Browsing by Author "Fujita, R."
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Item 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 GmbHItem Determining vector competence of Aedes aegypti from Ghana in transmitting dengue virus serotypes 1 and 2(Parasites & Vectors, 2021) Amoa‑Bosompem, M.; Kobayashi, D.; Itokawa, K.; Murota, K.; Faizah, A.N.; Azerigyik, F.A.; Hayashi, T.; Ohashi, M.; Bonney, J.H.K.; Dadzie, S.; Tran, C.C.; Tran, P.V.; Fujita, R.; Maekawa, Y.; Kasai, S.; Yamaoka, S.; Ohta, N.; Sawabe, K.; Iwanaga, S.; Isawa, H.Background: Dengue virus (DENV) is a mosquito-borne arbovirus transmitted by Aedes mosquitoes, but is not endemic in all areas where this vector is found. For example, the relatively sparse distribution of cases in West Africa is generally attributed to the refractory nature of West African Aedes aegypti (Ae. aegypti) to DENV infection, and particularly the forest-dwelling Ae. aegypti formosus. However, recent studies have shown these mosquitoes to be competent vectors within some West African countries that have suffered outbreaks in the past, such as Senegal. There is however little information on the vector competence of the Ae. aegypti in West African countries such as Ghana with no reported outbreaks. Methods: This study examined the vector competence of 4 Ae. aegypti colonies from urban, semi-urban, and two rural locations in Ghana in transmitting DENV serotypes 1 and 2, using a single colony from Vietnam as control. Midgut infection and virus dissemination were determined by quantitative reverse transcription polymerase chain reaction (qRT-PCR), while the presence and concentration of DENV in the saliva of infectious mosquitoes was determined by the focus forming assay. Results: There were significant differences in the colonies’ susceptibility to virus infection, dissemination, and transmission. All examined Ghanaian mosquitoes were refractory to infection by DENV serotype 2, while some colonies exhibited potential to transmit DENV serotype 1. None of the tested colonies were as competent as the control group colony. Conclusions: These findings give insight into the possible risk of outbreaks, particularly in the urban areas in the south of Ghana, and highlight the need for continuous surveillance to determine the transmission status and outbreak risk. This study also highlights the need to prevent importation of different DENV strains and potential invasion of new highly vector-competent Ae. aegypti strains, particularly around the ports of entry.Item 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.