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

Abstract 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

Falciparum Malaria in Febrile Patients at Sentinel Sites for Influenza Surveillance in the Central African Republic from 2015 to 2018

Malaria is a major public health issue in the Central African Republic (CAR) despite massive scale-up of malaria interventions. However, no information is available on the incidence of malaria in febrile illness cases or on the distribution of malaria infection according to demographic characteristics, which are important indicators and valuable epidemiological surveillance tools. This study therefore aimed to characterize malaria in the network of sentinel sites set up for influenza surveillance. A retrospective analysis was conducted to explore the data from these sentinel sites from 2015 to 2018. The Paracheck-Pf® rapid diagnosis test kit was used to screen for malaria in febrile illness cases. A total of 3609 malaria cases were identified in 5397 febrile patients, giving an incidence rate of 66.8%. The age group of 1–4 years was the most affected by malaria (76.0%). Moreover, prevalence varied across different sentinel sites, with the Bossembele Health Center, located in a rural area, showing an incidence of 96%, the Saint Joseph Health Center in a semiurban area of Bangui showing an incidence of 75%, and the Bangui Pediatric Complex in an urban site with an incidence of only 44.6%. Malaria transmission was holoendemic over the four-year study period, and malaria incidence decreased from 2016 to 2018. The incidence of malaria coinfection with influenza was 6.8%. This study demonstrated clear microspatial heterogeneity of malaria. Malaria was consistently the most frequent cause of febrile illness. Including sites in different climate zones in the CAR will allow for a more representative study

Entomological profile of yellow fever epidemics in the Central African Republic, 2006–2010

Abstract Background The causative agent of yellow fever is an arbovirus of the Flaviviridae family transmitted by infected Aedes mosquitoes, particularly in Africa. In the Central African Republic since 2006, cases have been notified in the provinces of Ombella-Mpoko, Ouham-Pende, Basse-Kotto, Haute-Kotto and in Bangui the capital. As the presence of a vector of yellow fever virus (YFV) represents a risk for spread of the disease, we undertook entomological investigations at these sites to identify potential vectors of YFV and their abundance. Findings Between 2006 and 2010, 5066 mosquitoes belonging to six genera and 43 species were identified. The 20 species of the Aedes genus identified included Ae. aegypti, the main vector of YFV in urban settings, and species found in tropical forests, such as Ae. africanus, Ae. simpsoni, Ae. luteocephalus, Ae. vittatus and Ae. opok. These species were not distributed uniformly in the various sites studied. Thus, the predominant Aedes species was Ae. aegypti in Bangui (90.7 %) and Basse-Kotto (42.2 %), Ae. africanus in Ombella-Mpoko (67.4 %) and Haute-Kotto (77.8 %) and Ae. vittatus in Ouham-Pende (62.2 %). Ae. albopictus was also found in Bangui. The distribution of these dominant species differed significantly according to study site (P Aedes mosquitoes analysed by polymerase chain reaction contained the YFV genome. Conclusion The results indicate a wide diversity of vector species for YFV in the Central African Republic. The establishment of surveillance and vector control programs should take into account the ecological specificity of each species.</p

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

Abstract 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

Temporal and biting dynamics of the chromosomal inversion 2La in the malaria vectors Anopheles gambiae and Anopheles coluzzii in Bangui, Central African Republic

International audienceThe chromosomal rearrangement 2La has been directly involved in the ecological and deadly epidemiological success of the malaria mosquitoes Anopheles gambiae and Anopheles coluzzii in sub-Saharan Africa. However, little is known about the biological and ecological factors that drive the local and temporal dynamics of this inversion in both species. Here, we performed a year-round longitudinal survey in Bangui, Central African Republic. We monthly sampled A. gambiae and A. coluzzii mosquitoes indoor and outdoor using human landing catches (HLC) for 48 h non-stop. We molecularly karyotyped all specimens to study the 2La inversion frequency variations, and monitored the mosquito spatial and temporal biting behavior throughout the year. In total, we successfully karyotyped 5121 A. gambiae and 986 A. coluzzii specimens. The 2La inversion frequency was higher in A. coluzzii than in A. gambiae across the year. In A. gambiae and A. coluzzii , the inversion frequency or karyotypes did not influence the biting behavior, either location or time. Moreover, the inversion frequency variation in both species was also independent of local climatic changes. Overall, our results revealed that in Bangui, the 2La inversion segregates at different frequency in each species, but this is not influenced by their trophic behavior. Studying the impact of urban settings and the population genetic structure of these two A. gambiae complex members could bring insights into the intrinsic relationship between 2La inversion and local conditions. More studies are needed to understand the polymorphic equilibrium of this inversion in Bangui

Bayesian inference hypothesis of <i>Ae. albopictus</i> phylogeny based on <i>COI</i> (A) and <i>ND5</i> (B) sequence data.

<p>The phylogeny was constructed with MrBayes 3.1.2, ngen = 2 000 000. Best-fitting models selected with the MR model test (under AIC) were HKY for <i>COI</i> and HKY+I+G for the <i>ND5</i> nucleotide datasets. Branch support is indicated by the posterior probability values. Accession numbers of <i>COI</i> and <i>ND5</i> out-group sequences are given in supporting information file <a href="http://www.plosntds.org/article/info:doi/10.1371/journal.pntd.0002590#pntd.0002590.s001" target="_blank">Table S1</a>.</p

Genetic characterization of Chikungunya virus in the Central African Republic.

International audienceChikungunya virus (CHIKV) is an alphavirus transmitted by the bite of mosquito vectors. Over the past 10 years, the virus has gained mutations that enhance its transmissibility by the Aedes albopictus vector, resulting in massive outbreaks in the Indian Ocean, Asia and Central Africa. Recent introduction of competent A. albopictus vectors into the Central African Republic (CAR) pose a threat of a Chikungunya fever (CHIKF) epidemic in this region. We undertook this study to assess the genetic diversity and background of CHIKV strains isolated in the CAR between 1975 and 1984 and also to estimate the ability of local strains to adapt to A. albopictus. Our results suggest that, local CHIKV strains have a genetic background compatible with quick adaptation to A. albopictus, as previously observed in other Central African countries. Intense surveillance of the human and vector populations is necessary to prevent or anticipate the emergence of a massive CHIKF epidemic in the CAR

Total abundance of immature stages of <i>Aedes aegypti</i> and <i>Ae. albopictus</i> per container.

<p>Each two-letter abbreviation on the x-axis corresponds to a type of container as follows: WS, water storage; FP, flower pot; WP, watering place; UT, used tyres; DT, discarded tanks; MI, miscellaneous; NA, natural.</p

Immature mosquito sampling in southern Central African Republic.

<p>Immature mosquito sampling in southern Central African Republic.</p