In recent years, there has been a rise in the emergence of arboviruses of public health importance, including Zika, chikungunya, dengue, and yellow fever viruses. Insecticide-based mosquito control has been the primary method for mitigating transmission of arboviruses. The consequences for the application of insecticides include both lethal and sublethal effects, and associated development of insecticide resistance. However, little is known about the influence on arboviral transmission. Mosquitoes with phenotypes that exhibit insecticide resistance or experience sublethal effects may be associated with altered susceptibility to arbovirus infection and transmission. Juvenile hormone analogs (JHAs) are insecticides that prevent pupa to adult molting of mosquitoes by mimicking the action of their natural juvenile hormone. Here, we examined whether the JHA pyriproxyfen interacts with ambient temperature (20 °C and 30 °C) during juvenile stages to influence life-history traits, population growth (λ'), and Zika virus (ZIKV) infection in Aedes aegypti. Development time of females was lengthened at 20 °C and in the presence of JHA. Prevention of pupa to adult molting by JHA was differentially higher at elevated temperature than low temperature. Size of females was larger at 20 °C and smaller at 30 °C. Infection, disseminated infection, and transmission of ZIKV in females were enhanced by JHA at both 20 °C and 30 °C relative to the controls. These results demonstrate that mosquito life-history and vector competence parameters are strongly influenced by interactive effects of JHA and temperature. The JHA-induced enhancement of ZIKV infection in females should be a consideration when implementing JHA in vector control strategies.
Zika virus (ZIKV) is an emerging mosquito-borne pathogen that can cause global public health threats. In the absence of effective antiviral medications, prevention measures rely largely on reducing the number of adult mosquito vectors by targeting juvenile stages. Despite the importance of juvenile mosquito control measures in reducing adult population size, a full understanding of the effects of these measures in determining mosquito phenotypic traits and in mosquito-arbovirus interactions is poorly understood. Pyriproxyfen is a juvenile hormone analog that primarily blocks adult emergence, but does not cause mortality in larvae. This mechanism has the potential to work in combination with other juvenile sources of mortality in nature such as predation to affect mosquito populations. Here, we experimentally evaluated the effects of juvenile exposure to pyriproxyfen and predatory mosquito Toxorhynchites rutilus on Aedes aegypti phenotypes including susceptibility to ZIKV infection and transmission. We discovered that combined effects of pyriproxyfen and Tx. rutilus led to higher inhibition of adult emergence in Ae. aegypti than observed in pyriproxyfen or Tx. rutilus treatments alone. Adult body size was larger in treatments containing Tx. rutilus and in treatments mimicking the daily mortality of predation compared to control or pyriproxyfen treatments. Susceptibility to infection with ZIKV in Ae. aegypti was reduced in predator treatment relative to those exposed to pyriproxyfen. Disseminated infection, transmission, and titers of ZIKV in Ae. aegypti were similar in all treatments relative to controls. Our data suggest that the combination of pyriproxyfen and Tx. rutilus can inhibit adult Ae. aegypti emergence but may confer a fitness advantage in survivors and does not inhibit their vector competence for ZIKV relative to controls. Understanding the ultimate consequences of juvenile mosquito control measures on subsequent adults’ ability to transmit pathogens is critical to fully understand their overall impacts.
Lethal and nonlethal effects of predation are likely to impact phenotypic traits of potential prey that elude capture. Nonlethal effects of predation on prey can include alterations in behavior or morphology in response to predation risk which may impair prey growth and fitness. The application of pesticide in mosquito control during aquatic stages can interact with predation stress and alter density and phenotypic traits of prey. Insect growth regulator (IGR) pyriproxyfen is a pesticide that mainly prevents pupal-adult metamorphosis by mimicking juvenile hormone, whereas the larval stage is not targeted. The use of IGR can therefore act in conjunction with natural aquatic predators that target the larval stage to affect population of prey. In this study, we assessed the invasive mosquito prey Aedes aegypti responses to lethal and nonlethal effects of a combination of IGR and predatory mosquito larvae of Toxorhynchites rutilus. The combination of IGR and Tx. rutilus heavily lowered Ae. aegypti metamorphosis to adulthood more than the independent effects of IGR or Tx. rutilus. Exposing Ae. aegypti larvae to the combination shortened life span of adults after metamorphosis for both males and females, whereas control and numerical density reduction "removals" treatments lengthened life span. Our results show strong lethal and nonlethal outcomes of the combination on Ae. aegypti. These findings suggest an additional benefit, decreases adult life span, of the use of an IGR when combined with a natural predator of mosquitoes that may be exploited to improve mosquito control strategies to reduce the risk of disease transmission.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.