November 15, 2021 | Week 44 | Volume 1 | Issue 18 |
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Welcome to the Florida Disease Activity Update, from the desk of Dr. Jonathan Day! It is Clarke’s privilege to share Dr. Day's weekly analysis of arbovirus disease activity in Florida with mosquito control professionals across the state. Our shared goal with Dr. Day is to provide timely and actionable information that mosquito control programs can use to make operational decisions and protect the public from vector-borne diseases.
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What's Ahead for this Newsletter?
One more weekly Newsletter for the 2021 arboviral transmission season will be published on 11/22/21. A Year-End Summary for the 2021 Florida Arboviral Transmission Season will be published as Volume 1, Issue 20 on 1/5/22.
Looking ahead to 2022, the Newsletter will continue! In late May 2022, we will publish a Year in Review for 2021 where we will include information about malaria, Zika virus, and Chikungunya virus. We will resume weekly Newsletter updates for the 2022 arboviral transmission season in June. We continue to welcome your feedback and reader questions for future issues. Thank you for your readership and continued interest in this Newsletter!
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Sarah from Vero Beach, FL asks: “Are there any adaptive advantages to the color patterns of mosquitoes?”
A*: I don’t think the amazing diversity of mosquito scale patterns and colors is really appreciated. For example, my personal favorite is Uranotaenia sapphirina (shown here), a species that appears to have sapphires draped around its head and thorax. There are numerous other examples of brilliantly colored mosquitoes, including Aedes purpureipes from the US Southwest, and Aedes fulvus from Florida.
Mosquito scale patterns and coloration may serve more than one function. Some genera (i.e., Culex and Anopheles) have countershading, where upper surfaces are darker than bottom surfaces. Countershading gives the body uniform darkness and lack of depth. This may be a form of predator avoidance, as is cryptic coloration, where mosquitoes blend into their surroundings. Other color patterns in mosquitoes, such as the contrasting white and black of Aedes albopictus and Ae. aegypti may serve to confuse predators or hosts that try to swat blood-feeding females. Brightly colored scale patterns may be important for sexual selection, as is the case in birds. Mosquitoes in the genus Sabethes have brightly colored metallic scales on the body along with elaborate elongated scales on the tibia of their middle legs that may be important for mating and sexual selection. Finally, environmental factors and seasonal variation may be important in determining mosquito color patterns. For example, Culex nigripalpus specimens collected during the winter are darker than those collected in the summer.
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THE WEEK IN REVIEW:
ARBOVIRAL TRANSMISSION IN FLORIDA
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Low-level background transmission of EEEV, SLEV, and WNV continued in Florida during Week 44 of the 2021 arboviral transmission season, including:
- Two EEEV antibody-positive sentinel chickens.
- Two SLEV antibody-positive sentinel chickens.
- Five WNV antibody-positive sentinel chickens and one WNV-positive equine.
West Nile continues to be the only mosquito-borne virus that currently threatens humans and equines in Florida.
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WHAT ARE WE CURRENTLY SEEING? |
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Eastern Equine Encephalitis (EEEV) Activity
Two (2) EEEV antibody-positive sentinel chickens were reported in Duval and Walton Counties during Week 44, bringing the total number of EEEV antibody-positive sentinel chickens reported in Florida during the 2021 arboviral transmission season to 180. This is well above the 11-year (2010-2020) annual Florida EEEV seroconversion rate of 101 per year.
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Find a review of 2020 EEEV activity in the archived Vol 1, Issue 1 report.
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West Nile Virus (WNV) Activity
Five (5) new WNV antibody-positive sentinel chickens were reported during Week 44 in Indian River, Nassau, St. Johns, St. Lucie, and Walton Counties. This brings the total number of WNV-positive sentinel chickens reported in Florida during 2021 to 128, which is well below the 11-year (2010-2020) annual seroconversion rate of 408 per year. There was also a WNV-positive equine reported in Glades County. This horse was likely infected with WNV in early October. There is still active WNV transmission in Florida and the area of greatest concern for human transmission remains Central and North Florida and all of the Florida Panhandle.
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Find a review of 2020 WNV activity in the archived Vol 1, Issue 1 report. |
Dengue (DENV) Activity
There was no change in the number of travel-related dengue cases (n = 11) reported in Florida during Week 44.
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Find a review of 2020 DENV activity in the archived Vol 1, Issue 1 report.
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St. Louis Encephalitis Virus (SLEV) Activity
Two (2) new SLEV antibody-positive sentinel chickens were reported in Citrus and Palm Beach Counties during Week 44, bringing the total number of SLEV antibody-positive sentinel chickens reported in Florida during 2021 to 14.
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Find a review of 2020 SLEV activity in the archived Vol 1, Issue 1 report.
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OPERATIONAL STRATEGIES TO CONSIDER |
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Vector and arbovirus surveillance remains one of the most important tools that vector control agencies currently have at their disposal. Arboviral transmission indices (sentinel chickens, positive equines, positive exotics (i.e., emus), positive humans, and positive mosquito pools) provide indicators of local virus transmission, although sometimes not in a timely manner. Monitoring mosquito populations and their age structure provides added information about potential transmission risk. Additional vector control efforts in and around sites where virus transmission is known or suspected of recently occurring provides another potential mechanism to mitigate viral transmission.
The Florida regions with the highest current concern for arboviral transmission are those where indicators of WNV transmission (sentinel chickens and WNV-positive equines) continue to be reported. These include counties from Central Florida, North Florida, and the Florida Panhandle, especially the counties surrounding Walton County.
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Jonathan Day, Professor Emeritus of Medical Entomology from the University of Florida, is a national expert on mosquitoes and other blood-feeding arthropods that transmit diseases to humans, domestic animals, and wildlife. In collaboration with other researchers, Dr. Day has developed an effective system for monitoring and predicting epidemics of mosquito-borne diseases.
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Acknowledgments: This analysis would not be possible without the tireless efforts of multiple agencies across Florida. At least 27 Florida agencies collect serum samples from sentinel chickens each week and mail them to the Florida Department of Health Tampa Branch Laboratory for analysis and reporting. Data are summarized by researchers at the Florida Department of Health in Tallahassee and reported weekly as the Florida Arbovirus Surveillance report.
Contributors to this summary and full report include: Andrea Morrison, PhD, MSPH, Rebecca Zimler, PhD, MPH, and Danielle Stanek, DVM, Florida Department of Health, Bureau of Epidemiology; Lea Heberlein-Larson, DrPH; Alexis LaCrue, PhD, MS; Maribel Castaneda, and Valerie Mock, BS, Florida Department of Health Bureau of Public Health Laboratories, and Carina Blackmore, DVM, PhD, FDOH Division of Disease Control and Health Protection. And, Dr. Rachel Lacey, Florida Department of Agriculture and Consumer Services, Animal Disease Diagnostic Laboratory in Kissimmee, FL.
Daily updates of the Keetch-Byram Drought Index (KBDI) are produced by the Florida Department of Agriculture and Consumer Services, Forest Service and are posted at: fireweather.fdacs.gov/wx/kbdi_4km.html.
All of the graphics used in issues of this Newsletter are designed and developed by Gregory Ross.
* The reader question this week was answered with the assistance of Dr. Lawrence Reeves at the Florida Medical Entomology Laboratory in Vero Beach.
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Clarke has been helping make communities more livable, safe and comfortable since 1946.
Learn more about our work in protecting public health on clarke.com.
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