High Aedes spp. larval indices in Kinshasa, Democratic Republic of Congo

Abstract

Background Dengue, yellow fever, chikungunya and Zika are among the most important emerging infectious vector-borne diseases worldwide. In the Democratic Republic of Congo (DRC), increases in cases of dengue and outbreaks of yellow fever and chikungunya have been reported since 2010. The main vectors of these arboviruses, Aedes aegypti and Aedes albopictus, have been reported in DRC, but there is a lack of detailed information on their presence and spread to guide disease control efforts. Methods In 2018, two cross-sectional surveys were conducted in Kinshasa province (DRC), one in the rainy (January/February) and one in the dry season (July). Four hundred houses were visited in each of the four selected communes (N’Djili, Mont Ngafula, Lingwala and Kalamu). Within the peri-domestic area of each household, searches were conducted for larval habitats, which were then surveyed for the presence of Aedes larvae and pupae. A subset of the immature specimens were reared to adults for morphological identification followed by DNA barcoding of the specimens to validate identifications. Results The most rural commune (Mont Ngafula) had the highest pupal index (number of Aedes spp. pupae per 100 inspected houses) at 246 (20) pupae/100 houses, and Breteau index (BI; number of containers positive for immature stages of Aedes spp. per 100 households) at 82.2 (19.5) positive containers/100 houses for the rainy (and dry) season, respectively. The BI was 21.5 (4.7), 36.7 (9.8) and 41.7 (7.5) in Kalamu, Lingwala and N’Djili in the rainy (and dry) season, respectively. The house index (number of houses positive for at least one container with immature stages of Aedes spp. per 100 inspected houses) was, on average, across all communes, 27.5% (7.6%); and the container index (number of containers positive for immature stages of Aedes spp. per 100 inspected containers) was 15.0% (10.0%) for the rainy (and dry) season, respectively. The vast majority of Aedes-positive containers were found outside the houses [adjusted odds ratio 27.4 (95% confidence interval 14.9–50.1)]. During the dry season, the most productive containers were the ones used for water storage, whereas in the rainy season rubbish and tires constituted key habitats. Both Ae. aegypti and Ae. albopictus were found. Anopheles larvae were found in different types of Aedes larval habitats, especially during the rainy season. Conclusions In both surveys and in all communes, the larval indices (BI) were higher than the arbovirus transmission threshold values established by the World Health Organization. Management strategies for controlling Aedes in Kinshasa need to target the key types of containers for Aedes larvae, which are mainly located in outdoor spaces, for larval habitat destruction or reduction.

First observation of Aedes albopictus in the Tshuapa province (Boende) of the Democratic Republic of the Congo

“…albopictus larvae and eggs 20 . This assumption is further supported by the fact that the identified haplotype in Boende is shared with ones recorded in Kinshasa and Kongo Central (Figure 1) 16 , also being the most frequent in the latter study (Haplotypefrequency = 0.71). Furthermore, the average precipitation (210.9 cm per year) and daily temperatures (ranging between 24°C and 30°C year-round) fall within the optimal boundaries for Ae.…”

“…The morphological identifications were validated by DNA-barcoding, a technique based on the amplification of the partial mitochondrial cytochrome c oxidase subunit I (COI) gene 15 . Sanger sequencing of the 658-base pair barcode and phylogenetic analyses followed laboratory protocols and methodologies described in Wat’senga Tezzo et al 2021 16 . In short, PCR amplicons (EPPO 2016; LCO1490 and HCO2198 universal primers) and negative controls were checked on an agarose gel, purified and sequenced in both directions on an ABI 3230xl capillary DNA sequencer using BigDye Terminator v3.1 chemistry (ThermoFisher Scientific).…”

“…To check the phylogenetic relation of the sequences, we compiled a list of Aedes species (belonging to the genus Stegomyia ) that are considered to be of medical importance in the Afrotropical region by consulting the WRBU and the APHC databases 16 . Publically available COI sequences from these species were cleaned and aligned using ClustalW in Geneious® R11.…”

“…These previous results indicate that Ae. albopictus has now well-established populations in South-Western DRC, highlighting the potential for future outbreaks of Aedes -borne diseases and the urgent need for additional surveillance and control methods in the entire country 11,12 .…”

“…albopictus in Africa was reported four decades ago (Nigeria), its presence in the Democratic Republic of Congo (DRC) was only described for the first time in 2018 9 . One year later, we linked a major CHIKV outbreak to its recent colonization in that area (the provinces Kinshasa and Kongo Central during 2019-2020) 10,11 . Indeed, Ae.…”