Evidence for serial founder events during the colonization of North America by the yellow fever mosquito, Aedes aegypti.

The Aedes aegypti mosquito first invaded the Americas about 500 years ago and today is a widely distributed invasive species and the primary vector for viruses causing dengue, chikungunya, Zika, and yellow fever. Here, we test the hypothesis that the North American colonization by Ae. aegypti occurred via a series of founder events. We present findings on genetic diversity, structure, and demographic history using data from 70 Ae. aegypti populations in North America that were genotyped at 12 microsatellite loci and/or ~20,000 single nucleotide polymorphisms, the largest genetic study of the region to date. We find evidence consistent with colonization driven by serial founder effect (SFE), with Florida as the putative source for a series of westward invasions. This scenario was supported by (1) a decrease in the genetic diversity of Ae. aegypti populations moving west, (2) a correlation between pairwise genetic and geographic distances, and (3) demographic analysis based on allele frequencies. A few Ae. aegypti populations on the west coast do not follow the general trend, likely due to a recent and distinct invasion history. We argue that SFE provides a helpful albeit simplified model for the movement of Ae. aegypti across North America, with outlier populations warranting further investigation.

A Cross-Sectional Household Survey in the US Virgin Islands (2019) Reveals Cisterns as Challenging Peridomestic Aedes aegypti Habitats.

Most residences in the United States Virgin Islands (USVI) rely on household rainwater-catchment systems and subterranean cisterns for long-term water storage that may provide suitable habitats for mosquitoes of public health relevance. We conducted a household cistern survey (n = 164) on the islands of St. Croix, St. John, and St. Thomas in 2019. The survey revealed that 45.7% (95% CI: 38.3-53.4%) of cisterns contained mosquitoes (adult and/or immature mosquitoes). Aedes aegypti, a vector of chikungunya, dengue, and Zika viruses in the USVI, was found in 27.4% (95% CI: 21.2-34.7%) of cisterns and accounted for 83.3% of the total mosquitoes identified in the study. The odds of detecting mosquitoes in a cistern were 5.45 times higher at locations where the residents reported that they had observed adult mosquitoes coming out of their cisterns (95% CI: 2.25-14.21), suggesting that vector control personnel should consider resident complaints about mosquitoes in their cistern as valid and likely reliable self-assessments. Resident mosquito management practices in cisterns did not correspond with decreased odds of mosquito detection. We conclude that cisterns in the USVI commonly provide habitat for immature and adult Ae. aegypti, which may decrease the effectiveness of area-wide mosquito control strategies. Additional studies are necessary to evaluate the importance of these cisterns as they relate to mosquito production and arbovirus transmission risk, and to assess physical and chemical control methods.

First Record of Mansonia dyari From Saint Croix, United States Virgin Islands.

The first report of Mansonia dyari on Saint Croix, United States Virgin Islands (USVI), is confirmed. Adult and larval specimens were collected in 2018 and 2019 through adult surveillance and larval collections. Specimens were identified by microscopic methods, and a representative specimen was confirmed by DNA sequencing (mitochondrial cytochrome c oxidase subunit I). Morphological features are reviewed and compared with Mansonia flaveola, a species previously reported in the USVI. Notes are provided on the locations, collection methods, and mosquito associates found with Ma. dyari in the USVI.

Community Assessments for Mosquito Prevention and Control Experiences, Attitudes, and Practices - U.S. Virgin Islands, 2017 and 2018.

Aedes aegypti, the mosquito that carries dengue, chikungunya, and Zika viruses, is present throughout the U.S. Virgin Islands (USVI). To reduce mosquitoborne disease transmission, the USVI Department of Health (VIDOH) is responsible for integrated mosquito management. During January 2016-January 2018, USVI experienced its first Zika outbreak, with most cases reported during January-December 2016, as well as two Category 5 hurricanes (Irma on St. Thomas/St. John on September 6, 2017, and Maria on St. Croix on September 19, 2017). The hurricanes severely damaged mosquito protection-related building structures (e.g., screens, roofs) and infrastructure (e.g., electricity, air conditioning) and might have created an environment more conducive to mosquito breeding. VIDOH, with requested technical assistance from CDC, conducted three Community Assessments for Public Health Emergency Response (CASPERs) to provide rapid community information at the household level. The three CASPERs were conducted to inform 1) the Zika outbreak response, 2) the hurricane response, and 3) the hurricane recovery. The CASPERs assessed mosquito prevention and control-related experiences, attitudes, and practices; household and environmental conditions associated with mosquito breeding, prevention, and control; and other nonmosquito-related information to inform outbreak and disaster response planning. Approximately 40% of households were very concerned about contracting Zika virus during the Zika outbreak and hurricane responses. Environmental conditions were reported to become more favorable for mosquito breeding between the Zika outbreak and hurricane response. Between 75%-80% of the community supported mosquito-spraying in all assessments. VIDOH used these data to support real-time outbreak and hurricane response planning. Mosquito prevention and control community assessments can provide rapid, actionable information to advise both mosquito education and control and emergency response and recovery efforts. The CASPER design can be used by vector control programs to enhance routine and response operations.