Biology subjects

Regilme, M. A. F.

Publications and source records attributed to Regilme, M. A. F..

6 recordsLinked to original sources

bioRxiv2024

Wolbachia infection in Aedes aegypti does not affect its vectorial capacity for Dirofilaria immitis

Mosquito-borne diseases such as dengue and filariasis are a growing public health concern in endemic countries. Biological approaches, such as the trans-infection of Wolbachia pipientis in mosquitoes, are an alternative vector control strategy, especially for arthropod-borne viruses such as dengue. In the present study, the effect of Wolbachia (wMel strain) on the vectorial capacity of Aedes aegypti for Dirofilaria immitis was studied. Our results showed that Wolbachia does not affect the phenotype of mosquito survival or the prevalence, number, and molting rate of third-stage larvae in both susceptible and resistant strains of Ae. aegypti. RNA-seq analysis of Malpighian tubules at 2 days post-infection with D. immitis showed the differentially expressed genes (DEGs) with and without wMel infection. No characteristic immune-related gene expression patterns were observed among the DEGs. No significant change in the amount of Wolbachia was observed in the Ae. aegypti after D. immitis infection. Our results suggest that infection of D. immitis in Ae. aegypti populations will not interfere with Wolbachia-based vector control strategies in dengue-endemic areas where cases of D. immitis are present. This study demonstrated the veterinary medical validity of a dengue control program using Wolbachia.

microbiology↗

bioRxiv2023

Fine-scale adaptive divergence of Aedes aegypti in heterogeneous landscapes and among climatic conditions in Metropolitan Manila, Philippines

The adaptive divergence of Aedes aegypti populations to heterogeneous environments may be a driving force behind the recent expansion of their habitat distribution and outbreaks of dengue disease in urbanized areas. In this study, we investigated the population genomics of Ae. aegypti at a regional scale in Metropolitan Manila, Philippines using double digestion restriction-site association DNA sequencing (ddRAD-Seq). Specifically, we used a Pool-Seq approach to generate a high number of single nucleotide polymorphisms (SNPs), which were used to determine local adaptation and population structure. We detected 65,473 SNPs in 217 Ae. aegypti individuals from 14 populations with 76 non-neutral SNP loci. Additionally, 57 of these non-neutral SNP loci were associated with 8 landscape variables (e.g., open space, forest, etc) and 4 climate variables (e.g., air temperature, humidity, etc). Furthermore, the percentage of the area of landscape variables, such as forest, parks and recreation, air temperature, man-made building, and open space per local population was frequently associated with non-neutral SNP loci. Most non-neutral SNP loci formed four clusters that were in linkage disequilibrium with each other in physical proximity on the chromosome and were associated with a common environmental variable. Male and female populations exhibited contrasting spatial divergence, i.e., males exhibited greater divergence, likely reflecting their different dispersal abilities. In comparative analysis of the same Ae. aegypti individuals, the pairwise FST values of 11 microsatellite markers were lower than those of neutral SNP loci, indicating that the neutral SNP loci generated via ddRAD-Seq were more sensitive in terms of detecting genetic differences between populations at fine-spatial scales. Overall, this study demonstrates the utility of ddRAD-Seq for examining genetic differences in Ae. aegypti populations, and our data on mosquito dispersal at a regional spatial scale could inform vector control programs. Author SummaryThe population expansion of dengue vector, Aedes aegypti mosquitoes is one of the factors that may promote the outbreak of the diseases. Understanding the population genomics of Ae.aegypti may contribute to better knowledge about mosquito expansion and how they can adapt to the change in environment. In this study, we used pool-based ddRAD-Seq (Double Digest Restriction site Association DNA Sequencing) to generate SNPs that occur between the Ae.aegypti populations in Metropolitan Manila, Philippines. We found that non-neutral SNP loci are frequently associated with landscape variables compared to climatic variables. Landscape variables such as forest, park and recreation, air temperature, man-made building and open space are more frequently associated with non-neutral SNPs loci. Those landscape variables may relate to the mosquitos fitness, therefore, induce the adaptive divergence within Ae.aegypti population. We also found male and female populations are exhibiting a contrast spatial divergence by using neutral SNP loci. In addition, neutral SNPs loci showed higher resolution in population structuring than microsatellite markers using the same individuals.

genomics↗

bioRxiv2022

Relationship of Rickettsia infection rates and population genetic structure of ixodid ticks along an altitudinal gradient

Ixodid ticks, such as Ixodes ovatus and Haemaphysalis flava, are important vectors of tick-borne diseases in Japan, such as Japanese spotted fever caused by Rickettsia japonica. This study describes the population genetic structure and gene flow of I. ovatus and H. flava and their Rickettsia infection rates along an altitudinal gradient. A total of 346 adult I. ovatus and 243 H. flava were analyzed for the presence of Rickettsia by nested PCR targeting the 17kDA, gltA, rOmpA, and rOmpB genes. Population genetic structure was performed using the mitochondrial cytochrome oxidase 1 (cox1) marker. The Rickettsia infection rates were 13.26% in I. ovatus and 6.17% in H. flava. For I. ovatus, the global FST value revealed significant genetic differentiation among the different populations, whereas H. flava showed non-significant genetic differentiation. The cox1 I. ovatus cluster dendrogram showed two cluster groups, while the haplotype network and phylogenetic tree showed three genetic groups. The two cluster groups and the three genetic groups found in I. ovatus showed a significant difference in their Rickettsia infection rates and mean altitude per group. No significant differences were found in the mean altitude or Rickettsia infection rates of H. flava. Our results suggest that low gene flow in the I. ovatus populations has caused spatially heterogenous Rickettsia infection rates along the altitudinal gradient. This information can be used in understanding the relationship between the tick vector, its pathogen, and environmental factors, such as altitude, and for the control of tick-borne diseases in Japan.

ecology↗

bioRxiv2021

Detection and phylogeny of Wolbachia in field-collected Aedes albopictus and Aedes aegypti from Manila City, Philippines

BackgroundWolbachia is the most common bacterial endosymbiont of arthropods, such as the medically important Aedes albopictus and recent reports also detected in Aedes aegypti. Our study showed additional support for the presence of wolbachia in Ae. albopictus and Ae. aegypti using Wolbachia specific markers, wsp, and 16S. Main textThis study collected 12 adult Ae. albopictus and 359 Ae. aegypti from 183 households in a dengue-prone area, Manila, Philippines, between June and September 2017. Aedes larvae (n = 509) were also collected from 17 water containers from 11 households. The DNA of the Aedes larvae and adults were screened for the presence of Wolbachia using the wsp and 16S markers, following optimized polymerase chain reaction (PCR) conditions, and sequenced. Our results showed that 3 out of 359 (0.84%) adult Ae. aegypti and 12 out of 12 (100%) adult Ae. albopictus were Wolbachia positive, whereas all larvae tested negative for Wolbachia (0/509; 0%). The wsp marker revealed six Wolbachia-positive Ae. albopictus, whereas the 16S marker showed Wolbachia in three Ae. aegypti and ten Ae. albopictus ConclusionOur results suggest that the utilization of two Wolbachia specific markers, wsp and 16S demonstrated Wolbachia presence in individual Ae. albopictus and Ae. aegypti. The results of the Wolbachia infection in Ae. albopictus showed that the detected strains were from either supergroups A and B. Despite the low infection rate of Wolbachia in Ae. aegypti, our results demonstrated the presence of Wolbachia in field-collected Ae. aegypti supporting previous studies.

microbiology↗

bioRxiv2020

The influence of roads on the fine-scale population genetic structure of the dengue vector Aedes aegypti (Linnaeus)

Dengue is endemic in tropical and subtropical countries and is transmitted mainly by Aedes aegypti. Mosquito movement can be affected by human-made structures such as roads that can act as a barrier. Roads can influence the population genetic structure of Ae. aegypti. We investigated the genetic structure and gene flow of Ae. aegypti as influenced by a primary road, Espana Boulevard (EB) with 2000-meter-long stretch and 24-meters-wide in a very fine spatial scale. We hypothesized that Ae. aegypti populations separated by EB will be different due to the limited gene flow as caused by the barrier effect of the road. A total of 376 adults and larval Ae. aegypti were collected from June to September 2017 in 21 sites across EB. North (N1-N11) and South (S1-S10) comprised of 211 and 165 individuals, respectively. All mosquitoes were genotyped at 11 microsatellite loci. AMOVA FST indicated significant genetic differentiation across the road. The constructed UPGMA dendrogram found 4 genetic groups revealing the clear separation between North and South sites across the road. On the other hand, Bayesian cluster analysis showed four genetic clusters (K = 4) wherein each individual samples have no distinct genetic cluster thus genetic admixture. Moreover, significant positive spatial autocorrelation was observed at 100 - 200 m distance class, suggesting dispersal potential of the adult mosquitoes within a 200 m spatial scale. Our results suggest that human-made landscape features such as primary roads are potential barriers to mosquito movement thereby limiting its gene flow across the road. This information is valuable in designing an effective mosquito control program in a very fine spatial scale. Author SummaryDengue, a mosquito-borne viral infection is a serious health problem in tropical and subtropical countries such as Philippines. Most dengue prevention programs aim to eradicate its mosquito vector, Aedes aegypti. A successful population control program is reliant in understanding the mosquito behavior and ecology including how human-made structures such as roads influence its expansion and movement. Previous studies have discovered the barrier effect of roads in the movement of mosquitoes. In this study, we examined the influence of roads in the population genetic structure of Ae. aegypti in a fine spatial scale using 11 microsatellite markers. We found significant genetic differentiation of mosquito populations across the road. Our results suggest limited gene flow across the road and supports our hypothesis that roads are potential barriers to mosquito dispersal. This information can be used in designing an effective mosquito population control zones in perceived barrier to mosquito dispersal such as roads.

molecular biology↗

bioRxiv2019

Comparative population genetic structure of two Ixodidae ticks (Ixodes ovatus and Haemaphysalis flava) in Niigata Prefecture, Japan

Ixodid tick species such as Ixodes ovatus and Haemaphysalis flava are essential vectors of tick-borne diseases in Japan. In this study, we investigated the population genetic structures and gene flow of I. ovatus and H. flava as affected by the tick host mobility. We hypothesized that I. ovatus and H. flava may have differences in their genetic structure due to the low mobility of small rodent hosts of I. ovatus at the immature stage in contrast to the mediated dispersal of avian hosts for immature H. flava. We collected 307 adult I. ovatus and 220 adult H. flava from 29 and 17 locations across Niigata Prefecture, Japan. We investigated the genetic structure at two mitochondrial loci (cox1, 16S rRNA gene). For I. ovatus, pairwise FST and analysis of molecular variance (AMOVA) analyses of cox1 sequences indicated significant genetic variation among populations. Both cox1 and 16S rRNA markers showed non-significant genetic variation among locations for H. flava. The Bayesian tree and haplotype network of cox1 marker for I. ovatus samples in Niigata Prefecture found 3 genetic groups wherein most haplotypes in group 2 were distributed in low altitudinal areas. When we added cox1 sequences of I. ovatus from China to the phylogenetic analysis, three genetic groups (China 1, China 2, and Niigata and Hokkaido, Japan) were formed in the tree suggesting the potential for cryptic species in the genetic group in Japan. Our results support our hypothesis and suggest that the host preference of ticks at the immature stage may influence the genetic structure and gene flow of the ticks. This information is vital in understanding the tick-host interactions in the field to better understand the tick-borne disease transmission and in designing an effective tick control program.

genetics↗