bioRxiv Science⌕ Search
Home/Archive/bioRxiv

bioRxiv · 10.1101/2025.06.02.657347

Unravelling the distribution of vectors of major vector-borne diseases in Koshi Province of Nepal: A concern of expansion in diverse geo-ecological and climatic regions

Roy, L.·Uranw, S.·Pote Shrestha, R. R.
View original source ↗Export metadata ↓

Abstract

BackgroundVector-borne diseases, being major public health concerns, are either slated for elimination or projected for control in Nepal. One of the major challenges in controlling these VBDs is to halt their emergence and expansion in diverse geo-ecological and climatic regions. In this study, we collected vectors of major VBDs to understand their distribution, diversity, and association with ecological variances. Methodology/Principal findingsA descriptive cross-sectional survey was conducted to collect the vectors in five districts situated at altitudes of up to 98 - 1,274 meters in Koshi Province, Eastern Nepal, representing three distinct geo-ecological and climatic regions: mountain, hills and lowlands during May and June 2023. Adult vectors were captured using CDC miniature light traps, BG sentinel traps, and manual aspirators. Association of vectors abundance in function of the geo-ecological and climatic variables was assessed in two vector species (Culex quinquefasciatus and Phlebotomus argentipes). We found the malaria vector Anopheles annularis, the lymphatic filariasis vector Cu. quinquefasciatus and visceral leishmaniasis vector Ph. argentipes from all three geo-ecological regions. The other vectors of the malaria parasite, An. pseudowillmori and An. willmori, and Japanese encephalitis vector Cu. tritaeniorhynchus were recorded from hilly districts only. Mean temperature and rainfall had positive effect on Cu. quinquefasciatus density and deleterious on Ph. argentipes. Culex quinquefasciatus and Ph. argentipes were captured in high abundance per household in hills (IRR = 1.23 and IRR = 13.00, respectively) and mountain (IRR = 1.96 and IRR = 4.00, respectively) as compared to lowland. ConclusionTwo major vectors, Cu. quinquefasciatus and Ph. argentipes were indiscriminately present in all geo-ecological regions. Climatic variables favour vectors survival, distribution and growth in diverse altitudes, including areas previously impervious to the vectors and VBDs. Our findings alert the VBD control program and suggest regular monitoring, strengthening the existing surveillance system and evidence-based planning and implementation of vector control interventions in wider geo-ecological regions to prevent the disease transmission. Authors SummaryThe Government of Nepal is committed to eliminate and control major vector-borne diseases: malaria, visceral leishmaniasis, lymphatic filariasis, Japanese encephalitis and dengue as a public health problem by 2030. These diseases, once endemic to lowlands with tropical and subtropical climates only, have been spread to a wide geography, including hills and mountains. These high-altitude areas were considered unsuitable for the existence of vectors and transmission of pathogens. Considering the impact of climate change on founding a favorable environment for the establishment of viable populations of vectors for pathogens transmission and thus threatening all the efforts of VBDs control and elimination, we conducted a cross-sectional survey to explore the diversity of vectors in varied geo-ecological regions. We collected vectors from five districts situated at different altitudes and having fairly diverse geography. Major vectors of responsible of transmission of pathogens causing VL and LF were abundantly present in all geo-ecological regions, while vectors of malarial parasites and dengue virus were sparsely present in fewer areas. This study also examined the feasibility of the integrated vector survey in favour of maximising the available resources for entomological investigations. Further, this study provides updated information on the diversity of the vectors in the areas having cases of VBDs and suggests authorities for regular monitoring, strengthening the existing surveillance system and evidence-based planning and implementation of vector control interventions to prevent the disease transmission in wider geo-ecological regions.

Source connections

Explore related subjects

zoologyPreprint

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Roy, L., Uranw, S., Pote Shrestha, R. R.. 2025-06-04. Unravelling the distribution of vectors of major vector-borne diseases in Koshi Province of Nepal: A concern of expansion in diverse geo-ecological and climatic regions. https://doi.org/10.1101/2025.06.02.657347

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related preprints

bioRxiv2026

Comparing the Influence of Habitat Configuration on Population Connectivity and Genetic Structure Using Congeneric Species Across Multiple Taxa

Abstract Habitat configuration influences population connectivity and, consequently, genetic structure. River networks provide heterogeneous, hierarchically arranged environments that shift drastically from upstream to downstream. We compared congeneric species across Ephemeroptera, Plecoptera, and Trichoptera, emphasizing longitudinal replacement (upstream to downstream) and the rarely studied wet rock (hygropetric) habitats. We surveyed six rivers on the Muroto Peninsula, Japan, qualitatively sampling aquatic insects at 63 sites. Cluster analysis based on the environmental data classified surveyed sites into four clusters. We analyzed a total of 10 species from four genera that exhibit longitudinal replacement patterns within genera. Genetic analyses based on the mitochondrial cytochrome c oxidase subunit I region revealed that upstream species showed higher genetic diversity than downstream species. In contrast, species adapted to hygropetric exhibited the lowest genetic differentiation among all habitat types. A novel contribution of this study is the inclusion of hygropetric species. The surprisingly low differentiation in hygropetric species suggests high connectivity, similar to lentic species. By comparing congeneric taxa across orders within environmentally similar rivers, we reduce phylogenetic and environmental confounds, strengthening inference that habitat configuration and dispersal traits jointly shape genetic structure. These findings provide a new perspective on riverine spatial ecology and underscore the importance of microhabitat-aware comparisons for evolutionary inference.

zoology↗
bioRxiv2026

Late lactation represents the main window for sow-to-piglet transmission of persistent gut strains

The gut microbiota plays a key role in piglet health, and maternal microbial transmission may represent a promising lever to shape early-life microbiota and prevent post-weaning digestive disorders. This study aimed to better characterize sow-to-piglet microbiota transmission and persistence using a long-read metabarcoding approach targeting the 16S-ITS-23S region. Fecal samples (n = 204) were collected from 17 families, a family being as sow and three of her piglets, at multiple stages: late gestation (G110), early (L6) and late lactation (L28) for sows; early lactation (L6), late lactation (L28), and 5 days post-weaning for piglets. To approximate strain-level resolution, a putative strain (PS) approach was developed by clustering ASVs (n = 6064) affiliated with the same species based on abundance covariance (r > 0.9), resulting in 4857 PS. Piglet microbiota progressively diversified during lactation and converged toward that of sow. In sows, 27 {+/-} 6% of PS were persistent from late gestation to late lactation. In piglets, only 4.2 {+/-} 2.5% of PS persisted from d6 to 5 days post-weaning. Persistent PS in piglets were mainly affiliated with Limosilactobacillus reuteri and Lactobacillus amylovorus followed with Holdemanella porci and H. biformis, Lentihominibacter hominis and Dorea formicigenerans. Shared PS were significantly higher within families than between unrelated pairs (p < 0.05). Maternal transmission peaked at the end of lactation (35 {+/-} 7% at L28). Persistent transmitted PS represented 2.7 {+/-} 1.6% (d6-post-weaning) and 15.4 {+/-} 5.6% (d28-post-weaning). Early-transmitted persistent PS were mainly affiliated with Limosilactobacillus reuteri, Lactobacillus amylovorus, and Paraeggerthella hominis, whereas late-transmitted persistent PS were associated with Prevotella spp., Sphaerochaeta globosa, and Bariatricus comes. These findings highlight the significance of maternal transmission in shaping the post-weaning microbiota and identify late lactation as a critical window for microbiota transfer.

zoology↗
bioRxiv2026

RISC-Bound Small RNA Sequencing Provides Insights into Guide Strand Selection and siRNA Trimming and Tailing Following Insecticidal dsRNA Delivery

RNA interference (RNAi) offers a sequence-specific approach to pest control. In insects, Dicer-2 processes double-stranded RNA (dsRNA) into small interfering RNA (siRNA) duplexes, from which the RNA-induced silencing complex (RISC) retains a guide strand. Only antisense-loaded RISC can mediate cleavage of the target transcript. However, how sequence features shape the RISC-bound siRNA pool in pests remains poorly understood, limiting opportunities for sequence optimization. Here, we profiled RISC-bound siRNAs following injection of 34 insecticidal dsRNAs targeting 11 essential genes in Tribolium castaneum larvae. We computationally reconstructed 7,879 siRNA pairs and examined associations between sequence features and strand bias. Differences in GC identity at terminal paired positions 1 to 5, used as a proxy for local thermodynamic asymmetry, correlated with strand bias, with the strongest correlations at the first two paired positions. ORF targeting and reduced predicted antisense self-folding were also associated with higher antisense fractions. Analysis of non-templated terminal additions revealed predominantly 3-prime uridylation, a known signature of small RNA turnover, along with putative 3-prime trimming. Among ORF-associated siRNA pairs, sense strands showed higher relative U-tailing abundance, based on 3-prime uridylated and putatively trimmed-and-3-prime-uridylated reads relative to perfect 21-nt reads, than antisense strands. Antisense strands with the least predicted self-folding also showed low relative U-tailing abundance. These observations are consistent with sequence-dependent contributions from both guide-strand selection and differential post-RISC-loading siRNA retention, although a causal link remains to be established. The identified associations provide a basis for testing whether dsRNA sequence optimization can improve pest control efficacy and reduce off-target activity.

zoology↗