Concurrent Clade I and Clade II Monkeypox Virus Circulation, Cameroon, 1979-2022

During 1979-2022, Cameroon recorded 32 laboratory-confirmed mpox cases among 137 suspected mpox cases identified by the national surveillance network. The highest positivity rate occurred in 2022, indicating potential mpox re-emergence in Cameroon. Both clade I (n = 12) and clade II (n = 18) monkeypox virus (MPXV) were reported, a unique feature of mpox in Cameroon. The overall case-fatality ratio of 2.2% was associated with clade II. We found mpox occurred only in the forested southern part of the country, and MPXV phylogeographic structure revealed a clear geographic separation among concurrent circulating clades. Clade I originated from eastern regions close to neighboring mpox-endemic countries in Central Africa; clade II was prevalent in western regions close to West Africa. Our findings suggest that MPXV re-emerged after a 30-year lapse and might arise from different viral reservoirs unique to ecosystems in eastern and western rainforests of Cameroon.

Interactions between vector competence to chikungunya virus and resistance to deltamethrin in Aedes aegypti laboratory lines?

The urban mosquito species Aedes aegypti is the main vector of arboviruses worldwide. Mosquito control with insecticides is the most prevalent method for preventing transmission in the absence of effective vaccines and available treatments; however, the extensive use of insecticides has led to the development of resistance in mosquito populations throughout the world, and the number of epidemics caused by arboviruses has increased. Three mosquito lines with different resistance profiles to deltamethrin were isolated in French Guiana, including one with the I1016 knock-down resistant allele. Significant differences were observed in the cumulative proportion of mosquitoes with a disseminated chikungunya virus infection over time across these lines. In addition, some genes related to resistance (CYP6BB2, CYP6N12, GST2, trypsin) were variably overexpressed in the midgut at 7 days after an infectious bloodmeal in these three lines. Our work shows that vector competence for chikungunya virus varied between Ae. aegypti laboratory lines with different deltamethrin resistance profiles. More accurate verification of the functional association between insecticide resistance and vector competence remains to be demonstrated.

Cotrimoxazole versus sulfadoxine-pyrimethamine for intermittent preventive treatment of malaria in HIV-infected pregnant women in Bangui, Central African Republic: A pragmatic randomised controlled trial

OBJECTIVE

The main objective of the MACOMBA (Maternity and Control of Malaria-HIV co-infection in Bangui) trial was to show that cotrimoxazole (CTX) is more effective than sulphadoxine-pyremethamine-IPTp (IPTp-SP) to prevent placental malaria infection (primary end point) among HIV-positive pregnant women with a CD4+ count ≥350 cells/mm³ in Bangui, CAR.

METHODS

MACOMBA is a multicentre, open-label randomised trial conducted in four maternity hospitals in Bangui. Between 2013 and 2017, 193 women were randomised and 112 (59 and 53 in CTX and IPTp-SP arms, respectively) were assessed for placental infection defined by microscopic parasitaemia or PCR.

RESULTS

Thirteen women had a placental infection: five in the CTX arm (one by microscopic placental parasitaemia and four by PCR) and eight by PCR in the SP-IPTp (8.5% vs. 15.1%, p = 0.28). The percentage of newborns with low birthweight (<2500 g) did not differ statistically between the two arms. Self-reported compliance to CTX prophylaxis was good. There was a low overall rate of adverse events in both arms.

CONCLUSION

Although our results do not allow us to conclude that CTX is more effective, drug safety and good compliance among women with this treatment favour its widespread use among HIV-infected pregnant women, as currently recommended by WHO.

Genomic history of human monkey pox infections in the Central African Republic between 2001 and 2018

Monkeypox is an emerging infectious disease, which has a clinical presentation similar to smallpox. In the two past decades, Central Africa has seen an increase in the frequency of cases, with many monkeypox virus (MPXV) isolates detected in the Democratic Republic of Congo (DRC) and the Central African Republic (CAR). To date, no complete MPXV viral genome has been published from the human cases identified in the CAR. The objective of this study was to sequence the full genome of 10 MPXV isolates collected during the CAR epidemics between 2001 and 2018 in order to determine their phylogenetic relationships among MPXV lineages previously described in Central Africa and West Africa. Our phylogenetic results indicate that the 10 CAR isolates belong to three lineages closely related to those found in DRC. The phylogenetic pattern shows that all of them emerged in the rainforest block of the Congo Basin. Since most human index cases in CAR occurred at the northern edge of western and eastern rainforests, transmissions from wild animals living in the rainforest is the most probable hypothesis. In addition, molecular dating estimates suggest that periods of intense political instability resulting in population movements within the country often associated also with increased poverty may have led to more frequent contact with host wild animals. The CAR socio-economic situation, armed conflicts and ecological disturbances will likely incite populations to interact more and more with wild animals and thus increase the risk of zoonotic spillover.

Fatal Outcome in a Hepatitis E Virus/Human Immunodeficiency Virus Co-Infected Malnourished Child in the Central African Republic

Hepatitis E virus (HEV) infection is responsible for major endemic outbreaks in developing countries. Human immunodeficiency virus (HIV) and HEV are widespread in the Central African Republic. We report the first documented case of an HEV infection in a 36-month-old child already suffering from HIV and severe acute malnutrition (SAM). The HIV patient was hospitalized for SAM with persistent diarrhea and prolonged fever. The presence of IgG anti-HEV antibodies was noted. Sequencing of the amplified HEV RNA revealed the presence of genotype 3c. The alanine aminotransferase level was slightly above average. The patient died despite being treated by antiretroviral therapy accompanied by probabilistic antibiotic therapy and nutritional rehabilitation. HEV/HIV co-infection in a malnourished patient can accelerate a fatal outcome. In the presence of biological abnormalities in a severe acutely malnourished HIV-infected patient, HEV RNA detection should be added to the standard medical assessment in sub-Saharan African countries.

Impact of Zika Virus Emergence in French Guiana: A Large General Population Seroprevalence Survey

BACKGROUND

Since the identification of Zika virus (ZIKV) in Brazil in May 2015, the virus has spread throughout the Americas. However, ZIKV burden in the general population in affected countries remains unknown.

METHODS

We conducted a general population survey in the different communities of French Guiana through individual interviews and serologic survey during June-October 2017. All serum samples were tested for anti-ZIKV immunoglobulin G antibodies using a recombinant antigen-based SGERPAxMap microsphere immunoassay, and some of them were further evaluated through anti-ZIKV microneutralization tests.

RESULTS

The overall seroprevalence was estimated at 23.3% (95% confidence interval [CI], 20.9%-25.9%) among 2697 participants, varying from 0% to 45.6% according to municipalities. ZIKV circulated in a large majority of French Guiana but not in the most isolated forest areas. The proportion of reported symptomatic Zika infection was estimated at 25.5% (95% CI, 20.3%-31.4%) in individuals who tested positive for ZIKV.

CONCLUSIONS

This study described a large-scale representative ZIKV seroprevalence study in South America from the recent 2015-2016 Zika epidemic. Our findings reveal that the majority of the population remains susceptible to ZIKV, which could potentially allow future reintroductions of the virus.

Hepatitis E virus outbreak associated with rainfall in the Central African Republic in 2008-2009

BACKGROUND

Infection by hepatitis E virus (HEV) can cause a high burden of morbidity and mortality in countries with poor access to clean water and sanitation. Our study aimed to investigate the situation of HEV infections in the Central African Republic (CAR).

METHODS

A retrospective analysis of the blood samples and notification forms collected through the national yellow fever (YF) surveillance program, but for which a diagnosis of YF was discarded, was carried out using an anti-HEV IgM ELISA and a HEV-specific RT-PCR.

RESULTS

Of 2883 YF-negative samples collected between January 2008 and December 2012, 745 (~ 26%) tested positive by at least either of the 2 tests used to confirm HEV cases. The results revealed that the CAR was hit by a large HEV outbreak in 2008 and 2009. The results also showed a clear seasonal pattern with correlation between HEV incidence and rainfall in Bangui. A phylogenetic analysis showed that the circulating strains belonged to genotypes 1e and 2b.

CONCLUSIONS

Overall, this study provides further evidences that HEV can be a significant cause of acute febrile jaundice, particularly among adults during rainy season or flood, in a country from Sub-Saharan Africa.

Vaccination coverage in the context of the emerging Yellow Fever threat in French Guiana

Background

French Guiana, a French overseas department located in South America between Brazil and Surinam, is the only European territory geographically located in the Amazonian forest complex and is considered endemic for yellow fever (YF).

In the context of the emergent threat of YF in Latin America, we conducted a large household cross-sectional survey from June to October 2017 to estimate vaccination coverage in the population and to determine associations with sociodemographic and geographical characteristics.

Methodology/Principal findings

In total, 1,415 households and 2,697 individuals were included from the 22 municipalities of French Guiana. YF vaccination coverage was estimated at 95.0% (95% CI: 93.4–96.2) in the entire territory but was spatially heterogeneous, with the lowest levels estimated in the western part of the territory along the Surinamese cross-border region, particularly in children under 16 years who were not enrolled in school, immigrant adults and disadvantaged populations with low socioeconomic indexes.

Conclusions/Significance

Despite the good vaccination coverage against YF in the general population of French Guiana resulting from the compulsory nature of YF vaccination for residents and travelers, there is an urgent need to improve vaccination coverage in vulnerable populations living in the northwestern part of the territory to limit the risk of transmission in the context of the emerging YF threat in South America.

Despite the relative rarity of YF and the significant number of infectious and tropical diseases in French Guiana, clinicians should adopt a high index of suspicion for YF, particularly in vulnerable and at-risk populations.

Yellow fever (YF) is the most severe arbovirus to circulate in the Americas. French Guiana, a French overseas department located in South America between Brazil and Surinam, is the only European territory geographically located in the Amazonian forest complex and is considered endemic for YF. We conducted a large general population survey from June to October 2017 to estimate vaccination coverage in the population and to identify target vulnerable populations for catch-up vaccination strategies. In total, 1,415 households and 2,697 individuals were included from the 22 municipalities of French Guiana. YF vaccination coverage was estimated at 95.0% (95% CI: 93.4–96.2) in the entire territory but was spatially heterogeneous, with the lowest levels estimated in the western part of the territory along the Surinamese cross-border region, particularly in children under 16 years who were not enrolled in school, immigrant adults and disadvantaged groups of populations with low socioeconomic indexes. Our findings showed that vaccination campaigns should be prioritized and adapted to improve vaccination coverage among vulnerable populations living in the northwestern part of the territory to limit the risk of transmission in the context of the emerging YF threat in South America. Despite the relative rarity of YF and the significant number of infectious and tropical diseases in French Guiana, clinicians should adopt a high index of suspicion for YF, particularly in vulnerable and at-risk populations.

Current challenges and implications for dengue, chikungunya and Zika seroprevalence studies worldwide: A scoping review

BACKGROUND

Arboviral infections are a public health concern and an escalating problem worldwide. Estimating the burden of these diseases represents a major challenge that is complicated by the large number of unapparent infections, especially those of dengue fever. Serological surveys are thus required to identify the distribution of these diseases and measure their impact. Therefore, we undertook a scoping review of the literature to describe and summarize epidemiological practices, findings and insights related to seroprevalence studies of dengue, chikungunya and Zika virus, which have rapidly expanded across the globe in recent years.

METHODOLOGY/PRINCIPAL FINDINGS

Relevant studies were retrieved through a literature search of MEDLINE, WHOLIS, Lilacs, SciELO and Scopus (2000 to 2018). In total, 1389 publications were identified. Studies addressing the seroprevalence of dengue, chikungunya and/or Zika written in English or French and meeting the inclusion and exclusion criteria were included. In total, 147 studies were included, from which 185 data points were retrieved, as some studies used several different samples. Most of the studies were exclusively conducted on dengue (66.5%), but 16% were exclusively conducted on chikungunya, and 7 were exclusively conducted on Zika; the remainder were conducted on multiple arboviruses. A wide range of designs were applied, but most studies were conducted in the general population (39%) and in households (41%). Although several assays were used, enzyme-linked immunosorbent assays (ELISAs) were the predominant test used (77%). The temporal distribution of chikungunya studies followed the virus during its rapid expansion since 2004. The results revealed heterogeneity of arboviruses seroprevalence between continents and within a given country for dengue, chikungunya and Zika viruses, ranging from 0 to 100%, 76% and 73% respectively.

CONCLUSIONS/SIGNIFICANCE

Serological surveys provide the most direct measurement for defining the immunity landscape for infectious diseases, but the methodology remains difficult to implement. Overall, dengue, chikungunya and Zika serosurveys followed the expansion of these arboviruses, but there remain gaps in their geographic distribution. This review addresses the challenges for researchers regarding study design biases. Moreover, the development of reliable, rapid and affordable diagnosis tools represents a significant issue concerning the ability of seroprevalence surveys to differentiate infections when multiple viruses co-circulate.

Zika virus outbreak in Suriname, a report based on laboratory surveillance data

INTRODUCTION

Since the identification of ZIKV in Brazil in May 2015, the virus has spread extensively throughout the Americas. Cases of ZIKV infection have been reported in Suriname since October 2, 2015.

METHODS

A laboratory-based surveillance system was quickly implemented according to previous experience with the emergence of chikungunya. General practitioners and public health centers located in different districts of Suriname were asked to send blood samples from suspicious cases to Academic Hospital for molecular diagnosis of Zika virus infection. We investigated Zika-related laboratory data collected during surveillance and response activities to provide the first outbreak report in Suriname in terms of time, location and person.

RESULTS

A total of 791 molecularly confirmed cases were reported during a 48-week interval from October 2015 to August 2016. The majority of ZIKV-positive cases involved women between 20 and 39 years of age, reflecting concern about Zika infection during pregnancy. The outbreak peaked in mid-January and gradually spread from the district of Paramaribo to western coastal areas.

DISCUSSION

This report provides a simple and comprehensive description of the outbreak in Suriname and demonstrates the utility of laboratory data to highlight the spatiotemporal dynamics of the outbreak in that country.

The proportion of asymptomatic infections and spectrum of disease among pregnant women infected by Zika virus: systematic monitoring in French Guiana, 2016

Zika virus (ZIKV) infection has been associated with complications during pregnancy. Although the presence of symptoms might be a risk factor for complication, the proportion of ZIKV-infected pregnant women with symptoms remains unknown. Following the emergence of ZIKV in French Guiana, all pregnancies in the territory were monitored by RT-PCR and/or detection of ZIKV antibodies. Follow-up data collected during pregnancy monitoring interviews were analysed from 1 February to 1 June 2016. We enrolled 3,050 pregnant women aged 14–48 years and 573 (19%) had laboratory-confirmed ZIKV infection. Rash, arthralgia, myalgia and conjunctival hyperaemia were more frequently observed in ZIKV-positive women; 23% of them (95% confidence interval (CI): 20–27) had at least one symptom compatible with ZIKV infection. Women 30 years and older were significantly more likely to have symptoms than younger women (28% vs 20%). The proportion of symptomatic infections varied from 17% in the remote interior to 35% in the urbanised population near the coast (adjusted risk ratio: 1.6; 95% CI: 1.4–1.9.). These estimates put findings on cohorts of symptomatic ZIKV-positive pregnant women into the wider context of an epidemic with mainly asymptomatic infections. The proportion of symptomatic ZIKV infections appears to vary substantially between populations.

Emerging trends of Zika apprehension in an epidemic setting

Background

French Guiana is a territory that has a decades-long history of dengue outbreaks and more recently, in 2014, a chikungunya outbreak. Zika virus (ZIKV) emerged in late 2015 and subsequently led to an important outbreak.

Methodology/Principal findings

A cross-sectional phone survey was conducted among the general population during the outbreak in June 2016 with a total of 1,129 individuals interviewed to assess perceptions, knowledge and behaviors regarding zika infection. The population seemed aware of zika, and perceived the infection as a more serious health threat than other common mosquito-borne diseases. Furthermore, both the perceptions and behaviors related to zika and its prevention were found to vary considerably among different social groups, geographic areas and gender; less educated female participants were found to perceive the disease as more worrisome and were less likely to adopt protective behaviors. Moreover, female population has been particularly responsive to awareness campaigns and rapidly understood the extent of risks associated with ZIKV infection.

Conclusions/Significance

These results revealed that ZIKV appeared at the time of the survey as a new health threat that concerns the public more than chikungunya and dengue fever with differences observed among subgroups of population. These results have implications for the development of multifaceted infection control programs, including strategies for prevention and awareness, helping the population to develop an accurate perception of the threat they are facing and encouraging behavior changes.

Although dengue fever has been a focus of many awareness campaigns in Latin America, very little information is available about beliefs, attitudes and behaviors regarding vector-borne diseases among the population of French Guiana. Following the end of the first chikungunya outbreak and at the initial onset of the first zika outbreak, a quantitative survey was conducted among 1129 individuals aiming to study the emotional, cognitive and behavioral response to the risk of zika infection and assess variations among different groups of population. People from French Guiana were found to perceive zika substantially differently from other Aedes mosquito-borne diseases. Overall, ZIKV appeared at the time of the survey as a new health threat that makes the population more scared than chikungunya and dengue fever. Furthermore, both the beliefs and behaviors related to zika and its prevention were found to vary considerably among different social groups, gender and geographic areas. Education had an impact on perceptions and behaviors among women. Female population has been particularly responsive to awareness campaigns and rapidly understood the extent of risks associated with ZIKV infection. Overall, findings emphasize the importance of developing appropriate and relevant strategies helping population to engage in protective behaviors adapted to the health threat they are facing. Given the importance of the public response and precautionary actions to control the spread of an emergent threat, additional research on risk perceptions and other behavioral determinants is warranted.

A Nosocomial Outbreak of Human Monkeypox in the Central African Republic

An outbreak of familial monkeypox occurred in the Central African Republic in 2015/2016 by 3 transmission modes: familial, health care–related, and transport-related. Ten people (3 children and 7 adults) were infected. Most presented with cutaneous lesions and fever, and 2 children died. The viral strain responsible was a Zaire genotype strain.

Sentinel surveillance of influenza-like illness in the Central African Republic, 2010-2015

Background

Influenza-like illness (ILI) is an important public health problem worldwide. In the Central African Republic, acute infectious diseases are the commonest reason for consultation. The Institut Pasteur of Bangui set up a surveillance network in 2008 to monitor the circulation of influenza viruses. We report the results of use of this surveillance system during the period 2010–2015.

Methods

The first surveillance centre covered Bangui, the capital of the country, and neighbouring areas and epidemiological data on syndromes similar to ILI. Throat and nasopharyngeal swab samples are transmitted weekly to the Institut Pasteur of Bangui, where real-time and multiplex reverse transcription polymerase chain reaction are used to detect and subtype influenza A (H1N1 and H3N2) and B viruses. The demographic characteristics of all patients and of positive cases according to age and the seasonal patterns of influenza virus circulation were analysed.

Results

Between January 2010 and December 2015, 5385 throat swabs were collected; 454 (8.4%) of the samples were positive. Of these, 450 yielded at least one influenza virus and four showed co-infections. Children under the age of 5 years were the most frequently infected (257/450, 57.1%), with irregular peaks of ILI. Influenza B predominated (56.2%; n = 201), with 39.0% H3N2 and 16.7%H1N1pdm09. Influenza viruses were detected mainly in the rainy season (July–December).

Conclusion

The sentinel surveillance site is yielding important information about the seasonality and age pattern of circulating influenza virus. Nationwide distribution of sentinel sites is warranted.

Diagnostic Validation of the RealStar® Zika Virus Reverse Transcription Polymerase Chain Reaction Kit for Detection of Zika Virus RNA in Urine and Serum Specimens

With the Zika virus outbreak in South America starting in 2015 and its potential to cause malformation of the fetus in infected women, the need for diagnostic methods became obvious. Until now, only limited data are available on the diagnostic performance of commercial kits. Here, we present data comparing the RealStar^® Zika Virus RT-PCR Kit 1.0 for detection of Zika virus from 208 serum and urine samples collected in French Guiana with a reference method. Of these, 114 samples tested positive with the RealStar^® Kit and 111 with the reference method.

Non-malarial infectious diseases of antenatal care in pregnant women in Franceville, Gabon

Background

In sub-tropical countries, infectious diseases remain one of the main causes of mortality. Because of their lack of active immunity, pregnant women and their unborn children represent the most susceptible people. In Gabon, data on infectious diseases of pregnant women such as syphilis and rubella are either scarce or very old. Few studies have assessed T. gondii infection during pregnancy in the country. Here, we evaluate seroprevalence of HIV, HTVL-1, syphilis and T. gondii and rubella infection during antenatal care among women living in Franceville, Gabon.

Methods

A retrospective study was conducted on data collected from May 2007 to July 2010. After signing an informed written consent form, all pregnant women consulting in two hospitals of Franceville (Gabon) and in offices of maternity and childbirth health centers were included. Demographic and clinical data were collected. Serum samples were collected and analysed using immunological assays relevant for HIV (Genscreen HIV-1 version 2, Bio-Rad®, Marne la Roquette, France).HTLV-1 (Vironostika HTLV-1, Biomérieux®, Marcy l’Etoile, France), T. pallidum (TPHA/VDRL), BIOLABO®SA), rubella virus (Vidas Biomerieux®, Marcy l’Etoile, France) and T. gondii (Vidas Biomerieux®, Marcy l’Etoile, France) diagnoses were performed. Data analysis was done using the Stat view 5.0 software.

Results

A total of 973 pregnant women were assessed. The mean age was 25.84 ± 6.9 years, with a minimum age of 14.0 years and a maximum of 45.0 years. Women from 26 to 45 years old and unemployed women were the most prevalent: 41.93% and 77.18%, respectively. The prevalence of studied infectious diseases were 2.50% for syphilis, 2.88% for HTLV-1, 4.00% for HIV with no significant difference between them (p = 0.1). Seropositivity against rubella was higher (87.56%, n = 852) than seropositivity against T. gondii (57.35%, n = 557), (p < 0.0001). Only 5 (0.51%) co-infection cases were found: 2 co-infected with HIVand T. pallidum, 2 co-infected with HIV and HTLV-1, and one co-infected with T. pallidum and HTLV-1. Sixty-two pregnant women were seronegative against toxoplasmosis and rubella (6.37%).

Conclusion

High levels of seropositivity against T. gondii and the rubella virus were observed. The prevalence of T. pallidum and HTLV-1 were lowest but HIV prevalence in young women was worrying.

Molecular Characterization of the Kamese Virus, an Unassigned Rhabdovirus, Isolated from Culex pruina in the Central African Republic

Rhabdoviridae is one of the most diversified families of RNA viruses whose members infect a wide range of plants, animals, and arthropods. The members of this family are classified into 13 genera and >150 unassigned viruses. Here, we sequenced the complete genome of a rhabdovirus belonging to the Hart Park serogroup, the Kamese virus (KAMV), isolated in 1977 from Culex pruina in the Central African Republic. The genomic sequence showed an organization typical of rhabdoviruses with additional genes in the P-M and G-L intergenic regions, as already reported for the Hart Park serogroup. Our Kamese strain (ArB9074) had 98% and 78.8% nucleotide sequence similarity with the prototypes of the KAMV and Mossuril virus isolated in Uganda and Mozambique in two different Culex species, respectively. Moreover, the protein sequences had 98-100% amino acid similarity with the prototype of the KAMV, except for an additional gene (U3) that showed a divergence of 6%. These molecular data show that our strain of the KAMV is genetically close to the Culex annuliorus strain that was circulating in Uganda in 1967. However, this study suggests the need to improve our knowledge of the KAMV to better understand its behavior, its life cycle, and its potential reservoirs.

Potential of Aedes aegypti and Aedes albopictus populations in the Central African Republic to transmit enzootic chikungunya virus strains

Background

Major chikungunya outbreaks have affected several Central African countries during the past decade. The chikungunya virus (CHIKV) was isolated from humans and sylvan mosquitoes in the Central African Republic (CAR) during the 1970 and 1980s but has not been found recently, despite the presence of Aedes albopictus since 2010. The risk of a massive chikungunya epidemic is therefore potentially high, as the human populations are immunologically naïve and because of the presence of the mosquito vector. In order to estimate the risk of a large outbreak, we assessed the vector competence of local Ae. aegypti and Ae. albopictus populations for ancient local strains of CHIKV in CAR. Mosquitoes were orally infected with the virus, and its presence in mosquito saliva was analysed 7 and 14 days post-infection (dpi) by quantitative reverse transcriptase polymerase chain reaction.

Results

The two species had similar infection rates at 7 and 14 days, and the dissemination rate of both vectors was ≥ 80% at 14 dpi. Only females followed up to 14 dpi had CHKV in their saliva.

Conclusion

These results confirm the risk of transmission of enzootic CHIKV by anthropophilic vectors such as Ae. aegypti and Ae. albopictus.

Susceptibility profile and metabolic mechanisms involved in Aedes aegypti and Aedes albopictus resistant to DDT and deltamethrin in the Central African Republic

Background

Aedes aegypti and Ae. albopictus are the main epidemic vectors of dengue, chikungunya and Zika viruses worldwide. Their control during epidemics relies mainly on control of larvae and adults with insecticides. Unfortunately, loss of susceptibility of both species to several insecticide classes limits the efficacy of interventions. In Africa, where Aedes-borne viruses are of growing concern, few data are available on resistance to insecticides. To fill this gap, we assessed the susceptibility to insecticides of Ae. aegypti and Ae. albopictus populations in the Central African Republic (CAR) and studied the mechanisms of resistance.

Methods

Immature stages were sampled between June and September 2014 in six locations in Bangui (the capital of CAR) for larval and adult bioassays according to WHO standard procedures. We also characterized DDT- and pyrethroid-resistant mosquitoes molecularly and biochemically, including tests for the activities of nonspecific esterases (α and β), mixed-function oxidases, insensitive acetylcholinesterase and glutathione S-transferases.

Results

Larval bioassays, carried out to determine the lethal concentrations (LC₅₀ and LC₉₅) and resistance ratios (RR₅₀ and RR₉₅), suggested that both vector species were susceptible to Bacillus thuringiensis var. israeliensis and to temephos. Bioassays of adults showed susceptibility to propoxur and fenitrothion, except for one Ae. albopictus population that was suspected to be resistant to fenithrothion. None of the Ae. aegypti populations was fully susceptible to DDT. Ae. albopictus presented a similar profile to Ae. aegypti but with a lower mortality rate (41%). Possible resistance to deltamethrin was observed among Ae. aegypti and Ae. albopictus, although some were susceptible. No kdr mutations were detected in either species; however, the activity of detoxifying enzymes was higher in most populations than in the susceptible Ae. aegypti strain, confirming decreased susceptibility to DDT and deltamethrin.

Conclusion

These findings suggested that regular, continuous monitoring of resistance is necessary in order to select the most effective adulticides for arbovirus control in Bangui.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-016-1887-5) contains supplementary material, which is available to authorized users.

Rift Valley Fever Virus Circulating among Ruminants, Mosquitoes and Humans in the Central African Republic

BACKGROUND

Rift Valley fever virus (RVFV) causes a viral zoonosis, with discontinuous epizootics and sporadic epidemics, essentially in East Africa. Infection with this virus causes severe illness and abortion in sheep, goats, and cattle as well as other domestic animals. Humans can also be exposed through close contact with infectious tissues or by bites from infected mosquitoes, primarily of the Aedes and Culex genuses. Although the cycle of RVFV infection in savannah regions is well documented, its distribution in forest areas in central Africa has been poorly investigated.

METHODOLOGY/PRINCIPAL FINDINGS

To evaluate current circulation of RVFV among livestock and humans living in the Central African Republic (CAR), blood samples were collected from sheep, cattle, and goats and from people at risk, such as stock breeders and workers in slaughterhouses and livestock markets. The samples were tested for anti-RVFV immunoglobulin M (IgM) and immunoglobulin G (IgG) antibodies. We also sequenced the complete genomes of two local strains, one isolated in 1969 from mosquitoes and one isolated in 1985 from humans living in forested areas. The 1271 animals sampled comprised 727 cattle, 325 sheep, and 219 goats at three sites. The overall seroprevalence of anti-RVFV IgM antibodies was 1.9% and that of IgG antibodies was 8.6%. IgM antibodies were found only during the rainy season, but the frequency of IgG antibodies did not differ significantly by season. No evidence of recent RVFV infection was found in 335 people considered at risk; however, 16.7% had evidence of past infection. Comparison of the nucleotide sequences of the strains isolated in the CAR with those isolated in other African countries showed that they belonged to the East/Central African cluster.

CONCLUSION AND SIGNIFICANCE

This study confirms current circulation of RVFV in CAR. Further studies are needed to determine the potential vectors involved and the virus reservoirs.

Improved assembly procedure of viral RNA genomes amplified with Phi29 polymerase from new generation sequencing data

Background

New sequencing technologies have opened the way to the discovery and the characterization of pathogenic viruses in clinical samples. However, the use of these new methods can require an amplification of viral RNA prior to the sequencing. Among all the available methods, the procedure based on the use of Phi29 polymerase produces a huge amount of amplified DNA. However, its major disadvantage is to generate a large number of chimeric sequences which can affect the assembly step. The pre-process method proposed in this study strongly limits the negative impact of chimeric reads in order to obtain the full-length of viral genomes.

Findings

Three different assembly softwares (ABySS, Ray and SPAdes) were tested for their ability to correctly assemble the full-length of viral genomes. Although in all cases, our pre-processed method improved genome assembly, only its combination with the use of SPAdes allowed us to obtain the full-length of the viral genomes tested in one contig.

Conclusions

The proposed pipeline is able to overcome drawbacks due to the generation of chimeric reads during the amplification of viral RNA which considerably improves the assembling of full-length viral genomes.

Electronic supplementary material

The online version of this article (doi:10.1186/s40659-016-0099-y) contains supplementary material, which is available to authorized users.

Composition and genetics of malaria vector populations in the Central African Republic

Background

In many African countries malaria has declined sharply due to a synergy of actions marked by the introduction of vector control strategies, but the disease remains a leading cause of morbidity and mortality in Central African Republic (CAR). An entomological study was initiated with the aim to characterize the malaria vectors in Bangui, the capital of CAR, and determine their vector competence.

Methods

A cross-sectional entomological study was conducted in 15 sites of the district of Bangui, the capital of CAR, in September–October 2013 and a second collection was done in four of those sites between November and December 2013. Mosquitoes were collected by human landing catch (HLC) indoors and outdoors and by pyrethrum spray catch of indoor-resting mosquitoes. Mosquitoes were analysed for species and multiple other attributes, including the presence of Plasmodium falciparum circumsporozoite protein or DNA, blood meal source, 2La inversion karyotype, and the L1014F kdr insecticide resistance mutation.

Results

Overall, 1292 anophelines were analysed, revealing a predominance of Anopheles gambiae and Anopheles funestus, with a small fraction of Anopheles coluzzii. Molecular typing of the An. gambiae complex species showed that An. gambiae was predominant (95.7 %) as compared to An. coluzzii (2.1 %), and Anopheles arabiensis was not present. In some areas the involvement of secondary vectors, such as Anopheles coustani, expands the risk of infection. By HLC sampling, An. funestus displayed a stronger endophilic preference than mosquitoes from the An. gambiae sister taxa, with a mean indoor-capture rate of 54.3 % and 67.58 % for An. gambiae sister taxa and An. funestus, respectively. Human biting rates were measured overall for each of the species with 28 or 29 bites/person/night, respectively. Both vectors displayed a strong human feeding preference as determined by blood meal source, which was not different between the different sampling sites. An. coustani appears to be highly exophilic, with 92 % of HLC samples captured outdoors. The mean CSP rate in head-thorax sections of all Anopheles was 5.09 %, and was higher in An. gambiaes.l. (7.4 %) than in An. funestus (3.3 %). CSP-positive An. coustani were also detected in outdoor HLC samples. In the mosquitoes of the An. gambiae sister taxa the kdr-w mutant allele was nearly fixed, with 92.3 % resistant homozygotes, and no susceptible homozygotes detected.

Conclusions

This study collected data on anopheline populations in CAR, behaviour of vectors and transmission levels. Further studies should investigate the biting behaviour and susceptibility status of the anophelines to different insecticides to allow the establishment of appropriate vector control based on practical entomological knowledge.

Electronic supplementary material

The online version of this article (doi:10.1186/s12936-016-1431-2) contains supplementary material, which is available to authorized users.

Insecticide resistance status of the Anopheles funestus population in Central African Republic: a challenge in the war

Background

In the Central African Republic, malaria is a major public health problem and the leading cause of death among children. This disease appears to be hyperendemic but no substantial entomological data, including data on Anopheles spp. susceptibility to insecticides, is available. This study evaluates, for the first time in the CAR, the status of insecticide resistance in the Anopheles funestus population, the second major vector of malaria in Africa.

Methods

WHO standard bioassay susceptibility tests were performed on the An. funestus population using F1 generation from gravid females mosquitoes (F0) collected by manual aspirator sampling of households in Gbanikola, Bangui in October 2014 to assess: (i) An. funestus susceptibility to bendiocarb, malathion, permethrin, lamda-cyhalothrin, deltamethrin and DDT, and (ii) the effect of pre-exposure to the piperonyl butoxide (PBO) synergist on insecticide susceptibility. Additional tests were conducted to investigate metabolic resistance status (cytochrome P450 monooxygenases, glutathione S-transferases, and esterases).

Results

A high phenotypic resistance of An. funestus population to malathion, DDT and pyrethroids was observed with a mortality rate ranging from 23 to 74 %. For the pyrethroid groups, the mortality rate was 35, 31 and 23 % for lambda-cyhalothrin, deltamethrin, and permethrin, respectively. In contrast a 100 % mortality rate to bendiocarb was recorded. Knockdown time (KDT) was long for all pyrethroids, DDT and malathion with KDT₅₀ higher than 50 min. Pre-exposure of An. funestus to PBO synergist significantly restored susceptibility to all pyrethroids (Fisher's exact test P <0.0001) but not in DDT (Fisher's exact test P = 0.724). Data from biochemical tests suggest the involvement of cytochrome P450 monooxygenases, esterases and glutatione S-transferases in the resistance of An. funestus population from Gbanikola (Wilcoxon test P <0.05).

Conclusion

Evidence of biochemical resistance to insecticide was detected in An. funestus population from the district of Gbanikola, Bangui. This study suggests that detoxifying enzymes are involved in insecticide resistance of An. funestus. However, despite disruptive violence, further research is urgently needed to assess the insecticide susceptibility status of An. funestus population in all CAR regions; insecticide resistance could rapidly compromise the success of malaria control programs.