Urbanization increases Aedes albopictus larval habitats and accelerates mosquito development and survivorship

Abstract

Introduction: Aedes albopictus is a very invasive and aggressive insect vector that causes outbreaks of dengue fever, chikungunya disease, and yellow fever in many countries. Vector ecology and disease epidemiology are strongly affected by environmental changes. Urbanization is a worldwide trend and is one of the most ecologically modifying phenomena. The purpose of this study is to determine how environmental changes due to urbanization affect the ecology of Aedes albopictus.

Methods: Aquatic habitats and Aedes albopictus larval population surveys were conducted from May to November 2013 in three areas representing rural, suburban, and urban settings in Guangzhou, China. Ae. albopictus adults were collected monthly using BG-Sentinel traps. Ae. albopictus larva and adult life-table experiments were conducted with 20 replicates in each of the three study areas.

Results: The urban area had the highest and the rural area had the lowest number of aquatic habitats that tested positive for Ae. albopictus larvae. Densities in the larval stages varied among the areas, but the urban area had almost two-fold higher densities in pupae and three-fold higher in adult populations compared with the suburban and rural areas. Larvae developed faster and the adult emergence rate was higher in the urban area than in suburban and rural areas. The survival time of adult mosquitoes was also longer in the urban area than it was in suburban and rural areas. Study regions, surface area, water depth, water clearance, surface type, and canopy coverage were important factors associated with the presence of Ae. albopictus larvae.

Conclusions: Urbanization substantially increased the density, larval development rate, and adult survival time of Ae. albopictus, which in turn potentially increased the vector capacity, and therefore, disease transmissibility. Mosquito ecology and its correlation with dengue virus transmission should be compared in different environmental settings.

Figure 1. Map of study areas in Guangzhou, Guangdong province, China.

The ecology study of Aedes albopictus was conducted in three areas. A: Rural, Dengcun in Conghua county, B: Suburban, Liangtian, in Baiyun district, C: Urban, Tonghe in Baiyun district.

Figure 2. Seasonal shifts in Ae. albopictus habitats in different areas.

Figure 3. Mean density of adult Aedes albopictus (adults/trap/night) in the three study sites from July to November.

Square root transformed data were used, and the 95% confidence interval is shown as a bar.

Figure 4. Survival rate and development time of Aedes albopictus larvae in urban, suburban and rural areas.

A and B: survival rate; A: natural habitat; B: food supplement. C and D: development time; C: natural habitat; D: food supplement. Values are the mean ±95%CI.

Figure 5. Stage survival rate and stage development time of Aedes albopictus larvae in urban, suburban and rural areas.

A and B: stage survival rate; A: natural habitat; B: food supplement. C and D: stage development time; C: natural habitat; D: food supplement. Values are the mean ±95%CI.

Figure 6. Survivorship curve of adult Aedes albopictus in different seasons.

The left panel is for August to September, and the right panel is for October and November. The top panel (A and B) is for male, and the bottom panel (C and D) is for female.