Association of State Wetland Managers - Protecting the Nation's Wetlands.

The Compleat Wetlander: Addressing the Zika Virus Based on Sound Science

By Jeanne Christie

The Zika Virus has been receiving a great deal of attention.  It should.  The documented cases of birth defects and neurological disorders potentially linked to the virus continues to grow.  As reported in a recent Washington Post article: ‘The more we learn, the worse things seem to get’.  The potential for a mosquito bite to lead to significant birth defects is a very serious public health issue, and many people around the world are hard at work trying to identify solutions.  These range from 1) further research to better document whether the Zika virus spread by mosquitos is in fact the source of the health issues, to 2) developing a vaccine, to 3) cleaning up areas that Aedes species of mosquito breed to 4) spraying pesticides to 5) introducing a genetically modified mosquito into the wild to reduce the mosquito population.

The Center for Disease Control and Prevention has an excellent web page with information about the Zika virus that is updated regularly.  This includes

  • A map of where the Zika virus disease (both travel associated and locally acquired cases are reported.  Note: As of March 9, 2016 there were 193 travel associated cases and 0 locally acquired vector born cases in the States. There are 173 locally acquired cases in U.S. territories –  Puerto Rico 159, American Samoa 13, US Virgin Islands 1.)  It is anticipated that the Zika virus may eventually spread into the states of Hawaii, Texas and Florida and possibly further into the southeastern US over time.
  • A recommended response for states.
  • How the virus is transmitted.
  • Surveillance and Control of Aedes aegypti and Aedes albopictus (mosquitos that transmit the virus) in the United States .


The Zika virus is not new. It was first identified in Uganda in the Zika forest in 1947 in monkeys and the first human case was reported in 1952.  It is generally spread to humans by Aedes species of mosquitoes (A. aegypti and A. albopictus). These mosquitoes typically lay eggs in and near standing water in things like buckets, bowls, animal dishes, flower pots and vases. They are found in tropical areas and in the southern U.S.

The most common symptoms of Zika are fever, rash, joint pain, and conjunctivitis (red eyes). People usually don’t get sick enough to go to the hospital, and they very rarely die of Zika. For this reason, many people might not realize they have been infected. Once a person has been infected, he or she is likely to be protected from future infections.  The virus was not linked to microcephaly until late in 2015.


The possibility that the Zika virus causes microcephaly – unusually small heads and often damaged brains – emerged only in October, when doctors in northern Brazil noticed a surge in babies with the condition.   There are suspicions that an outbreak in French Polynesia two years ago did follow a similar pattern. However, it has not been proven that Zika does cause microcephaly.  Circumstantial evidence suggests it does. But ultimately investigators may find the main cause is something else. One other hypothesis has been put forward that the problem is caused by a larvicide  – one that is added to drinking water tanks – is the cause of the birth defects.   (Please note that this larvicide is not sold by Monsanto despite some headlines).

So why now and why Brazil?  For the first time the Zika virus is occurring in a place where there is a large human population and a large population of the mosquito species that carry the disease.  The large mosquito population is the result of a couple factors, deforestation which leads to the creation of greatly improved habitat for Aedes species of mosquitoes and a reduction in efforts to control mosquito populations in recent decades in Brazil.

Reducing mosquito populations that spread the disease will not be easy.  Insects can become resistant to pesticides and Aedes species of mosquitoes have demonstrated increased resistance to some of the pesticides most commonly used to control them.  Plus there are a number of reports documenting the health risks that occur from exposure to pesticides for both humans and wildlife.  Another option currently being explored is the introduction of a genetically modified mosquito that (when introduced into the wild) would cause larvae to die.

In Brazil there is an education campaign underway to encourage people to eliminate from their yards containers that hold the still, shallow water that Aedes mosquitos breed in.  A strategy that is not being pursued would be to make large scale land management changes to establish and restore habit that is unfriendly to the Aedes mosquitoes and friendly to their predators.  A number of folks working in wetlands restoration are learning that a healthy wetland with lots of mosquito predators has few mosquitoes.  However, this broader approach is far removed from the current areas of public discussion on controlling the spread of the Zika virus.

In the coming months it will be important to carefully evaluate options.  Sound science is needed to ensure the cause and effect of the spread of the problem has been identified and that the benefits and consequences of different approaches are fully evaluated and vetted with the public. Accurate, timely information will also be essential.  The links above to the Center for Disease Control is a good place to start.

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