All spring and now with the Summer Olympics in Brazil soon to begin, the threat of people or mosquitoes infected with Zika virus coming to Athens or anywhere in the South is leading to considerable speculation and concern about how to prevent the spread of Zika fever, with its fearsome consequences, to pregnant women and other folks.
The main culprit involved in the passing of Zika virus among the people of Central and South America is the yellow fever mosquito, Aedes aegypti. This mosquito once was a native of Athens and the South, but it lost its residency to a close relative, the Asian tiger mosquito, Aedes albopictus. Daytime outside in Athens is spent slapping away tiger mosquitoes. So how is it that the Centers for Disease Control and Prevention in Atlanta and other scientists came up with widely published maps showing that the yellow fever mosquito could return this season to its former territory and with it, Zika virus?
Mosquitoes were the harpies of summer in the Southern states during the first hundred or so years of their union, secession and reunion. During European colonization, immigrant mosquitoes came in ships laden with goods and terrified people from Africa who were traded around the Americas. But the lethal viruses, protozoans and worms nurtured by mosquitoes were carried in the blood of passengers—the crew and captives that survived to be sold as slaves. The mosquito immigrants disembarked, found suitable habitats along the coast and thrived.
The most successful immigrant was the yellow fever mosquito. As the coastal communities grew, so did the coming and going of people and goods, and before long, the females of this mosquito began carrying the yellow fever virus in the blood taken from infected people and, within weeks, had passed it to more people, thus instigating deadly epidemics in coastal cities from Philadelphia to New Orleans and even up the Mississippi River valley from the late 1700s to the early 1900s. The protozoans that caused malaria were spread similarly by the native Anopheles mosquito species, and this wasting disease persisted throughout the South until the 1940s.
In time, the yellow fever mosquito moved inland on its own and with human assistance to Athens and on to a wide but not-so-deep swath of the Southern states. Here and elsewhere, it became a pesky nuisance during the afternoons and early evenings of summer but disappeared for the rest of the year. There were the occasional fevers and death of people around here caused by encephalitis viruses transmitted by Culex mosquitoes that preferred birds and late evenings, but no yellow fever. Instead, the yellow fever mosquito made do with another infective associate, the heartworm, that it found or brought here and passed on to dogs, which suffered a chronic lassitude.
The acceptance of this situation changed as the preparation and training of soldiers for World War II swept the South, bringing people and goods again from all over the world. The connection between mosquitoes, viruses and fevers that often resulted in chronic disability or death was not known until the turn of the 20th Century. So with the tumult of war, entomologists and physicians began to worry that dengue virus could be brought by infected people from the Americas or Asia as before and spread by the resident yellow fever mosquito.
Hygienic methods devised during the construction of the Panama Canal to prevent the spread of yellow fever were implemented that reduced mosquito numbers around military bases and cities, and later extensive use of the insecticide DDT provided a deceptively complete control of mosquitoes. So successful were these efforts that in 1963, federal and state agencies made plans to eradicate the yellow fever mosquito and consequently its threat of virus transmission from the United States. This program never received sufficient funding or interest, so the yellow fever mosquito continued its seasonal nuisance.
In the 1980s, a new immigrant, the Asian tiger mosquito, Aedes albopictus, was transported in tires from southeast Asia to the Texas coast, where it settled. Within less than a decade, it spread throughout the South and completely displaced the yellow fever mosquito here, where it is a remarkably numerous and persistent pest during the day in older neighborhoods. Laboratory studies showed this species is capable of transmitting the same viruses and heartworm as the yellow fever mosquito but, to date, it is not the primary vector of Zika or dengue viruses in the Americas. Only isolated populations of the yellow fever mosquito in Florida and Texas were involved in localized outbreaks of dengue fever in the past few years, and no cases of mosquito-acquired Zika fever have occurred in the United States.
The likelihood of our former mosquito denizen retaking Athens is remote, as is the acquisition and transmission of Zika virus by the tiger mosquito here. Nevertheless, it remains a possibility that people traveling to and from areas where Zika fever is present could be the source of the virus in local cases. And there is a unique aspect of Zika virus in that it can also be transmitted by sexual activity, as first reported by an entomologist who had a bout of Zika fever while in South America and later passed the virus to his wife, who also got the same symptoms after his return. Many such sexually-transmitted cases of Zika fever are now known, so Athenians should use safe-sex methods themselves while at the Olympics in Brazil or any other areas where Zika fever is endemic and for several weeks after returning.
Mark Brown is a professor of entomology in the University of Georgia’s College of Agricultural and Environmental Sciences and is affiliated with the Center for Tropical and Emerging Global Diseases.
Tips for Managing Mosquitos
Don’t let mosquitoes keep you indoors this summer. Instead, employ these eight tips to protect yourself and manage these pests in your yard.
1. Do a bit of yard and garden clean-up. Remove weeds, manage neglected gardens, and keep the lawn properly mowed to reduce resting spaces for adult mosquitoes.
2. Eliminate standing water where mosquitoes breed. Drain water that collects in buckets, kids toys, tarps, pool covers, clogged gutters and downspouts. Clear the gutters and downspouts so water can drain freely. Store items that tend to collect water in a shed or garage.
3. Evaluate drainage patterns in your landscape. Improve drainage by amending the soil with organic matter. Install French drains, drain tiles and other drainage systems if needed. Or turn it into a water feature.
4. Manage water in birdbaths, fountains, ponds and rain barrels. Change water weekly in birdbaths and wading pools. Add a pump to keep water moving and prevent breeding.
5. Add a fan to your outdoor décor. The gentle breeze keeps these weak flying insects away. Consider taking one to the garden when weeding.
6. Provide short-term relief when entertaining outdoors with the help of citronella oil or scented candles. Scatter lots of these throughout the area and within a few feet of your guests.
7. Cover as much of your skin as possible with loose fitting, light colored clothing. Mosquitoes are less attracted to the lighter colors and can’t readily reach your skin through loose clothing.
8. Further protect yourself from disease-carrying mosquitoes by using a personal repellent. For those looking to avoid DEET, the CDC has also approved products with the active ingredient picaridin, IR3535, and the synthetic oil of lemon and eucalyptus. Avoid products that contain both sunscreen and insect repellents, as you need to apply the sunscreen more often than the repellent.
Gardening expert Melinda Myers is the author of 20 books, hosts the syndicated “Melinda’s Garden Moment” TV and radio segments and is a columnist and contributing editor at Birds & Blooms magazine.
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