Zika is officially here, and cities are stepping up to spread information and reduce mosquito populations, often building strong partnerships to do so. And while Zika is making all the headlines at the moment, other mosquito-related diseases, like West Nile and dengue fever, have long been on cities’ radars, with many adjusting to combat aedes aegypti mosquitos’ and the aedus albopictus mosquito, which is another possible vector for Zika.
What to know
Dr. Janet McAllister, PhD, with the U.S. Centers for Disease Control and Prevention and a leading entomologist, recently participated in a National Recreation and Park Association webinar called “Zika and Parks: What You Need to Know” where she noted, “One in five infected show any symptoms (of Zika). It is not a severe disease.”
The disease — in addition to being spread by mosquito bites — can be sexually transmitted by both men and women and spread through blood transfusions. Symptoms, if they do show, include fever, rash, joint pain, conjunctivitis, or red eyes, and less commonly headaches. The danger comes from Zika’s ability to pass from a pregnant women to her fetus during pregnancy, resulting in microcephaly and other severe fetal brain defects.
“Future pregnancies are not going to be affected,” McAllister said, adding the CDC believes those who contract Zika receive lifetime immunity afterwards.
As for the vectors, the aedes aegypti mosquito is particularly of concern since it prefers to feed on humans. The aedus albopictus mosquito could also be a vector, McAllister said; however, since it feeds on animals, too, it is less likely to complete the cycle necessary to spread Zika.
When it comes to monitoring for ae. aegypti and ae. albopictus, forget about using the same procedures from the West Nile surveillance program. “The traps you use for that will not be effective,” McAllister said.
Monitoring programs will need BGSentinel mosquito traps and Ovitrap cups rather than the gravid and light traps used for culex pipiens mosquitos and culex quinquefasciatus, which can be vectors for West Nile disease. McAllister, however, noted ae. aegypti can be identified by the naked eye due to its striped legs and thorax, which has a white stripe that runs down it.
Site reduction and education
During mosquito season, the CDC recommends implementing all mosquito control strategies, including immature mosquito monitoring, adult mosquito monitoring, removal of water sources where larvae can grow, use of larvicides in water sources that cannot be dumped and insecticide resistance testing.
When it comes to control, McAllister stressed: “Sanitation, sanitation, sanitation.” Ae. aegypti mosquitos prefer manmade containers for their breeding grounds, so it is important to clear small containers, utensils, recreation objects, pots and similar items of standing water; these spaces are preferred because they are without natural predators. Advance stormwater features like bioswales should not be an issue since often such features are larger than these mosquitos prefer, have moving water or have natural predators like dragonfly larvae in them.
“During peak summer heat, it takes as little as five days for larval development,” she said, adding the eggs, which attach themselves to the sides of containers, can be viable for up to a month without water, hatching when water again returns to the container. This makes it important to scrub the eggs off containers after dumping.
It is vital to address junk and litter that might contain water not just in municipal maintenance yards or parks, but in residential properties and local businesses.
“Actively engage communities to perform source reduction,” McAllister said.
Weston, Fla., has been following that advice to the T, forming numerous partnerships to distribute information. Denise Barrett-Miller, director of communications for Weston, said, “Partnerships and having good relationships with community groups and organizations has really been essential for us. Numerous groups have taken the information that we have provided from the Florida Department of Health and then forwarded it on through their members, and those people in turn send information to people they know and so on and so forth.”
This network of distribution includes cable TV and radio, plus the city’s website, Twitter, Youtube and newsletter. “We have also sent the information to our schools, (homeowners associations), clergy, sports leagues, YMCA, community groups, CERT program, COP program, arts council and others to educate them and ask that they pass information to those within their organizations,” she added.
Materials from the health department and fliers — including some in Spanish — have been posted at Weston’s local Publix stores and taken to other locations with a lot of foot traffic like the library, Bonaventure Town Center, the YMCA and others.
“Our code enforcement officers also have door hangers and postcards to distribute and look for any possible large infestation such as an unkept pool,” Barrett-Miller said.
The spread of information — beyond encouraging site reduction — also gives the public information to avoid mosquito bites. “Preventing mosquito bites is also a huge, huge, huge part of our messaging,” McAllister said of the CDC. “Because it’s not just about what the government can do to help people, but what people can do to help protect themselves as well.”
To reduce bites in a parks and recreation setting, for an example, McAllister encouraged municipalities to use air conditioning in recreation buildings, or at least make sure good screens are in place and doors are not propped open — the same advice given to residential homes and businesses.
When it comes to municipal workers, particularly those who work outdoors, the Occupational Safety and Health Administration and the National Institute for Occupational Safety and Health have issued “Interim Guidance for Protecting Workers from Occupational Exposure to Zika Virus.” The guide provides suggestions to employers for reducing risk of bites and infection to outdoor workers and others who might come into contact with mosquitoes carrying the Zika virus.
Some of these guidances include providing workers with insect repellents and encouraging their use; providing workers, or encouraging them to wear, clothing that covers hands, arms, legs and other exposed skin; training workers about the importance of eliminating areas where mosquitos can breed at a worksite; potentially reassigning, if requested by a worker, anyone who is or may become pregnant, or who is male and has a sexual partner who is or may become pregnant, to indoor tasks to reduce their risk of mosquito bites; among others.
Targeted residential spraying is another option being used to combat Zika and other mosquito-related diseases. “Target areas near the foundation, under steps or behind junk on the front porch where adult mosquitos are going to be found,” McAllister advised for Aedes aegypti. “Don’t spray where pollinators are going to be.”
As an example, she said targeted areas to spray would be around visitors centers or other buildings where people gather rather than broadly spraying around a park or city property. Aedes aegypti mosquitoes are going to be where people are gathering.
Don Decker, director of parks and recreation for Weston, stated the city coordinates with Broward County to spray public parks since the county is responsible for mosquito spraying measures in the area; however, a more localized system was also installed.
“A number of years ago, we were introduced to a more localized, natural deterrent system offered by a company called Platinum Mosquito Protection. They installed a delivery system on the exteriors of our restroom and concession buildings,” Decker said, noting that it is made up of tanks, tubing and nozzles. “The system emits a mist of Pyrethrum, which is a natural insecticide derived from the chrysanthemum flower. This insecticide has the added benefit of repelling flies, wasps and other insects. So, while we cannot provide this additional measure throughout a 100-acre park, it does help in areas where people congregate.”
Should Zika be identified in an area, McAllister and the CDC recommend mobilizing a comprehensive mosquito control strategy without delay to prevent local transmission. This includes implementing a targeted vector control for adult and immature mosquitos in and within 150 yards around an infected individual’s location in addition to intensifying larval control and source reduction efforts. Cities and towns should also consider adding community-based mosquito control, which includes residual treatment and space treatments.
She added during her presentation the CDC has many resources available to cities through its website. “Borrow widely from what we’ve already developed and maybe tailor that to your specific situation as needed.”
Here are links to the CDC’s Zika homepage and the “Interim Guidance for Protecting Workers from Occupational Exposure to Zika Virus” PDF:
Below is a link to the “Zika and Parks: What You Need to Know” webinar: