Impacts of Low Temperatures on Wolbachia (Rickettsiales: Rickettsiaceae)-Infected Aedes aegypti (Diptera: Culicidae)

Abstract

In recent decades, the occurrence and distribution of arboviral diseases transmitted by Aedes aegypti mosquitoes has increased. In a new control strategy, populations of mosquitoes infected with Wolbachia are being released to replace existing populations and suppress arboviral disease transmission. The success of this strategy can be affected by high temperature exposure, but the impact of low temperatures on Wolbachia-infected Ae. aegypti is unclear, even though low temperatures restrict the abundance and distribution of this species. In this study, we considered low temperature cycles relevant to the spring season that are close to the distribution limits of Ae. aegypti, and tested the effects of these temperature cycles on Ae. aegypti, Wolbachia strains wMel and wAlbB, and Wolbachia phage WO. Low temperatures influenced Ae. aegypti life-history traits, including pupation, adult eclosion, and fertility. The Wolbachia-infected mosquitoes, especially wAlbB, performed better than uninfected mosquitoes. Temperature shift experiments revealed that low temperature effects on life history and Wolbachia density depended on the life stage of exposure. Wolbachia density was suppressed at low temperatures but densities recovered with adult age. In wMel Wolbachia there were no low temperature effects specific to Wolbachia phage WO. The findings suggest that Wolbachia-infected Ae. aegypti are not adversely affected by low temperatures, indicating that the Wolbachia replacement strategy is suitable for areas experiencing cool temperatures seasonally.

Pervasive Effects of Wolbachia on Host Temperature Preference

“…Future work should evaluate whether reductions in host T p lead to reduced Wolbachia titer and maternal transmission downstream over the course of offspring development. For example, mosquito larvae have reduced w AlbB titer when reared at temperatures of <20°C ( 63 ). Temperature shifts longer than 24 h may also be required to generate reductions in titer, especially if infected hosts seek their T p throughout their lifecycles.…”

“…Our results add to mounting literature showing that temperature is an important abiotic factor mediating interactions between Wolbachia and their hosts ( 112 ). Wolbachia titer seems to be especially sensitive to temperature ( 42 , 58 , 60 , 61 , 63 , 113 – 116 ). Our 24-h temperature shift experiments suggest that Wolbachia titer can change over very short time periods due to environmental conditions.…”

“…Our 24-h temperature shift experiments suggest that Wolbachia titer can change over very short time periods due to environmental conditions. Lau et al ( 63 ) similarly found that Wolbachia titer can change within a single host generation, such that cold temperatures (<20°C) reduce w AlbB titer in mosquitoes at the larval stage, but then titer rebounds in adulthood when fourth instar larvae are shifted to warmer conditions (>21°C) ( 63 ). Temperature-induced changes to Wolbachia titer are likely to have cascading effects, given that titer influences other host phenotypes ( 57 ).…”

“…Differences in T p between infected and uninfected flies could arise from conflicting physiological requirements of Wolbachia and their hosts. Wolbachia titer in host bodies is sensitive to temperature fluctuations (57), such that exceedingly cool (Ͻ20°C) and warm (Ͼ25°C) temperatures can reduce titer and the efficiency of maternal Wolbachia transmission (42,(57)(58)(59)(60)(61)(62)(63). Wolbachia-induced changes to T p could provide more favorable thermal conditions for bacterial replication in hosts.…”

Infertility and fecundity loss of Wolbachia-infected Aedes aegypti hatched from quiescent eggs is expected to alter invasion dynamics

“…aegypti under cool environments, which points to the w AlbB-infected Ae. aegypti being relatively better adapted to cool environments than uninfected mosquitoes [54]. Under hot environments, w AlbB is relatively more stable than w Mel in terms of density and its ability to induce cytoplasmic incompatibility [42].…”