, H.; Higa, Y.; Futami, K.; Muranami, Y.; Kawashima, E.; Osei, J.H.N.; Sakyi, K.Y.; Dadzie, S.; de Souza, D.K.; Appawu, M.; Ohta, N.; Suzuki, T.; Minakawa, N.
Yellow fever is endemic in some countries in Africa, and Aedes aegpyti is one of the most important vectors implicated in the outbreak. The mapping of the nation-wide distribution and the detection of insecticide resistance of vector mosquitoes will provide the beneficial information for forecasting of dengue and yellow fever outbreaks and effective control measures. Methodology/Principal Findings: High resistance to DDT was observed in all mosquito colonies collected in Ghana. The resistance and the possible existence of resistance or tolerance to permethrin were suspected in some colonies. High frequencies of point mutations at the voltage-gated sodium channel (F1534C) and one heterozygote of the other mutation (V1016I) were detected, and this is the first detection on the African continent. The frequency of F1534C allele and the ratio of F1534C homozygotes in Ae. aegypti aegypti (Aaa) were significantly higher than those in Ae. aegypti formosus (Aaf). We could detect the two types of introns between exon 20 and 21, and the F1534C mutations were strongly linked with one type of intron, which was commonly found in South East Asian and South and Central American countries, suggesting the possibility that this mutation was introduced from other continents or convergently selected after the introgression of Aaa genes from the above area. Conclusions/Significance: The worldwide eradication programs in 1940s and 1950s might have caused high selection pressure on the mosquito populations and expanded the distribution of insecticide-resistant Ae. aegypti populations. Selection of the F1534C point mutation could be hypothesized to have taken place during this period. The selection of the resistant population of Ae. aegypti with the point mutation of F1534C, and the worldwide transportation of vector mosquitoes in accordance with human activity such as trading of used tires, might result in the widespread distribution of F1534C point mutation in tropical countries. © 2016 Kawada et al.
Entomological Assessment of the Status and Risk of Mosquito-borne Arboviral Transmission in Ghana
(viruses, 2020-01-27) Amoa-Bosompem, M.; Kobayashi, D.; Murota, K.; Faizah, A.N.; Itokawa, K.; Fujita, R.; Osei, J.H.N.; Agbosu, E.; Pratt, D.; Kimura, S.; Kwofie, K.D.; Ohashi, M.; Bonney, J.H.K.; Dadzie, S.; Sasaki, T.; Ohta, N.; Isawa, H.; Sawabe, K.; Iwanaga, S.
Entomological surveillance is one of the tools used in monitoring and controlling vector-borne diseases. However, the use of entomological surveillance for arboviral infection vector control is often dependent on finding infected individuals. Although this method may su ce in highly endemic areas, it is not as e ective in controlling the spread of diseases in low endemic and non-endemic areas. In this study, we examined the e ciency of using entomological markers to assess the status and risk of arbovirus infection in Ghana, which is considered a non-endemic country, by combining mosquito surveillance with virus isolation and detection. This study reports the presence of cryptic species of mosquitoes in Ghana, demonstrating the need to combine morphological identification and molecular techniques in mosquito surveillance. Furthermore, although no medically important viruses were detected, the importance of insect-specific viruses in understanding virus evolution and arbovirus transmission is discussed. This study reports the first mutualistic relationship between dengue virus and the double-stranded RNA Aedes aegypti totivirus. Finally, this study discusses the complexity of the virome of Aedes and Culex mosquitoes and its implication for arbovirus transmission.
Implementing a community vector collection strategy using xenomonitoring for the endgame of lymphatic filariasis elimination
(Parasites and Vectors, 2018-12) Pi-Bansa, S.; Osei, J.H.N.; Joannides, J.; Woode, M.E.; Agyemang, D.; Elhassan, E.; Dadzie, S.K.; Appawu, M.A.; Wilson, M.D.et.al.
Background The global strategy for elimination of lymphatic filariasis is by annual mass drug administration (MDA). Effective implementation of this strategy in endemic areas reduces Wuchereria bancrofti in the blood of infected individuals to very low levels. This minimises the rate at which vectors successfully pick microfilariae from infected blood, hence requiring large mosquito numbers to detect infections. The aim of this study was to assess the feasibility of using trained community vector collectors (CVCs) to sample large mosquito numbers with minimal supervision at low cost for potential scale-up of this strategy. Methods CVCs and supervisors were trained in mosquito sampling methods, i.e. human landing collections, pyrethrum spray collections and window exit traps. Mosquito sampling was done over a 13-month period. Validation was conducted by a research team as quality control for mosquitoes sampled by CVCs. Data were analyzed for number of mosquitoes collected and cost incurred by the research team and CVCs during the validation phase of the study. Results A total of 31,064 and 8720 mosquitoes were sampled by CVCs and the research team, respectively. We found a significant difference (F(1,13) = 27.1606, P = 0.0001) in the total number of mosquitoes collected from southern and northern communities. Validation revealed similar numbers of mosquitoes sampled by CVCs and the research team, both in the wet (F(1,4) = 1.875, P = 0.309) and dry (F(1,4) = 2.276, P = 0.258) seasons in the southern communities, but was significantly different for both wet (F(1,4) = 0.022, P = 0.005) and dry (F(1,4 ) = 0.079, P = 0.033) seasons in the north. The cost of sampling mosquitoes per season was considerably lower by CVCs compared to the research team (15.170 vs 53.739 USD). Conclusions This study revealed the feasibility of using CVCs to sample large numbers of mosquitoes with minimal supervision from a research team at considerably lower cost than a research team for lymphatic filariasis xenomonitoring. However, evaluation of the selection and motivation of CVCs, acceptability of CVCs strategy and its epidemiological relevance for lymphatic filariasis xenomonitoring programmes need to be assessed in greater detail.
Mango anthracnose disease: the current situation and direction for future research
(Frontiers in Microbiology, 2023) Dofuor, A.K.; Quartey, N.K-A.; Osei, J.H.N.; et al.
Mango anthracnose disease (MAD) is a destructive disease of mangoes, with estimated yield losses of up to 100% in unmanaged plantations. Several strains that constitute Colletotrichum complexes are implicated in MAD worldwide. All mangoes grown for commercial purposes are susceptible, and a resistant cultivar for all strains is not presently available on the market. The infection can widely spread before being detected since the disease is invincible until after a protracted latent period. The detection of multiple strains of the pathogen in Mexico, Brazil, and China has prompted a significant increase in research on the disease. Synthetic pesticide application is the primary management technique used to manage the disease. However, newly observed declines in anthracnose susceptibility to many fungicides highlight the need for more environmentally friendly approaches. Recent progress in understanding the host range, molecular and phenotypic characterization, and susceptibility of the disease in several mango cultivars is discussed in this review. It provides updates on the mode of transmission, infection biology and contemporary management strategies. We suggest an integrated and ecologically sound approach to managing MAD.
Plasmodium falciparum isolates from southern Ghana exhibit polymorphisms in the SERCA-type PfATPase6 though sensitive to artesunate in vitro
(2011-07-11) Kwansa-Bentum, B.; Ayi, I.; Suzuki, T.; Otchere, J.; Kumagai, T.; Anyan, W.K.; Osei, J.H.N.; Asahi, H.; Ofori, M.F.; Akao, N.; Wilson, M.D.; Boakye, D.A.; Ohta, N.
Abstract Background In 2005, Ghana replaced chloroquine with artemisinin-based combination therapy as the first-line treatment for uncomplicated malaria. The aim of this work was to determine for the first time, polymorphisms in the putative pfATPase6 and pftctp, pfmdr1, pfcrt genes in Ghanaian isolates, particularly at a time when there is no report on artemisinin resistance in malaria parasites from Ghana. The sensitivity of parasite isolates to anti-malaria drugs were also evaluated for a possible association with polymorphisms in these genes. Methods The prevalence of point mutations in the above Plasmodium falciparum genes were assessed from filter-paper blood blot samples by DNA sequencing. In vitro drug sensitivity test was carried out on some of the blood samples from volunteers visiting hospitals/clinics in southern Ghana using a modified version of the standard WHO Mark III micro-test. Results All successfully tested parasite isolates were sensitive to artesunate; while 19.4%, 29.0% and 51.6% were resistant to quinine, amodiaquine and chloroquine respectively. The geometric mean of IC50 value for artesunate was 0.73 nM (95% CI, 0.38-1.08), amodiaquine 30.69 nM (95% CI, 14.18-47.20) and chloroquine 58.73 nM (95% CI, 38.08-79.38). Twenty point mutations were observed in pfATPase6 gene, with no L263E and S769N. All mutations found were low in frequency, except D639G which was observed in about half of the isolates but was not associated with artesunate response (p = 0.42). The pftctp gene is highly conserved as no mutation was observed, while CVIET which is chloroquine-resistant genotype at codon 72-76 of the pfcrt gene was identified in about half of the isolates; this was consistent with chloroquine IC50 values (p = 0.001). Mutations were present in pfmdr1 gene but were not associated with artemisinin response (p = 1.00). Conclusion The pfATPase6 gene is highly polymorphic with D639G appearing to be fixed in Ghanaian isolates. These may just be spontaneous mutations as all parasite isolates that were tested displayed satisfactory in vitro response to artesunate. However, there is no improvement in susceptibility of the parasites to chloroquine five years after its proscription.
Plasmodium falciparum isolates from southern Ghana exhibit polymorphisms in the SERCA-type PfATPase6 though sensitive to artesunate in vitro
(Malaria Journal, 2011) Kwansa-Bentum, B.; Ayi, I.; Suzuki, T.; Otchere, J.; Kumagai, T.; Anyan, W.K.; Osei, J.H.N.; Asahi, H.; Ofori, M.F.; Akao, N.; Wilson, M.D.; Boakye, D.A.; Ohta, N.
BACKGROUND: In 2005, Ghana replaced chloroquine with artemisinin-based combination therapy as the first-line treatment for uncomplicated malaria. The aim of this work was to determine for the first time, polymorphisms in the putative pfATPase6 and pftctp, pfmdr1, pfcrt genes in Ghanaian isolates, particularly at a time when there is no report on artemisinin resistance in malaria parasites from Ghana. The sensitivity of parasite isolates to anti-malaria drugs were also evaluated for a possible association with polymorphisms in these genes. METHODS: The prevalence of point mutations in the above Plasmodium falciparum genes were assessed from filter-paper blood blot samples by DNA sequencing. In vitro drug sensitivity test was carried out on some of the blood samples from volunteers visiting hospitals/clinics in southern Ghana using a modified version of the standard WHO Mark III micro-test. RESULTS: All successfully tested parasite isolates were sensitive to artesunate; while 19.4%, 29.0% and 51.6% were resistant to quinine, amodiaquine and chloroquine respectively. The geometric mean of IC50 value for artesunate was 0.73 nM (95% CI, 0.38-1.08), amodiaquine 30.69 nM (95% CI, 14.18-47.20) and chloroquine 58.73 nM (95% CI, 38.08-79.38). Twenty point mutations were observed in pfATPase6 gene, with no L263E and S769N. All mutations found were low in frequency, except D639G which was observed in about half of the isolates but was not associated with artesunate response (p = 0.42). The pftctp gene is highly conserved as no mutation was observed, while CVIET which is chloroquine-resistant genotype at codon 72-76 of the pfcrt gene was identified in about half of the isolates; this was consistent with chloroquine IC50 values (p = 0.001). Mutations were present in pfmdr1 gene but were not associated with artemisinin response (p = 1.00). CONCLUSION: The pfATPase6 gene is highly polymorphic with D639G appearing to be fixed in Ghanaian isolates. These may just be spontaneous mutations as all parasite isolates that were tested displayed satisfactory in vitro response to artesunate. However, there is no improvement in susceptibility of the parasites to chloroquine five years after its proscription.
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.
Predicting The Environmental Suitability For Anopheles Stephensi Under The Current Conditions In Ghana
(Scientifc Reports, 2024) Ismail, R.B.; Osei, J.H.N.; Bozorg‑Omid, F.; et al.
The emergence of vector-borne diseases, particularly malaria, presents a significant public health challenge worldwide. Anophelines are predominant malaria vectors, with varied distribution and influence. by environment and climate. This study, in Ghana, modelled environmental suitability for Anopheles stephensi, a potential vector that may threaten advances in malaria and vector control. Understanding this vector’s distribution and dynamics ensure effective malaria and vector control programmes implementation. We explored the MaxEnt ecological modelling method to forecast An. stephensi’s potential hotspots and niches. We analysed environmental and climatic variables to predict spatial distribution and ecological niches of An. stephensi with a spatial resolution of approximately 5 km2 . Analyzing geospatial and species occurrence data, we identified optimal environmental conditions and important factors in its presence. The model’s most important variables guided hotspot prediction across several ecological zones aside from urban and peri-urban regions. Considering the vector’s complex bionomics, these areas provide varying and adaptable conditions for the vector to colonise and establish. This is shown by the AUC= 0.943 prediction accuracy of the model, which is considered excellent. Based on our predictions, this vector species would thrive in Greater Accra, Ashanti Central, Upper East, Northern, and North East regions. Forecasting its environmental suitability Ecological niche modelling supports proactive surveillance and focused malaria management strategies. Public health officials can act to reduce the risk of malaria transmission by identifying areas where mosquitoes may breed, which will ultimately improve health outcomes and disease control.
Shifting the focus from open release of genetically modified mosquitoes, to controlled individualized treatment for infectious diseases
(Asia-Pacific Journal of Molecular Biology and Biotechnology, 2012-12) de Souza, D.K.; Dadzie, S.; Osei, J.H.N.; Boakye, D.A.; Suzuki, T.
Genetically modified (GM) vectors offer an opportunity for the control of many infectious diseases including malaria and dengue. However, they face issues of ethical consent, public and social acceptance and environmental concerns. Thus, strategies are needed to address these concerns before GM mosquitoes could be openly released. One example, the use of GM mosquitoes as "Flying Vaccinators" that have been designed to produce vaccine candidates, may provide some solutions to the concerns raised against GM vectors.
Species composition and risk of transmission of some Aedes-borne arboviruses in some sites in Northern Ghana
(PLOS, 2021) Joannides, J.; Dzodzomenyo, M.; Azerigyik, F.; Agbosu, E.E.; Pratt, D.; Osei, J.H.N.; Pwalia, R.; Amlalo, G.K.; Appawu, M.; Takashi, H.; Iwanaga, S.; Buchwald, A.; Rochford, R.; Boakye, D.; Koram, K.; Bonney, K.; Dadzie, S.
Aedes-borne viral diseases mainly Yellow Fever (YF), Dengue (DEN), Zika (ZIK) and Chi kungunya (CHK) have contributed to many deaths’ in the world especially in Africa. There have been major outbreaks of these diseases in West Africa. Although, YF outbreaks have occurred in Ghana over the years, no outbreak of DEN, ZIK and CHK has been recorded. However, the risk of outbreak is high due to its proximity to West African countries where outbreaks have been recently been recorded. This study surveyed the mosquito fauna to assess the risk of transmission of Yellow fever (YFV), Dengue (DENV), Chikungunya (CHKV) and Zika (ZIKV) viruses in Larabanga and Mole Game Reserve areas in Northern Ghana. The immature and adult stages of Aedes mosquitoes were collected from Larabanga and Mole Game Reserve area. There was a significant (P>0.001) number of mosquitoes collected during the rainy season than the dry season. A total of 1,930 Aedes mosquitoes were collected during the rainy season and morphologically identified. Of these, 1,915 (99.22%) were Aedes aegypti and 15 (0.22%) were Aedes vittatus. During the dry season, 27 Ae. aegypti mosquitoes were collected. A total of 415 Ae. aegypti mosquitoes were molecularly identified to subspecies level of which Ae. (Ae) aegypti aegypti was the predominant subspecies. Both Ae. aegypti aegypti and Ae aegypti formosus exist in sympatry in the area. All Aedes pools (75) were negative for DENV, ZIKV and CHKV when examined by RT- PCR. Three Larval indices namely House Index, HI (percentage of houses positive for Aedes larvae or pupae), Container Index, CI (the percentage of containers positive for Aedes larvae or pupae) and Breteau Index, BI (number of positive containers per 100 houses inspected) were assessed as a measure for risk of transmission in the study area. The HI, CI and BI for both sites were as follows; Mole Game Reserve (HI, 42.1%, CI, 23.5% and BI, 100 for rainy season and 0 for all indices for dry season) and Larabanga (39%, 15.5% and 61 for rainy season and 2.3%, 1.3% and 2.3 for dry season). The spatial distribution of Aedes breeding sites in both areas indicated that Aedes larvae were breeding in areas with close proximity to humans. Lorry tires were the main source of Aedes larvae in all the study areas. Information about the species composition and the potential role of Aedes mosquitoes in future outbreaks of the diseases that they transmit is needed to design efficient surveillance and vector control tools.