PhD Thesis

Parasitic health risk associated with ecosan toilet manure, wastewater, and flood -runoff water in and around Dhaka city

2026-08-04T00:00:00Z

Parasitic health risk associated with ecosan toilet manure, wastewater, and flood -runoff water in and around Dhaka city AKTER, TAMANNA Rapid urbanization in Dhaka, Bangladesh, has led to high population density, inadequate sanitation, and increased exposure to parasitic pathogens, posing significant environmental and public health risks. This study investigates the prevalence, spatial distribution, and environmental transmission pathways of parasitic organisms in ecosan toilet manure, wastewater, and flood runoff water, with particular emphasis on ecosan sanitation systems. The research was conducted in two phases (2017–2019 and 2022–2023) to capture temporal and spatial variations in contamination. A mixed-methods approach was applied, combining quantitative laboratory analysis with qualitative field investigations. Standard parasitological techniques, including microscopy, flotation, and concentration methods, were used to quantify helminth eggs (eggs per gram, EPG) and protozoan cysts (eggs per liter, EPL). Qualitative data were collected through focus group discussions (FGDs) and key informant interviews to assess sanitation practices and hygiene behaviors. Results revealed a high level of environmental contamination, with overall parasitic prevalence exceeding 60% across all sample types. The results indicated that eco-san manure from peri-urban wards (Keraniganj and Savar) exhibited the highest helminth egg counts (135 ± 10 and 115 ± 12 EPG, respectively). Wastewater samples from urban slum areas (Kamrangirchar) showed moderate contamination levels (95 ± 9 EPL). In contrast, flood-prone wards (Badda and Demra) recorded significantly higher parasitic loads in runoff water (150 ± 15 and 165 ± 18 EPL, respectively; ANOVA, F = 72.47, p = 0.0136). GIS-based spatial analysis further identified flood-prone areas as major contamination hotspots. Multiple parasite groups were detected, including protozoa, cestodes, and nematodes, with common organisms such as Hymenolepis nana, Ascaris lumbricoides, Trichuris trichiura, Entamoeba spp., and Giardia spp. Due to methodological limitations, some organisms were reported at the genus level or categorized as “parasite-like structures.” Seasonal variation indicated increased contamination during the rainy season due to flooding and enhanced pathogen dispersion. Qualitative findings highlighted limited awareness of safe compost handling, inadequate sanitation practices, and increased exposure risks during flooding events. Overall, parasitic contamination was strongly influenced by sample type, environmental conditions, and human behavior. This study underscores the need for integrated sanitation management, improved ecosan practices, effective wastewater treatment, flood-risk mitigation, and community-based health education to reduce environmental contamination and associated health risks. The adoption of advanced molecular diagnostic techniques is recommended to enhance the accuracy of parasite identification in future research. This thesis is submitted for the degree of Doctor of Philosophy.

Morphometric and Molecular Characterization of Mosquito Species from Different Larval Habitats in Gulshan Thana, Dhaka

2026-03-02T00:00:00Z

Morphometric and Molecular Characterization of Mosquito Species from Different Larval Habitats in Gulshan Thana, Dhaka Noor-E Jannat, Khandaker This comprehensive study, conducted in Gulshan Thana, Dhaka, investigated mosquito diversity, larval habitat characteristics, and cryptic species identification using an integrated approach combining wing morphometrics and molecular analysis. Larval habitats were systematically surveyed across natural and artificial breeding sites during pre-, peak-, and post-monsoon seasons over three consecutive years using a stratified random sampling design. GPS-referenced data analyzed in ArcGIS Pro revealed high-density breeding zones through kernel density and hotspot analyses. A total of 36 mosquito species across eight genera were identified, including 11 new records for Bangladesh: Aedes (Ae.) aegypti aegypti, Ae. aegypti var. luciensis, Ae. flavopictus, Culex (Cx.) annulirostris, Cx. pipiens, Cx. pipiens f. pipiens, Cx. pipiens f. molestus, Cx. pipiens pallens, Cx. pseudosinensis, Lutzia (Lt.) chiangmaiensis, and Ochlerotatus sp. The Breteau Index comparison between Ae. aegypti and Ae. albopictus was significant (U = 109.5, p = 0.032), peaking in September, with Korail slum identified as a year-round hotspot for Ae. aegypti. Habitat preferences varied, with Culex preferring drains (16.83%) and Aedes favoring water filter pots (27.07%). Morphometric analysis of wing landmarks (CVA and PCA) revealed significant interspecific variations in size and shape (p < 0.0001). Molecular characterization using COI and rRNA markers produced 33 COI and four ribosomal sequences, with an average length of 662.91 base pair. Genetic divergence among six mosquito genera was evaluated using the Kimura 2-parameter model, revealing an average pairwise distance of 21.62%. A Neighbor-Joining (NJ) tree was constructed with 1,000 bootstrap replicates using MEGA 11, to evaluate the robustness of the inferred clades. The Kruskal-Wallis test confirmed significant intergeneric variation (H = 33.14, p = 3.54 × 10⁻⁶). A median-joining network of 20 COI haplotypes revealed high intraspecific genetic diversity (HD = 1.000 ± 0.016; π = 0.11723 ± 0.00855). Notably, Ae. aegypti showed clear divergence from its cryptic subspecies: Ae. aegypti aegypti (distance: 0.21) and Ae. aegypti var. luciensis (distance: 2.15), with 2.30% divergence. The detection of geographically isolated taxa such as Cx. pipiens pallens and Ae. aegypti var. luciensis highlights ongoing ecological range expansion among invasive disease vectors. This thesis is submitted for the degree of Doctor of Philosophy.

Genetic Diversity, Phylogenetic Relationship and Status of Shrimps (Crustacea:Decapoda) of Bangladesh

2025-11-05T00:00:00Z

Genetic Diversity, Phylogenetic Relationship and Status of Shrimps (Crustacea:Decapoda) of Bangladesh Datta, Sujan Kumar Shrimp, a popular and delicious food item worldwide, holds significant commercial and food value, providing a vital source of protein and contributing to a multi-billion-dollar industry in both wild-caught and farmed varieties. Belonging to the order Decapoda, shrimp play a vital role in both marine and freshwater ecosystems. However, a comprehensive, systematic taxonomic study, especially in molecular taxonomy, has not been conducted for these species in Bangladesh. To address this gap, the present study aimed to explore the genetic diversity, phylogenetic relationships, and status of shrimp species found in Bangladesh. An integrative taxonomic approach was used, combining morphological examination, DNA barcoding, and molecular species delimitation to provide a broad understanding of the systematics of shrimps in the region. Specimens were initially identified morphologically, followed by molecular analysis using two genetic markers: the mitochondrial cytochrome c oxidase I (COI) gene and the 16S ribosomal RNA (16S rRNA) gene. 50 shrimp species, representing six families and 16 genera, were morphologically identified, and 38 species and two genera were further confirmed through molecular analysis. A total of 127 sequences were generated, comprising of 55 COI and 72 16S rRNA sequences. Sequence analysis revealed 136 conserved, 561 variable, and 321 parsimony-informative sites for the COI gene, and 101 conserved, 583 variable, and 372 parsimony-informative sites for the 16S rRNA gene. The average GC content was 40.87% for COI and 33.49% for 16S rRNA. Genetic divergence was assessed with mean distances of 1.18 ± 0.02%, 23.53 ± 0.08%, and 28.29 ± 0.05% within species, genus, and family for the COI gene. For the 16S rRNA gene, the corresponding values were 2.94 ± 0.09%, 13.91 ± 0.06%, and 25.26 ± 0.04%. Notably, the mean interspecific genetic distance for COI was 34 times greater than the intraspecific distance, while for 16S rRNA, it was 15 times greater, with barcode gaps of 38.54% and 40.91% for the two markers, respectively. Phylogenetic trees based on the Neighbor-Joining (NJ) method were generated for each gene marker to explore the phylogenetic relationships among the identified species. Additionally, 11 species were newly recorded from Bangladesh, marking their first geographic occurrence in the region. This is the first comprehensive study combining morpho-taxonomy, molecular analysis, and phylogenetic relationships of shrimps from Bangladesh. The study underscores the need for effective conservation strategies and sustainable management practices to preserve the rich shrimp diversity in Bangladesh, as revealed by the molecular and phylogenetic findings. The results not only enhance our understanding of shrimp biodiversity in Bangladesh but also lay a foundation for future research on the ecological and evolutionary dynamics of these crucial aquatic organisms. This thesis is submitted for the degree of Doctor of Philosophy.

Trichodinid ciliates (Ciliophora: Trichodinidae) of selected freshwater fishes of Hakaluki Haor, Bangladesh

2025-11-05T00:00:00Z

Trichodinid ciliates (Ciliophora: Trichodinidae) of selected freshwater fishes of Hakaluki Haor, Bangladesh Ahasan Habib, Md. Moin Uddin This dissertation presents a comprehensive study on the occurrence of trichodinid ciliates parasitizing freshwater fishes from Hakaluki Haor, Sylhet, Bangladesh, conducted between April 2018 and March 2022. A total of 44 host fish species, belonging to 8 orders, 18 families, and 32 genera, were examined; among them, 16 species were infested with trichodinid ciliates. Altogether, 29 species of trichodinid ciliates were identified belonging to three genera: Trichodina Ehrenberg, 1830; Trichodinella (Raabe, 1950) Šrámek-Hušek, 1953; and Tripartiella Lom, 1959. Twenty-four species of Trichodina were identified, of which 22 are redescribed, viz., T. acuta, T. ahmedi, T. anabasi, T. cancilae, T. caspialosae, T. cobitis, T. cubanensis, T. domerguei, T. glossogobae, T. gulshae, T. hafizuddini, T. heterodentata, T. hoffmani, T. japonica, T. kupermani, T. modesta, T. molae, T. nigra, T. notopterusi, T. ovonucleata, T. siluri and T. sylhetensis. Two species of Trichodina are described and new to science, viz., Trichodina sp. 1 n. sp. and sp. 2 n. sp. Two species of Trichodinella, viz., Trichodinella epizootica and Trichodinella sunderbanensis, were recorded, along with three species of Tripartiella, viz., Tripartiella bulbosa, Tripartiella copiosa, and Tripartiella obtusa. Among the 29 species, eight (T. ahmedi, T. cubanensis, T. caspialosae, T. glossogobae, T. kupermani, T. notopterusi, T. ovonucleata, and Trichodinella sunderbanensis) are recorded for the first time from Bangladesh. Taxonomic identification followed the protocols of Lom (1958), Wellborn (1967), Arthur and Lom (1984), and Van As and Basson (1989, 1992). All species descriptions were based on dry silver nitrate impregnated specimens following Klein (1958). Photomicrographs captured at 1000× magnification, detailed morphometric data for each trichodinid species, and diagrammatic illustrations of denticles for selected taxa are included. Observations on host specificity, distribution patterns, and seasonal incidence of infection contribute valuable insights into the diversity and ecology of trichodinid ciliates in freshwater ecosystems of Hakaluki Haor. This study significantly enhances knowledge of trichodinid diversity, distribution, and ecological interactions in Bangladesh, providing essential baseline data for future parasitological research and management strategies. This thesis is submitted for the degree of Doctor of Philosophy.