Zika “species of concern” in city

Standing water is a likely host for mosquito larvae. Photo by Bill Brown.


MAY 27 — Conditions are good for mosquitoes. After three weeks of mostly rainy days the sun is out and temperatures are rising, Warm weather and standing water are what mosquitoes need to breed.

Concern is high this year because mosquitoes can spread Zika virus – if they ingest the blood of a Zika-infected person. So far, this has not happened on the US mainland. The flu-like virus has broken out in the American territory of Puerto Rico and American Samoa, however, as well as several warm-climate countries in Central and South America and several islands in the Caribbean, Southeast Asia and Pacific regions. Click here to see affected regions and countries

Within the last year 52 American travelers have brought Zika home with them in their bloodstream. But, there have been no instances of local mosquitos picking up the virus from these individuals and spreading it.


Aedes aegypti drawing by E-A-Goeldi, 1905.

Takoma Park is home to a robust population of one of the mosquito species identified by the county as a “species of concern” responsible for spreading the Zika virus in South and Central America. The city was a center of an invasive Aedes aegypti mosquito infestation in 1995. Known as the “yellow fever mosquito” Aedes aegypti is a host for several tropical fevers including dengue fever and West-Nile Virus. Since those diseases are not currently present in Takoma Park, the local mosquito population does not currently carry any of these fevers or viruses.

Takoma Park has joined Montgomery County’s “Fight the Bite” prevention program. The program urges residents to eliminate potential mosquito breeding places and to avoid bites. At this time there are no plans for insecticide spraying.

The US Center for Disease Control guidelines call for early mosquito season control by breeding-ground elimination, use of larvicides and biological controls (i.e. larva-eating fish) in standing water, and surveillance. Insecticide spraying is recommended in the case of a Zika outbreak.

A statement from city emergency manager Ron Hardy urges residents to look for outdoor containers such as buckets, planters, toys, pools, birdbaths, trash containers, wheelbarrows and pet dishes. Remove them, place them so they don’t collect water, or refresh the water regularly, Hardy says. Attend also to tires, tarps, plastic wrappers and rain gutters.

To keep mosquitoes out of homes, he says, use window and door screens and use air conditioning when available, he says, and use mosquito netting over baby strollers and cribs and dress children in clothing that covers arms and legs.

Hardy says to use an Environmental Protection Agency-registered insect repellent with one of the following active ingredients: DEET, picaridin, IR3535, OLE, or PMD. All EPA-registered insect repellents are evaluated to make sure they are safe and effective. Hardy cautions against using insect repellent on babies under 2 months of age, or using products containing oil of lemon eucalyptus or para-menthane-diol on children younger than 3 years old.


Hardy recommends frequent birdbath water refreshing. Photo by Bill Brown.

The city emergency planner says that if child has been to an affected area, parents are urged to take him or her to a health care provider if he or she has symptoms: fever, rash, joint pain, or red eyes. Note that a baby less than two months old with a fever of 100.4° F or more always requires medical evaluation.

“Look for standing water where mosquitos may breed (gutters, flower pots, toys and furniture outside, etc) and dump out the water” urges Takoma Park city manager Suzanne Ludlow in her blog.

Hardy says Takoma Park requested the state Department of Agriculture to be added to it’s larval testing program. City staff will be making site visits to all public bio-retention areas to ensure they are functioning as designed and not holding water for more than 24 hours. Hardy says the city will make a list of known inlets or catch basins with standing water, and will monitor them to see if larvicide treatment is necessary.

The virus itself is not usually life-threatening nor does it require hospitalization. However the CDC says there is a link to a brain defect called microcephaly in babies of mothers infected with Zika virus while pregnant. Their website says “there is now enough evidence to conclude that Zika virus infection during pregnancy is a cause of microcephaly and other severe fetal brain defects and has been linked to problems in infants, including eye defects, hearing loss, and impaired growth.”

There have been three cases of travel-borne Zika in the District of Columbia, and one in Virginia. There have also been two in Pennsylvania and one in Delaware.l For information on any confirmed cases of Zika virus infection in Maryland, visit the Maryland Department of Health and Mental Hygiene website.

Though chances are slim, there is a potential for the virus to spread, and it could happen very quickly, said Daniel Schamberger, acting director of the state Mosquito Control Administration, as the Voice reported last February.


Aedes aegypti, CDC-Gathany.

The Voice article also quoted Center for Disease Control spokesperson Benjamin Haynes saying that for an outbreak in the continental US to occur, “People infected with a virus need to enter the United States. An Aedes mosquito must bite the infected person during the relatively short time that the virus can be found in the person’s blood. The infected mosquito must live long enough for the virus to multiply and for the mosquito to bite another person.”

Haynes said last February that the CDC cannot predict how much the Zika virus could spread in the US, or if it could take hold in Takoma Park. “Many areas have the type of mosquitoes that can become infected with and transmit the virus, however recent chikungunya and dengue outbreaks in the US suggest that Zika outbreaks in the continental United States may be relatively small and focal.”

According to the Center for Disease Control director Tom Frieden, “We could see isolated cases and small clusters of infections in other parts of the country where the mosquito is present. But from the information we know now, widespread transmission in the contiguous United States appears to be unlikely.”

Frieden’s online statement says, “For a disease such as Zika to spread widely, two things are necessary. The first is the specific mosquito species that spreads the virus. The second is the conditions in communities; places that are crowded and don’t have air conditioning enable viruses such as Zika to spread.”

Takoma Park has ample air conditioning, but it also has ample breeding conditions, as the persistent Aedes aegypti population attests.

When last February the Voice contacted Daniel Schamberger, acting director of the state Agricultural Department’s Mosquito Control Administration, he said that Takoma Park will be one of the areas included in mosquito trapping and surveillance.

Spraying is an option, he said, but there the emphasis will be on clearing up Aedes aegypti breeding grounds: containers and anywhere water can collect and remain standing.

The disease is spread by “multiple blood meals,” said Schamberger. Aedes aegeypti females feast several times. If they bite a Zita-infected human and then another human, they can pass on the virus to the next human, or humans, they bite.

According to CDC information the Zika virus is spread primarily through the bite of an infected mosquito, though it can also be spread via sexual contact.. Death from Zika is extremely rare. Only one in five people infected with Zika virus become ill. Common Zika symptoms are fever, rash, joint pain, or conjunctivitis (red eyes). Other common symptoms include muscle pain and headache.

The illness, according to the CDC, is usually mild with symptoms lasting for several days to a week. It rarely requires a hospital visit. Zika virus persists in the blood of an infected person for about a week but it can be found longer in some people. There is no vaccine or cure for Zika virus.



About the Author

Bill Brown
Bill Brown moved to Takoma Park in 1982. He has been involved in journalism in one way or another since he co-published an underground high-school newspaper in the late 1960s.