Editor’s Comments: On the Front Lines

Feb. 29, 2016

Just when we think we’ve got one problem solved, it can come back with a vengeance. In the US, most of us rarely worry about vector-borne diseases like malaria. But now the Zika virus—also spread by mosquitoes—is causing alarm throughout the Western Hemisphere; the World Health Organization a few weeks ago declared an international public health emergency. This is one problem, however, that stormwater professionals can contribute to solving.

The Zika virus is transmitted by the Aedes aegypti mosquito—the same one that transmits yellow fever, dengue, and chikungunya. Past Stormwater articles have detailed the connection between stormwater structures and vector-borne disease; generally speaking, the better maintained the infrastructure, the less likely it is to serve as a breeding ground. Two articles from our March/April 2002 issue ( http://bit.ly/245ZiCp, and http://bit.ly/1PAEUl8 ) still serve as excellent primers for understanding the lifecycle of the mosquito and how to control it.

The main reason we haven’t had to worry is because of the ongoing successful efforts of our vector-control agencies. But Brazil, too, had a successful mosquito-control program for several decades, and it might serve as a cautionary tale. The disease of most concern there was malaria; in the 1940s the country had about 6 million cases a year. Aggressive application of pesticides reduced the number of mosquitoes, and the number of malaria cases dropped to about 40,000 a year by the early 1960s. In the ’70s and ’80s mosquitos made a resurgence, some of them spreading from nearby countries, and incidence of the disease began to climb once again.

The drought in Brazil in recent years might have made the mosquito problem worse, because many residents have been storing up supplies of water in whatever containers are available. Now, in a desperate effort, the Brazilian Health Ministry is deploying 220,000 troops throughout the country to treat or eliminate areas of standing—containers as large as a retention pond or an open sewer, as small as an abandoned tire or a flowerpot. In Rio de Janeiro, the site of the 2016 Olympic Games, officials are fumigating with insecticides daily.

Infection with the Zika virus has not been considered a serious problem in the past. As the virus has spread throughout Brazil, though, rising incidence of two other medical conditions has accompanied it. One is a birth defect called microcephaly, in which children are born with an underdeveloped head and brain. Doctors believe that infection with the Zika virus early in pregnancy can lead to microcephaly, although the exact connection and how great the risk are still unknown. The other condition is Guillian-Barré syndrome, which causes muscle weakness or paralysis and can be fatal if it affects muscles that control breathing.

Zika apparently had not existed in the Americas before 2015, so no one has immunity; officials estimate it will be two years before the epidemic dies down. Doctors and health ministries in several South and Central American countries have advised women to delay pregnancy for up to two years. In the US, the Centers for Disease Control and Prevention has issued travel warnings, advising everyone to take precautions against mosquito bites and advising pregnant women especially to avoid traveling to more than 20 countries where the Zika virus is prevalent. Scientists are working to find a vaccine.

Another step—one not without controversy—that Brazil is taking is the release of genetically modified mosquitoes into the environment in hopes of reducing the mosquito population. A company called Oxitec is releasing genetically altered male mosquitos whose offspring die before they’re able to fly. The company is reporting a better-than-80% reduction in mosquito population in some areas where the modified mosquitoes have been released. This might turn out to be the best option, either in conjunction with or eventually in place of widespread use of insecticides.

For any number of reasons—geography and climate among them—the US is probably at less risk for an outbreak of Zika than countries to the south of us. But that doesn’t mean we should be complacent; the Aedes aegypti mosquito is found in many US states. Officials were surprised at how quickly West Nile virus spread across the US after it was first recorded on the East Coast in 1999. (West Nile, for the record, is transmitted by a different species of mosquito than Zika.)

One of our more recent articles, co-authored by one of the writers of the 2002 article, calls for stormwater agencies and vector-control agencies to work together. That’s good advice at any time, but especially so now.

About the Author

Janice Kaspersen

Janice Kaspersen is the former editor of Erosion Control and Stormwater magazines.