Diversity of midgut bacteria in larvae and females of Aedes aegypti and Aedes albopictus from Gampaha District, Sri Lanka.

The midgut microbiota of mosquitoes maintain basal immune activity and immune priming. In recent years, scientists have focused on the use of microbial communities for vector control interventions. In the present study, the midgut bacteria of larvae and adults of Aedes aegypti and Ae. albopictus were assessed using both field-collected and laboratory-reared mosquitoes from Sri Lanka. Adults and larvae of Ae. aegypti and Ae. albopictus were collected from three selected areas in Gampaha Medical Officer of Health area, Gampaha District, Western Province, Sri Lanka. Bacterial colonies isolated from mosquito midgut dissections were identified by PCR amplification and sequencing of partial 16S rRNA gene fragments. Adults and larvae of Ae. aegypti and Ae. albopictus harbored 25 bacterial species. Bacillus endophyticus and Pantoea dispersa were found more frequently in field-collected Ae. aegypti and Ae. albopictus adults, respectively. The midgut bacteria of Ae. aegypti and Ae. albopictus adults (X2 = 556.167, df = 72, P < 0.001) and larvae (X2 = 633.11, df = 66, P < 0.001) were significantly different. There was a significant difference among the bacterial communities between field-collected adults (X2 = 48.974, df = 10, P < 0.001) and larvae (X2 = 84.981, df = 10, P < 0.001). Lysinibacillus sphaericus was a common species in adults and larvae of laboratory-reared Ae. aegypti. Only P. dispersa occurred in the field-collected adults of Ae. aegypti and Ae. albopictus. Species belonging to genera Terribacillus, Lysinibacillus, Agromyces and Kocuria were recorded from Aedes mosquitoes, in accordance with previously reported results. This study generated a comprehensive database on the culturable bacterial community found in the midgut of field-collected (Ae. aegypti and Ae. albopictus) and laboratory-reared (Ae. aegypti) mosquito larvae and adults from Sri Lanka. Data confirm that the midgut bacterial diversity in the studied mosquitoes varies according to species, developmental stage and strain (field vs laboratory).

Ranasinghe K ，Gunathilaka N ，Amarasinghe D ，Rodrigo W ，Udayanga L ... -  《Parasites & Vectors》

Bacterial composition of midgut and entire body of laboratory colonies of Aedes aegypti and Aedes albopictus from Southern China.

Aedes aegypti and Aedes albopictus are invasive mosquito species and significantly impact human health in southern China. Microbiota are confirmed to affect the development and immunity of mosquitoes. However, scientists have focused more on midgut microbiota of female mosquitoes and bacterial differences between female and male Aedes mosquitoes. The relationship between the midgut and entire body microbiota of Aedes is unclear. In this study, we collected mosquito samples reared under the same laboratory conditions and compared the microbial composition of midgut and entire bodies of Aedes aegypti and Aedes albopictus using 16S rRNA gene sequencing. In this study, we collected mosquito samples reared under the same laboratory conditions and compared the microbial composition of midgut and entire bodies of Aedes aegypti and Aedes albopictus using 16S rRNA gene sequencing. A total of 341 OTUs were identified, showing that Proteobacteria was the dominant phylum and Methylobacterium the dominant genus in both Aedes aegypti and Aedes albopictus. The bacterial diversity and community structures of the entire bodies were similar between males and females in both Aedes aegypti and Aedes albopictus. Conversely, the bacterial compositions of male and female Aedes aegypti and Aedes albopictus were significantly different. NMDS analysis, UPGMA analysis, diversity indices and OTU distribution demonstrated that compositions and structures in midgut microbiota were similar but significantly different in the entire bodies of Aedes aegypti and Aedes albopictus. Functional prediction analysis showed that metabolism and environmental information processing were the dominant KEGG pathways at level 1. Our study showed that there were significantly different level 2 and 3 KEGG pathways in the midgut microbiota (16 level 2 and 24 level 3) and the entire bodies (33 level 2 and 248 level 3) between female Aedes albopictus and Aedes Aegypti. Our findings that Aedes aegypti and Aedes albopictus reared in the same laboratory harbor a similar gut bacterial microbiome but different entire body microbiota imply that the gut microbiota of adult mosquitoes is environmentally determined regardless of the host genotype, but the entire body microbiota is more genetically determined. Our findings improved the understanding of the microbiota in the entire and partial tissues of Aedes mosquitoes.

Lin D ，Zheng X ，Sanogo B ，Ding T ，Sun X ，Wu Z ... -  《Parasites & Vectors》

Molecular characterization of midgut microbiota of Aedes albopictus and Aedes aegypti from Arunachal Pradesh, India.

Yadav KK ，Bora A ，Datta S ，Chandel K ，Gogoi HK ，Prasad GB ，Veer V ... -  《Parasites & Vectors》

Bionomic aspects of dengue vectors Aedes aegypti and Aedes albopictus at domestic settings in urban, suburban and rural areas in Gampaha District, Western Province of Sri Lanka.

The lack of information on behavioural patterns of Aedes aegypti and Aedes albopictus has become a significant limitation in vector control and disease management programmes. Therefore, the current study was focused on determining some bionomics aspects: breeding, resting, host-seeking and feeding preferences of Ae. aegypti and Ae. albopictus in Sri Lanka. Larval and adult surveys were conducted from April 2017 to April 2019 monthly in six selected Medical Officer of Health (MOH) areas in Gampaha Distinct, Western province, Sri Lanka, representing urban, suburban and rural settings. Resting preferences of adult mosquitoes were observed from indoor and outdoor places using a Prockopack aspirator. The information on resting height, surface, material and locality was recorded. Human-baited double-net traps were used to determine the host-seeking time of Aedes mosquitoes. Statistical differences in the spatial distribution of mosquitoes in selected MOH areas and prevalence of vectors were analysed using general linear model (GLM). A chi-square test was used to analyse the resting behaviour. Total of 19,835 potential breeding sites were examined at 13,563 premises, and 18.5% (n = 1856) were positive for Aedes larvae. Distribution of Ae. aegypti and Ae. albopictus was statistically significant at species level (df = 1; F = 137.134; P < 0.05 GLM) and study setting (df = 2; F = 8.125; P < 0.05). Aedes aegypti breeding was found mainly in temporary removals (18.8%; n = 34), discarded non-degradables (12.15%; n = 22) and tyres (9.95%; n = 18). Natural (14.7%; n = 246) and temporary removals (13.6%; n = 227) and discarded non-reusable items were the key ovipositing sites for Ae. albopictus. In the adult mosquito survey, the majority was comprised of Ae. albopictus (54.5%; n = 999), which denoted exophilic nature (90.8%; n = 758), and 45.5% (n = 835) represented by Ae. aegypti mosquitoes who were mainly endophilic (84.3%; n = 842). Aedes aegypti rested on cloth hangings and curtains, followed by the furniture, while Aedes albopictus was predominant in outdoor vegetation. In both vectors, biting patterns denoted a typical diurnal pattern with two peaks of host-seeking and biting activity in the morning and afternoon. The majority (80%) of the larval habitats were artificial containers. The use of larvicides for vector control as the prominent measure is questionable since applying these chemicals may target only 20% of the total breeding grounds, which are permanent. The resting places of adult mosquitoes are mainly indoors. Therefore, using thermal space spraying of insecticide may not be appropriate, and indoor residual spraying is recommended as a suitable intervention to target adult mosquitoes. This study warrants a holistic vector control approach for all medically important mosquitoes and insects, ensuring the rational use of finance and resources.

Dalpadado R ，Amarasinghe D ，Gunathilaka N ，Ariyarathna N ... -  《Parasites & Vectors》

Relationship between deltamethrin resistance and gut symbiotic bacteria of Aedes albopictus by 16S rDNA sequencing.

Aedes albopictus is an important vector for pathogens such as dengue, Zika, and chikungunya viruses. While insecticides is the mainstay for mosquito control, their widespread and excessive use has led to the increased resistance in Ae. albopictus globally. Gut symbiotic bacteria are believed to play a potential role in insect physiology, potentially linking to mosquitoes' metabolic resistance against insecticides. We investigated the role of symbiotic bacteria in the development of resistance in Ae. albopictus by comparing gut symbiotic bacteria between deltamethrin-sensitive and deltamethrin-resistant populations. Adults were reared from field-collected larvae. Sensitive and resistant mosquitoes were screened using 0.03% and 0.09% deltamethrin, respectively, on the basis of the World Health Organization (WHO) tube bioassay. Sensitive and resistant field-collected larvae were screened using 5 × LC50 (lethal concentration at 50% mortality) and 20 × LC50 concentration of deltamethrin, respectively. Laboratory strain deltamethrin-sensitive adults and larvae were used as controls. The DNA of gut samples from these mosquitoes were extracted using the magnetic bead method. Bacterial 16S rDNA was sequenced using BGISEQ method. We isolated and cultured gut microorganisms from adult and larvae mosquitoes using four different media: Luria Bertani (LB), brain heart infusion (BHI), nutrient agar (NA), and salmonella shigella (SS). Sequencing revealed significantly higher gut microbial diversity in field-resistant larvae compared with field-sensitive and laboratory-sensitive larvae (P < 0.01). Conversely, gut microorganism diversity in field-resistant and field-sensitive adults was significantly lower compared with laboratory-sensitive adults (P < 0.01). At the species level, 25 and 12 bacterial species were isolated from the gut of field resistant larvae and adults, respectively. The abundance of Flavobacterium spp., Gemmobacter spp., and Dysgonomonas spp. was significantly higher in the gut of field-resistant larvae compared with sensitive larvae (all P < 0.05). Furthermore, the abundance of Flavobacterium spp., Pantoea spp., and Aeromonas spp. was significantly higher in the gut of field-resistant adults compared with sensitive adults (all P < 0.05). The dominant and differentially occurring microorganisms were also different between resistant larval and adult mosquitoes. These findings suggest that the gut commensal bacteria of Ae. albopictus adults and larvae may play distinct roles in their deltamethrin resistance. This study provides an empirical basis for further exploration of the mechanisms underlying the role of gut microbial in insecticide resistance, potentially opening a new prospect for mosquito control strategies.

Sun Y ，Li T ，Zhou G ，Zhou Y ，Wu Y ，Xu J ，Chen J ，Zhong S ，Zhong D ，Liu R ，Lu G ，Li Y ... -  《Parasites & Vectors》