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West Nile Virus Notes


2014 budget is $30,097,170 than last year.  Failing to solve the problem means more money and resources (personnel) involved the next time there’s a spike in temperatures and drop in precipitation.

Current drought map

Drought monitor archive

CDC West Nile Virus stats (2002-2012) PDF archives

Mother Jones (2012) interactive maps

The middle class suburban areas appeared to support the appropriate combination of vegetation, open space, and potential vector habitat favoring WNV transmission. Wealthier neighborhoods had more vegetation, more diverse land use, and less habitat fragmentation likely resulting in higher biological diversity potentially protective against the WNV human transmission, e.g. the avian host “dilution effect” [45].

CDC WNV stats 2002-2012 by state


 TIME 2/28/2014

The biggest indicator of whether West Nile virus will occur is the maximum temperature of the warmest month of the year, which is why the virus has caused the most damage in hot southern states like Texas.

The UCLA model indicates that higher temperatures and lower precipitation will generally lead to more cases of West Nile



2012 Scientific American

A nearly frost-free winter followed by the summer’s drought has worsened the epidemic


West Nile Virus outbreak map

west nile virus


West Nile Virus: Simple things you can do

00stop-west-nileNone of us really want to see the City of Dallas (or cities in Dallas County) begin aerial spraying for mosquitoes this year. In the report given to the City Council by the CDC, emphasis was placed on preventing mosquitoes before they start. It’s only February, and I’ve already seen mosquito larvae in some water samples, so I am starting a one-woman campaign to teach others what they can do to stop mosquitoes before they become a problem.

The key, of course, is preventing them from breeding and killing them off at the egg or larva stage (while they’re in the water) rather than waiting till they’re on the wing. It takes only 8 days for a mosquito to go from the egg stage to the adult stage, but most mosquito predators (except for bacteria) take a lot longer to grow to a size where they can eat mosquitoes. Furthermore, Mosquitoes are hardy little pests, and as most of you know, they really don’t fall over dead from one spritz of bug spray.

So here’s some simple things that you and your neighbors and friends can do to stop West Nile Virus outbreaks by stopping mosquitoes.

• Probably the MOST important thing you can do is to make a habit of picking up trash and putting it in a trash can.  This may sound simplistic, but the trash on our streets clogs drains and clogs waterways, making pools of water that last long enough to breed mosquitoes.  So please don’t just walk by that plastic bag — snag it and keep it from becoming a mosquito breeding source.
• If you have a patio, buy and maintain a mosquito trap.
• Use fans rather than misting to keep mosquitoes away.  It’s popular to use misters because of the heat here, but that actually creates nice damp spots where mosquitoes can breed.
• Don’t kill mosquito predators like spiders and lizards.  Move them outside, where they can nosh on these nuisances.
• Protect dragonflies and damselflies — they’re one of the most effective predators of adult mosquitoes!
• If you’re out somewhere and you’re getting munched by mosquitoes, report it to the Code Enforcement Department of that city (they’re the ones who come investigate these problems.)
• If you see leaky faucets or standing pools of water, report them to the building’s landlord (or supervisor.  If they’re at your house, get them fixed before you end up in the center of your own cloud of mosquitoes!)
• Look for hidden water around your house and place of work (buckets, wheelbarrows, flowerpots, ponds, ditches, etc.)  If those can’t be dried up, then see about putting BTI tablets (available at garden stores — a bacteria that kills mosquitoes) in these watery spots.  Using fish is a better option (gambusia minnows) but some places like flowerpots don’t have enough water for a fish.
• Use insecticides wisely, spraying only the trouble spots.  Whole yard treatments can kill valuable mosquito predators and make a “safe zone” for mosquitoes.
• Patch holes in your trees — those can be hidden sources of water that mosquitoes can use for breeding.
• Plant native plants (ask your nursery to recommend some native plants).
• Consider planting (or potting) flowers that mosquitoes do not like, including citronella grass, catnip, marigolds, lemongrass.
•  Put up a birdhouse for chimney swifts and purple martins.  You can find lots of plans for these houses online (you can even buy pre-made ones online.)
• Put up a bat house.
• Keep lawns mowed and report lawns with tall grass.  Tall grass areas in a city are prime mosquito habitat.
• If you have enough property to be able to have a pond, make the area dragonfly and frog friendly — and stock the pond with fish.
• You can make a simple mosquito trap for your yard by setting out a bowl of water and dissolving BTI (Bacillus thuringiensis) granules in it (talk to your garden store and see how much is approprite.)  Mosquitoes land to lay eggs, but the eggs never develop.
• Consider giving your support (either through donations or as a volunteer or even just as a visitor) to wildlife centers which maintain areas for dragonflies, frogs, bats, and other urban mosquito predators.

And finally, spread the word.  Tell folks about these tips.  Add your own suggestions.


One person can’t solve this problem, but all of us doing just one thing can make a huge impact on the number of mosquitoes we see this year.




Community Science Initiatives logo

West Nile Virus: A small list of mosquito predators for the Dallas area

This list is not comprehensive and will be updated as I find new information.  Nothing listed is 100% effective (as in, “kills every single mosquito”) and everything on the list does eat things other than mosquitoes (which might be a problem if your bats are eating all your dragonflies.)  This list is simply a “starting point” to consider.


Predators of adult (flying) mosquitoes:

Note: predators of adult mosquitoes are general insectivores, which means they will also go after the things that eat mosquitoes.  They should not be viewed as a first layer of defense, but as a second (“backup”) layer of defense:

* bats
* chimney swifts
* swallows
* flycatchers (these are migratory and don’t live here all year around)
* Nighthawks and nightjars
* dragonflies
* damsel flies
* spiders
* toads
* frogs


Larva predators

Note: these are the most effective ones against mosquitoes

* gambusia (minnows)
* Predaceous diving beetles
* copeopods
* dragonfly nymphs
* damselfly nymphs
* bacillus thuringiensis (bacteria, available at home improvement stores.  Very eco-friendly but not long-lasting)
* tadpoles (many frog species)
* backswimmer (insect)
* tadpole shrimp


This report suggests that mosquitoes can “taste” when a site has gambusia minnows and will not deposit eggs there (indirectly controlling WHERE eggs are laid).


And for those who like hard science, a very readable study from Europe on “who eats whom in a pond.”


Something that I continue to look into is “what nectar sources do mosquitoes favor?”  The adults use nectar (blood is only used by females and only when they are ready to lay eggs) as a rule — surely there’s flower shapes that they can’t utilize well.  Reduce the food for adults, and you help reduce the population.



National Science Foundation: Emerging Vector-Borne Diseases Create New Public Health Challenge

Press Release 12-218
Emerging Vector-Borne Diseases Create New Public Health Challenge

Land-use change, globalization of trade and travel, and social upheaval drive emergence of diseases

Close-up photo of a tick.

Vector-borne diseases are transmitted by ticks, mosquitoes and fleas.
Credit and Larger Version

November 30, 2012

Human activities are advancing the spread of vector-borne, zoonotic diseases such as West Nile virus, Lyme disease and dengue fever, report scientists publishing a series of papers today in the journal The Lancet.

Vector-borne zoonotic diseases result from disease-causing agents or pathogens that naturally infect wildlife, and are transmitted to humans by carriers such as mosquitoes and ticks. In short, they’re diseases transmitted between animals and humans.

Widespread land-use change, globalization of trade and travel, and social upheaval are driving the emergence of zoonotic diseases around the world, said biologist Marm Kilpatrick, who studies the ecology of infectious diseases at the University of California, Santa Cruz.

Kilpatrick co-authored one of several papers in The Lancet, along with Sarah Randolph of the University of Oxford. The Lancet papers are part of a special series in the journal focused on emerging zoonotic diseases.

“Increasing human population, and the urbanization and agricultural intensification of landscapes, put strong selective pressure on vector-borne pathogens to infect humans–and to be transmitted by vectors and hosts that live around humans,” Kilpatrick said.

“Humans are altering the environment and moving ourselves and other organisms around the globe at an ever-increasing pace,” said Sam Scheiner, a program director for the Ecology and Evolution of Infectious Diseases (EEID) program at the National Science Foundation. “Our fast-track has led to a growing disease threat.”

EEID is a joint effort with NSF and the National Institutes of Health. At NSF, the Directorate for Biological Sciences and Directorate for Geosciences fund the program.

EEID funded much of the research discussed in The Lancet papers. “These papers show how and why zoonotic diseases are emerging, and what we need to know to ease the disease burden,” said Scheiner.

The papers “offer a bridge between ecologists and clinicians whose combined efforts are needed to address the ongoing challenges of emerging zoonotic diseases,” said Kilpatrick.

Added scientist Peter Daszak, president of the EcoHealth Alliance in New York City and author of a paper in the series, “Pandemic zoonoses such as SARS, Ebola and HIV/AIDS are devastating when they emerge. What this series shows is that we have new ways of predicting their origins, of discovering them even before they reach our population–truly a brave new world for pandemic prevention.”

There are roughly two types of emerging infectious diseases: introduced and locally emerging.

Introduced diseases arise from the spread of a pathogen to a new location, as when West Nile virus arrived in New York in 1999 and subsequently spread across North America.

Locally emerging diseases increase in importance in areas where they are endemic, as with Lyme disease in the United States during the past three decades.

These two types of emerging diseases can differ markedly with respect to infection dynamics or the number of cases over time, Kilpatrick said.

“Introduced diseases often cause a big spike in infections, and then decrease substantially. Locally emerging diseases often show a steady, sustained rise.”

The movement of pathogens by global trade and travel results in the emergence of diseases in new regions.

Once established, introduced pathogens often evolve to take advantage of their new environments, including new hosts and vectors.

With much of the landscape shaped by human activities, pathogens may thrive by infecting hosts and vectors that do well in man-made environments.

Emergence of endemic vector-borne diseases can result from changes in land use, such as movement of people into new habitats, or environmental changes that affect wild animals that serve as natural hosts–and the insect vectors that spread the disease to humans.

Although vector-borne diseases are sensitive to climate, climate change does not appear to be a major driving force behind emerging diseases.

“So far, climate change has been a relatively minor player compared to land use and socioeconomic factors in the emergence of vector-borne disease,” Kilpatrick said.

Social and economic changes, ranging from economic downturns to displacement of populations by armed conflict, frequently precipitate disease outbreaks through their effects on public health systems, sanitation systems, behavioral patterns and uses of natural environmental resources.

The incidence of any vector-borne disease involves a complex interplay of multiple factors affecting animal hosts, vectors and people.

Kilpatrick and Randolph emphasize that control of these diseases requires combined efforts by clinicians and public health officials to treat patients; promote behavior likely to minimize the risk of infection; and advise on efforts to reverse the ecological drivers of transmission through vector control, urban planning and ecological restoration.

The Lancet papers are published ahead of a special 20th anniversary symposium to be held on Dec. 11 and 12, 2012, in Washington, D.C.

The symposium is hosted by the National Academies’ Institute of Medicine’s Forum on Microbial Threats. The symposium will take a retrospective look at the Institute of Medicine’s 1992 report on Emerging Infections and its 2003 report on Microbial Threats to Health, as well as its creation of the forum in 1996.


Media Contacts

Cheryl Dybas, NSF (703) 292-7734

Tim Stephens, UCSC (831) 459-2495

Anthony Ramos, EcoHealth Alliance (212) 380-4469

Related Websites
NSF-NIH Special Report: Ecology and Evolution of Infectious Diseases:
West Nile Virus Transmission Linked with Land-Use Patterns and “Super-spreaders”:
Social Bats Pay a Price: Fungal Disease, White-Nose Syndrome … Extinction?:
Controlling the Spread of Diseases Among Humans, Other Animals and the Environment:
Snails in the Waters, Disease in the Villages:

The National Science Foundation (NSF) is an independent federal agency that supports fundamental research and education across all fields of science and engineering. In fiscal year (FY) 2012, its budget is $7.0 billion. NSF funds reach all 50 states through grants to nearly 2,000 colleges, universities and other institutions. Each year, NSF receives over 50,000 competitive requests for funding, and makes about 11,000 new funding awards. NSF also awards nearly $420 million in professional and service contracts yearly.


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Why We Need Insects–Even "Pesky" Ones

Press Release 12-189
Why We Need Insects–Even “Pesky” Ones

Hard evidence of evolution: a five-year study shows that plants may quickly lose important traits through evolution soon after insects are removed from the environment

Photo of yellow flowers of evening primrose in Ithaca, New York.

A large natural population of evening primrose (yellow flowers) in Ithaca, New York.
Credit and Larger Version

October 4, 2012

View a video interview with Anurag Agrawal of Cornell University.

At first blush, many people would probably love to get rid of insects, such as pesky mosquitoes, ants and roaches. But a new study indicates that getting rid of insects could trigger some unwelcome ecological consequences, such as the rapid loss of desired traits in plants, including their good taste and high yields.

Specifically, the study–described in the Oct. 5, 2012 issue of Science and funded by the National Science Foundation showed that evening primroses grown in insecticide-treated plots quickly lost, through evolution, defensive traits that helped protect them from plant-eating moths. The protective traits lost included the production of insect-deterring chemicals and later blooms that gave evening primroses temporal distance from plant-eating larvae that peak early in the growing season.

These results indicate that once the plants no longer needed their anti-insect defenses, they lost those defenses. What’s more, they did so quickly–in only three or four generations.

Anurag Agrawal, the leader of the study and a professor of ecology and evolutionary biology at Cornell University, explains, “We demonstrated that when you take moths out of the environment, certain varieties of evening primrose were particularly successful. These successful varieties have genes that produce less defenses against moths.”

In the absence of insects, the evening primroses apparently stopped investing energy in their anti-insect defenses, and so these defenses disappeared through natural selection. Agrawal says that he was “very surprised” by how quickly this process occurred, and that such surprises, “tell us something about the potential speed and complexities of evolution. In addition, experiments like ours that follow evolutionary change in real-time provide definitive evidence of evolution.”

Agrawal believes that his team’s study results are applicable to many other insect-plant interactions beyond evening primroses and moths.  Here’s why: The ubiquitous consumption of plants by insects represents one of the dominant species interactions on Earth. With insect-plant relationships so important, it is widely believed that many plant traits originally evolved solely as defenses against insects. Some of these anti-insect plant defenses, such as the bitter taste of some fruits, are desirable.

“This experimental demonstration of how rapid evolution can shape ecological interactions supports the idea that we need to understand feedbacks between evolutionary and ecological processes in order to be able to predict how communities and ecosystems will respond to change,” said Alan Tessier, a program director in NSF’s Directorate for Biological Sciences.

“One of the things farmers are trying to do is breed agricultural crops to be more resistant to pests,” said Agrawal. “Our study indicates that various genetic tradeoffs may make it difficult or impossible to maintain certain desired traits in plants that are bred for pest resistance.”

In addition, oils produced by evening primroses have been used medicinally for hundreds of years and are beginning to be used as herbal remedies. Agrawal’s insights about pests that attack these plants and about chemical compounds produced by these plants may ultimately be useful to the herbal and pharmaceutical industries.

Agrawal says that most previous real-time experiments on evolution have been conducted with bacteria in test tubes in laboratories. “One of things we were excited about is that we were able to repeat that kind of experiment in nature. You can expect to see a lot more of this kind of thing in future. We will keep our experiment running as a long-term living laboratory. ”

More information about this study is available from a Cornell University press release.


Media Contacts

John Carberry, Cornell University (607) 255-5353

Lily Whiteman, National Science Foundation (703) 292-8310

Program Contacts

Alan Tessier, National Science Foundation (703) 292-7198

Principal Investigators

Anurag Agrawal, Cornell University (607) 254-4255

The National Science Foundation (NSF) is an independent federal agency that supports fundamental research and education across all fields of science and engineering. In fiscal year (FY) 2012, its budget is $7.0 billion. NSF funds reach all 50 states through grants to nearly 2,000 colleges, universities and other institutions. Each year, NSF receives over 50,000 competitive requests for funding, and makes about 11,000 new funding awards. NSF also awards nearly $420 million in professional and service contracts yearly.


 Get News Updates by Email 

Useful NSF Web Sites:

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Tarrant County’s guide to Gambusia (mosquito fish)

This humble little Texas minnow is one of the primary resources used by cities to fight mosquitoes — and they do a very good job of it, too.   They don’t come in pretty colors and they never get very large (up to 2 inches for females) but each fish can eat over 100 mosquito larvae in a day.  This makes them an ideal method of controlling mosquitoes, since when they’re in the larval or egg stage, mosquitoes don’t move about much and they float on top of the water.  They’re easier for predators such as the gambusia to spot… and eat.  Once they hatch out and are flying around, they’re much harder to catch, even for quick chimney swifts and other birds that catch flying insects. And they are the mosquito control method preferred by many Texas cities.


But this year in North Texas, the much-needed fish were in very short supply due to problems with the hatchery, leaving cities scrambling to find other sources — or resorting to spraying techniques (which residents don’t like.)


For people interested in these fish, Tarrant County has a local stocking guide for city governments that can be applied on a smaller scale.

Homeowners with ponds can get these fish from Keller Fish Farms:


National Science Foundation Press Release: West Nile Virus Transmission Linked with Land-Use Patterns and "Super-spreaders"

One of the three birds that are most commonly associated with West Nile virus is the robin (the other two are blue jays and crows.)  Infected jays and crows typically die within 3-4 days, but robins can live much longer with this illness.

Now the National Science Foundation has published some information about land use and the spread of West Nile Virus.

Press Release 11-229
West Nile Virus Transmission Linked with Land-Use Patterns and “Super-spreaders”

Spread highest in urbanized and agricultural habitats

Image of an American robin.

American robins play a key role in the spread of West Nile virus.
Credit and Larger Version

October 20, 2011

After its initial appearance in New York in 1999, West Nile virus spread across the United States in just a few years and is now well established throughout North and South America.

Both the mosquitoes that transmit it and the birds that are important hosts for the virus are abundant in areas that have been modified by human activities.

As a result, transmission of West Nile virus is highest in urbanized and agricultural habitats.

“The virus has had an important impact on human health in the United States partly because it took advantage of species that do well around people,” said Marm Kilpatrick, a biologist at the University of California, Santa Cruz, who studies the ecology of infectious diseases.

West Nile virus can infect a wide range of animals, including more than 300 species of birds and 60 species of mosquitoes. It also infects mammals, reptiles and even amphibians.

But researchers have found that in most places only a few key species of bird “hosts” and mosquito “vectors” are important in transmission of the virus.

“We now know that in any given location, only one or two species of mosquitoes play a big role, and only a handful of birds appear to be important in overall transmission rates,” said Kilpatrick, who reviewed a decade of research on the ecology and evolution of West Nile virus in a paper published in this week’s issue of the journal Science.

According to Kilpatrick, the familiar American robin plays a key role in the transmission of West Nile virus across much of North America.

It is such an important host species that Kilpatrick calls robins “super-spreaders” of West Nile virus.

The reason is not so much the abundance of robins, but rather the feeding patterns of the mosquitoes that transmit the virus.

Mosquito species important in transmission seem to prefer robins over other, more abundant species of birds such as house sparrows.

“Robins are more important in transmission than their abundance alone would suggest,” Kilpatrick said.

“The peculiar feeding habits of the vectors play a really important role in transmission, and this idea applies to many different diseases. It’s one of the really interesting things we’ve learned from the past decade of research on West Nile virus.”

Insights gained from research on West Nile virus could help public health officials deal with other introduced diseases in the future.

“The spread of disease-causing organisms is likely to only increase in the coming years,” said Sam Scheiner, director of the Evolution and Ecology of Infectious Diseases program at the National Science Foundation (NSF). The program is a joint effort of NSF and the National Institutes of Health (NIH).

“West Nile virus has provided a test of our ability to respond to such spread,” Scheiner said. “This research shows that predicting disease incidence in humans and other animals is more complex than first imagined, but that greater understanding of such complexities is possible–knowledge that can be applied to the next threat.”

The globalization of trade and travel has spread many invasive species, including infectious pathogens like West Nile virus.

Although its exact route of entry to New York is unknown, West Nile virus may have arrived in an infected mosquito carried across the Atlantic in an airplane.

The virus then adapted quickly to its new environment, evolving a new strain that was transmitted more efficiently by local mosquitoes than the introduced strain. By 2005, the new strain had completely displaced the introduced one throughout North America.

Three species of mosquitoes are key vectors for transmitting West Nile virus in much of North America. Interestingly, these mosquitoes are not among the species that feed frequently on people.

They are bird specialists that happen to bite people often enough to cause human infections.

“The mosquitoes that bite humans most are actually not as important in transmission of West Nile virus to humans because they rarely bite birds and thus rarely get infected in the first place,” Kilpatrick said.

“Instead, it’s the species that feed mostly on birds and frequently get infected, but occasionally feed on people, that are most important.”

Millions of birds have died from West Nile virus infection, with dramatic effects on the populations of some species. Crows, for example, are much less abundant than they were before the virus arrived.

The robin population, which had been growing rapidly, has leveled off.

“Robins were on a steady upward trajectory thought to be linked to human land use–they love lawns and agricultural fields,” Kilpatrick said.

“Crow populations were growing even faster.  Now crow populations have crashed downward and robins have leveled off, and we suspect that’s due to West Nile virus.”

The worst human outbreaks of West Nile virus in the United States occurred in 2002 and 2003.

According to Kilpatrick, it’s not clear whether the reduction in human disease since then represents a long-term trend or short-term variability.

“It may be that with climatic conditions favorable for the virus we could again get very intense years of transmission,” he said.

“We don’t know yet how much of the year-to-year variation can be explained by climatic conditions or other factors, such as acquired immunity in birds or humans.”

Many other diseases caused by mosquito-borne or tick-borne viruses could potentially be introduced to the United States from overseas, Kilpatrick said.

Understanding the ecology of these viruses may lead to strategies that could prevent a newly introduced pathogen from establishing itself as successfully as West Nile virus.


Media Contacts

Cheryl Dybas, NSF (703) 292-7734

Tim Stephens, UCSC (831) 459-2495

Related Websites
NSF Special Report: The Ecology of Infectious Diseases:

The National Science Foundation (NSF) is an independent federal agency that supports fundamental research and education across all fields of science and engineering. In fiscal year (FY) 2011, its budget is about $6.9 billion. NSF funds reach all 50 states through grants to nearly 2,000 universities and institutions. Each year, NSF receives over 45,000 competitive requests for funding, and makes over 11,500 new funding awards. NSF also awards over $400 million in professional and service contracts yearly.


 Get News Updates by Email 

Useful NSF Web Sites:

NSF Home Page:
NSF News:
For the News Media:
Science and Engineering Statistics:
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Defining Dallas — forgetting the drought

Beaver Chewed Trees

It finally rained in Dallas — three inches over at Trinity River Audubon Center, but half an inch up north. The weather turned cooler, too, dropping from the long sequence of brutal 100 degree days to the 80’s, which seems fall-like in comparison.  I was surprised to notice that I felt cheerfully optimistic that the drought had ended, probably because of the cooler weather and the fact that the three inches of rain dumped enough water into Trailhead pond to fill it out a bit.


But the three inches of rain doesn’t cure the situation.  It makes things temporarily better and slows some of the decline, but it’s not a cure.  After two days of the 80 degree weather (and a chance for the soil to finally absorb some of the moisture) the ponds are shrinking again.  So I took my trusty thermometer in hand and went out to answer the question, “So it’s 82 degrees outside.  Has it all cooled down?”

Trailhead Pond Before The Rain


The answer is “yes and no.”  Yes, the air temperature is cooler (82 degrees).  But when you start looking at vegetation, the numbers climb.  Dried grass, in particular, isn’t very cool — it was 105 degrees.  The path (on black clay) was a startling 122 degrees (I measured it four different times with two thermometers.  Yes.  122 degrees.)  The air over the dried area of the mudflats (which you can see in this picture) — and measured at 3 feet above the surface — was 94 degrees.  The temperature of the baked and cracked mud was 108 degrees.  The water itself in the shallow area was 91.5 degrees.


So I measured an area where the vegetation was still green and came up with an 82 degree reading 3 feet above the ground.  I waded into the pond where a bit of vegetation was left on the edge (this is right next to the area where I measured 108 degrees on the mud) and found that the area covered by plants was much cooler — 84 degrees.


I’m hoping for slow fall rains… an inch here, two there, and so on.  The trees are very vulnerable now, and a hard storm will bring many down.  But the bottom line is that in spite of the optimistic feel brought on by recent rain, the drought isn’t over.  We’re still getting evaporation, but it’s not as fast and water rationing could still be an issue this winter.