Study on the Bionomics and Pathogen Infection Status of Aedes Mosquitoes in Metema District, Northwest Ethiopia
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Date
2025-10-10
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Addis Ababa University
Abstract
Background: Female Aedes Species Transmit Viral Diseases Such as Yellow Fever, Dengue Fever, Chikungunya and Zika in Humans. Dengue Fever and Chikungunya Have Been Reported in Metema District, Northwest, Ethiopia However, Entomological Evidence Scares to Guide Vectors Control Strategies. Therefore, This Study Examined the Physicochemical Characteristics of Larval Breeding Habitats, Biting Time, Resting Habitats, And Wolbachia and Viral Infectious State of Aedes Mosquitoes.
Methodology: Entomological Studies Were Conducted in Metema-Yohannes, Kokit and Gend-Wuha Towns, Metema Distinct, Northwestern Ethiopia from January 2022-December, 2023. A Longitudinal Entomological Study Was Carried Out on the Physico-Chemical Characteristics of Larvae/Pupae Habitats, Adult Biting Hours, Resting Habit and Cross Section Study Was Carried Out Viral and Wolbachia Strains Infection Status of Aedes Aegypti. Physical Characteristics of Larvae/Pupae Habitat Were Observed in Situ and Chemical Composition of Habitat’s Water Sample Was Analyzed Under Laboratory Condition. Aedes Mosquitoes Were Identified to Species Under Microscope Using a Taxonomic Key and Confirmed Using Molecular Technique Based on Mitochondrial Cytochrome Oxidase Subunit -1
(COI-1) And Internal Transcribed Spacer -1 & 2 (ITS-1 & 2) Genes. Biting Hour of Adult Ae. Aegypti And Ae. Vittatus Was Deterred By CDC-LT Collection from Indoor and Outdoor Each Hour For 24hrs And Their Host Seeking Behavior Was Determined by Collecting Them from Human (Indoor & Outdoor), Cattle, Goat, Sheep and Donkey Shelters Overnight. Adult Aedes Species Were Collected from Their Resting Places by Prokopenko Aspirators, Pyrethrum Spray Catches and Mouth Aspirator. Dengue Virus, Chikungunya Viruse and Zika Viruses Were Detected by SYBR Green RT-PCR And Also Wmel Strain Wolbachia Was Detected by Conventional RT-PCR. Statistical Method Used to Data Analysis Was Considered Significant When to P < 0.05.
Results: Aedes Larvae/Pupae Were Abundant in Metema-Yohannes, Kokit and Genda-Wuha Towns During Wet Seasons. Breteau, House, And Container Indices Exceeded the World Health Organization (WHO) Risk Levels for Arboviral Diseases. Aedes Larvae/Pupae Density Increased in Habitat with High Water Temperature, Total Hardness, Sulphate, And with the Decrease Distance Between Households and Habitat. Adult Ae. Aegypti Larvae/Pupae Were the Most Abundant (56.77%; 5106/8993) Followed by Aedes Vittatus (37.25%; 3350/8993), Aedes Communis (2.39%; 215/8993), Aedes Opok (0.66%; 60/8993) And Aedes Albopictus (0.26; 24/8993). The Mean Ranks of Ae. Aegypti Emerged from the Larvae/Pupae of Artificial, Algae Positive and Tadpole Free Habitats Were Analyzed by Mann-Whitney U Test. Results Were Considered Significant When P < 0.05 Higher Than the Corresponding Results from the Natural, Algae Free, And Tadpole Infested, respectively. Adults Of Ae. Vittatus Followed a Similar Trend. The Mean Number of Ae. Aegypti Emerged from Larvae/Pupae of Habitats Closer to Human Habitations, Not Exposed to Sunlight, Free of Emergent Vegetation and Tyre Substrates Were Analyzed by Kruskal Wallis H Test. Results Were Considered Significantly (P<0.001) Higher Than from Habitats with No These Attributes. Aedes Aegypti And Ae. Vittatus Exhibited Two Peak Biting Rates Were Observed Indoor and Outdoor at Sunrise and Sunset. Both Ae. Aegypti And Ae. Vittatus Was Abundantly Collected from Nearby Human Sleeping Arrangements Than from the Animal Shelters Like Cattle, Sheep, Goats, And Donkeys. The Highest Proportions of Ae. Aegypti (91.21%) And Ae. Vittatus (89.87%) Was Unfed. A Total Of 4,054 Aedes Mosquitoes Were Collected That Belonged to Ae. Aegypti (3026; 58.49%), Ae. Vittatus (N = 723; 29.08%), Ae. Communis (N= 186; 7.24%), Ae Albopictus (N = 77; 3.30%), And Ae. Opok (N = 42; 1.88%). A Greater Number of Aedes Species Were Collected During the Wet Season (June to September) Than During the Dry (October to May), 2022-2023. Ae. Aegypti And Ae. Vittatus Occurred in Metema-Yohannes, Kokit, And Genda-Wuha, Aedes Communis in Genda-Wuha and Kokit, But Ae. Albopictus And Ae. Opok Only in Metema-Yohannes. Large Numbers of Ae. Aegypti, Ae. Vittatus And Ae. Communis Was Collected Resting in Cattle Shade, While Ae. Albopictus Within Larvae Hatching Containers but Ae. Opok Was Collected from Inside Bridge. The Wmel Strain of Wolbachia Was Detected in Both the First and Second Generations of Aedes Aegypti Under Laboratory Conditions, Indicating Successful Transovarian Transmission. Additionally, All Ae. Aegypti Pools Were Tested Negative For DENV, CHIKV And ZIKV.
Conclusion: The Predominant Aedes Species Identified in the Study Area Was Ae. Aegypti, Followed by Ae. Vittatus. Other Aedes Species Was Observed in the Towns Included Ae. Communis, Ae. Albopictus, And Ae. Opok. Larvae And Pupae of Ae. Aegypti, Ae. Vittatus, And Ae. Albopictus Were Primarily Found in Discarded Tyres, While Ae. Communis Was Associated with Metal Containers, And Ae. Opok With Tree Holes. Peak Biting Activity for Ae. Aegypti And Ae. Vittatus Occurred During the Morning and Early Night Hours. The Resting Habitats of Aedes Species Varied with Seasonal Changes. The Pathogenic Infection Status of Ae. Aegypti May Be Influenced by Natural Suppressive Agents. Findings From This Study Can Serve as A Baseline for Implementing Targeted Aedes Mosquitoes Control Programs, Particularly in Managing Larval and Pupal Breeding Containers Within the Study Towns. Additionally, Control Efforts Should Include Community Engagement on the Elimination of Common Larval and Pupal Breeding Habitats.