First documented evidence of dengue and malaria co-infection in children attending two health centers in Yaoundé, Cameroon

Clinical description of dengue and chikungunya virus infections amongst acute febrile patients in a malaria endemic area of Mfou, the Centre region of Cameroon

This study aims to determine the frequency and clinical manifestations of dengue and chikungunya viral infections in the district hospital of Mfou, Centre region of Cameroon where malaria is endemic. Blood samples were collected from suspected cases and tested for Plasmodium parasites and for the molecular detection of viral RNAs (dengue, zika and chikungunya viruses) using TRIOPLEX qPCR. A total of 108 patients were clinically suspected among which 25 % were male and 50 % were less than 15.5 years old. Of these 14.8 % (16/108) and 2.8 % (3/108) had acute dengue and chikungunya fevers respectively. Co-infection with malaria was reported in 56.3 % (9/16) of Dengue cases and 33.3 % (1/3) of chikungunya cases. Clinical profiling further revealed that nausea and vomiting show a significant difference in dengue infected individuals to those of non-infected individuals (P = 0.027). The presence of dengue fever and chikungunya fever and the absence of specific clinical manifestations highlight the need to strengthen surveillance of acute febrile infections for a better estimation of the burden of arboviruses.

Seroprevalence study of dengue-malaria coinfection in an East-Cameroonian public hospital: A comparison between malarial and non-malarial groups

BACKGROUNDS OBJECTIVES

Recent research in Cameroon reported several occurrences of dengue in urban settings, but concurrent dengue-malaria infection has received less attention, particularly in the East region.

METHODS

A two-month cross-sectional and comparative research was performed at Bertoua Regional Hospital which included 50 malaria-positive participants and 90 non-malaria subjects. Participants were selected and provided with a questionnaire to collect sociodemographic data. Blood samples were collected and tested for dengue infection and hematological parameters were assessed.

RESULTS

Dengue fever was found in 14% of malarial patients vs 66.66% of controls. Secondary dengue infection was more prevalent in malarial patients than in non-malarial patients. Gender, age, and place of residence were positively correlated to dengue seropositivity. Platelets were substantially lower (P<0.001) in the malarial group than in the non-malarial group.

INTERPRETATION CONCLUSION

In the study, coinfected patients were found to be more vulnerable to dengue, emphasizing the importance of epidemiological surveillance.

Mosquito-Borne Arboviruses Occurrence and Distribution in the Last Three Decades in Central Africa: A Systematic Literature Review

Arboviruses represent a real public health problem globally and in the Central African subregion in particular, which represents a high-risk zone for the emergence and re-emergence of arbovirus outbreaks. Furthermore, an updated review on the current arbovirus burden and associated mosquito vectors is lacking for this region. To contribute to filling this knowledge gap, the current study was designed with the following objectives: (i) to systematically review data on the occurrence and distribution of arboviruses and mosquito fauna; and (ii) to identify potential spillover mosquito species in the Central African region in the last 30 years. A web search enabled the documentation of 2454 articles from different online databases. The preferred reporting items for systematic reviews and meta-analyses (PRISMA) and the quality of reporting of meta-analyses (QUORUM) steps for a systematic review enabled the selection of 164 articles that fulfilled our selection criteria. Of the six arboviruses (dengue virus (DENV), chikungunya virus (CHIKV), yellow fever virus (YFV), Zika virus (ZIKV), Rift Valley fever virus (RVFV), and West Nile virus (WNV)) of public health concern studied, the most frequently reported were chikungunya and dengue. The entomological records showed >248 species of mosquitoes regrouped under 15 genera, with Anopheles (n = 100 species), Culex (n = 56 species), and Aedes (n = 52 species) having high species diversity. Three genera were rarely represented, with only one species included, namely, Orthopodomyia, Lutzia, and Verrallina, but individuals of the genera Toxorhinchites and Finlayas were not identified at the species level. We found that two Aedes species (Ae. aegypti and Ae. albopictus) colonised the same microhabitat and were involved in major epidemics of the six medically important arboviruses, and other less-frequently identified mosquito genera consisted of competent species and were associated with outbreaks of medical and zoonotic arboviruses. The present study reveals a high species richness of competent mosquito vectors that could lead to the spillover of medically important arboviruses in the region. Although epidemiological studies were found, they were not regularly documented, and this also applies to vector competence and transmission studies. Future studies will consider unpublished information in dissertations and technical reports from different countries to allow their information to be more consistent. A regional project, entitled "Ecology of Arboviruses" (EcoVir), is underway in three countries (Gabon, Benin, and Cote d'Ivoire) to generate a more comprehensive epidemiological and entomological data on this topic.

Whole genome sequencing of outbreak strains from 2017 to 2018 reveals an endemic clade of dengue 1 virus in Cameroon

Dengue fever is expanding as a global public health threat including countries within Africa. For the past few decades, Cameroon has experienced sporadic cases of arboviral infections including dengue fever. Here, we conducted genomic analyses to investigate the origin and phylogenetic profile of Cameroon DENV-1 outbreak strains and predict the impact of emerging therapeutics on these strains. Bayesian and maximum-likelihood phylogenetic inference approaches were employed in virus evolutionary analyses. An in silico analysis was performed to assess the divergence in immunotherapeutic and vaccine targets in the new genomes. Six complete DENV-1 genomes were generated from 50 samples that met a clinical definition for DENV infection. Phylogenetic analyses revealed that the strains from the current study belong to a sub-lineage of DENV-1 genotype V and form a monophyletic taxon with a 2012 strain from Gabon. The most recent common ancestor (TMRCA) of the Cameroon and Gabon strains was estimated to have existed around 2008. Comparing our sequences to the vaccine strains, 19 and 15 amino acid (aa) substitutions were observed in the immuno-protective prM-E protein segments of the Dengvaxia® and TetraVax-DV-TV003 vaccines, respectively. Epitope mapping revealed mismatches in aa residues at positions E155 and E161 located in the epitope of the human anti-DENV-1 monoclonal antibody HMAb 1F4. The new DENV strains constitute a conserved genomic pool of viruses endemic to the Central African region that needs prospective monitoring to track local viral evolution. Further work is needed to ascertain the performance of emerging therapeutics in DENV strains from the African region.

Cross-reactivity of SARS-CoV-2 with other pathogens, especially dengue virus: A historical perspective

Dengue is a vector-borne viral disease caused by a Flavivirus whereas the COVID-19 pandemic was caused by a highly contagious virus, SARS-CoV-2 belonging to the family Coronaviridae. However, COVID-19 severity was observably less in dengue-endemic countries and vice versa especially during the active years of the pandemic (2019-2021). We observed that dengue virus (DENV) antibodies (Abs) could cross-react with SARS-CoV-2 spike antigen. This resulted in SARS-CoV-2 false positivity by rapid Ab test kits. DENV Abs binding to SARS-CoV-2 receptor-binding domain (and the reverse scenario), as revealed by docking studies further validated DENV and SARS-CoV-2 cross-reactivity. Finally, SARS-CoV-2 Abs were found to cross-neutralize DENV1 and DENV2 in virus neutralization test (VNT). Abs to other pathogens like Plasmodium were also cross-reactive but non-neutralizing for SARS-CoV-2. Here, we analyze the existing data on SARS-CoV-2 cross-reactivity with other pathogens, especially dengue to assess its impact on health (cross-protection?) and differential sero-diagnosis/surveillance.

Arboviruses as an unappreciated cause of non-malarial acute febrile illness in the Dschang Health District of western Cameroon

Acute febrile illness is a common problem managed by clinicians and health systems globally, particularly in the Tropics. In many regions, malaria is a leading and potentially deadly cause of fever; however, myriad alternative etiologies exist. Identifying the cause of fever allows optimal management, but this depends on many factors including thorough knowledge of circulating infections. Arboviruses such as dengue (DENV) cause fever and may be underdiagnosed in sub-Saharan Africa where malaria is a major focus. We examined cases of fever in western Cameroon that tested negative for malaria and found 13.5% (13/96) were due to DENV, with 75% (9/12) of these being DENV serotype 2 infections. Two complete DENV2 genomes were obtained and clustered closely to recent isolates from Senegal and Burkina Faso. The seroprevalence of DENV in this region was 24.8% (96/387). Neutralizing antibodies to DENV2 were detected in all (15/15) seropositive samples tested. Chikungunya (CHIKV) is an arthritogenic alphavirus that is transmitted by Aedes mosquitoes, the same principal vector as DENV. The seroprevalence for CHIKV was 15.7% (67/427); however, CHIKV did not cause a single case of fever in the 96 subjects tested. Of note, being seropositive for one arbovirus was associated with being seropositive for the other (Χ² = 16.8, p<0.001). Taken together, these data indicate that Aedes-transmitted arboviruses are endemic in western Cameroon and are likely a common but underappreciated cause of febrile illness. This work supports the need for additional study of arboviruses in sub-Saharan Africa and efforts to improve diagnostic capacity, surveillance systems, and arbovirus prevention strategies.

Acute illness with fever is common but can be challenging for clinicians to manage, particularly in resource-limited settings. In sub-Saharan Africa, malaria is a major cause of fever, but other causes of fever are poorly documented or monitored, which impairs optimal medical care to patients and implementation of public health interventions to control leading causes of disease. Viruses transmitted by mosquitoes are a prevalent and expanding problem throughout the tropics and beyond; however, there is concern that these infections frequently go undetected in sub-Saharan Africa. We discovered a previously unrecognized outbreak of dengue virus in western Cameroon by testing remnant samples from over 400 patients that presented with fever. Our results indicate that dengue has circulated in this region for decades with little recognition. This study adds important information about causes of fever in sub-Saharan Africa and advocates for increasing investment in surveillance systems and prevention strategies for mosquito-borne viruses.

Assessment of Dengue and Chikungunya Infections among Febrile Patients Visiting Four Healthcare Centres in Yaoundé and Dizangué, Cameroon

Dengue and chikungunya are now widely distributed in Cameroon, but there is still not enough information on their prevalence in different epidemiological settings. This study was undertaken to assess the prevalence of dengue and chikungunya in both urban and rural settings in Cameroon using three diagnostic tools. From December 2019 to September 2021, willing febrile (temperature >38 °C) outpatients visiting four healthcare facilities in the cities of Yaoundé and Dizangué were screened for dengue, and chikungunya. Clinical features of patient were recorded in a form, and their blood samples were analysed using real-time reverse transcriptase-polymerase chain reaction (rtRT-PCR), rapid diagnostic tests (RDTs) and enzyme-linked immuno-sorbent assays (ELISA). Odds ratios were used to determine the level of association between socio-demographic factors, clinical features, and infection status. The Kappa coefficient permitted to assess the level of agreement between RDTs and ELISA. Overall, 301 febrile patients were recruited in the study: 198 in Yaoundé and 103 in Dizangué. The prevalence of infection varied with the diagnostic tool used. For dengue diagnostics, 110 patients were positive to rtRT-PCR: 90 (45.45%) in Yaoundé, and 20 (19.42%) in Dizangué. The prevalence of dengue IgM using ELISA varied from 22.3% in Dizangué to 30.8% in Yaoundé. Dengue IgM rate using RDTs was 7.6% in Yaoundé and 3.9% in Dizangué. For chikungunya, one (0.5%) patient (Yaoundé, suburb) was positive to rtRT-PCR. The prevalence of chikungunya IgM according to ELISA varied from 18.4% in Dizangué to 21.7% in Yaoundé, while it was 4.5% in Yaoundé and 12.6% in Dizangué with RDTs. Only abdominal and retro-orbital pains were significantly associated with acute dengue infection. All four dengue serotypes were recorded, with a predominance of DENV-3 (35.45%) and DENV-4 (25.45%). Rapid Diagnostic Tests for either chikungunya or dengue displayed very poor sensitivity. This study further confirms the high endemicity of both dengue and chikungunya in Yaoundé and Dizangué. These data stress the need for active surveillance and the implementation of vector control measures to prevent the occurrence of outbreaks across the country.

Aedes Mosquito Surveillance Using Ovitraps, Sweep Nets, and Biogent Traps in the City of Yaoundé, Cameroon

Arbovirus diseases represent a significant public health problem in Cameroon and vector surveillance is a key component of prevention strategies. However, there is still not enough evidence of the efficacy of different sampling methods used to monitor Aedes mosquito population dynamic in different epidemiological settings. The present study provides data on the evaluation of ovitraps and different adult sampling methods in the city of Yaoundé and its close vicinity. Entomological surveys were carried out from February 2020 to March 2021 in two urban (Obili, Mvan), two peri-urban (Simbock, Ahala), and two rural (Lendom, Elig-essomballa) sites in the city of Yaoundé. The efficacy of three sampling methods, namely ovitraps, Biogent Sentinel trap, and sweep nets, was evaluated. Different ovitrap indices were used to assess the infestation levels across study sites; a general linear model was used to determine if there are statistical differences between positive ovitraps across ecological zones. A total of 16,264 Aedes mosquitoes were collected during entomological surveys. Ovitraps provided the highest mosquito abundance (15,323; 91.14%) and the highest species diversity. Of the five Aedes species collected, Aedes albopictus (59.74%) was the most commonly recorded in both urban and rural settings. Different Aedes species were collected in the same ovitrap. The ovitrap positivity index was high in all sites and varied from 58.3% in Obili in the urban area to 86.08% in Lendom in the rural area. The egg density index varied from 6.42 in Mvan (urban site) to 13.70 in Lendom (rural area). Adult sampling methods recorded mostly Aedes albopictus. The present study supports high infestation of Aedes species in the city of Yaoundé. Ovitraps were highly efficient in detecting Aedes distribution across study sites. The situation calls for regular surveillance and control of Aedes population to prevent sudden occurrence of outbreaks.

Dengue and Chikungunya virus circulation in Cameroon and Gabon: molecular evidence among symptomatic individuals

We report the molecular evidence of dengue virus (DENV) and chikungunya virus (CHIKV) infection in symptomatic individuals in Cameroon and Gabon, respectively. Arthropod-borne viruses (arboviruses) are distributed in the tropical or subtropical regions, with DENV having the highest burden. The morbidity and mortality related to arboviral diseases raise the concern of timely and efficient surveillance and care. Our aim was to assess the circulation of arboviruses [DENV, CHIKV, Zika virus (ZIKV)] among febrile patients in Dschang (West Cameroon) and Kyé-ossi (South Cameroon, border with Gabon and Equatorial Guinea). Dried blood spots were collected from 601 consenting febrile patients, and 194 Plasmodium spp.-negative samples were tested for the molecular detection of cases of DENV, CHIKV and ZIKV infection. Overall, no case of ZIKV infection was found, whereas one case of DENV infection and one case of CHIKV infection were detected in Dschang and Kyé-ossi, respectively, with the CHIKV-infected patient being resident in Gabon. Our findings suggest the need to establish an active surveillance of arbovirus transmission in Cameroon and bordering countries.

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.

Concurrent circulation of dengue serotype 1, 2 and 3 among acute febrile patients in Cameroon

Acute febrile patients presenting at hospitals in Douala, Cameroon between July and December 2020, were screened for dengue infections using real time RT-PCR on fragments of the 5’ and 3’ UTR genomic regions. In total, 12.8% (41/320) of cases examined were positive for dengue. Dengue virus 3 (DENV-3) was the most common serotype found (68.3%), followed by DENV-2 (19.5%) and DENV-1 (4.9%). Co-infections of DENV-3 and DENV-2 were found in 3 cases. Jaundice and headache were the most frequent clinical signs associated with infection and 56% (23/41) of the cases were co-infections with malaria. Phylogenetic analysis of the envelope gene identified DENV-1 as belonging to genotype V, DENV-2 to genotype II and DENV-3 to genotype III. The simultaneous occurrence of three serotypes in Douala reveals dengue as a serious public health threat for Cameroon and highlights the need for further epidemiological studies in the major cities of this region.

Acute febrile patients presenting at hospitals in Douala, Cameroon between July and December 2020, were screened for dengue infections by Polymerase chain reaction. In total, 12.8% (41/320) of cases examined were infected by dengue virus. Dengue virus 3 (DENV-3) was the most common serotype found (68.3%), followed by DENV-2 (19.5%) and DENV-1 (4.9%). Co-infections of DENV-3 and DENV-2 were found in 3 cases. Jaundice and headache were the most frequent clinical signs associated with infection and 56% (23/41) of the cases were co-infections with malaria. The simultaneous occurrence of three serotypes in Douala reveals dengue as a serious public health threat for Cameroon and highlights the need for further epidemiological studies in the major cities of this region.

Investigation of dengue-malaria coinfection among febrile patients consulting at Ngaoundere Regional Hospital, Cameroon

This study aimed at evaluating the seroprevalence of dengue among malarious patients consulting at the Ngaoundere Regional Hospital. During 2 months and a half, 174 participants were recruited and their blood samples were screened for Plasmodium spp and then for Dengue virus (DENV) infection using rapid diagnostic tests. Also, hematological asparameters were measured using a hematology autoanalyzer. Among patients tested, 134 (77.01%) were malaria-positive, and 12/134 (8.95%) were coinfected. In this population, 8/12 (66.67%) were only anti-DENV IgM-positive, 3/12 (25%) were both NS1 and anti-DENV IgM positive, and 1/12 (8.33%) were anti-DENV IgG-positive. Furthermore, women were more affected (58.3%) than men (41.7%). The most affected age groups were young people aged less than or equal to 15 years (33.3%) and adults aged between 30 and 45 years (33.3%). A significant association (p < .05; odds ratio [OR] = 5.16) was found between the age range (30-45) and dengue-malaria coinfection. Similarly, we noted a significant association between the coinfection, and joint pain (p < .05; OR = 6.15), fatigue (p < .01; OR = 5.74), and chills (p < .05; OR = 0). Analysis of hematologic parameters showed a significant decrease (p < .001) in platelets in coinfected patients compared with monoinfected patients. In conclusion, dengue-malaria coinfection is a reality in Ngaoundere city and associated with the appearance of clinical features which predict the disease severity.

Enhanced passive surveillance dengue infection among febrile children: Prevalence, co-infections and associated factors in Cameroon

Dengue virus (DENV) causes a spectrum of diseases ranging from asymptomatic, mild febrile to a life-threatening illness: dengue hemorrhagic fever. The main clinical symptom of dengue is fever, similar to that of malaria. The prevalence of dengue virus infection, alone or in association with other endemic infectious diseases in children in Cameroon is unknown. The aim of this study was to determine the prevalence of dengue, malaria and HIV in children presenting with fever and associated risk factors.

Dengue overall prevalence was 20.2%, Malaria cases were 52.7% and HIV cases represented 12.6%. The prevalence of dengue-HIV co-infection was 6.0% and that of Malaria-dengue co-infection was 19.5%. Triple infection prevalence was 4.3%. Dengue virus infection is present in children and HIV-Dengue or Dengue- Malaria co-infections are common. Dengue peak prevalence was between August and October. Sex and age were not associated with dengue and dengue co-infections. However, malaria as well as HIV were significantly associated with dengue (P = 0.001 and 0.028 respectively). The diagnosis of dengue and Malaria should be carried out routinely for better management of fever.

Fever is a symptom common to several infectious diseases such as malaria, yellow fever, dengue fever and typhoid which are all present in Cameroon. In most cases, fever in Cameroon is assumed to be due to malaria and treated as such. This study present the prevalence of dengue fever among febrile children. Dengue fever as well as malaria is common among Cameroonian children. Since Cameroon is endemic for malaria, fever may indicate either malaria or dengue. Clinicians should be aware of the presence of dengue in Cameroon. Knowing the risk factors, parents are encouraged to use the bed net to protect their children and clean stagnant water from their environment. Children could be co-infected by dengue, malaria as well as HIV. Management of patients with dengue fever and HIV infection should be studied, especially in infants where both viral diseases are more severe. Close monitoring may prevent complications among HIV-infected individuals who contract dengue fever.

Dengue in Western Uganda: a prospective cohort of children presenting with undifferentiated febrile illness

BACKGROUND

The spatial distribution and burden of dengue in sub-Saharan Africa remains highly uncertain, despite high levels of ecological suitability. The goal of this study was to describe the epidemiology of dengue among a cohort of febrile children presenting to outpatient facilities located in areas of western Uganda with differing levels of urbanicity and malaria transmission intensity.

METHODS

Eligible children were first screened for malaria using rapid diagnostic tests. Children with a negative malaria result were tested for dengue using a combination NS1/IgM/IgG rapid test (SD Bioline Dengue Duo). Confirmatory testing by RT-PCR was performed in a subset of participants. Antigen-capture ELISA was performed to estimate seroprevalence.

RESULTS

Only 6 of 1416 (0.42%) children had a positive dengue rapid test, while none of the RT-PCR results were positive. ELISA testing demonstrated reactive IgG antibodies in 28 (2.2%) participants with the highest prevalence seen at the urban site in Mbarara (19 of 392, 4.9%, p < 0.001).

CONCLUSIONS

Overall, these findings suggest that dengue, while present, is an uncommon cause of non-malarial, pediatric febrile illness in western Uganda. Further investigation into the eocological factors that sustain low-level transmission in urban settings are urgently needed to reduce the risk of epidemics.

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.

First detection of F1534C knockdown resistance mutation in Aedes aegypti (Diptera: Culicidae) from Cameroon

Background

Aedes borne viral diseases, notably dengue, are increasingly reported in Cameroon with Aedes aegypti being a major vector. Data on insecticide resistance of this vector and underlying mechanisms needed for outbreak preparedness remain scarce in Cameroon. Here, we present the nationwide distribution of insecticide resistance in Ae. aegypti and investigate the potential resistance mechanisms involved.

Methods

Immature stages of Ae. aegypti were collected between March and July 2017 in 13 locations across Cameroon and reared until G1/G2/G3 generation. Larval, adult bioassays, and piperonyl butoxide (PBO) synergist assays were carried out according to World Health Organization guidelines. F1534C mutation was genotyped using allele specific polymerase chain reaction in field collected adults (Go) and the polymorphism of the sodium channel gene was assessed. The χ² test was used to compare the mortality rate between bioassays with insecticides only and bioassays after preexposure to PBO synergist.

Results

Larval bioassay revealed that all the three populations tested with temephos were susceptible. Adult bioassays showed a good level of susceptibility toward both pyrethroids tested, 0.25% permethrin and 0.05% deltamethrin, with six out of 10 populations susceptible. However, two populations (Douala and Edéa) were resistant (deltamethrin [73.2–92.5% mortality], permethrin [2.6–76.3% mortality]). The resistance to 4% dichlorodiphenyltrichloroethane was observed in four out of 10 populations tested (16.8–87.1% mortality). Resistance was also reported to carbamates including 0.1% propoxur (60.8–87.1% mortality) and to 0.1% bendiocarb (82.9% mortality). All populations tested were fully susceptible to 1% fenitrothion. A partial recovery of susceptibility was observed in the pyrethroid resistant population of Douala after pre-exposed to PBO suggesting the implication of cytochrome P450 monoxygenases permethrin resistance. Genotyping and sequencing detected the F1534C kdr mutation in the two pyrethroid resistant locations of Edéa and Douala, with allelic frequency of 3.3% and 33.3% respectively. However, the high genetic diversity of the sodium channel gene supports the recent introduction of this mutation in Cameroon.

Conclusions

This study revealed the contrasting resistance profiles to insecticides of Ae. aegypti populations in Cameroon suggesting that, instead of a unique nationwide control approach, a regionally adapted strategy will be needed to control this vector. The localised distribution of the F1534C kdr mutation supports this region-specific control strategy.

Understanding immunopathology of severe dengue: lessons learnt from sepsis

Endothelial dysfunction leading to vascular permeability and plasma leakage are characteristic features of severe dengue and sepsis. However, the mechanisms underlying these immune-pathologies remain unclear. The risk of severe dengue and sepsis development depend on patient-related and pathogen-related factors. Additionally, comorbidities increase the risk of severe disease and their incidence hampers correct diagnosis and treatments. To date, there is no efficient therapy to combat severe dengue and sepsis. Here, we discuss the differences and similarities between the pathogenesis of severe dengue and that of bacterial sepsis. We identify gaps in knowledge that need to be better understood in order to move towards the rational development and/or usage of therapeutic strategies to ameliorate severe dengue disease.

TLR2 on blood monocytes senses dengue virus infection and its expression correlates with disease pathogenesis

Vascular permeability and plasma leakage are immune-pathologies of severe dengue virus (DENV) infection, but the mechanisms underlying the exacerbated inflammation during DENV pathogenesis are unclear. Here, we demonstrate that TLR2, together with its co-receptors CD14 and TLR6, is an innate sensor of DENV particles inducing inflammatory cytokine expression and impairing vascular integrity in vitro. Blocking TLR2 prior to DENV infection in vitro abrogates NF-κB activation while CD14 and TLR6 block has a moderate effect. Moreover, TLR2 block prior to DENV infection of peripheral blood mononuclear cells prevents activation of human vascular endothelium, suggesting a potential role of the TLR2-responses in vascular integrity. TLR2 expression on CD14 + + classical monocytes isolated in an acute phase from DENV-infected pediatric patients correlates with severe disease development. Altogether, these data identify a role for TLR2 in DENV infection and provide insights into the complex interaction between the virus and innate receptors that may underlie disease pathogenesis.

Patterns of Ecological Adaptation of Aedes aegypti and Aedes albopictus and Stegomyia Indices Highlight the Potential Risk of Arbovirus Transmission in Yaoundé, the Capital City of Cameroon

The dynamic of arbovirus vectors such as Aedes aegypti and Ae. albopictus remains poorly understood in large cities in central Africa. Here, we compared the larval ecology, geographical distribution and degree of infestation of Ae. aegypti and Ae. albopictus in Yaoundé, the capital city of Cameroon, and estimated their Stegomyia indices revealing a significant potential risk of arbovirus transmission. An entomological survey was conducted in April-May 2018 in a cluster of houses randomly selected. Each selected house was inspected, the number of inhabitants was recorded, and potential and positive containers for Aedes were characterized. Stegomyia and pupae-based indices were estimated. Overall, 447 houses and 954 containers were inspected comprising 10,801 immature stages of Aedes with 84.95% of Ae. albopictus and 15.05% of Ae. aegypti. Both species bred mainly in discarded tanks and used tyres, associated with turbid water and the presence of plant debris inside containers. Aedes albopictus was the most prevalent species in almost all neighbourhoods. The house index, Breteau index, and container index were higher for Ae. albopictus (38.26%, 71.81%, and 29.61%) compared to those of Ae. aegypti (25.73%, 40.93%, and 16.88%). These indices are high compared to the thresholds established by Pan American Health Organization and World Health Organization, which suggests a high potential risk of arbovirus transmission.

Evidence of Low-Level Dengue Virus Circulation in the South Region of Cameroon in 2018

Dengue fever is an understudied disease in many parts of Africa and little is known about its prevalence in Cameroon. We tested blood from 629 individuals from the South Region of Cameroon, collected over the course of one year, for flavivirus RNA using conventional broad range PCR. Flavivirus RNA corresponding to dengue virus (DENV) serotype 1 was identified in two individuals who were also diagnosed with malaria. This finding confirms previous reports that indicate the presence of low-level circulation of DENV in Cameroon and supports the concern that dengue fever may be underdiagnosed due to more prevalent diseases that have similar symptomology and insufficient diagnostic capacity.

Risk of dengue in Central Africa: Vector competence studies with Aedes aegypti and Aedes albopictus (Diptera: Culicidae) populations and dengue 2 virus

Introduction

Dengue is the most important mosquito-borne diseases worldwide but was considered scarce in West-Central Africa. During the last decade, dengue outbreaks have increasingly been reported in urban foci in this region suggesting major epidemiological changes. However, in Central Africa where both vectors, Aedes aegypti and Aedes albopictus are well established, the role of each species in dengue transmission remains poorly investigated.

Methodology/Principal findings

Field-collected strains of Ae. aegypti and Ae. albopictus from different ecological settings in Central Africa were experimentally challenged with dengue 2 virus (DENV-2). Mosquitoes were analysed at 14- and 21-days post-infection. Analysis provide evidence that both Ae. aegypti and Ae. albopictus in Central Africa were able to transmit dengue virus with Ae. aegypti exhibiting a higher transmission rate. Unexpectedly, two Ae. aegypti populations from Bénoué and Maroua, in northern Cameroon, were not able to transmit DENV-2.

Conclusions/Significance

We conclude that both Ae. aegypti and Ae. albopictus are susceptible to DENV-2 and may intervene as active dengue vectors. These findings highlight the urgent need to plan a vector surveillance program and control methods against dengue vectors in Central Africa in order to prevent future outbreaks.

Dengue virus (DENV) is a flavivirus mainly transmitted to humans through the bite of infected mosquitoes notably Aedes aegypti and Aedes albopictus. In Central Africa where both vectors, Ae. aegypti and Ae. albopictus are well established, the role of each species in dengue transmission remains poorly investigated. Here, we assessed the vector competence of Ae. aegypti and Ae. albopictus collected in different ecological settings in Central Africa to transmit dengue 2 virus (DENV-2). We provide evidence that both Ae. aegypti and Ae. albopictus in Central Africa were able to transmit dengue virus with Ae. aegypti exhibiting a higher transmission rate. These findings could increase the risk of dengue outbreak in the region and emphasize the need for a comprehensive vector surveillance program to prevent and preparedness for an intervention in case of outbreaks.

Update on the geographical distribution and prevalence of Aedes aegypti and Aedes albopictus (Diptera: Culicidae), two major arbovirus vectors in Cameroon

Introduction

Arboviral diseases including dengue are increasingly spreading in the tropical/subtropical world including Africa. Updated knowledge on the distribution and abundance of the major vectors Aedes aegypti and Aedes albopictus constitutes crucial surveillance action to prepare African countries such as Cameroon for potential arbovirus outbreaks. Here, we present a nationwide survey in Cameroon to assess the current geographical distribution and prevalence of both vectors including a genetic diversity profiling of Ae. albopictus (invasive species) using mitochondrial DNA.

Methods

Immature stages of Aedes were collected between March and August 2017 in 29 localities across Cameroon following north-south and east-west transects. Larvae and pupae were collected from several containers in each location, reared to adult and morphologically identified. Genetic diversity of Ae. albopictus from 16 locations were analysed using Cytochrome Oxidase I gene (COI).

Results

In total, 30,381 immature stages of Aedes with an average of 646.40±414.21 per location were identified across the country comprising 69.3% of Ae. albopictus and 30.7% of Ae. aegypti. Analysis revealed that Ae. aegypti is still distributed nation widely whereas Ae. albopictus is limited to the southern part, around 6°4’N. However, Ae. albopictus is the most prevalent species in all southern locations where both species are sympatric except in Douala where Ae. aegypti is predominant. This suggests that factors such as climate, vegetation, and building density impact the distribution of both species in Cameroon. Mitochondrial DNA analysis revealed a low genetic diversity in Ae. albopictus populations with a major common haplotype resulting in low haplotype diversity ranging from 0.13 to 0.65 and 0.35 for the total sample. Similarly, low nucleotide diversity was also reported varying from 0.0000 to 0.0017 with an overall index of 0.0008. This low genetic polymorphism is consistent with the recent introduction of Ae. albopictus in Cameroon.

Conclusion

This updated distribution of arbovirus vectors across Cameroon will help in planning vector control programme against possible outbreak of arbovirus related diseases in the country.

Aedes albopictus and Ae. aegypti are the most important arbovirus vectors worldwide. Ae. albopictus, native of Asia, was recorded for the first time in early 2000s in Cameroon, central Africa. Previous studies performed a decade ago in Cameroon showed that Ae. albopictus has a geographical distribution limited to the south under 6°N. Whereas the native species Ae. aegypti was present across the country. To update our knowledge in this regards, a nationwide survey was performed in Cameroon to assess the current geographical distribution and prevalence of both vectors including a genetic diversity profiling of Ae. albopictus (invasive species) using mitochondrial DNA. Analysis revealed that Ae. aegypti is still distributed nation widely whereas Ae. albopictus is limited to the southern part, around 6°4’N. However, Ae. albopictus is the most prevalent species in all southern locations where both species are sympatric except in Douala where Ae. aegypti is predominant. This suggests that factors such as climate, vegetation and building density impact the distribution of both species in Cameroon. Mitochondrial DNA analysis revealed a low genetic diversity in Ae. albopictus populations with a major common haplotype detected in almost all locations. This study provides the relevant data that can be helpful to establish the vector surveillance of epidemic arbovirus vectors across the country.

Detection and serotyping of dengue viruses in febrile patients consulting at the New-Bell District Hospital in Douala, Cameroon

Arboviruses are a major public health problem worldwide and are predominantly present in intertropical areas. Chikungunya, dengue and zika viruses have been implicated in recent epidemics in Asia, America and Africa. In Cameroon, data on these viruses are fragmentary. The purpose of this study was to determine the frequency of detection of these three viruses in febrile patients in Douala, Cameroon. A cross-sectional and descriptive study was conducted from March to April 2017 at the New-Bell District Hospital in Douala. Blood samples were collected from febrile patients and tested for malaria infections using Rapid Diagnostic test. Plasma harvested was later analyzed for the presence of chikungunya, dengue and zika viruses by a Trioplex real-time RT-PCR at Centre Pasteur of Cameroon. A total of 114 participants were included, of which 63.2% were females, reflecting a sex ratio (female/male) of 1.7. The median age was 26 years, range [0.25–81]. Eight (7%) of the 114 participants were infected with Dengue virus (DENV) among which 5 were identified as serotype 1. No cases of infection by either Zika virus or Chikungunya virus were detected. Three cases of dengue-malaria co-infection (13%) were recorded. No association was found between socio-demographic factors and dengue infection. The phylogenetic analysis of the partial envelope E gene showed that all the five DENV serotype 1 samples belonged to subtype V, similarly to strains from West African countries, particularly those from Nigeria, Senegal and Côte d’Ivoire. This study showed the circulation of DENV serotype 1 in febrile patients and raises the alarm for the establishment of a sustained surveillance system to detect cases and prevent potential outbreaks in Cameroon. The existence of dengue-malaria co-infections suggests that surveillance of arboviruses should not be limited to febrile, non-malarial cases.