Browsing by Author "Dadzie, S."

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Bio-efficacy, user perception and acceptability of pyrethroid based mosquito coils in controlling Anopheles gambiae s.l., in some parts of Accra, Ghana
(Japanese Journal of Medical Entomology and Zoology. Vol. 65 No. 3p. 139-145, 2014) Adu-Acheampong, S.; Kyerematen, R.; Dadzie, S.; Appawu, M.; Boakye, D.; Williams, J.
This study was to provide baseline information on patterns of coil usage, user acceptability and susceptibility levels of mosquito coils in some parts of Accra, Ghana. Three hundred and twenty questionnaires were administered to obtain information on knowledge and perception of respondents on the usage of mosquito coils. Adult Anopheles gambiae mosquitoes were tested for resistance to pyrethroid based mosquito coils using WHO standard protocol for testing household insecticide products. A total of 152 out of 320 respondents were direct users of coils. Close to 62% of this number frequently changes brands of coil they use. Over 61% of coil users indicated their willingness to continue to use coils even though there are adverse effects after use. Anopheles gambiae s.s. was the only species that was found in the study area. Mortalities of An. gambiae s.s. after exposure to coils were 37% for Angel®, 37.5% for Lord® and 15% for Heaven mosquito coil brands. More than half of the inhabitants in the area used coils to prevent mosquito bites. However, high levels of resistance was detected for all the three pyrethroid-based coils because West African kdr was detected in about 59% of samples of Anopheles gambiae s.s. that survived the exposure.
Characteristics of asymptomatic Plasmodium spp. parasitaemia in Kwahu-Mpraeso, a malaria endemic mountainous district in Ghana, West Africa
(2016-01-22) Owusu, E.D.A.; Buabeng, V.; Dadzie, S.; Brown, C.A.; Grobusch, M.P.; Mens, P.
Abstract Background Malaria control efforts in Ghana have reduced the countrywide average malaria prevalence from 71 % in 2000 to about 51 % in 2012; however, its main focus is on symptomatic malaria. If further progress is to be made, parasite reservoirs in asymptomatic carriers need to be moved into focus. This study profiles asymptomatic Plasmodium spp. parasitaemia amongst residents of mountainous Kwahu-Mpraeso in the Eastern region of Ghana. Methods A cross-sectional study of 360 residents was carried out from October to December 2013. This included recording demographics, malaria testing of asymptomatic residents, and gathering of their malaria history. Assessment of malaria transmission was done with molecular identification of vectors, determination of sporozoite rate, insecticide resistance status and biting pattern. Univariate and multivariate analysis were used to establish risk determinants. Results In Mpraeso, in the Kwahu highland of Eastern Region, children were at higher risk of asymptomatic parasitaemia, thereby contributing to the parasite reservoir and hence sustained malaria transmission. As well, findings suggested Hb AC genotype influenced susceptibility to asymptomatic malaria with 8.03-fold increase in odds (univariate) and 11.92-fold higher odds (multivariate) than the normal Hb AA. The mosquito vector predominant in the area was Anopheles gambiae sensu stricto of the homozygous pyrethroid resistant form (RR); with biting mainly occurring indoors. Conclusion For an effective malaria control in this area, interventions should be formulated and implemented to target asymptomatic parasite reservoirs; especially in children and people with Hb AC. The dominant vector species An. gambiae s.s. and its feeding patterns of biting indoors should also be considered.
A community-wide study of malaria reduction: Evaluating efficacy and user-acceptance of a low-cost repellent in Northern Ghana
(American Journal of Tropical Medicine and Hygiene, 2013-02) Dadzie, S.; Boakye, D.; Asoala, V.; Koram, K.; Kiszewski, A.; Appawu, M.
NO MAS (NM) mosquito repellent was evaluated in two farming villages (4 km apart) in the Kassena Nankana district of northern Ghana. We determined its efficacy against local malaria vectors, degree of user acceptance, and its effect on malaria prevalence in households using insecticide-treated bed nets. The average protective efficacy of NM against Anopheles mosquitoes over 9 hours was 89.6%. Controls averaged 86 bites/person/night versus 9 bites/ person/night with the use of NM. Use of repellent was associated with a decrease of absolute malaria prevalence by 19.2% in the repellent village and by 6.5% in the control village (45.5 to 26.3, and 29.5 to 23.0, respectively). The user-acceptance rate of NM repellent was 96.1%. Ten percent (10%) of repellent users reported irritation as the main adverse effect during the period. Eighty-five percent (85%) of the users found the odor of NM appealing and 87% reported no inconvenience in applying the repellent daily. Copyright © 2013 by The American Society of Tropical Medicine and Hygiene.
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
Detection of malaria sporozoites by standard ELISA and VecTest™ dipstick assay in field-collected anopheline mosquitoes from a malaria endemic site in Ghana.
(Tropical Medicine & International Health, 2003-10-22) Appawu, M.A.; Bosompem, K.M.; Dadzie, S.; McKakpo, U.S.; Anim-Baidoo, l.; Dykstra, E.; Fryauff, D.J.
We compared the VecTestTM dipstick assay for detection of Plasmodium sporozoites in Anopheles vectors of malaria with standard circumsporozoite (CS) microplate ELISA for detection of Plasmodium falciparum circumsporozoite protein (PfCSP) in Anopheles mosquitoes. Mosquitoes were collected from a malaria endemic site (Kassena Nankana district) in northern Ghana. Of 2620 randomly sampled mosquitoes tested, the standard CS-ELISA gave a sporozoite rate of 10.8% compared with 11.2% by VecTestTM, which was not statistically different (P = 0.66). Visual reading of the CS-ELISA results gave a sporozoite rate of 13.4%, which was higher than the other tests (P > 0.05). To allow a more objective evaluation of the sensitivity of the dipstick, an additional 136 known CS-ELISA-positive specimens were analysed. The prevalence of the test (including the additional samples) was 14.6% and 14.7% for CS-ELISA and dipstick, respectively (P > 0.05). The estimated prevalence by visual assessment of the CS-ELISA results was 17.5%. The relative specificity and sensitivity of the VecTestTM dipstick and visually read ELISA were estimated based on the CS-ELISA as a gold standard. The specificities of the dipstick and visual ELISA were high, 98.0% and 96.6%, respectively. However, the sensitivities of the two assays were 88.8% for VecTest and 100% for visual ELISA (P < 0.01). Concordance between VecTest and CS-ELISA was good (κ = 0.86). Similarly, there was a good concordance between the dipstick and the visually read ELISA (κ = 0.88). Extrapolating from PfCSP controls (titrated quantities of P. falciparum sporozoites), mean sporozoite loads of CS-ELISA-positive An. gambiae (286 ± 28.05) and An. funestus (236 ± 19.32) were determined (P = 0.146). The visual dipstick grades showed high correlation with sporozoite load. The more intense the dipstick colour, the higher the mean sporozoite load (+ = 108, ++ = 207, +++ = 290, r = 0.99, r2 = 1). The VecTest dipstick offers practical advantages for field workers needing rapid and accurate means of detection of sporozoites in mosquitoes.
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.
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.
Food and feeding habits of the black pomfret, Parastromateus Niger (Carnagidae) in the Kuwaiti waters of the Arabian Gulf
(Cyblium 1(31): 77-84, 2007) Dadzie, S.
Examination of 1108 stomach contents of black pomfret, parastromateus niger (Bloch, 1795) from October, 2003 to September, 2004 revealed eight major food groups by a decreasing order of abundance: Bacillariophyceae (23%), fish eggs and larvae (21%), crustaneans (20$%), poriferns (15%) aenelids (10%), cnidarians (5%), fish scales (4%) and chaetognaths (2%). Copepods were the commonest prey types, with an annual frequency of occurrence of 77%, followed, among the crustaceans, by brachyuran zones (65%), postlarvae of shrimp (29%) and penacid shrimps (16%). These were followed by cnidarians, with hydroid medasae (67%), the annelids, with polyehaete larvae (63%), then spnger spicules (poriferans) (54%) and fish scales (45%). Coscinodiscus spp. and Rhizosolenia spp. Were the commonest prey types among the phytoplankton diet with frequencies of occurrence of 50% and 40%, respectively. While copepods, brachyuran zones, chaetognaths, polychaete larvae, sponge spicules and hydroid modusae were ingested throughout the year, the remaining prey types exhibited some seasonal fluctuations. A low feeding intensity was recorded as the temperature increased from March to August, a period coinciding with the highest number of fish with empty stomachs. Conversely, a greater feeding activity was recorded s the temperature decreased from September to February, a period coinciding with the highest number of fish with 1.2, 3/4 and fallstomachs. The proportion of fish eggs and larvae in stomach contents increased significantly with increasing size of P. niger, while the proportion of crustaceans significantly decreased with increasing fish size. Although the proportions of poriferans and annelids also decreased with increasing size of P. niger, these decreases were not significant.
Genome-wide association studies reveal novel loci associated with pyrethroid and organophosphate resistance in Anopheles gambiae and Anopheles coluzzii
(Nature Communications, 2023) Lucas, E.R.; Nagi, S.C.; Dadzie, S.; et al.
Resistance to insecticides in Anopheles mosquitoes threatens the effectiveness of malaria control, but the genetics of resistance are only partially understood. We performed a large scale multi-country genome-wide association study of resistance to two widely used insecticides: deltamethrin and pirimiphos methyl, using sequencing data from An. gambiae and An. coluzzii from ten locations in West Africa. Resistance was highly multi-genic, multi-allelic and variable between populations. While the strongest and most consistent asso ciation with deltamethrin resistance came from Cyp6aa1, this was based on several independent copy number variants (CNVs) in An. coluzzii, and on a non CNV haplotype in An. gambiae. For pirimiphos-methyl, signals included Ace1, cytochrome P450s, glutathione S-transferases and the nAChR target site of neonicotinoid insecticides. The regions around Cyp9k1 and the Tep family of immune genes showed evidence of cross-resistance to both insecticides. These locally-varying, multi-allelic patterns highlight the challenges involved in genomic monitoring of resistance, and may form the basis for improved surveillance methods.
An Investigation into Impact of Unsprayed Surfaces on Mosquito Behaviour and Malaria Transmission in an Area Undergoing Indoor Residual Spraying In Northern Ghana.
(University of Ghana, 2014-07) Mante, O.A.; Appawu, M.; Dadzie, S.; Kyerematen, R.; University of Ghana, College of Basic and Applied Sciences, School of Biological Sciences, Department of Animal Biology and Conservation Science (DABCS)
Indoor Residual Spraying (IRS) is one of the malaria vector control tools used in the control of malaria and has helped to reduce malaria transmission in many areas in Sub-Saharan Africa. This involves spraying the walls of rooms with insecticides so as to kill any mosquito that rest on the insecticide treated walls after feeding. However, recent discussions have been centered on the role unsprayed surfaces such as hanging cloths play in sprayed rooms in malaria transmission. In this study, the effect of hanged clothes on mosquito resting and exiting behaviour as well as on malaria transmission was investigated using mosquitoes captured by pyrethrum spray (PSC) and window exit trap (ETC) collections. The study was undertaken in Tarikpaa, in the Savelugu-Nanton district in Northern Ghana, an area undergoing Indoor Residual Spraying. Kulaa in the Tamale district of Northern Ghana was used as the control area with no IRS. Mosquitoes were sampled from August to December 2013. Anopheles gambiae s.l., Anopheles funestus, Anopheles nili and Anopheles rufipes were the Anopheles species collected during the period of the study making up 97.1%, 2.0%, 0.3% and 0.6% of the species respectively. Both An. coluzzi (M form) and S molecular forms occurred in all rooms in both areas. An. gambiae s.l. collected in rooms with hanging clothes in the IRS community (Tarikpaa) was lower (14.68%) compared to rooms with no hanging clothing (85.32%). The same was observed for the non-IRS community (Kulaa). A total of 18 and 100 Anopheles mosquitoes were collected from rooms with hanging clothes and rooms without hanging clothes in Tarikpaa respectively. The mean Indoor Resting Density (IRD) of Anopheles collected from rooms in the IRS area without hanging clothes was higher than that of rooms with hanging clothes (2.7 mosquitoes/room vs 0.36 mosquitoes/room). However, this difference was not significant (F (1, 12) = 2.078, P = 0.175). The same trend was observed for the unsprayed community, Kulaa. A Fed to Gravid ratio of 0.9:1 and 1:1 was estimated for mosquitoes collected exiting rooms with hanging clothes and without hanging clothes respectively. The sporozoite rate for both rooms with hanging clothes and rooms without hanging clothes in Tarikpaa was zero. The only positive mosquito samples were from the rooms without hanging clothes in the non-sprayed area (1.83%). An Entomological Inoculation Rate (EIR) of 0.0043 infective bites/man/night was estimated for An. gambiae collected from Kulaa. The fed: gravid ratio also indicated that more blood fed mosquitoes left the rooms immediately after feeding in the presence of insecticide on the walls. The number of Anopheles species collected by ETC from rooms with hanging clothes in the IRS area was significantly higher than in rooms without hanging clothes. The practice of hanging clothes in the area undergoing indoor residual spraying did not affect malaria transmission. Anopheles mosquitoes tend to exit rooms in the morning after feeding. This has implications for the effectiveness of the IRS in the area because many of the mosquitoes will not rest on the insecticide treated walls to be killed.
Lymphatic filariasis in Ghana: Establishing the potential for an urban cycle of transmission
(Tropical Medicine and international Health, 2005) Gbakima, A.A.; Appawu, M.A.; Dadzie, S.; Karikari, C.; Sackey, S.O.; Baffoe-Wilmot, A.; Scott, A.L.
Lymphatic filariasis is a significant public health and economic problem in many tropical and subtropical regions. Unplanned urbanization leading to a lack of proper sanitary conditions has resulted in an increase in the urban-based transmission of a number of vector-borne diseases, including lymphatic filariasis. It has been well established that lymphatic filariasis is endemic in rural areas of Ghana. The goal of this study was to determine if there is a potential of establishing urban transmission cycles in Ghana's major cities. We clinically and immunologically assessed 625 individuals from the three major urban areas (Bawku, Bolgatanga and Secondi/Takoradi), finding that the prevalence of infection with Wuchereria bancrofti ranged from 0 to 12.5%. The results of a polymerase chain reaction based analysis of mosquitoes collected from these areas suggested that there is a low but detectable prevalence of mosquitoes infected with W. bancrofti. We conclude that there may be a potential for an established urban transmission of lymphatic filariasis in Ghana. © 2005 Blackwell Publishing Ltd.
Malaria transmission dynamics at a site in northern Ghana proposed for testing malaria vaccines.
(Tropical Medicine and International Health, 2004-01-01) Appawu, M.; Owusu-Agyei, S.; Dadzie, S.; Asoala, V.; Anto, F.; Koram, K.A.; Fryauff, D.J.
We studied the malaria transmission dynamics in Kassena Nankana district (KND), a site in northern Ghana proposed for testing malaria vaccines. Intensive mosquito sampling for 1 year using human landing catches in three micro-ecological sites (irrigated, lowland and rocky highland) yielded 18 228 mosquitoes. Anopheles gambiae s.l. and Anopheles funestus constituted 94.3% of the total collection with 76.8% captured from the irrigated communities. Other species collected but in relatively few numbers were Anopheles pharoensis (5.4%) and Anopheles rufipes (0.3%). Molecular analysis of 728 An. gambiae.s.l. identified Anopheles gambiae s.s. as the most dominant sibling species (97.7%) of the An. gambiae complex from the three ecological sites. Biting rates of the vectors (36.7 bites per man per night) were significantly higher (P < 0.05) in the irrigated area than in the non-irrigated lowland (5.2) and rocky highlands (5.9). Plasmodium falciparum sporozoite rates of 7.2% (295/4075) and 7.1% (269/3773) were estimated for An. gambiae s.s. and An. funestus, respectively. Transmission was highly seasonal, and the heaviest transmission occurred from June to October. The intensity of transmission was higher for people in the irrigated communities than the non-irrigated ones. An overall annual entomological inoculation rate (EIR) of 418 infective bites was estimated in KND. There were microecological variations in the EIRs, with values of 228 infective bites in the rocky highlands, 360 in the lowlands and 630 in the irrigated area. Approximately 60% of malaria transmission in KND occurred indoors during the second half of the night, peaking at daybreak between 04.00 and 06.00 hours. Vaccine trials could be conducted in this district, with timing dependent on the seasonal patterns and intensity of transmission taking into consideration the micro-geographical differences and vaccine trial objectives.
Metabolic and target-site mechanisms combine to confer strong DDT resistance in Anopheles gambiae
(Public Library of Science, 2014) Mitchell, S.N.; Rigden, D.J; Dowd, A.J.; Lu, F.; Wilding, C.S.; Weetman, D.; Dadzie, S.; Jenkins, A.M.; Regna, K.; Boko, P.; Djogbenou, L.; Muskavitch, M.A.T.; Ranson, H.; Paine, M.I.J.
The development of resistance to insecticides has become a classic exemplar of evolution occurring within human time scales. In this study we demonstrate how resistance to DDT in the major African malaria vector Anopheles gambiae is a result of both target-site resistance mechanisms that have introgressed between incipient species (the M- and S-molecular forms) and allelic variants in a DDT-detoxifying enzyme. Sequencing of the detoxification enzyme, Gste2, from DDT resistant and susceptible strains of An. gambiae, revealed a non-synonymous polymorphism (I114T), proximal to the DDT binding domain, which segregated with strain phenotype. Recombinant protein expression and DDT metabolism analysis revealed that the proteins from the susceptible strain lost activity at higher DDT concentrations, characteristic of substrate inhibition. The effect of I114T on GSTE2 protein structure was explored through X-ray crystallography. The amino acid exchange in the DDT-resistant strain introduced a hydroxyl group nearby the hydrophobic DDT-binding region. The exchange does not result in structural alterations but is predicted to facilitate local dynamics and enzyme activity. Expression of both wild-type and 114T alleles the allele in Drosophila conferred an increase in DDT tolerance. The 114T mutation was significantly associated with DDT resistance in wild caught M-form populations and acts in concert with target-site mutations in the voltage gated sodium channel (Vgsc-1575Y and Vgsc-1014F) to confer extreme levels of DDT resistance in wild caught An. gambiae.
Molecular detection of dengue virus in patients suspected of Ebola virus disease in Ghana
(PLoS ONE, 2018-12) Bonney, J.H.; Hayashi, T.; Dadzie, S.; Agbosu, E.; Pratt, D.; Nyarko, S.; Asiedu-Bekoe, F.; Ido, E.; Sarkodie, B.; Ohta, N.; Yamaoka, S.
Dengue fever is known to be one of the most common arthropod-borne viral infectious diseases of public health importance. The disease is now endemic in more than 100 countries in Africa, the Americas, the Eastern Mediterranean, Southeast Asia and the Western Pacific with an estimated two fifths of the world's population being at risk. The notable endemic viral hemorrhagic fevers (VHFs) found in West Africa, including yellow fever, Lassa fever, Rift Valley fever, dengue fever and until recently Ebola have been responsible for most outbreaks with fatal consequences. These VHFs usually produce unclear acute febrile illness, especially in the acute phase of infection. In this study we detected the presence of 2 different serotypes (DENV-2 and DENV-3) of Dengue virus in 4 sera of 150 patients clinically suspected of Ebola virus disease during the Ebola Virus Disease (EVD) outbreak in West Africa with the use of serological and molecular test assays. Sequence data was successfully generated for DENV-3 and phylogenetic analysis of the envelope gene showed that the DENV-3 sequences had close homology with DENV-3 sequences from Senegal and India. This study documents molecular evidence of an indigenous Dengue fever viral infection in Ghana and therefore necessitates the need to have an efficient surveillance system to rapidly detect and control the dissemination of the different serotypes in the population which has the potential to cause outbreaks of dengue hemorrhagic fevers.
Population dynamic of Arastromateus Niger in Kuwaiti waters as assessed using length-frequency analysis
(Journal of Applied Ichthyology (23): 592-597, 2007) Dadzie, S.; Abou-Seedo, F.; Moreau, J.
The population dynamics of the black pomfret, Parastromateus niger, sampled from commercial gill-net catches from Kuwaiti waters of the Arabian Gulf, were investigated from October, 2003 to September, 2005. Length-based stock assessment using the FISAT software package showed an asymptotic length of 65 cm TL and growth curvature of 0.34 year-1. Raw data as well as that corrected for probability of capture indicated a recruitment from February to September. The total mortality coefficient was estimated to be 1.20, a natural mortality of 0.58 and fishing mortality of 0.52. The selectivity model based on the running average showed that 25% of 14.0 cm TL fish, 50% of specimens reaching 15.3 cm TL, and 75% of all specimens of 20.2 cm. TL encountering the gear were retained. Relative yield-per-recruit analyses revealed a current exploitation rate of 0.43%; this is below the maximum sustainable yield index, indicating for sustainable fishery of P. niger that the exploitation rate could be increased 0.6, provided size of fish at the first capture, i.e., the legal size, is also increased to 32.5 cm TL. These results suggest that P. niger stocks in Kuwaiti waters, contrary to existing views, are moderately exploited. These conclusions, however, is critically dependent on the estimate of natural morality, which requires further confirmation.
Reproductive aspects of the black pomfret, Parastromaleus Niger in the Kuwaiti waters of the Arabian Gulf
(Asian Fisheries Science (22): 265-275, 2009) Dadzie, S.; Abou-Seedo, F.; Gomes, T.
The reproductive activities of the male and female black promfret parastromateus niger in Kuwaiti waters were investigated from October, 2003 to September, 2005. Analysis of seasonal variations in the gonadosomatic index (GSI) during the two-year study period revealed high values from February to September, suggesting that the black pomfret has a prolonged spawning season, from February to September, suggesting that the black pomfret has a prolonged spawning season, from February to September. GSI fluctuations correlated positively with rising water temperatures in Kuwait from low values in both parameters in January to high values in February/March (r = 0.836, p < 0.05) for males and r = 0.764, p < 0.05 for females), suggesting that temperature plays a role in triggering spawning in both the sexes. Analysis of seasonal distribution of maturity stages for the two years revealed the presence of ripe/running males and females from February to September, thus confirming the spawning periodicity revealed through the analysis of fluctuations in the GSL. Macroscopic and microscopic studies of maturity stages revealed six stages in the males and seven in the females. The logistic function based on pooled data for the two years revealed that the minimum size at sexual maturity (L50) was attained at a size of 30.9 cm SL in males (r2 = 0.284) and 36.5 cam SL in females (r2 = 9.355). The ratio of males to females in monthly samples did not depart significantly from the hypothetical 1:1 during the entire study period (÷ 2 = 61.9, d.f. = 11, p < 0.05). Total fecundity ranged from 71 305 in a fish measuring 39.8 cm SL and weighing 1 572.5 g to 3.895 in a 49 cm SL and 3 630 g fish, with a mean of 1 216.734 eggs. Positive correlations were found between fecundity and ovary-free body weight standard length and ovary weight, and a negative one with egg size. The average relative fecundity was 948 eggs/g ovary-free body weights, which was neither a function of fish standard length nor ovary-free body weight.
Reproductive aspects of the black pomfret, parastromaleus niger in the Kuwaiti waters of the Arabian Gulf
(Asian Fisheries Science (22): 265-275, 2010) Dadzie, S.; Abou-Seedo, F.; Gomes, T.
The reproductive activities of the male and female black promfret parastromateus Niger in Kuwaiti waters were investigated from October, 2003 to September, 2005. Analysis of seasonal variations in the gonadosomatic index (GSI) during the two-year study period revealed high values from February to September, suggesting that the black pomfret has a prolonged spawning season, from February to September, suggesting that the black pomfret has a prolonged spawning season, from February to September. GSI fluctuations correlated positively with rising water temperatures in Kuwait from low values in both parameters in January to high values in February/March (r = 0.836, p < 0.05) for males and r = 0.764, p < 0.05 for females), suggesting that temperature plays a role in triggering spawning in both the sexes. Analysis of seasonal distribution of maturity stages for the two years revealed the presence of ripe/running males and females from February to September, thus confirming the spawning periodicity revealed through the analysis of fluctuations in the GSL. Macroscopic and microscopic studies of maturity stages revealed six stages in the males and seven in the females. The logistic function based on pooled data for the two years revealed that the minimum size at sexual maturity (L50) was attained at a size of 30.9 cm SL in males (r2 = 0.284) and 36.5 cam SL in females (r2 = 9.355). The ratio of males to females in monthly samples did not depart significantly from the hypothetical 1:1 during the entire study period (÷ 2 = 61.9, d.f. = 11, p < 0.05). Total fecundity ranged from 71 305 in a fish measuring 39.8 cm SL and weighing 1 572.5 g to 3.895 in a 49 cm SL and 3 630 g fish, with a mean of 1 216.734 eggs. Positive correlations were found between fecundity and ovary-free body weight standard length and ovary weight, and a negative one with egg size. The average relative fecundity was 948 eggs/g ovary-free body weights, which was neither a function of fish standard length nor ovary-free body weight.
Reproductive guilds (maturation, spawning frequency and fecundity pomfret, parastromateus niger (Caranguidae) in the Kuwaiti water Gulf
(Journal of Applied Ichthyology (24): 562-568, 2008) Dadzie, S.; Abou-Seedo, F.; Moreau, J.
Oogenesis, oocyte maturation pattern, spawning rhythm, spawning frequency, batch fecundity and oocyte diameter-frequency distribution of the black pomfret, Parastromateus niger (Block, 1795) in Kuwaiti waters were investigated from October, 2003 to September, 2005, using histological and morphological methods. The process of development is divided into four major phases: (i) primary growth phase; (ii) secondary growth; (iii) maturation phase; and (iv) spawning phase, followed by the regressed phase. Development of the yolky oocyte maturation, in dear differentiation between a ready batch of oocytes (ready for spawning ) and a reserve pool. Consequently, P. niger is capable of spawning multiple times throughout the reproductive season. Spawning frequency estimates, based on final oocyte maturation (FOM) method indicated that the species spawns once every 2.8 days during an 8-month spawning season lasting from February to September, with a potential annual number of 22.4 spawns. Batch fecundity (BF) (2132-2001 648, mean 406 010 eggs), was significantly positively related to both standard length (SL) P < 0.05) and ovary-free body weight (OFBW) (P < .0.05), both parameters being good predictors of BF (r2 = 30.8% for SL, from 22 cm onwards, and r2 = 29.6% for OFBW, from 129.5 g onwards). No significant differences in monthly BF were found throughout the spawning season. Relative batch fecundity was 336 eggs/g OFBW; thus, estimate for potential annual relative batch fecundity was 7525 eggs g-1 OFBW. The oocyte diameter-frequency distribution analysis revealed a multimodal distribution (at 100-200, 300-400 and 500-700 µm), confirming the evidence of multiple spawning.
Resistance to pirimiphos-methyl in West African Anopheles is spreading via duplication and introgression of the Ace1 locus
(PLOS, 2021) Grau-Bove, X.; Lucas, E.; Pipini, D.; Rippon, E.; van ‘t Hof, A.E.; Constant, E.; Dadzie, S.; Egyir-Yawson, A.; Essandoh, J.; Chabi, J.; Djogbe´nou, L.; Harding, N.J.; Miles, A.; Kwiatkowski, D.; Donnelly, M.J.; Weetman, D.
Vector population control using insecticides is a key element of current strategies to prevent malaria transmission in Africa. The introduction of effective insecticides, such as the organo phosphate pirimiphos-methyl, is essential to overcome the recurrent emergence of resis tance driven by the highly diverse Anopheles genomes. Here, we use a population genomic approach to investigate the basis of pirimiphos-methyl resistance in the major malaria vec tors Anopheles gambiae and A. coluzzii. A combination of copy number variation and a sin gle non-synonymous substitution in the acetylcholinesterase gene, Ace1, provides the key resistance diagnostic in an A. coluzzii population from Coˆte d’Ivoire that we used for sequence-based association mapping, with replication in other West African populations. The Ace1 substitution and duplications occur on a unique resistance haplotype that evolved in A. gambiae and introgressed into A. coluzzii, and is now common in West Africa primarily due to selection imposed by other organophosphate or carbamate insecticides. Our findings highlight the predictive value of this complex resistance haplotype for phenotypic resistance and clarify its evolutionary history, providing tools to for molecular surveillance of the current and future effectiveness of pirimiphos-methyl based interventions.