Community Composition and Year-round Abundance of Vector Species of Mosquitoes make Miami-Dade County, Florida a Receptive Gateway for Arbovirus entry to the United States

www.nature.com/scientificreports OPEN Received: 11 January 2019 Accepted: 5 June 2019 Published: xx xx xxxx Community Composition and Year-round Abundance of Vector Species of Mosquitoes make MiamiDade County, Florida a Receptive Gateway for Arbovirus entry to the United States André B. B. Wilke & John C. Beier1 1 , Chalmers Vasquez2, Johana Medina2, Augusto Carvajal2, William Petrie2 Vector-borne diseases are a heavy burden to human-kind. Global warming and urbanization have a significant impact on vector-borne disease transmission, resulting in more severe outbreaks, and outbreaks in formerly non-endemic areas. Miami-Dade County, Florida was the most affected area in the continental United States during the 2016 Zika virus outbreak. Miami is an important gateway and has suitable conditions for mosquitoes year-round. Therefore, it was critical to establish and validate a surveillance system to guide and improve mosquito control operations. Here we assess two years of mosquito surveillance in Miami established after the 2016 Zika virus outbreak. Our results show that the most abundant mosquito species are either well adapted to urban environments or are adapting to it. The five most abundant species comprised 85% of all specimens collected, with four of them being primary vectors of arboviruses. Aedes aegypti and Culex quinquefasciatus were found year-round throughout Miami regardless of urbanization level, vegetation, or socioeconomic variations. This study serves as a foundation for future efforts to improve mosquito surveillance and control operations. Vector-borne diseases (VBDs) affect more than half of all human populations living in endemic areas of the globe1. Current estimates show that dengue virus (DENV) infects around 390 million people every year2. The Pan American Health Organization (PAHO) officially confirmed 1,003,509 cases of Zika virus (ZIKV) between 2015 and 2018 in the Americas3, and subsequent studies have also shown the increase in fetus malformation with ZIKV infection during pregnancy4,5. Considerable efforts have been allocated to fight vector mosquitoes. However, the efforts to control mosquito populations have only achieved limited success, and the global incidence of VBDs is currently on the rise6–9. Not only have more severe VBD outbreaks been reported but outbreaks have occurred in formerly non-endemic countries such as Italy, France and Croatia10–13. Furthermore, several arboviruses are circulating in tropical regions of the world, and many more are circulating under the radar14–19. There are only limited options for the treatment of arbovirus infections and their prevention by vaccination. Therefore, controlling vector mosquito populations is widely accepted as the most effective way to prevent the transmission of VBDs20. Controlling vector mosquitoes rely on many steps that logically build on each other. Effective surveillance is fundamental as mosquitoes are often locally concentrated, abundant, and harder to control primarily in those specific, definable habitats at the neighborhood level. These favorable habitats provide optimal conditions and environmental resources needed for mosquito survival, a key determinant of their vectorial capacity. It is critical for the development of any mosquito control strategy to know through effective surveillance 1 Department of Public Health Sciences, Miller School of Medicine, University of Miami, Miami, FL, United States of America. 2Miami-Dade County Mosquito Control Division, Miami, FL, United States of America. Correspondence and requests for materials should be addressed to A.B.B.W. (email: ) Scientific Reports | (2019) 9:8732 | https://doi.org/10.1038/s41598-019-45337-2 1 www.nature.com/scientificreports/ www.nature.com/scientificreports the geographic distribution, community composition and relative abundance of vector mosquitoes as well as the risk of introduction of arboviruses21,22. Miami-Dade County, Florida was the most affected area in the continental United States during the 2016 Zika virus outbreak23. Miami is not only one of the most important gateways to the U.S. with an increased flow of people coming and going from endemic areas, but its proximity to the Caribbean region and Latin America substantially increases the risk of introduction of arboviruses to the U.S. Moreover, Miami also has the appropriate conditions for mosquitoes, its climate is defined as tropical monsoon24, and is conducive for mosquitoes even during the winter. Miami is also undergoing an intense increase in urbanization25 that impacts the population dynamics of vector mosquitoes and patterns of VBD transmission26. Historically, Miami-Dade County and, in a broader perspective, South Florida have been afflicted by arbovirus outbreaks for decades, including DENV, West Nile virus (WNV) and YFV27–32. However, as seen during the most recent ZIKV outbreak, the virus was introduced in Miami multiple times on different occasions33, exposing the real vulnerability of Miami to the introduction of arboviruses and subsequent VBD outbreaks. Therefore, it was critical to establish a state-of-the-art surveillance system to determine the community composition and abundance of mosquitoes in Miami-Dade County, Florida, to help inform, guide and improve mosquito control operations. Here our objective was to assess the last two years of mosquito surveillance data in Miami-Dade County, Florida. Results Mosquito composition and abundance. A total of 2,711,983 mosquitoes were collected in Miami-Dade County from August 2016 to November 2018 by the 157 BG-Sentinel and 34 CDC traps. The collected mosquitoes comprised 41 species from 9 genera. The most abundant species was Culex nigripalpus comprising 1,057,485 (38%) specimens collected, followed by Aedes taeniorhynchus 626,163 (23%), Culex quinquefasciatus 373,571 (13%), Aedes aegypti 150,588 (5%) and Anopheles crucians 132,741 (4%). These 5 species comprised 85% of all collected specimens. BG-Sentinel traps collected a total of 568,565 mosquitoes, from which 355,381 were Cx. quinquefasciatus (62%) and 134,652 Ae. aegypti (23%), comprising 85% of all collected mosquitoes. CDC traps collected a total of 2,143,418 mosquitoes, from which 1,034,119 were Cx. nigripalpus (48%), 610,547 Ae. taeniorhynchus (28%), 131,077 An. crucians (6%) and 95,193 Aedes tortilis (4%), comprising 85% of all collected mosquitoes. BG-Sentinel traps did not collect Aedes fulvuspallens, Aedes scapularis, Anopheles walker, Culex bahamensis, Culex cedecei, Psorophora howardii and Psorophora johnstonii. CDC traps failed to collect Culex biscaynensis (Table 1). Biodiversity indices. Mosquito counts obtained by both BG-Sentinel and CDC traps displayed higher levels of variation for the Shannon index and log evenness. However, the log abundance remained stable (Fig. 1A). The analysis of the mosquito counts obtained by the BG-Sentinel traps pointed out many oscillations on the index values (represented (...truncated)