Rutgers study shows best home treatments for bed bugs

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bed bug on mattress ticking
Even the best over-the-counter insecticides are most effective when spraying bed bugs directly. Insecticides are no substitute for a good integrated control program.

Even the best over-the-counter insecticides are most effective when spraying bed bugs directly. Insecticides are no substitute for a good integrated control program.

Bed bugs are best treated by an experienced professional.  Let me say that again…  If you have bed bugs, and you can hire a professional who knows what they’re doing, then do it.  It can save you much grief and lost sleep. Now that I’ve said that, let me address those who, for whatever reason, must fight bed bugs without professional help.

If professional service is not in the cards for you right now, you have some options. First consider the approach outlined in my fact sheet on do-it-yourself bed bug control. Much of this approach is based on non-chemical tactics; however, to completely eliminate bed bugs you will usually need to use at least some form of insecticide.

Fortunately, a new study by Narinderpal Singh and others from Rutgers University has identified two low-toxicity products that are surprisingly effective against both bed bugs and their eggs.  EcoRaider™ and Bed Bug Patrol™ are essential oil-based insecticides available over the counter and via the Internet.  Both of these products were the most effective of 11 plant oil- or detergent-based insecticides tested. When sprayed directly on bed bugs in two trials, these products were the only ones that provided greater than 90% control of bed bug nymphs.  EcoRaider™ caused 100 percent mortality after 10 days in two trials.  Bed Bug Patrol™ caused 91-92 percent mortality after 10 days in two trials. Though these essential oil products were slower than the professional insecticide Temprid® SC, they provided equal control after 10 days.

The toughest life stage of bed bugs to kill is the egg stage. In direct spray tests only EcoRaider™ caused high mortality (86%).  All other products, including the professional standards, provided less than 17% control.

Ideally with an insecticide you want a product that will not only kill on direct contact, but one that will leave a residue that continues to kill insects, and not repel them, after it dries. Singh and colleagues tested their two top plant oil-based insecticides against two professional products, Temprid® SC and Demand® CS.  Bugs were confined on one-day old residues on cotton fabric for five minutes and then put in a clean dish and watched for mortality.  After ten days, 93% of bugs exposed to EcoRaider™ and Bed Bug Patrol™ residues died. This was impressive, even though the residues were only one day old. Even more surprising was that these products were equivalent to Temprid® SC, and were significantly better than Demand® CS after even only one day of spraying.  However when bed bugs were allowed to choose between resting on treated or untreated surfaces, the two professional products were significantly better.  This suggests that bed bugs might avoid surfaces treated with the plant oil based products when given a choice.

If you are reading this and thinking you’ve now found the solution to bed bugs at your home, think again. The authors of the study emphasize that all spray exposures were done under ideal conditions.  It is likely that results in the field, where bed bugs are usually protected in cracks and crevices of furniture and bedding, will not be as good. Also, professional products like Temprid® SC and others are designed to continue to kill for more than one day after spraying.  Our plant-based residues in this test were not aged more than one day, and given the volatility of plant oils I would not expect them to last very long.

That said, if you are looking for an insecticide to kill bed bugs on contact, I would carefully look at one of these two, based on this research. I would not waste my time on rubbing alcohol (flammable) or bleach or other common home remedies. Other insecticides evaluated in this study included “Bed Bug 911, Eradicator, Bed Bug Bully, Bed Bug Fix, Ecoexempt IC2, Essentria, Rest Assured, Green Rest Easy, and Stop Bugging Me”.

Not addressed in the Rutgers’ study are the dessicant dusts, like diatomaceous earth and silica aerogels.  Dessicants will also kill bed bugs when properly applied, and are good low-cost, low-risk treatment options.  But more about those in another posting.

Remember that DIY insecticides alone are not likely to rid your home of bed bugs, especially products that do not keep killing after they dry. If you cannot afford, or can’t find, an experienced professional, read through the recommendations in my fact sheet.  Please note that mentions of trade names in this article does not imply endorsement of a products, but are included for educational purposes only.

Possible impact of Emerald Ash Borer in Texas

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green ash tree
green ash tree

Green ash is a common east Texas forest tree, and could be heavily impacted by emerald ash borer.

Last summer the Arkansas Agriculture Department and USDA’s Animal and Plant Health Inspection Service (APHIS) announced that emerald ash borer (EAB) had been discovered in five counties in southwest Arkansas, bringing this pest only one county away from Texas.  Despite the fact that it feeds only on ash (trees in the genus Fraxinus), the EAB is considered to be the most destructive forest pest ever seen in north America.

Because it is getting so close to Texas, I thought I would speculate a little about what impact EAB might have on our state.

The good news is that almost certainly the economic impact of this pest in Texas will be less than its impact in other states like Michigan and Ohio. That’s because ash is less frequently planted here, and it makes up less of the native forest canopy compared to the Midwest. In east Texas, where most ash is located, less than 2% of the forest canopy consists of ash. Fewer trees generally means less economic damage, and lower visual impact to city streets.

According to Missouri Forest Entomologist, Rob Lawrence, that state’s average ash percentage on urban streets is 14% with a few parks reaching 30-40%; but in its native forest ash constitutes only 3% of trees.  According to entomologist Eric Rebek in Oklahoma, in his state’s two biggest cities, Oklahoma City and Tulsa, ash trees make up 10% of planted trees; but only 2% of the hardwood harvest in natural forests.

Compare these numbers with ash numbers in Iowa (average of 16.5% of urban trees, some communities up to 87% ash), Pennsylvania (14% of all trees).  Even Colorado reports ash composition of city trees at between 15 and 25% of all shade trees. In the Chicago area, where EAB has hit hard, 12% of city trees are estimated to be ash, and about 15% in Minneapolis.

The other thing in Texas’ favor is that there has now been over ten years of research on control of EAB; and some effective treatments are available for at-risk trees.  The most effective treatments are systemic insecticides which can be applied to the base of the trunk, or injected, or sprayed on the bark.  These insecticides include emamectin benzoate, imidacloprid, and dinotefuran.  There is even a naturally-derived treatment, azadirachtin, that can protect trees for up to a year.

David Smitley, Michigan State University entomologist, reports that in 2010, the city of Midland injected all ash trees felt to be worth protecting (about 50% of the ash in the city) with emamectin benzoate.  Results exceeded expectations when all treated (and most untreated!) trees survived. This contrasted with four other surrounding communities that treated lower percentages of their trees.  Although treated trees were well protected, nearly all the untreated (control) ash trees in these other communities died within four years.  Smitley attributes the high survival rate of the untreated control trees in Midland to beetle populations crashing from exposure to the high number of treated trees (adult beetles feeding on leaves of a treated tree will die). Once a city stops an EAB outbreak with mass tree treatment, and enters a maintenance phase, experience shows that ash trees should not need to be treated more than once every 2-3 years.

The point of all this is that there are good management strategies for communities who decide to protect their street trees.  Texas Forest Service urban forester, Courtney Blevins, doubts whether most Texas cities will opt to treat because ashes are not widely planted as shade trees here.  Most of the ash in the Dallas area is Arizona ash, was planted 30-40 years ago, and is no longer in favor as a city tree.  The greater impact will likely occur in the native Texas forest, where stately ash trees add to the diversity and beauty of the east Texas woods.

This may be of little consolation to you if you have a valued ash tree in your yard. If this is the case, there are good treatments (mentioned above), should you decide to protect your tree. By the way, there is no need to worry about treating your tree(s) until emerald ash borer is confirmed withing 10-15 miles of your home.

We will continue to monitor for emerald ash borer throughout east Texas in 2015 as part of an APHIS-funded survey.  For more information about emerald ash borer from a multistate collaboration, see http://www.emeraldashborer.info.

 

Scale insect misery loves company

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Crape myrtle bark scale on bark
Crape myrtle bark scale on bark is most evident in the summer when all life stages are present.

Crape myrtle bark scale on bark is most evident in the summer when all life stages are present.

It’s probably true that misery loves company. For the past several years we gardeners in the Dallas area have sadly watched our beautiful crape myrtle trees succumb to a new insect pest.  The crape myrtle bark scale is a messy little critter that causes trunks to blacken and plants to drip sticky bug poop.

True, it’s small consolation to know that the scale that invaded Texas has now spread to at least six other states and appears to be ready to follow crape myrtle in the U.S. wherever it is grown.  But at least we’re no longer alone in our woes.

The scale was positively identified this year as Eriococcus lagerstroemiae, an insect previously found only in and around China (including Korea and Japan). Most likely introduced to the Dallas area by a traveler smuggling a crape myrtle cutting to plant in a private backyard, we’ve known the scale problem for over ten years.  Now the crape myrtle bark scale has its own website, and a distribution map that you can help update.

Identifying the pest is not difficult.  It is one of very few white scale-like insects that will cluster on the bark of crape myrtle trunks and branches.  When crushed they ooze a purplish blood.

The current range of the crape myrtle bark scale. You can help document the spread of this new pest at www.eddmaps.org/cmbs

The current range of the crape myrtle bark scale. You can help document the spread of this new pest at www.eddmaps.org/cmbs

The fine folks at EDDMaps (Early Detection & Distribution Mapping Sytem) have just finished creating an interactive way to share pictures and data about suspected crape myrtle infestations at your backyard or town.  If you suspect you have the scale in your neighborhood, take a picture of the infested tree and save to your phone or computer.  Then go to http://www.eddmaps.org/cmbs/ and register if you are a first time user.  After you’re official, click on the Report Sightings tab and start filling in your information about your suspected infestation.  You don’t have to manually enter Latitude and Longitude, simply use the interactive map to locate where your crape myrtles are located.  If you zoom in and turn on the satellite image option (my favorite part) , chances are that you can point to the actual tree in question.

After you mark your location, you can upload up to five digital images and submit your report.  The report goes to a local entomologist who verifies the image and your report goes into the mapping database.  If your sighting is confirmed, your county will light up with a color indicating the year of your report, and your record will go down in the entomological archives forever.

The map itself will likely not help keep the scale from spreading.  The USDA has determined that the cat is already out of the bag, and so there is no real use for quarantining nurseries in infested states.  Nevertheless, we entomologists would like to know how fast it’s spreading.  And, like telling teacher about a naughty child on the playground, even if we can’t stop this pest from spreading at least it will make you feel better to report it.

For more information about crape myrtle bark scale and its control, click here.

Plan Bee: Insecticide tags on nursery plants

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Many greenhouse and nursery reared plants are treated with insecticides to ensure they are pest-free in the store.

Many greenhouse and nursery reared plants are treated with insecticides to ensure they are pest-free when you make your purchase in the store.

Lobbying efforts by “defenders of the bees” have been rewarded by one of the largest retailers of nursery plants requiring new tags on plants.  As reported today by Nursery Management magazine, all Home Depot plants treated by greenhouse or nursery producers with one of the neonicotinoid insecticides will have to carry a special tag informing customers of the treatment and potential residues.

What’s this about?  It’s all part of a political and scientific brouhaha over a group of insecticides that were recently discovered to have some subtle, and possibly deadly, effects on bees at very low concentrations.  It’s not that we haven’t known all along that these insecticides were toxic to bees; it’s all about HOW toxic they really are when applied according to label instructions, and whether these insecticides are responsible for the recent condition known as colony collapse disorder in honey bees.

You might think of this as a “Plan B” for those groups seeking to ban neonicotinoids. After first requesting EPA to outright ban these insecticides from the market (Plan A) and being turned down due to lack of scientific consensus on the issue, some advocacy groups have used grass-roots efforts to influence the market sector, and  legislatures to press the issue.

I don’t know what the new warning tags will look like, but they are likely to confuse consumers and scare them away from purchasing these plants–regardless of the virtue of the warning. Nurserymen understand the issue.  According to one producer quoted in Nursery Magazine, “We view…labeling of the plant with that tag [as] potentially creating customers’ perception that the plant should not be purchased.”

For the record, the majority of my colleagues who work in the ornamentals IPM area seem to feel the science does not back up the current level of alarm over neonicotinoids. Not all agree, but bee researchers in particular seem to favor Varroa mites and some new virus-caused diseases of bees as top suspects in colony collapse disorder.

What puts applied entomologists (who dedicate their careers to the practical task of protecting crops, humans and animals from pests) in a tough spot is that neonicotinoids have proved to be great tools for controlling some really tough pests, like emerald ash borer, bed bugs, house flies, cockroaches, whiteflies, scales and many others.  For many of these pests there are no effective or safer alternatives.

And not all uses of neonicotinoids are likely to pose equal risks to pollinators.  Many applications are made to plants that don’t attract many bees.  Some formulations are designed to control ants, bed bugs and termites, with almost zero risk of contacting bees.  Unfortunately, the public and legislative campaigns going on now are not very nuanced in this regard.  All seem designed to paint the issue as black and white, with the ultimate goal of eliminating neonicotinoid use in all its forms.

So by all means educate yourself about the issue before deciding for or against purchasing a neonicotinoid-treated plant. Just keep in mind that science can’t always be rushed, but it will ultimately provide the answers.

Kids, bee careful out there

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Bee nest exposed hive

Entomologists often walk a fine line between sounding alarmist and underplaying the importance of pest problems. Africanized honey bees and children are a good example.

The potential seriousness of living with these bees was underscored yesterday when a gym class of middle schoolers disturbed a bee hive in a water controller box on a campus soccer field.  According to news accounts, 20 students were stung, and several were taken to the hospital. Presumably the bees in this case were Africanized.

Bee nest are usually hidden in a tree or wall, but this exposed hive is hanging from a tree branch. Stay away from any hive or bees that you see going in and out of a hole in the ground or in a tree or building.

Honey bee nests are usually hidden inside a tree or wall, but occasionally bees will build an exposed hive, like this one hanging from a tree. It’s best to stay away from any bee hive, or wherever you see bees entering and exiting a hole in the ground, or in a tree or building.

Coincidentally this month, BBC News magazine interviewed Texas A&M entomologist, Dr. Juliana Rangel, about what it is that makes the Africanized honey bee (AHB) so dangerous.  She summarized the challenge by noting that the AHB is “more aggressive and more easily agitated than other bees. The banana-scented pheromone they release – the one that tells the rest of the colony to join in the attack – can be detected across a wider radius” than our domesticated European strain of honey bee.  Although any honey bee nest can be dangerous, she said that the AHB is likely to send more bees out to defend its nest.  And the defenders will chase a victim farther than our domestic bees.

The AHB entered Texas almost 25 years ago and has since spread across the state, hybridizing with our feral European honey bee population. It’s best to assume that any wild bee hives you see in your back yard or park are Africanized and worthy of respect.

Bee stings can be much more than just a painful experience.  About 1% of people experience more serious reactions to bee or wasp venom, requiring a visit to the emergency room. For this reason, it’s important to be ready with some instruction to your children about bees.

While most kids can handle dozens to even hundreds of stings, the experience is not fun, and will likely be traumatic for some children.  And for allergic kids (and adults), even a few stings can be deadly.  A few things you and your children should know about bees:

  • Run if you encounter bees that sting you!  Run straight to shelter like a car or building where you can close a door.  Don’t jump into a pool or other water.  The bees will not go away quickly, and people who jump in water usually get more stings.
  • Bees usually leave a stinger in your skin after an attack.  Gently scrape out the stingers, and you will get less venom and it won’t hurt as much.  If it makes you feel better, all bees that leave their stingers in your skin die soon, and cannot sting again.
  • It’s normal for bee stings to hurt, and even swell a little, where you are stung. But if your whole arm or leg or throat or face starts to hurt or swell  let an adult know right away. If you start to itch all over, or get red bumps (hives) on different places on your body, or if you have difficulty breathing, don’t panic. But it is important to find an adult to help you get to a doctor or nurse right away.
  • Parents, Benadryl™ is a good first aid measure to help slow the allergic response and relieve swelling. Also, a child’s dosage of an analgesic like Tylenol or Advil can help relieve the temporary pain associated with bee stings.

    yellowjacket wasp

    Yellowjacket wasps are smaller than bees and have yellow and black stripes.  The yellow and black color of this wasp means “I’m dangerous!”

  • Don’t be afraid of bees on flowers or around trash cans (where they are looking for sweets). The only time bees are likely to sting, is if you get too close to their nest.
  • Yellowjacket wasps are small, yellow and black wasps that nest in the ground.  Their nests are even more common than bee nests in the fall. Learn what yellowjacket wasps look like and avoid them like bees.

Although bees are good for our crops and gardens, and 99% of the time cause absolutely no harm, the risk from bees is real. I’m not exaggerating. So kids and parents, bee careful out there.

 

Powwowing about pollinators

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halictid bee on flower
bumble bee on salvia

Bumble bees, important pollinators of many native plants, are becoming less common in many parts of Texas and around the country.

Pollinator protection has become almost trendy recently. One of the spin offs of the honey bee controversy over CCD, is that the spotlight has come to rest not just on honey bees, but on all insects that pollinate plants. And this is a good thing.

Today nearly everyone at some point is taught in school, or via Discovery Channel, that bees pollinate flowers; but I’ll wager that relatively few understand what this really means to all of us.  Pollination is the biological process by which female plant parts are fertilized by the carrying of pollen from one plant to another.  It is the plant’s equivalent of sex, only in this case it’s a ménage à trois.  Without an insect middle man to carry male pollen to female plant parts, many plants could not produce seeds, or at least seed production would be much less.

Pollination is an essential part of the machinery of plant health and evolution.  The hybrid vigor of cross pollinated plants, and the genetic diversity enabled by pollination would dwindle over time. Without pollination plants won’t necessarily die , but many plant populations would cease to thrive, and nature’s ability to respond to a changing earth environment would be gravely at risk.

So why the fuss over protecting pollinators?  Why do they need our help? Pollinator populations in many areas are in decline, and not just in urban areas.  Take the bumble bee…or I should say bumble bees.  There are over 40 different species of bumble bees in the U.S. alone. In Europe, where bumble bees have been studied more carefully, over 18 species of bumble bees are considered threatened today.  In the United Kingdom, a similar story can be told.  There, three species have recently gone extinct. In the few studies of bumble bee population change in the U.S., many formerly common bumble bee species are found in fewer places, and bumble bee species are disappearing from many sites.  And these aren’t the only kind of pollinator to be concerned about.  There are 3,500 species of all kinds of bees in North America, each of which are pollinators, most of these are at some level of risk of decline.

Many pollinators, like this metallic halictid bee, are small enough to be overlooked by most people; but their value to plants goes far beyond their size.

Many pollinators, like this metallic halictid bee, are small enough to be overlooked by most people; but their value to plants goes far beyond their size.

Much of the concern about pollinator decline concerns loss of habitat.  Bumble bees, for example, thrive best in diverse grassland habitats.  And grasslands are one of our most threatened ecosystems, losing up to 400,000 acres a year to expanding crop production alone.  Much less than 1% of original historic prairie remains in Texas, and less than 2% remains nationwide.

While one could argue that this is the necessary cost of human progress, there is much we can do to preserve our native pollinators.  The first step is education.  The Xerces Society maintains a Bring Back the Pollinators page and Texas Parks and Wildlife maintains an informative site on Texas bumble bees.  In addition, for those of you in the north Texas area, there will be a Pollinator Powwow on Saturday, November 15, in Mansfield, TX.  Cost is $15 for a full day of training and lunch.  If you have any interest in making a difference for pollinators, you owe it to yourself to check this out.

Late chigger season

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chigger bites

Chiggers seem to settle and bite most under areas of snug clothing. Note the bites around the ankles and sock line.

It’s October, I’m still scratching chigger bites.  Two weeks ago I gave a talk for Master Naturalists at the Hagerman National Wildlife Refuge headquarters, and we took a 15 minute “field trip” to the flower garden around the building.  The next day I counted 30 plus bites.  Last weekend I swear I never left a sidewalk, and still felt the tell-tale itch of chigger bites. It could be just me but I’ve been getting calls from others, too, about chiggers over the past month.

Chiggers are my personal least favorite arthropod.  They’re nearly impossible to see. They show up when you’re outdoors and don’t expect them.  They itch like blazes, in all the wrong places.  And this year they seem to be active later than usual.

So what’s happening?  I know of no one who formally studies chiggers in Texas, but in my experience chigger activity usually in highest in spring and early summer, and trails off during the heat and dryness of mid summer.  Because of their delicate nature and small size, chigger larvae are sensitive to heat and low humidity. Perhaps it was our cooler summer this year, or maybe it’s due to timeliness of the few showers we got in north Texas during July and August (this was not a wet summer and September was the driest on record); but for whatever reason my chigger meter is pegging out.

chigger life stages.

Adult and larval chigger. Only the newly hatched larva is parasitic. After a blood meal the almost invisible larva leaves its host and becomes a predator of tiny arthropods in the soil. (Modified from Michener 1946)

There are relatively few researchers who want to do field research with chiggers. Imagine that!  But several years ago some work that was done in Nebraska, that gives us some ideas about what can be done about chiggers.  Dr. Fred Baxendale and his student Tom Eickhoff published a report on the effectiveness of several different insecticides on chiggers.  They marked out and sprayed some grassy plots, and to evaluate the treatments they threw a black clipboard on the ground for 45-50 seconds, retrieved it and counted all the chiggers (chiggers quickly crawl on to dark, warm objects on the ground).  Not my idea of fun research… I hope Tom was not as highly attractive to chiggers as I am.  Anyway, they found that bifenthrin performed the best, eventually resulting in 96% control.  Two other pyrethroid insecticides, lambda-cyhalothrin and cyfluthrin, did almost as well; but none of the insecticides provided 100% control. Liquid sprays worked better overall than granular insecticides.

Most of us do not encounter chiggers in our back yards, but if you do, you should consider treating with bifenthrin spray.  The easiest way would be to purchase a liquid concentrate (Ortho Home Defense™ is one brand) and apply it to grass and higher vegetation using a hose-end sprayer.  You should expect two weeks or more control with a single application.

The other chigger defense is to apply a good repellent.  DEET repellent applied to the shoes, socks and pants will significantly repel chiggers.  Old-timers in Texas will also tell your to use a sock filled with dusting sulfur.  Banging the sock against your shoes, pants, socks and legs will give you a dusting that seems to repel chiggers.  I don’t know if it’s as effective as DEET, but it is cheap and easy to use.  Farmers often just keep a sock in the back of the pickup truck and dust themselves when they have to wade into possible chigger territory.

Tucking your pants legs into your socks also seems to help keep chiggers from getting quick access to your skin.  Since most chiggers seem to crawl onto the skin after climbing from shoes and socks, tucking pants into socks makes them have to work harder to strike pay dirt.  And because chiggers may crawl around for an hour or more after hitching a ride, taking a hot shower just after a chigger exposure seems to help reduce chigger bites.

For more information about chiggers, see the factsheet E-365 Chiggers.

 

 

The NYT on CCD

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colony collapse disorder video shot
colony collapse disorder video shot

USDA researcher Dr. Jeff Pettis provides context to the CCD problem in a recent NYT video report.

The New York Times just published an article and video on the complex nature of colony collapse disorder (CCD) in honey bees.  Author Clyde Haberman does a good job of presenting the case for the side of the debate that argues for multiple interacting causes of the bee problem.

If you’re not familiar with CCD, it is a mysterious disorder that has afflicted 30% or so of commercial bee hives in the U.S. since 2006.  Something about the problem has touched a nerve with many Americans who fear that we might be losing the battle to preserve our environment in the face of mounting pressures from climate change and pollution.  I think the feeling is that if we can’t stop climate change, then by golly we will surely save our bees.

The NYT article does an excellent job of putting the crisis into perspective.  The real concern, according to the story, is not so much about losing our honey bees, but losing our beekeepers.

One weakness of the reporting is that it does not do full justice to the contentious nature of the fight over root causes of the condition, nor did it probe the depth of feelings over pesticide concerns among many of the public and environmentalists. Nevertheless, I recommend this read if you want to get some more understanding of this important issue.  To watch the video, click here.

Mosquito juice and science

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Mosquito pool ready for juicing

Have you ever heard some scientific claim on radio or TV say something that made you stop and ask: “How do they do that?” Apparently this question bugged someone enough this week to call their extension agent and ask “How do you guys really know if a mosquito has west Nile virus?”  I thought that was a pretty good question; and given the level of WNV testing going on right now in many Texas cities, it was one that deserved a public answer.

Military airman prepares a stink trap to catch Culex mosquitoes for testing. Photo courtesy Joint Base McGuire-Dix-Lakehurst, USAF.

Monitoring mosquito-borne diseases has been an important part of military strategy for many years. Here an airman prepares a stink trap to catch Culex mosquitoes for testing. Photo courtesy Joint Base McGuire-Dix-Lakehurst, USAF.

You might wonder… Do they have veterinarians waiting in labs somewhere to take mosquito temperatures and read little mosquito pulses?  Do we ask the mosquitoes, “How are you feeling today?” In reality, the whole process of mosquito testing is complex and pretty amazing. There are a number of steps involved, but first the mosquitoes have to be caught. To do this health officials use special traps that catch the mosquitoes that are most likely to be infected.

Mosquito pool ready for juicing. Photo courtesy Texas Department of State Health Services.

Mosquito pool ready for juicing. Photo courtesy Texas Department of State Health Services.

The most common mosquito traps for west Nile virus (WNV) use buckets of bacterial rich, highly stinky water as a lure.  This is the kind of water that pregnant (gravid) female mosquitoes seek out for breeding. Stink traps typically have a little vacuum that sucks up the egg laying females and blows them into a lightweight sack for collection. Single mosquitoes are not commonly tested for WNV.  Instead, a mosquito “pool” is a group of up to 50 mosquitoes taken from a single stink trap.  Back in a lab, the mosquito pool is dumped into a vial with a little water and copper-coated bbs to give a little crushing power. The vial is shaken vigorously by a machine and presto!  Mosquito juice!  Mosquito juice is the starting point for all testing procedures. The juice of pulverized mosquitoes is rich in DNA, the genetic coding material that all life is based on. Thanks to amazing technological advances of the past 50 years, we can now amplify the minute amounts of DNA present in samples like mosquito juice, and determine what species it codes for.  Also, if a mosquito is infected with a virus, we can look for specific RNA pieces that are unique to the virus we are interested in. If we find those pieces, we know we have infected mosquitoes.

The difference between healthy (left) and virus infected tissue culture cells. Photo courtesy Texas Department of State Health Services.

The difference between healthy (left) and virus infected tissue culture cells. Photo courtesy Texas Department of State Health Services.

Before DNA testing is done, mosquito samples sent to the Texas Department of State Health Services will be run through a Vero cell culture. In this method mosquito juice is squeezed onto a specially prepared plate with a thin layer of living cells.  After a few days of incubating the cells with the mosquito juice, a technician can look at the cells under magnification and determine if they look healthy. The presence of sick cells tells the technician that the mosquito pool carried one of several viruses that attack these cells. The health department prefers the Vero cell culture method because it is sensitive to many kinds of mosquito borne viruses.  When a sample is positive for virus, then one of the molecular tests for specific virus RNA is run.  These tests are highly specific, so that a test for WNV will not detect say St. Louis encephalitis (SLE) or chikungunya (CHIK), other important mosquito-borne diseases. Several tests will be run on any cell culture positive sample of mosquito juice. The problem with cell culture is that it’s expensive and takes several days to get results.  Some cities are now using a faster method known as Real-time PCR.  The results of a RT-PCR test can be returned sometimes as quickly as overnight.  A WNV-specific RT-PCR test is less expensive and faster, however it is not sensitive to all mosquito borne diseases.  The disadvantage is that it is highly specific for one kind of virus, so a health department looking for WNV without cell culture might miss a budding SLE  or CHIK epidemic, for example. This kind of technology, by the way, is an example of a public benefit that can come from basic science.  Before these tests could be invented, we had to know what mosquitoes carry disease and how to catch them, how RNA fingerprints of different viruses differ, how to multiply teeny amounts of DNA or RNA in mosquito juice so that it can be detected (a major advance of biotechnology in the 1980s), and how to build machines that can do these things quickly and inexpensively.  A lot of research that seems academic eventually results in applications that can save human life.  And that is pretty amazing.

Caution in the Caribbean

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DSCN1120I had an inquiry today about the safety of travel to Caribbean destinations on cruises.  The person was concerned about Chikungunya and whether a spouse with health problems should risk taking a Caribbean cruise.  The answer is that Chikungunya is a risk if you decide to go ashore on most of the Caribbean islands.  If you are planning a trip to warm Caribbean waters, don’t necessarily cancel your plans; but you should arm yourself with the information to know the risks.

The Centers for Disease Control still rate travel to the Caribbean at Watch Level 1, which simply means to “Practice normal precautions” (Watch Levels 2 and 3 are “Practice enhanced precautions” and “Avoid unessential travel”).  As of mid-August the CDC listed 25 countries (islands) with active cases of Chikungunya.  It is not recommending against people traveling to these countries, but urges travelers to the Caribbean to “protect themselves from mosquito bites”.

The CDC adds that some travelers may be more likely to get chikungunya, have severe disease, or be at higher risk for other reasons. If you fall into one of these high-risk groups, you are encouraged to discuss your travel plans with your doctor.  Examples of high risk includes people with arthritis, high blood pressure, heart disease, late term pregnancies, people over 65, and others.  If you are planning to spend much time outdoors, or sleep in locations without air conditioning or mosquito screens, you should also expect to be at higher risk.

From last December 2013 to August 29th, there were 659,367 cases of Chikungunya in the Americas. The most heavily infected nations include the Dominican Republic, Guadaloupe, Haiti and Martinique. Cases are also present in El Salvador and some other central American countries.  Many Caribbean countries have had only very low numbers of cases, so check out this article and graph to see where risk is highest.

Chikungunya is rarely fatal, but is a potentially debilitating and unpleasant mosquito borne disease.  Symptoms include fever and joint pain.  It is carried by container-breeding Aedes mosquitoes that are especially common in cities.  See this link for more information about insect repellents.