Detection of Dengue Virus among Children with Suspected Malaria, Accra, Ghana

Molecular epidemiology and evolutionary characteristics of dengue virus 2 in East Africa

Despite the increasing burden of dengue, the regional emergence of the virus in Kenya has not been examined. This study investigates the genetic structure and regional spread of dengue virus-2 in Kenya. Viral RNA from acutely ill patients in Kenya was enriched and sequenced. Six new dengue-2 genomes were combined with 349 publicly available genomes and phylogenies used to infer gene flow between Kenya and other countries. Analyses indicate two dengue-2 Cosmopolitan genotype lineages circulating in Kenya, linked to recent outbreaks in coastal Kenya and Burkina Faso. Lineages circulating in Western, Southern, and Eastern Africa exhibiting similar evolutionary features are also reported. Phylogeography suggests importation of dengue-2 into Kenya from East and Southeast Asia and bidirectional geneflow. Additional lineages circulating in Africa are also imported from East and Southeast Asia. These findings underscore how intermittent importations from East and Southeast Asia drive dengue-2 circulation in Kenya and Africa more broadly.

Risk of arboviral transmission and insecticide resistance status of Aedes mosquitoes during a yellow fever outbreak in Ghana

BACKGROUND

In late 2021, Ghana was hit by a Yellow Fever outbreak that started in two districts in the Savannah region and spread to several other Districts in three regions. Yellow fever is endemic in Ghana. However, there is currently no structured vector control programme for Aedes the arboviral vector in Ghana. Knowledge of Aedes bionomics and insecticide susceptibility status is important to control the vectors. This study therefore sought to determine Aedes vector bionomics and their insecticide resistance status during a yellow fever outbreak.

METHODS

The study was performed in two yellow fever outbreak sites (Wenchi, Larabanga) and two non-outbreak sites (Kpalsogu, Pagaza) in Ghana. Immature Aedes mosquitoes were sampled from water-holding containers in and around human habitations. The risk of disease transmission was determined in each site using stegomyia indices. Adult Aedes mosquitoes were sampled using Biogents Sentinel (BG) traps, Human Landing Catch (HLC), and Prokopack (PPK) aspirators. Phenotypic resistance to permethrin, deltamethrin and pirimiphos-methyl was determined with WHO susceptibility tests using Aedes mosquitoes collected as larvae and reared into adults. Knockdown resistance (kdr) mutations were detected using allele-specific multiplex PCR.

RESULTS

Among the 2,664 immature Aedes sampled, more than 60% were found in car tyres. Larabanga, an outbreak site, was classified as a high-risk zone for the Yellow Fever outbreak (BI: 84%, CI: 26.4%). Out of 1,507 adult Aedes mosquitoes collected, Aedes aegypti was the predominant vector species (92%). A significantly high abundance of Aedes mosquitoes was observed during the dry season (61.2%) and outdoors (60.6%) (P < 0.001). Moderate to high resistance to deltamethrin was observed in all sites (33.75% to 70%). Moderate resistance to pirimiphos-methyl (65%) was observed in Kpalsogu. Aedes mosquitoes from Larabanga were susceptible (98%) to permethrin. The F1534C kdr, V1016I kdr and V410 kdr alleles were present in all the sites with frequencies between (0.05-0.92). The outbreak sites had significantly higher allele frequencies of F1534C and V1016I respectively compared to non-outbreak sites (P < 0.001).

CONCLUSION

This study indicates that Aedes mosquitoes in Ghana pose a significant risk to public health. Hence there is a need to continue monitoring these vectors to develop an effective control strategy.

First report of V1016I, F1534C and V410L kdr mutations associated with pyrethroid resistance in Aedes aegypti populations from Niamey, Niger

BACKGROUND

Ae. aegypti is the vector of important μ arboviruses, including dengue, Zika, chikungunya and yellow fever. Despite not being specifically targeted by insecticide-based control programs in West Africa, resistance to insecticides in Ae. aegypti has been reported in countries within this region. In this study, we investigated the status and mechanisms of Ae. aegypti resistance in Niamey, the capital of Niger. This research aims to provide baseline data necessary for arbovirus outbreak prevention and preparedness in the country.

METHODS

Ovitraps were used to collect Ae. aegypti eggs, which were subsequently hatched in the insectary for bioassay tests. The hatched larvae were then reared to 3-5-day-old adults for WHO tube and CDC bottle bioassays, including synergist tests. The kdr mutations F1534C, V1016I, and V410L were genotyped using allele-specific PCR and TaqMan qPCR methods.

RESULTS

Ae. aegypti from Niamey exhibited moderate resistance to pyrethroids but susceptibility to organophosphates and carbamates. The kdr mutations, F1534C, V1016I and V410L were detected with the resistant tri-locus haplotype 1534C+1016L+410L associated with both permethrin and deltamethrin resistance. Whereas the homozygote tri-locus resistant genotype 1534CC+1016LL+410LL was linked only to permethrin resistance. The involvement of oxidase and esterase enzymes in resistance mechanisms was suggested by partial restoration of mosquitoes' susceptibility to pyrethroids in synergist bioassays.

CONCLUSION

This study is the first report of Ae. aegypti resistance to pyrethroid insecticides in Niamey. The resistance is underpinned by target site mutations and potentially involves metabolic enzymes. The observed resistance to pyrethroids coupled with susceptibility to other insecticides, provides data to support evidence-based decision-making for Ae. aegypti control in Niger.

The role of car tyres in the ecology of Aedes aegypti mosquitoes in Ghana

Aedes aegypti is an important vector of arboviral diseases including dengue and yellow fever. Despite the wide distribution of this mosquito species, there are limited data on the ecology of Ae. aegypti in Ghana. In this study, we report on the oviposition preference and the larval life tables of Ae. aegypti mosquitoes in Accra, Ghana. The oviposition preference of the mosquitoes to three habitat types (car tyres, drums and bowls) was measured by setting up ovitraps. We recorded the presence and abundance of larvae every 3 days. Two-hour-old Ae. aegypti larvae were introduced and raised in three habitat types to undertake larval life tables. The number of surviving larvae at each developmental stage was recorded daily until they emerged as adults. Car tyres showed a higher abundance of Ae. aegypti larvae (52.3%) than drums (32.5%) and bowls (15.1%) (ANOVA, F(2,159) = 18.79, P < 0.001). The mean development time of Ae. aegypti larvae was significantly lower in car tyres (7 ± 1 days) compared to that of bowls (9 ± 0.0 days) and drums (12.6 ± 1.5 days) (P = 0.024). The differences in pupation rates and emergence rates were not significant across the habitat types; however, the highest pupation rate was observed in bowls (0.92 ± 0.17) and the emergence rate was highest in tyres (0.84 ± 0.10). The proportion of first-instar larvae that survived to emergence was significantly higher in car tyres (0.84 ± 0.10) compared to that of bowls (0.72 ± 0.20) and drums (0.62 ± 0.20) (P = 0.009). No mortalities were observed after 9 days in car tyres, 10 days in bowls and 15 days in drums. The results confirm that discarded car tyres were the preferred habitat choice for the oviposition of gravid female Ae. aegypti mosquitoes and provide the best habitat conditions for larval development and survival. These findings are necessary for understanding the ecology of Ae. aegypti to develop appropriate strategies for their control in Ghana.

Concurrent infection of dengue virus with malaria parasites among outpatients attending healthcare facilities in Benin city, Nigeria

Background

Dengue virus (DENV) and malaria parasites (MP) are among the common febrile diseases affecting the tropics and subtropics of the world. Both are mosquito-borne pathogens affecting humans and other animals.

Methods

Blood samples were collected from 280 consented out-patients attending the selected hospitals and were analyzed. Malaria parasites were detected using microscopy and Malaria Ag Pf/Pan Rapid Test Device. Dengue virus was detected by serology and heminested reverse transcriptase PCR (hnRT-PCR) to target the flavivirus polymerase (NS5) gene.

Results

Malaria parasites recorded a total positivity of 151 patients (53.9%) using microscopy, while DENV antibodies (DENV IgM and DENV IgG) were positive in 16 (5.7%) and 39 (13.9%) patients, respectively. There was a concurrent infection between MP/DENV IgM in 13 (4.6%) patients and MP/DENV IgG in 27 (9.6%) patients. Molecular identification revealed DENV serotype 2 in circulation.

Conclusion

This study documents molecular evidence of dengue virus coexisting with malaria parasites in the study population, hence the need for efficient surveillance and control system.

The Spatiotemporal Distribution and Molecular Characterization of Circulating Dengue Virus Serotypes/Genotypes in Senegal from 2019 to 2023

Dengue virus is becoming a major public health threat worldwide, principally in Africa. From 2016 to 2020, 23 outbreaks were reported in Africa, principally in West Africa. In Senegal, dengue outbreaks have been reported yearly since 2017. Data about the circulating serotypes and their spatial and temporal distribution were limited to outbreaks that occurred between 2017 and 2018. Herein, we describe up-to-date molecular surveillance of circulating DENV serotypes in Senegal between 2019 to 2023 and their temporal and spatial distribution around the country. For this purpose, suspected DENV-positive samples were collected and subjected to dengue detection and serotyping using RT-qPCR methods. Positive samples were used for temporal and spatial mapping. A subset of DENV+ samples were then sequenced and subjected to phylogenetic analysis. Results show a co-circulation of three DENV serotypes with an overall predominance of DENV-3. In terms of abundance, DENV-3 is followed by DENV-1, with scarce cases of DENV-2 from February 2019 to February 2022. Interestingly, data show the extinction of both serotype 1 and serotype 2 and the only circulation of DENV-3 from March 2022 to February 2023. At the genotype level, the analysis shows that sequenced strains belong to same genotype as previously described: Senegalese DENV-1 strains belong to genotype V, DENV-2 strains to the cosmopolitan genotype, and DENV-3 strains to Genotype III. Interestingly, newly obtained DENV 1-3 sequences clustered in different clades within genotypes. This co-circulation of strains belonging to different clades could have an effect on virus epidemiology and transmission dynamics. Overall, our results highlight DENV serotype replacement by DENV-3, accompanied by a wider geographic distribution, in Senegal. These results highlight the importance of virus genomic surveillance and call for further viral fitness studies using both in vitro and in vivo models, as well as in-depth phylogeographic studies to uncover the virus dispersal patterns across the country.

Entomological risk assessment for transmission of arboviral diseases by Aedes mosquitoes in a domestic and forest site in Accra, Ghana

Dengue, Zika and chikungunya are Aedes-borne viral diseases that have become great global health concerns in the past years. Several countries in Africa have reported outbreaks of these diseases and despite Ghana sharing borders with some of these countries, such outbreaks are yet to be detected. Viral RNA and antibodies against dengue serotype-2 have recently been reported among individuals in some localities in the regional capital of Ghana. This is an indication of a possible silent transmission ongoing in the population. This study, therefore, investigated the entomological transmission risk of dengue, Zika and chikungunya viruses in a forest and domestic population in the Greater Accra Region, Ghana. All stages of the Aedes mosquito (egg, larvae, pupae and adults) were collected around homes and in the forest area for estimation of risk indices. All eggs were hatched and reared to larvae or adults for morphological identification together with larvae and adults collected from the field. The forest population had higher species richness with 7 Aedes species. The predominant species of Aedes mosquitoes identified from both sites was Aedes aegypti (98%). Aedes albopictus, an important arbovirus vector, was identified only in the peri-domestic population at a prevalence of 1.5%, significantly higher than previously reported. All risk indices were above the WHO threshold except the House Index for the domestic site which was moderate (19.8). The forest population recorded higher Positive Ovitrap (34.2% vs 26.6%) and Container (67.9% vs 36.8%) Indices than the peri-domestic population. Although none of the mosquito pools showed the presence of dengue, chikungunya or Zika viruses, all entomological risk indicators showed that both sites had a high potential arboviral disease transmission risk should any of these viruses be introduced. Continuous surveillance is recommended in these and other sites in the Metropolis to properly map transmission risk areas to inform outbreak preparedness strategies.

Infections transmitted via the faecal-oral route: a simple score for a global risk map

INTRODUCTION

Faecal-oral transmission refers to the process whereby disease is transmitted via the faeces of an infected individual to the mouth of a susceptible individual. This transmission can occur through failures in sanitation systems leading to exposure via various routes in particular contaminated water, food, and hands. Travellers' diarrhoea is the most common travel-related illness. A score could enhance risk assessment and pre-travel advice.

METHODS

A simple score was developed based on the frequency of defecating in the open (country prevalence > 1%), occurrence of cholera in the period between 2021 and 2017 (one or more case in a country) and reported typhoid fever cases between 2015 and 2019.

RESULTS

Data were available for 199 out of 214 countries for the score to be applied. 19% of the 199 countries scored as high risk countries for faecal-oral transmission (score 3), 47% as medium risk (score 2), and 34% as minimal risk (score 0). The percentage of countries scoring 3 was highest in Africa (63%) and lowest in Europe and Oceania (score 0).

CONCLUSIONS

A global risk map was developed based on a simple score that could aid travel medicine providers in providing pre-travel risk assessment. For travellers to high and medium risk countries, pre-travel consultation must include detailed advice on food and water hygiene.

Analysis of dengue fever disease in West Africa

Dengue fever disease (DFD) which is caused by four antigenically distinct dengue viruses (DENV) presents a global health threat, with tropical and subtropical regions at a greater risk. The paucity of epidemiological data on dengue in West African subregion endangers efforts geared toward disease control and prevention. A systematic search of DFD prevalence, incidence, and DENV-infected Aedes in West Africa was conducted in PubMed, Scopus, African Index Medicus, and Google Scholar in line with the Preferred Reporting Items for Systematic reviews and Meta-analyses (PRISMA) guidelines. A total of 58 human prevalence studies involving 35,748 people from 8 countries were identified. Two incidence and six DENV-infected studies were also reviewed. Nigeria and Burkina Faso contributed the majority of the prevalence studies which spanned between 1968 and 2018, with a considerable variation in coverage among the countries reviewed in this study. An average prevalence of 20.97% was observed across both general prevalence and acute DENV infection study categories, ranging between 0.02% and 93%. The majority of these studies were conducted in acute febrile patients with a prevalence range of 0.02-93% while 19% (n = 11) of all studies were general population-based studies and reported a prevalence range of 17.2-75.8%. DENV-infected Aedes aegypti were reported in four out of the five countries with published reports; with DENV-2 found circulating in Cape Verde, Senegal, and Burkina Faso while DENV-3 and DENV-4 were also reported in Senegal and Cape Verde, respectively. High prevalence of DFD in human populations and the occurrence of DENV-infected A. aegypti have been reported in West Africa, even though weaknesses in study design were identified. Epidemiological data from most countries and population in the subregion were scarce or non-existent. This study highlights the epidemic risk of DFD in West Africa, and the need for research and surveillance to be prioritized to fill the data gap required to enact effective control measures.

Co-occurrence of multiple kdr mutations (F1534C, V1016I, V410L) in Aedes aegypti from coastal areas in Ghana and assessment of the role of mosquito coil in causing pyrethroid resistance

The rapid spread of knockdown-resistance (kdr) mutations in Africa calls for monitoring and investigation into the cause of pyrethroid resistance to inform management strategies. This study investigated the pyrethroid resistance profile of Aedes aegypti from coastal towns in Ghana and the impact of mosquito coil, a popular household pyrethroid-based anti-mosquito tool, on the development of pyrethroid resistance. Susceptibility to deltamethrin and the presence of kdr mutations was determined in adult female mosquitoes reared from larvae. Furthermore, the LT₅₀ of a mosquito coil (meperfluthrin) against a laboratory colony was determined, and the value was used as a sublethal dose in an experimental study. The laboratory colony of Ae. aegypti was exposed to the sublethal dose of the coil once per generation for six generations (F6). The susceptibility of the exposed colony to deltamethrin (0.05%) was determined. The Ae. aegypti populations from the coastal towns were resistant to deltamethrin with co-occurrence of F1534C, V1016I and V410L kdr mutations. In the experimental study, the LT₅₀ (95% CI) of the selected colony against the coil rose from 8 minutes (95% CI; 6-9) at F0 to 28 minutes (95% CI; 23-34) at F6. Nonetheless, deltamethrin caused similar mortalities in the selected and control colonies. The mutant allele frequencies of 1534C and 410L were similar but 1016I was higher in the selected colony (17%) than in the control (5%). However, the increased tolerance to the coil and high mutant allele frequency of 1016I in the selected colony did not affect the mosquito's resistance level to deltamethrin insecticide. Further study is needed to elucidate the role of pyrethroid-based mosquito coils in the development of insecticide resistance in mosquito vectors.

Insecticide resistance status of Aedes aegypti in southern and northern Ghana

BACKGROUND

Outbreaks of Aedes-borne arboviral diseases are becoming rampant in Africa. In Ghana, there is no organized arboviral control programme with interventions restricted to mitigate outbreaks. Insecticide application is a crucial part of outbreak responses and future preventative control measures. Thus, knowledge of the resistance status and underlying mechanisms of Aedes populations is required to ensure optimal insecticide choices. The present study assessed the insecticide resistance status of Aedes aegypti populations from southern Ghana (Accra, Tema and Ada Foah) and northern Ghana (Navrongo) respectively.

METHODS

Phenotypic resistance was determined with WHO susceptibility tests using Ae. aegypti collected as larvae and reared into adults. Knockdown resistance (kdr) mutations were detected using allele-specific PCR. Synergist assays were performed with piperonyl butoxide (PBO) to investigate the possible involvement of metabolic mechanisms in resistance phenotypes.

RESULTS

Resistance to DDT was moderate to high across sites (11.3 to 75.8%) and, for the pyrethroids deltamethrin and permethrin, moderate resistance was detected (62.5 to 88.8%). The 1534C kdr and 1016I kdr alleles were common in all sites (0.65 to 1) and may be on a trajectory toward fixation. In addition, a third kdr mutant, V410L, was detected at lower frequencies (0.03 to 0.31). Pre-exposure to PBO significantly increased the susceptibility of Ae. aegypti to deltamethrin and permethrin (P < 0.001). This indicates that in addition to kdr mutants, metabolic enzymes (monooxygenases) may be involved in the resistance phenotypes observed in the Ae. aegypti populations in these sites.

CONCLUSION

Insecticide resistance underpinned by multiple mechanisms in Ae. aegypti indicates the need for surveillance to assist in developing appropriate vector control strategies for arboviral disease control in Ghana.

Changing Ecotypes of Dengue Virus 2 Serotype in Nigeria and the Emergence of Cosmopolitan and Asian I Lineages, 1966–2019

Dengue virus (DENV) is a leading mosquito-borne virus with a wide geographical spread and a major public health concern. DENV serotype 1 (DENV-1) and serotype 2 (DENV-2) were first reported in Africa in 1964 in Ibadan, Nigeria. Although the burden of dengue is unknown in many African countries, DENV-2 is responsible for major epidemics. In this study, we investigated the activities of DENV-2 to determine the circulating strains and to appraise the changing dynamics in the epidemiology of the virus in Nigeria. Nineteen DENV-2 sequences from 1966–2019 in Nigeria were retrieved from the GenBank of the National Center of Biotechnology Information (NCBI). A DENV genotyping tool was used to identify the specific genotypes. The evolutionary history procedure was performed on 54 DENV-2 sequences using MEGA 7. There is a deviation from Sylvatic DENV-2 to other genotypes in Nigeria. In 2019, the Asian I genotype of DENV-2 was predominant in southern Edo State, located in the tropical rainforest region, with the first report of the DENV-2 Cosmopolitan strain. We confirmed the circulation of other non-assigned genotypes of DENV-2 in Nigeria. Collectively, this shows that DENV-2 dynamics have changed from Sylvatic transmission reported in the 1960s with the identification of the Cosmopolitan strain and Asian lineages. Sustained surveillance, including vectorial studies, is required to fully establish the trend and determine the role of these vectors.

Arthropod-borne diseases among travellers arriving in Europe from Africa, 2015 to 2019

BackgroundTravellers are generally considered good sentinels for infectious disease surveillance.AimTo investigate whether health data from travellers arriving from Africa to Europe could provide evidence to support surveillance systems in Africa.MethodsWe examined disease occurrence and estimated risk of infection among travellers arriving from Africa to Europe from 2015 to 2019 using surveillance data of arthropod-borne disease cases collected through The European Surveillance System (TESSy) and flight passenger volumes from the International Air Transport Association.ResultsMalaria was the most common arthropod-borne disease reported among travellers from Africa, with 34,235 cases. The malaria travellers' infection rate (TIR) was 28.8 cases per 100,000 travellers, which is 36 and 144 times higher than the TIR for dengue and chikungunya, respectively. The malaria TIR was highest among travellers arriving from Central and Western Africa. There were 956 and 161 diagnosed imported cases of dengue and chikungunya, respectively. The highest TIR was among travellers arriving from Central, Eastern and Western Africa for dengue and from Central Africa for chikungunya in this period. Limited numbers of cases of Zika virus disease, West Nile virus infection, Rift Valley fever and yellow fever were reported.ConclusionsDespite some limitations, travellers' health data can efficiently complement local surveillance data in Africa, particularly when the country or region has a sub-optimal surveillance system. The sharing of anonymised traveller health data between regions/continents should be encouraged.

Evidence of High Frequencies of Insecticide Resistance Mutations in Aedes aegypti (Culicidae) Mosquitoes in Urban Accra, Ghana: Implications for Insecticide-based Vector Control of Aedes-borne Arboviral Diseases

The most widespread arboviral diseases such as Dengue, Chikungunya, and Zika are transmitted mainly by Aedes mosquitoes. Due to the lack of effective therapeutics for most of these diseases, vector control remains the most effective preventative and control measure. This study investigated and compared the species composition, insecticide susceptibility, and resistance mechanisms in Aedes mosquito populations from a forest reserve converted to an eco-park and a peri-domestic sites in urban Accra, Ghana. Immature Aedes were sampled from the study sites, raised to adults, and exposed to deltamethrin, permethrin, DDT, fenitrothion, bendiocarb, permethrin + PBO, and deltamethrin + PBO using WHO tube assays. Melting curve analyses were performed for F1536C, V1016I, and V410L genetic mutations in surviving and dead mosquitoes following exposure to deltamethrin and permethrin. Microplate assay was used to access enzyme activity levels in adult mosquitoes from both populations. Aedes aegypti was found to be the dominant species from both study populations. The susceptibility test results revealed a high frequency of resistance to all the insecticides except fenitrothion. F1534C mutations were observed in 100% and 97% of mosquitoes from the peri-domestic and forest population, respectively but were associated with pyrethroid resistance only in the forest population (P < 0.0001). For the first time in Aedes mosquitoes in Ghana, we report the existence V410L mutations, mostly under selection only in the forest population (HWE P < 0.0001) and conclude that Aedes vectors in urban Accra have developed resistance to many commonly used insecticides. This information is important for the formulation of vector control strategies for Aedes control in Ghana.

Arbovirus Epidemiology: The Mystery of Unnoticed Epidemics in Ghana, West Africa

It is evident that all the countries surrounding Ghana have experienced epidemics of key arboviruses of medical importance, such as the recent dengue fever epidemic in Burkina Faso. Therefore, Ghana is considered a ripe zone for epidemics of arboviruses, mainly dengue. Surprisingly, Ghana never experienced the propounded deadly dengue epidemic. Indeed, it is mysterious because the mosquito vectors capable of transmitting the dengue virus, such as Aedes aegypti, were identified in Ghana through entomological investigations. Additionally, cases may be missed, as the diagnostic and surveillance capacities of the country are weak. Therefore, we review the arbovirus situation and outline probable reasons for the epidemic mystery in the country. Most of the recorded cases of arbovirus infections were usually investigated via serology by detecting IgM and IgG immunoglobulins in clinical samples, which is indicative of prior exposure but not an active case. This led to the identification of yellow fever virus and dengue virus as the main circulating arboviruses among the Ghanaian population. However, major yellow fever epidemics were reported for over a decade. It is important to note that the reviewed arboviruses were not frequently detected in the vectors. The data highlight the necessity of strengthening the diagnostics and the need for continuous arbovirus and vector surveillance to provide an early warning system for future arbovirus epidemics.

Animal contact and paediatric acute febrile illness in Greater Accra Region, Ghana

Objective

To examine the association between animal contact (primarily dogs and cats) and non-malarial fever, as well as with secondary symptoms of headache, nausea, vomiting, and cough, in 687 children in Greater Accra Region, Ghana.

Design

Cross-sectional study of acute febrile illness among children aged 1-15 years old between October 2016 and August 2017.

Setting

Ledzokuku-Krowor Municipal Assembly (LEKMA) Hospital, Teshie, Greater Accra Region.

Participants

The study included children with acute fever, defined as a measured temperature of greater than 37.5°C, occurring less than seven days before the hospital visit, and afebrile children as controls.

Main outcome measures

Measured fever, self-reported fever, and secondary symptoms, each adjusting for patient household characteristics.

Results

Animal contact was neither associated with measured fever (OR = 1.04, 95% CI 0.73-1.49) nor with self-reported fever (OR = 0.97, 95% CI 0.68-1.39). Animal contact was associated with headache (OR = 3.26, 95% CI 2.23-4.77, P < .01) and nausea (OR = 3.05, 95% CI 1.99-4.68, P < .01), but not with vomiting or cough. Additional models that used alternate inclusion criteria to define non-malarial fever yielded similar results. Several bacterial zoonoses that could plausibly have been transmitted by dogs and cats were diagnosed in the study population.

Conclusion

These findings suggest the need for future studies to evaluate animal contact as a risk factor for bacterial zoonoses that may serve as an etiological driver of acute febrile illness.

Funding

no external funding.

Ticks and prevalence of tick-borne pathogens from domestic animals in Ghana

Background

Ticks are important vectors of various pathogenic protozoa, bacteria and viruses that cause serious and life-threatening illnesses in humans and animals worldwide. Estimating tick-borne pathogen prevalence in tick populations is necessary to delineate how geographical differences, environmental variability and host factors influence pathogen prevalence and transmission. This study identified ticks and tick-borne pathogens in samples collected from June 2016 to December 2017 at seven sites within the Coastal, Sudan and Guinea savanna ecological zones of Ghana.

Methods

A total of 2016 ticks were collected from domestic animals including cattle, goats and dogs. Ticks were morphologically identified and analysed for pathogens such as Crimean-Congo haemorrhagic fever virus (CCHFV), Alkhurma haemorrhagic fever virus (AHFV), Rickettsia spp. and Coxiella burnetii using polymerase chain reaction assays (PCR) and sequence analysis.

Results

Seven species were identified, with Amblyomma variegatum (60%) most frequently found, followed by Rhipicephalus sanguineus sensu lato (21%), Rhipicephalus spp. (9%), Hyalomma truncatum (6%), Hyalomma rufipes (3%), Rhipicephalus evertsi (1%) and Rhipicephalus (Boophilus) sp. (0.1%). Out of 912 pools of ticks tested, Rickettsia spp. and Coxiella burnetii DNA was found in 45.6% and 16.7% of pools, respectively, whereas no CCHFV or AHFV RNA were detected. Co-infection of bacterial DNA was identified in 9.6% of tick pools, with no statistical difference among the ecozones studied.

Conclusions

Based on these data, humans and animals in these ecological zones are likely at the highest risk of exposure to rickettsiosis, since ticks infected with Rickettsia spp. displayed the highest rates of infection and co-infection with C. burnetii, compared to other tick-borne pathogens in Ghana.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-022-05208-8.

Spatiotemporal distribution and insecticide resistance status of Aedes aegypti in Ghana

Background

Vector control is the main intervention used to control arboviral diseases transmitted by Aedes mosquitoes because there are no effective vaccines or treatments for most of them. Control of Aedes mosquitoes relies heavily on the use of insecticides, the effectiveness of which may be impacted by resistance. In addition, rational insecticide application requires detailed knowledge of vector distribution, dynamics, resting, and feeding behaviours, which are poorly understood for Aedes mosquitoes in Africa. This study investigated the spatiotemporal distribution and insecticide resistance status of Aedes aegypti across ecological extremes of Ghana.

Methods

Immature mosquitoes were sampled from containers in and around human dwellings at seven study sites in urban, suburban, and rural areas of Ghana. Adult Aedes mosquitoes were sampled indoors and outdoors using Biogents BG-Sentinel 2 mosquito traps, human landing catches, and Prokopack aspiration. Distributions of immature and adult Aedes mosquitoes were determined indoors and outdoors during dry and rainy seasons at all sites. The phenotypic resistance status of Aedes mosquitoes to insecticides was determined using World Health Organization susceptibility bioassays. The host blood meal source was determined by polymerase chain reaction.

Results

A total of 16,711 immature Aedes were sampled, with over 70% found in car tyres. Significantly more breeding containers had Aedes immatures during the rainy season (11,856; 70.95%) compared to the dry season (4855; 29.05%). A total of 1895 adult Aedes mosquitos were collected, including Aedes aegypti (97.8%), Aedes africanus (2.1%) and Aedesluteocephalus (0.1%). Indoor sampling of adult Aedes yielded a total of 381 (20.1%) and outdoor sampling a total of 1514 (79.9%) mosquitoes (z = − 5.427, P = 0.0000) over the entire sampling period. Aedes aegypti populations were resistant to dichlorodiphenyltrichloroethane at all study sites. Vectors showed suspected resistance to bendiocarb (96–97%), permethrin (90–96%) and deltamethrin (91–96%), and were susceptible to the organophosphate for all study sites. Blood meal analysis showed that the Aedes mosquitoes were mostly anthropophilic, with a human blood index of 0.9 (i.e. humans, 90%; human and dog, 5%; dog and cow, 5%).

Conclusions

Aedes mosquitoes were found at high densities in all ecological zones of Ghana. Resistance of Aedes spp. to pyrethroids and carbamates may limit the efficacy of vector control programmes and thus requires careful monitoring.

Graphical abstract

Uncovering the Burden of Dengue in Africa: Considerations on Magnitude, Misdiagnosis, and Ancestry

Dengue is a re-emerging neglected disease of major public health importance. This review highlights important considerations for dengue disease in Africa, including epidemiology and underestimation of disease burden in African countries, issues with malaria misdiagnosis and co-infections, and potential evidence of genetic protection from severe dengue disease in populations of African descent. The findings indicate that dengue virus prevalence in African countries and populations may be more widespread than reported data suggests, and that the Aedes mosquito vectors appear to be increasing in dissemination and number. Changes in climate, population, and plastic pollution are expected to worsen the dengue situation in Africa. Dengue misdiagnosis is also a problem in Africa, especially due to the typical non-specific clinical presentation of dengue leading to misdiagnosis as malaria. Finally, research suggests that a protective genetic component against severe dengue exists in African descent populations, but further studies should be conducted to strengthen this association in various populations, taking into consideration socioeconomic factors that may contribute to these findings. The main takeaway is that Africa should not be overlooked when it comes to dengue, and more attention and resources should be devoted to this disease in Africa.

Seroprevalence and associated risk factors of chikungunya, dengue, and Zika in eight districts in Tanzania

BACKGROUND

This study was conducted to determine the seroprevalence and risk factors of chikungunya (CHIKV), dengue (DENV), and Zika (ZIKV) viruses in Tanzania.

METHODS

The study covered the districts of Buhigwe, Kalambo, Kilindi, Kinondoni, Kondoa, Kyela, Mvomero, and Ukerewe in Tanzania. Blood samples were collected from individuals recruited from households and healthcare facilities. An ELISA was used to screen for immunoglobulin G antibodies against CHIKV, DENV, and ZIKV.

RESULTS

A total of 1818 participants (median age 34 years) were recruited. The overall CHIKV, DENV, and ZIKV seroprevalence rates were 28.0%, 16.1%, and 6.8%, respectively. CHIKV prevalence was highest in Buhigwe (46.8%), DENV in Kinondoni (43.8%), and ZIKV in Ukerewe (10.6%) and Mvomero (10.6%). Increasing age and frequent mosquito bites were significantly associated with CHIKV and DENV seropositivity (P < 0.05). Having piped water or the presence of stagnant water around the home (P < 0.01) were associated with higher odds of DENV seropositivity. Fever was significantly associated with increased odds of CHIKV seropositivity (P < 0.001). Visiting mines had higher odds of ZIKV seropositivity (P < 0.05).

CONCLUSIONS

These findings indicate that DENV, CHIKV, and ZIKV are circulating in diverse ecological zones of Tanzania. There is a need to strengthen the control of mosquito-borne viral diseases in Tanzania.

Multifoci and multiserotypes circulation of dengue virus in Senegal between 2017 and 2018

Background

Dengue fever is a mosquito born disease associated with self-limited to life threatening illness. First detected in Senegal in the nineteenth century, and despite its growing incidence this last decade, significant knowledge gaps exist in our knowledge of genetic diversity of circulating strains. This study highlights the circulating serotypes and genotypes between January 2017 and December 2018 and their spatial and temporal distribution throughout all regions of Senegal.

Methods

We used 56 dengue virus (DENV) strains for the analysis collected from 11 sampling areas: 39 from all regions of Senegal, and 17 isolates from Thiès, a particular area of the country. Two real time RT-qPCR systems were used to confirm dengue infection and corresponding serotypes. For molecular characterization, CprM gene was sequenced and submitted to phylogenetic analysis for serotypes and genotypes assignment.

Results

Three dengue virus serotypes (DENV-1–3) were detected by all used methods. DENV-3 was detected in 50% (28/56) of the isolates, followed by DENV-1 and DENV-2, each representing 25% (14/56) of the isolates. DENV-3 belongs to genotype III, DENV-1 to genotype V and DENV-2 to Cosmopolitan genotype. Serotype 3 was detected in 7 sampling locations and a co-circulation of different serotypes was observed in Thiès, Fatick and Richard-toll.

Conclusions

These results emphasize the need of continuous DENV surveillance in Senegal to detect DENV cases, to define circulating serotypes/genotypes and to prevent the spread and the occurrence of severe cases.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-021-06580-z.

Dengue virus serotype 2 imported case from Côte d'Ivoire to Senegal, 2017

Dengue fever is the most common arboviral infection worldwide. Its epidemiology in Africa is not yet fully understood due to the lack of awareness, the presence of other dengue-like febrile diseases, and insufficient laboratory capabilities. This paper reports on the import of dengue virus serotype 2 case from Côte d'Ivoire to Senegal in West Africa. Phylogenetic analysis based on full-length genome sequence revealed that the isolate clustered with strains of cosmopolitan genotypes from the Burkina Faso outbreak in 2016 and those from the ongoing dengue fever outbreak in Côte d'Ivoire. This suggests a possible spread of strains from the Burkina Faso outbreak to other West African countries including Côte d'Ivoire and Senegal.

Species composition and risk of transmission of some Aedes-borne arboviruses in some sites in Northern Ghana

Aedes-borne viral diseases mainly Yellow Fever (YF), Dengue (DEN), Zika (ZIK) and Chikungunya (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.

Mosquito-Associated Viruses and Their Related Mosquitoes in West Africa

Mosquito-associated viruses (MAVs), including mosquito-specific viruses (MSVs) and mosquito-borne (arbo)viruses (MBVs), are an increasing public, veterinary, and global health concern, and West Africa is projected to be the next front for arboviral diseases. As in-depth knowledge of the ecologies of both western African MAVs and related mosquitoes is still limited, we review available and comprehensive data on their diversity, abundance, and distribution. Data on MAVs’ occurrence and related mosquitoes were extracted from peer-reviewed publications. Data on MSVs, and mosquito and vertebrate host ranges are sparse. However, more data are available on MBVs (i.e., dengue, yellow fever, chikungunya, Zika, and Rift Valley fever viruses), detected in wild and domestic animals, and humans, with infections more concentrated in urban areas and areas affected by strong anthropogenic changes. Aedes aegypti, Culex quinquefasciatus, and Aedes albopictus are incriminated as key arbovirus vectors. These findings outline MAV, related mosquitoes, key knowledge gaps, and future research areas. Additionally, these data highlight the need to increase our understanding of MAVs and their impact on host mosquito ecology, to improve our knowledge of arbovirus transmission, and to develop specific strategies and capacities for arboviral disease surveillance, diagnostic, prevention, control, and outbreak responses in West Africa.

Determining vector competence of Aedes aegypti from Ghana in transmitting dengue virus serotypes 1 and 2

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.

Graphic Abstract

Dengue Virus Infection and Associated Risk Factors in Africa: A Systematic Review and Meta-Analysis

Dengue contributes a significant burden on global public health and economies. In Africa, the burden of dengue virus (DENV) infection is not well described. This review was undertaken to determine the prevalence of dengue and associated risk factors. A literature search was done on PubMed/MEDLINE, Scopus, Embase, and Google Scholar databases to identify articles published between 1960 and 2020. Meta-analysis was performed using a random-effect model at a 95% confidence interval, followed by subgroup meta-analysis to determine the overall prevalence. Between 1960 and 2020, 45 outbreaks were identified, of which 17 and 16 occurred in East and West Africa, respectively. Dengue virus serotype 1 (DENV-1) and DENV-2 were the dominant serotypes contributing to 60% of the epidemics. Of 2211 cases reported between 2009 and 2020; 1954 (88.4%) were reported during outbreaks. Overall, the prevalence of dengue was 29% (95% CI: 20-39%) and 3% (95% CI: 1-5%) during the outbreak and non-outbreak periods, respectively. Old age (6/21 studies), lack of mosquito control (6/21), urban residence (4/21), climate change (3/21), and recent history of travel (3/21) were the leading risk factors. This review reports a high burden of dengue and increased risk of severe disease in Africa. Our findings provide useful information for clinical practice and health policy decisions to implement effective interventions.

Epidemiology of dengue fever in Gabon: Results from a health facility-based fever surveillance in Lambaréné and its surroundings

Background

In Africa, information on dengue is limited to outbreak reports and focused on some countries with continuing transmission in West and East Africa. To estimate the proportion of dengue-positive cases among febrile patients and identify clinical indicators of dengue cases, we conducted passive facility-based fever surveillance in a catchment area population of 70,000 residents of Lambaréné and its surroundings in Gabon.

Methods

Non-malarial febrile patients with current fever or history of fever (≤7 days) between 1 and 55 years of age, were enrolled at Albert Schweitzer Hospital (ASH). Acute (visit 1, day of enrollment) and convalescent blood samples were collected between 10 and 21 days after enrollment. Acute/convalescent samples were tested with IgM/IgG ELISA, and a selected subset of acute samples with RT-PCR.

Results

Among 682 non-malarial febrile patients enrolled, 119 (17.4%) were identified as dengue-positive (94 dengue-confirmed and 25 dengue-probable cases). Of these dengue-positive cases, 14 were confirmed with PCR, and based on serotyping, two infections were identified to be DENV-2 and two were DENV-3. The majority of our enrolled patients were <25 years of age and close to 80% of our dengue-positive cases were <15 years of age. In adjusted analyses, retro-orbital pain and abdominal pain were 2.7 and 1.6 times more frequently found among dengue-positive cases, compared to non-dengue cases.

Conclusion

Lambaréné is not considered dengue-endemic. However, one in six non-malarial febrile episodes was found to be dengue-positive in the study period. Dengue should be considered more frequently in clinicians’ diagnosis among non-malarial febrile patients in Lambaréné. Given the lack of data on dengue in Gabon, additional prospective and longitudinal studies would help to further define the burden and patterns of dengue for improved case detection.

In Africa, information on dengue is limited to outbreak reports focused on some countries in West and East Africa. To estimate the proportion of dengue-positive cases among febrile patients and identify clinical indicators of dengue cases, we conducted passive health facility-based fever surveillance in a catchment area population of 70,000 residents of Lambaréné and its surroundings, Gabon. Among the patients with negative malaria RDT results, those with current fever or history of fever (≤7 days) between 1 and 55 years of age were enrolled at Albert Schweitzer Hospital (ASH). Two samples were collected with an interval of 10 to 21 days after enrollment. Samples underwent different testing for dengue confirmation. Among 682 febrile patients enrolled, 17.4% were identified as dengue-positive. Of these dengue-positive cases, we found DENV-2 and DENV-3 serotypes. Close to 80% of our dengue-positive cases were < 15 years old. Retro-orbital pain and abdominal pain were more commonly found among dengue-positive cases, compared to non-dengue cases. Lambaréné is not considered dengue-endemic. However, one in six non-malarial febrile episodes was found to be dengue-positive in the study period. Clinicians should consider dengue more frequently among non-malarial febrile patients. Given the lack of data on dengue in Gabon, more data should be generated to understand the burden and patterns of dengue for improved case detection.

The evolution of dengue-2 viruses in Malindi, Kenya and greater East Africa: Epidemiological and immunological implications

Kenya experiences a substantial burden of dengue, yet there are very few DENV-2 sequence data available from this country and indeed the entire continent of Africa. We therefore undertook whole genome sequencing and evolutionary analysis of fourteen dengue virus (DENV)-2 strains sampled from Malindi sub-County Hospital during the 2017 DENV-2 outbreak in the Kenyan coast. We further performed an extended East African phylogenetic analysis, which leveraged 26 complete African env genes. Maximum likelihood analysis showed that the 2017 outbreak was due to the Cosmopolitan genotype, indicating that this has been the only confirmed human DENV-2 genotype circulating in Africa to date. Phylogeographic analyses indicated transmission of DENV-2 viruses between East Africa and South/South-West Asia. Time-scaled genealogies show that DENV-2 viruses shows spatial structure at the country level in Kenya, with a time-to-most-common-recent ancestor analysis indicating that these DENV-2 strains were circulating for up to 5.38 years in Kenya before detection in the 2017 Malindi outbreak. Selection pressure analyses indicated sampled Kenyan DENV strains uniquely being under positive selection at 6 sites, predominantly across the non-structural genes, and epitope prediction analyses showed that one of these sites corresponds to a putative predicted MHC-I CD8+ DENV-2 Cosmopolitan virus epitope only evident in a sampled Kenyan virus. Taken together, our findings indicate that the 2017 Malindi DENV-2 outbreak arose from a strain which had circulated for several years in Kenya before recent detection, has experienced diversifying selection pressure, and may contain new putative immunogens relevant to vaccine design. These findings prompt further genomic epidemiology studies in this and other Kenyan locations to further elucidate the transmission dynamics of DENV in this region.

Clinical and epidemiologic characteristics associated with dengue fever in Mombasa, Kenya

OBJECTIVES

Information on dengue in Africa is limited. To estimate the proportion of dengue-positive cases among febrile patients and describe clinical indicators of dengue, we conducted passive health facility-based fever surveillance in Mombasa, Kenya.

METHODS

Non-malarial febrile patients between one and 55 years were enrolled at three health facilities between March 2016 and May 2017. Acute and convalescent blood samples were collected with an interval of 10-21 days. Acute samples were tested with dengue RDT and a selected subset with RT-PCR, and acute/convalescent samples with IgM/IgG ELISA.

RESULTS

Among 482 enrollees, 295 (61.2%) were dengue-positive based on laboratory results. The surveillance covered the beginning of a dengue outbreak in April-May 2017, during which 73.9% of enrollees were dengue-positive. By contrast, during the non-outbreak period, 54.6% were dengue-positive. Dengue case status was positively associated with rash, fatigue, headache, retro-orbital pain, nausea/vomiting, nose bleeding, gum bleeding, loss of appetite, myalgia, and arthralgia. Dengue-positive cases in our study had mostly mild disease, with only two requiring observation, and no DHF.

CONCLUSIONS

The clinical response was generally mild relative to what was observed in SE Asia and the Americas. Given the high level of DENV transmission in Mombasa, more data would be needed to further understand the disease burden and improve case detection for surveillance/monitoring of outbreaks.

Establishment and characterization of a cell line from Ghanaian Aedes aegypti (Diptera: Culicidae) focusing on Aedes-borne flavivirus susceptibility

Mosquitoes are generally considered one of the most important vectors of arboviruses, with Aedes aegypti regarded as the most important in transmission of yellow fever and dengue viruses. To investigate why there are differences in the incidence of dengue fever and Zika in different geographical areas and an absence of outbreaks in Ghana in spite of an abundance of A. aegypti mosquitoes, we established a continuous cell line from embryonic cells of A. aegypti collected in Ghana and assessed its susceptibility to dengue, yellow fever, and Zika viruses. The new cell line (designated AeAe-GH98), having an adhesive spindle-shaped web-like morphology, was serially subcultured in both VP-12 and Schneider's medium supplemented with 10% heat-inactivated fetal bovine serum. AeAe-GH98 cells were found to have a population doubling time of 1.3 d during exponential growth. The mosquito colony used to establish the cell line was confirmed to have originated from Africa using microsatellite assay. In terms of susceptibility to Aedes-borne flaviviruses, AeAe-GH98 cells were found to have different degrees of susceptibility to yellow fever, Zika, and dengue virus infection and propagation. While susceptibility of AeAe-GH98 cells to yellow fever and Zika viruses was comparable with that of C6/36 cells, susceptibility to dengue virus was significantly lower. This cell line will serve as a useful tool for determining molecular factors influencing virus-vector susceptibility in vitro.

Entomological surveillance to assess potential outbreak of Aedes-borne arboviruses and insecticide resistance status of Aedes aegypti from Cape Coast, Ghana

This study was conducted in Cape Coast, a major tourist destination in Ghana to assess the risk of an outbreak of Aedes-borne arboviruses based on entomological indicators and determine their susceptibility to pyrethroid insecticides. A larval survey was conducted in 414 houses between April and July 2017. Larvae collected were reared to adult for WHO susceptibility bioassay against four pyrethroid insecticides (Deltamethrin 0.05%, Permethrin 0.75%, Cyfluthrin 0.15%, Etofenprox 0.5%) and three different brands of mosquito coil; Heaven® (Dimefluthrin 0.03%), Sasso® (Esbiothrin 0.25%), and Fastkit® (D-allethrin 0.25%) as well as four enzyme-activities and F1534C kdr-mutation. Some physicochemical parameters were also measured in Aedes breeding sites. Three larval indices and water quality index (WQI) were calculated. The estimated larval indices were: House index - 68%, Container index - 44%, and Breteau index - 2.4. The level of resistance of the vector to the different pyrethroid insecticides and mosquito coils varied. F1534C kdr-mutation with an allele frequency of 35% and metabolic detoxifying enzyme activities are suspected to be the cause of resistance. Ae. aegypti breeding sites were found to contain organic and other anthropogenic pollutants. Based on the larval indices estimated, the population density of Ae. aegypti in Cape Coast was found to be sufficient to promote an outbreak of arboviruses. Pyrethroid resistance in the vector population could compromise the effectiveness of pyrethroid-based control strategies as was seen with the reduced efficacy of mosquito coils. With large number of international travellers to the city, there is a need to put in place a regular Aedes surveillance program for early response to any potential outbreaks.

Entomological Assessment of the Status and Risk of Mosquito-borne Arboviral Transmission in Ghana

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 suffice in highly endemic areas, it is not as effective in controlling the spread of diseases in low endemic and non-endemic areas. In this study, we examined the efficiency 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.

Clinical and epidemiologic characteristics associated with dengue during and outside the 2016 outbreak identified in health facility-based surveillance in Ouagadougou, Burkina Faso

Background

In Africa, the magnitude of dengue virus (DENV) transmission is largely unknown. In Burkina Faso, several outbreaks have been reported and data are often based on findings from outbreak investigations.

Methods

To better understand dengue epidemiology and clinical characteristics in Burkina Faso, a fever surveillance study was conducted among patients aged 1–55 years, who presented with non-malarial febrile illness at five primary healthcare facilities in Ouagadougou, Burkina Faso from December 2014 to February 2017, encompassing a 3-month dengue outbreak in September-November 2016. Acute and convalescent blood samples were collected within an interval of 10–21 days between visits. Acute samples were tested with dengue rapid diagnostic tests (RDT) and a selected subset with RT-PCR, and all acute/convalescent samples with IgM/IgG ELISA.

Results

Among 2929 non-malarial febrile patients, 740 (25%) were dengue–positive based on RT-PCR and/or IgM/IgG ELISA; 428 out of 777 patients (55%) and 312 out of 2152 (14%) were dengue-positive during outbreak and non-outbreak periods, respectively. There were 11% (316/2929) and 4% (129/2929) patients showing positive for NS1 and IgM, on the RDT, respectively. DENV 2 predominated during the outbreak, whereas DENV 3 predominated before the outbreak. Only 25% of dengue-positive cases were clinically diagnosed with suspected dengue. The odds of requiring observation for ≤3 days (versus routine outpatient care) were 11 times higher among dengue-positive cases than non-dengue cases. In adjusted analyses, dengue-positivity was associated with rash and retro-orbital pain (OR = 2.6 and 7.4, respectively) during the outbreak and with rash and nausea/vomiting (OR = 1.5 and 1.4, respectively) during the non-outbreak period.

Conclusion

Dengue virus is an important pathogen in Burkina Faso, accounting for a substantial proportion of non-malarial fevers both during and outside outbreak, but is only infrequently suspected by clinicians. Additional longitudinal data would help to further define characteristics of dengue for improved case detection and surveillance.

There is not much evidence on dengue in Africa, relative to the Asia-Pacific and Latin American regions. To estimate the proportion of dengue among patients with fever, and to identify clinical features of dengue during outbreak and non-outbreak periods, we studied 2929 patients with non-malarial fever, aged 1–55 years, who attended five primary healthcare centers in Ouagadougou, Burkina Faso. Patients were tested with a rapid test for dengue, and further tests were carried out on paired blood samples taken 10–21 days apart. Overall, a quarter of non-malarial febrile episodes identified between December 2014 and February 2017 were dengue-positive. Dengue-positive cases were 11 times more likely than non-dengue cases to require observation for ≤3 days. During the study period in 2016, there was a dengue outbreak where more than half of non-malarial febrile patients were identified to be dengue-positive. DENV 2 was the main serotype in circulation during the outbreak, whereas DENV 3 was the main serotype before the outbreak. Rash and retro-orbital pain were more frequently found among dengue-positive cases, compared to non-dengue cases, during the outbreak. During the non-outbreak period, rash and nausea/vomiting were more likely in dengue-positive versus non-dengue cases. There was a low level of clinical suspicion of dengue even during the 2016 outbreak. Therefore, a broader use of rapid diagnostic tests and more epidemiologic data would help to improve dengue case detection and surveillance in Burkina Faso.

Molecular detection of dengue virus in patients suspected of Ebola virus disease in Ghana

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.