Effect of Temperature on the Development of Culiseta melanura (Diptera: Culicidae) and its Impact on the Amplification of Eastern Equine Encephalomyelitis Virus in Birds

Abstract

Eastern equine encephalomyelitis virus (EEE) is perpetuated in a maintenance cycle that involves Culiseta melanura (Coquillett) as the enzootic vector and passerine birds as the amplifying hosts. Amplification of virus in any given year requires an influx of nulliparous Cs. melanura in the presence of susceptible avian hosts. We conducted laboratory experiments at constant temperatures from 10 to 34 degrees C to develop thermal heat summation models to predict emergence in nature. Embryonic development progresses slowly at 10 degrees C, and the time to eclosion decreased significantly as temperatures increased to 28 degrees C. High temperature were lethal and eggs failed to hatch at 32 degrees C. The thermal minimum (t0) for embryonic development was 9.38 degrees C, and 38.46 degrees-days (DD) were required for egg hatch. The time for larval development decreased with increasing temperatures. Cs. melanura larvae develop in subterranean habitats (crypts) where water temperatures remain below 20 degrees C throughout the summer. Under controlled conditions, egg hatch to emergence took 8 mo at 10 degrees C, 3 mo at 16 degrees C, and 1 mo at 22 degrees C. The thermal minimum for larval development (t0) was 8.5 degrees C, and 467.29 DD were required from eclosion to adult emergence. Our findings indicate that Cs. melanura is well suited to develop in cold water crypts where the larvae are collected most frequently. The mosquito appears to be bivoltine in the northeast with an overwintering generation of larvae that emerges as a spring brood of adults and a summer generation of larvae that emerges in fall. Higher than normal water temperatures hasten development of the summer generation and increase the probability for amplification of EEE by bringing large numbers of nulliparous mosquitoes into contact with recrudescing virus for subsequent transfer to the growing population of susceptible juveniles. Water temperatures in the crypts also may regulate the northern limit for virus amplification each year.

Temperature Effects on the Immature Development Time of Culex eduardoi Casal & García (Diptera: Culicidae)

“…As expected, the total development time (from irst instar larva to adult emergence) was inversely related to the rearing temperature in the range of 7 o C to 25 o C, as observed for several mosquito species (e.g., Rueda et al 1990, Mahamood & Crans 1998, Ribeiro et al 2004, Monteiro et al 2007. The time required by the immatures maintained at the lowest temperatures to reach adulthood was extended between six to eight orders of magnitude as compared for those maintained at 25°C.…”

Evolutionary strategies and adaptations for survival between mosquito-parasitic microsporidia and their intermediate copepod hosts: a comparative examination of Amblyospora connecticus and Hyalinocysta chapmani (Microsporidia: Amblyosporidae)

“…The overwintering generation of larvae emerge as adults in the spring (June) and produce summer broods which are active from July through November. Eggs laid by the late-fall brood of adults produce larvae that make up the overwintering generation that emerge the following spring (Mahmood and Crans 1998).…”

Bats as Potential Reservoir Hosts for Vector-Borne Diseases

“…Regarding the latter species, they conclude with Kelser (1933) that it could not be the transmitting species at it did not occur sufficiently far northwards. Generally, epizootics of EEE occur every 5-10 years and are associated with increased mosquito populations resulting from heavy rainfall and warm weather (Grady et al 1978;Letson et al 1993;Mahmood and Crans 1998;Nalca et al 2003). Although birds seem to be the main reservoir hosts of EEEV, the virus has also been detected in bats.…”