COS 251-1 - The impact of environmental and geographical factors on the occurrence and abundance of Culex quinquefasciatus mosquito in Hawai'i

Background/Question/Methods

Endemic Hawaiian forest bird populations have been declining more rapidly in recent years due to climate-driven spread of the invasive avian malaria parasite Plasmodium relictum and the invasive mosquito Culex quinquefasciatus, the main avian malaria vector in Hawai'i. Environmental and geographical factors play an important role in shaping mosquito-borne disease transmission dynamics through their influence on the distribution and abundance of mosquitoes. We assess the effects of trap type (CO2 and gravid), environmental (temperature, precipitation, rainfall seasonality, and temperature and precipitation time lags), and geographic (site, elevation, and distance to anthropogenic features) factors on mosquito occurrence and abundance that were continuously collected at 9 locations for three years along an elevation gradient on Hawai'i Island. Occurrence (detection/non-detection) was analyzed using classification and regression tree models (CART) and generalized linear models (glm); abundance (count data) was analyzed using Generalized Linear Mixed Models (GLMMs).

Results/Conclusions

For occurrence, both models, CART and glm, have similar predictions with sites at mid-elevation having the highest Cx. quinquefasciatus occurrence. The months from July to December show the highest Cx. quinquefasciatus occurrence. Mean temperature, cumulative precipitation one and two months prior to the sampling month, and the interaction between mean temperature and cumulative precipitation have a positive effect on Cx. quinquefasciatus occurrence. For abundance, the best model based on AIC values is the zero-inflated negative binomial model using year as a random effect. Carbon dioxide (CO2) traps were able to capture a higher number of mosquitoes and estimated mosquito abundance was better matched with observed mosquito abundance compared with gravid traps (Reiter). Mosquito abundance peaks between May and November in all locations with higher abundance at mid-elevation sites. Estimation of occurrence and abundance of mosquitoes is key for control of avian malaria necessary to prevent native bird extinctions.