Semi-field and surveillance data define the natural diapause timeline for Culex pipiens across the United States

Field, Eleanor N.; Shepard, John J.; Clifton, Mark; Price, Keith J.; Witmier, Bryn J.; Johnson, Kirk; Boze, Broox; Abadam, Charles F.; Ebel, Gregory D.; Armstrong, Philip M.; Barker, Christopher M.; Smith, Ryan C.

doi:10.1038/s42003-022-04276-x

Cited by 5 publications

(11 citation statements)

References 85 publications

(150 reference statements)

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“…WNV exhibits clear seasonal transmission trends in Culex populations and human cases, with infections peaking in the late summer across the United States (5,6), yet the mechanisms driving these seasonal trends have been largely unexplored. Although previous studies have suggested that the spatiotemporal abundance of Culex vector populations in the summer and late summer can lead to increased levels of WNV infection in mosquito populations (14,52), overall Culex abundance in Iowa typically peaks much earlier in the season (i.e., May/June) (5,11,14,51,52). Therefore, combining both mosquito abundance and infection data (vector index) is more predictive than mosquito abundance alone in predicting human WNV cases (63-66), demonstrating the importance of identifying the physiological components that contribute to mosquito infection and transmission of WNV.…”

Section: Discussionmentioning

confidence: 99%

“…Several mosquito-borne pathogens, such as malaria, dengue, and West Nile virus (WNV), display seasonal patterns in their transmission (1)(2)(3)(4)(5)(6) that are driven by environmental variables that influence mosquito life-history traits (7)(8)(9), physiology (10,11), and abundance (11)(12)(13)(14), which ultimately shape mosquito-borne disease transmission (15). However, there is little information on how seasonal trends may influence mosquito susceptibility to pathogen infection.…”

Section: Introductionmentioning

confidence: 99%

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Seasonality influences key physiological components contributing to Culex pipiens vector competence

Field

Smith

2023

Front. Insect Sci.

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Mosquitoes are the most important animal vector of disease on the planet, transmitting a variety of pathogens of both medical and veterinary importance. Mosquito-borne diseases display distinct seasonal patterns driven by both environmental and biological variables. However, an important, yet unexplored component of these patterns is the potential for seasonal influences on mosquito physiology that may ultimately influence vector competence. To address this question, we selected Culex pipiens, a primary vector of the West Nile virus (WNV) in the temperate United States, to examine the seasonal impacts on mosquito physiology by examining known immune and bacterial components implicated in mosquito arbovirus infection. Semi-field experiments were performed under spring, summer, and late-summer conditions, corresponding to historically low-, medium-, and high-intensity periods of WNV transmission, respectively. Through these experiments, we observed differences in the expression of immune genes and RNA interference (RNAi) pathway components, as well as changes in the distribution and abundance of Wolbachia in the mosquitoes across seasonal cohorts. Together, these findings support the conclusion that seasonal changes significantly influence mosquito physiology and components of the mosquito microbiome, suggesting that seasonality may impact mosquito susceptibility to pathogen infection, which could account for the temporal patterns in mosquito-borne disease transmission.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Seasonality influences key physiological components contributing to Culex pipiens vector competence

Field

Smith

2023

Front. Insect Sci.

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“…Semi-field studies have found that 50% of Cx. pipiens initiate diapause around mid-September in Ames, Iowa (latitude 32.0°N; [ 24 ]) and at higher latitudes, diapause initiation occurs earlier with 50% of the population entering diapause around mid-July in Guelph, Ontario, Canada (latitude 43.4°N; [ 25 ]). One field study in Boston, Massachusetts (latitude 42.4°N; [ 26 ]) found that adult Cx.…”

Section: Introductionmentioning

confidence: 99%

“…Although previous semi-field studies have characterized how photoperiod and temperature induce diapause in larvae of Cx. pipiens [ 24 , 25 ] and another study characterized the diapause incidence of female Cx. pipiens collected in a single overwintering site from August to mid-November [ 26 ], our study is unique in that it determined how long non-diapausing and reproductively active mosquitoes persist in the field across multiple sites.…”

Section: Introductionmentioning

confidence: 99%

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Characterizing seasonal changes in the reproductive activity of Culex mosquitoes throughout the fall, winter, and spring in Ohio

Siperstein,

Pomeroy,

Robare

et al. 2023

Parasites Vectors

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Background Culex mosquitoes are the primary vectors of West Nile virus (WNV) across the USA. Understanding when these vectors are active indicates times when WNV transmission can occur. This study determined the proportion of female Culex mosquitoes that were in diapause during the fall and winter and when they terminated diapause and began blood feeding in the spring. Methods Mosquitoes were collected from parks using various traps and/or aspirated from culverts in Franklin County, Ohio, from October to mid-May from 2019 to 2022. Culex mosquitoes were morphologically identified to species, and the ovaries of females were dissected to determine their diapause and parity statuses. Results By early October 2021, roughly 95% of Culex pipiens collected in culverts were in diapause and 98% of Cx. erraticus were in diapause. Furthermore, gravid and blood-fed Culex salinarius, Cx. pipiens, and Cx. restuans were collected in late November in 2019 and 2021 in standard mosquito traps. In the winter of 2021, the proportions of non-diapausing Culex decreased within culverts. The last non-diapausing Cx. erraticus was collected in late December 2021 while the final non-diapausing Cx. pipiens was collected in mid-January 2022, both in culverts. Roughly 50% of Cx. pipiens terminated diapause by mid-March 2022, further supported by our collections of gravid females in late March in all 3 years of mosquito collection. In fact, male mosquitoes of Cx. pipiens, Cx. restuans, and Cx. territans were collected by the 1st week of May in 2022, indicating that multiple species of Culex produced a second generation that reached adulthood by this time. Conclusions We collected blood-fed and gravid Culex females into late November in 2 of the 3 years of our collections, indicating that it might be possible for WNV transmission to occur in late fall in temperate climates like Ohio. The persistence of non-diapausing Cx. pipiens and Cx. erraticus throughout December has important implications for the winter survival of WNV vectors and our overall understanding of diapause. Finally, determining when Culex terminate diapause in the spring may allow us to optimize mosquito management programs and reduce the spread of WNV before it is transmitted to humans. Graphical Abstract

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Abundance, distribution, and dynamics of Anopheles species (Diptera: Culicidae) in Iowa, United States

Lee,

Leonard,

Smith

2024

Journal of Medical Entomology

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Malaria was once endemic in the United States prior to its elimination in 1951. However, due to consistent introductions of travel-associated malaria cases and the presence of several native Anopheles species (Diptera: Culicidae) that are competent vectors of malaria, the potential for local (autochthonous) malaria transmission remains a persistent threat in the United States. While several intermittent cases of local malaria transmission have occurred in the United States in the decades since elimination, the emergence of autochthonous transmission in 4 states in 2023 demonstrates the continued risk for future outbreaks. Moreover, these recent examples also highlight significant gaps in current mosquito surveillance efforts that have predominantly focused on threats of arboviral disease, such that our understanding of Anopheles distributions relies only on historical records and offers limited insight into the ecological factors that influence their abundance. Herein, we summarize mosquito surveillance data collected over the last 20 years (2004–2023) across 59 Iowa counties to provide essential information into the spatial distribution, temporal abundance, and trap preferences of Anopheles species in the state. Further analyses of the 2 most abundant species, Anopheles punctipennis Say and Anopheles quadrimaculatus Say, reveal the additional influence of precipitation and forested habitats in defining An. punctipennis abundance. Together, we believe these results provide an increased understanding of previously neglected Anopheles species that have the potential for autochthonous malaria transmission in Iowa and that can be extended to other regions of the United States to enhance preparedness for future malaria outbreaks.

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Semi-field and surveillance data define the natural diapause timeline for Culex pipiens across the United States

Cited by 5 publications

References 85 publications

Seasonality influences key physiological components contributing to Culex pipiens vector competence

Seasonality influences key physiological components contributing to Culex pipiens vector competence

Characterizing seasonal changes in the reproductive activity of Culex mosquitoes throughout the fall, winter, and spring in Ohio

Abundance, distribution, and dynamics of Anopheles species (Diptera: Culicidae) in Iowa, United States

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