November 9, 2022 | Volume 2 | Issue 22 | As of Week 44 |
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Welcome to the Florida Disease Activity Update from the desk of Dr. Jonathan Day. |
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It continues to be 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 public health from vector-borne diseases.
An archive of all past newsletter issues remains available on the Clarke website.
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CONFESSIONS OF A MOSQUITO PRODUCER
Tale 1: My name is Jon, and I am a mosquito producer. This week, I'll be sharing some of my experiences within the mosquito surveillance and control industry, starting with a mini case study from the field regarding reducing mosquitoes and the threat of vector disease from your yard.
Source: A 2.5-gallon plastic pail used for sprouting plants (Figure 1).
Production: Culex nigripalpus and Cx. quinquefasciatus (about 4:1 quinquefasciatus:nigripalpus).
Production Rate: About 50 adults per week.
The Larger Problem: Producing Culex mosquitoes is by itself a problem. However, there is a larger underlying issue. Gravid Culex mosquitoes are attracted to my yard by potential oviposition sites. If the gravid females are old and on their second or third gonotrophic cycle, they may be infected with the West Nile virus. Once they oviposit, they will immediately search for a new blood meal, and if I am in the line of fire, I may be infected with WNV.
Problem Solution: Dump the water and throw away the bucket (Figure 2).
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Figure 1. A 2.5 gallon bucket produces Culex mosquitoes at a rate of about 50 per week. |
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Figure 2. Solution to the mosquito-producing problem: dump the water and throw away the bucket. |
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THE CURRENT OUTLOOK FOR ARBOVIRAL TRANSMISSION IN FLORIDA DURING 2022
We continue to receive reports of arboviral transmission and travel-related dengue and malaria cases in Florida. Thanksgiving typically marks the end of the arboviral transmission season in Florida, but 2022 seems to be a year of extended transmission.
One new WNV-positive equine and one new WN human case (both in St. Johns County) were reported last week. The human was infected in late September and the horse in mid-October. Twenty-five new WNV antibody-positive sentinel chickens were reported in Florida last week bringing the total number of positive sentinels to 334 in 25 Florida Counties (Figure 3).
Two new EEEV antibody-positive sentinel chickens were reported in Hernando and Pasco Counties last week bringing the total number of positive sentinels reported in 2022 to 64.
Ten new SLEV antibody-positive sentinel chickens were reported last week, bringing the 2022 total to 18 positive sentinels in 11 Florida Counties.
Two new travel-related malaria cases were reported last week in Flagler and Palm Beach Counties.
Two new locally-acquired dengue cases were reported last week in Miami-Dade County, bringing the total number of locally-acquired dengue cases in Florida to 38.
Twenty-five new travel-related dengue cases were reported in Florida last week, bringing the total number of travel-related dengue cases reported during 2022 to 664 in 28 Counties (Figure 4).
The risk of EEEV, HJV, and SLEV transmission in Florida is currently low, but it is important to remember that arboviral transmission risk in Florida is never zero. The risk of WNV transmission in some parts of Florida, especially the Panhandle is currently moderate to high. The risk of dengue transmission throughout South Florida remains high.
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Figure 3. Sentinel chickens testing positive for antibody to WNV. Counties colored red indicate positive chickens reported during the 2022 arboviral transmission season. Counties colored blue indicate sentinel chicken seroconversions during the current reporting week (Week 44). Numbers indicate the total number of positive sentinel chickens reported in each county during 2022. |
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Figure 4. Travel-related dengue cases in Florida during 2022. Counties colored blue indicate travel-related dengue cases reported during 2022. Counties colored red indicate travel-related dengue cases reported during last week (Week 44). Numbers indicate the total number of travel-related dengue cases reported in each county during 2022. |
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Year to Date Summary of Mosquito-Borne Disease Transmission
As of Week 44, 2022, the following mosquito-borne disease transmission events and pathogen introductions have been reported in Florida:
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Table 1. Summary of mosquito-borne disease transmission and travel-related cases in Florida as of November 5, 2022. |
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As we approach the end of the 2022 arboviral transmission season in Florida, many travel-related dengue cases are still entering the state (Figure 4). The origin of 92% of these has been Cuba and 63% of the cases have been DENV 3. All four dengue serotypes are circulating in Florida, which increases the risk of severe dengue infections in the state. Hopefully, the number of travel-related and locally-acquired dengue cases will start to decline in the coming weeks. |
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OPERATIONAL STRATEGIES TO CONSIDER |
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Vector and arboviral surveillance remain some of the most important tools that vector control agencies currently have at their disposal. Arboviral transmission indices (sentinel chickens, positive equines, positive exotics such as 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 gives additional information about potential transmission risks. Supplemental vector control efforts in and around sites where virus transmission is known or suspected of recently occurring provide another mechanism to mitigate viral transmission.
Specific operational strategies will be discussed during the 2022 arboviral transmission season depending on where and when vector-borne disease transmission becomes obvious in Florida.
There is currently a low risk of EEEV transmission in Florida.
There is currently an extremely low risk of SLEV transmission in Florida.
The current risk of WNV transmission remains high in some regions of Florida and low in others (Figure 3). We are rapidly approaching the time of year when the risk of a widespread outbreak of human WN is low.
The only reasonable way to reduce the number of locally-acquired dengue cases in Florida is to reduce Aedes aegypti and Ae. albopictus populations. Every home in South Florida has an associated population of these two efficient dengue vectors. A single travel-related dengue case coming into a neighborhood dramatically increases the likelihood of infecting local mosquitoes and starting a round of local dengue transmission. Source reduction and public education are two techniques that will begin to reduce the number of dengue infections originating in Florida.
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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, compilation 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.
All of the graphics used in issues of this Newsletter are designed and developed by Gregory Ross. |
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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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