Friday, September 20, 2019

Upcoming classes in Dallas and Austin

Just a quick post to let readers know about a couple of pest control classes coming up soon, one in Dallas and one in Austin.

Dr. Bob Davis, BASF, has been teaching ACE Prep Classes
for more than ten years. I guarantee this will be one of the
best training classes you will attend this year.
On September 25 we still have room in our first Bed Bug Academy at the IPM Experience House in Dallas.  The class will cover basic bed bug biology and state of the art information on monitoring and control. The class will be taught by Mr. Alan Brown of ABC Home and Commercial Services in Austin, and myself.  It's an all day class (8:15 am to 5 pm) with CEUs and verifiable training hours for apprentices. Cost is only $60 preregistration. Class size is limited, so don't procrastinate. Registration, agenda, map and more information can be found at

For anyone who has considered becoming an Associate Certified Entomologist, ABC Home and Commercial Services in Austin is hosting an ACE Prep Class on October 1.  I've talked about this class in the past on Insects in the City blog, but if you are unfamiliar, this is a chance to either inspire your study or to do some last minute cramming before the test.  Even if you're not sure whether you want to be an ACE, the class provides an excellent overview of the technical side of being a pest management professional.  Led by Randy McCarty, myself and Dr. Bob Davis, this will be an intense but fun class. Best of all, there is no charge!  To get in there is no fancy registration, simply contact Randy McCarty and let him know you would like to attend (, 512-534-5772). The class will run from 8 am to 4 pm and will be held at ABC Home and Commercial Services office, 9475 East Highway 290, Austin, TX 78724.  Parking on the left side of building.

Remember you can never stop learning. The day you stop learning you might as well hang it up.

Friday, September 13, 2019

Unnecessary trauma: Fire ants in nursing homes

Nursing home patient with with fire ant stings.
(Laquna Ross)
This week Vietnam veteran Joel Marrable died at a Georgia VA Hospital following a vicious attack by fire ants.

According to his daughter, Mr. Marrable was found by staff last week covered with ants. Even worse, family wasn't notified by the hospital after the attack. His daughter learned of the incident only after inquiring about the red bumps on her father's body. Although Mr. Marrable's death has not been directly blamed on fire ants, the incident was traumatizing to all involved.

This story would be more shocking to me, except I have been involved in at least two lawsuits where fire ants attacked patients unable to respond or call for help. And despite the fact that stinging cases are often hushed up, many other incidents occur every year.

It doesn't have to be this way. Fire ants are highly manageable given our scientific understanding of fire ants, and today's pesticide tools. But fire ant management always requires attention to detail. It also requires cooperation and communication between the health care facility and its pest control provider. 

If your company provides pest control for health care facilities, here are some essential elements needed to keep your customer (and you) out of the headlines.

  • Ensure the facility has a policy regarding indoor ants. The plan should include clear staff instructions on how to immediately report signs of ants to your company. 
  • Be sure your staff is always updated on what wings/rooms house high-risk patients.
  • Require patients to be immediately removed from any room with ants to another ant-free location. In this Georgia incident, the patient was returned to his original room only to have fire ants return and attack again a second day. No patient should be returned to an infested room until the indoor and outdoor areas around the room have been inspected, treated and cleared by a pest control professional.  
  • Clean infested rooms with a soap solution and disinfect before allowing any patient to return.  Holes and suspected ant entry points should be either sealed or treated. Cleaning with soap removes traces of trail pheromone that might lure other ants back into the room.
  • Conduct periodic staff training classes to let nurses and other caregivers know how to identify fire ants. In this week's incident it is telling that none of the staff interviewed referred to the ants as fire ants, only "ants."  Fire ants pose perhaps the greatest immediate health threat to aphasic patients, and should not be difficult to recognize with training. 
  • Inspect outdoor areas regularly for fire ants, and train maintenance staff to recognize and report evidence of fire ant nesting around the facility. 
  • Fire ant infestations inside a building can almost always be traced back to a fire ant mound or colony outdoors. It's important to know who is responsible for grounds treatment ahead of time. When one contractor is assigned duty for indoor pest control and another for outdoor pest control, blame-shifting is inevitable. The losers in this game are the patients. Ideally, one contractor should be responsible for both indoor and outdoor fire ant control, so there is no confusion.  
  • Don't rely solely on mound treatments for fire ant control. Broadcast applications of either baits or residual insecticides are always a better option. Fire ant baits are ideal for large turf areas and are typically applied once or twice a year. Residual granular insecticides containing fipronil or bifenthrin can be used annually in landscape areas immediately adjacent to buildings.  The idea is to keep fire ant mounds as far away from the building as possible. Fire ant control should start at the property line, not the final two feet to the building.  
  • Don't allow unlicensed applicators to apply insecticides for fire ants. In Texas, pest control at health care facilities must be performed by a licensed pest control technician or certified applicator. This includes control of ants and other insects, pest birds, plant diseases, rodents, and weeds.
  • Document everything you do in writing on your service report. Document both pesticide and non-pesticide-related actions taken during the visit. Be specific about what pests are found during inspections. Remember, there is no such thing as just an "ant."  Fire ants should be clearly identified. Assume that any of your service tickets could be examined by a lawyer some day. 
If doing pest control around nursing home facilities sounds risky, it is. But a conscientious company can succeed at this business. And a nursing home can be one of the most rewarding accounts you have.  As a friend and colleague points out, the biggest risks happen with "low-bid contractors who are not willing to address underlying problems."  

Mr. Marrable's daughter told the Washington Post that her father "deserved better" than the treatment he received in his last days. Let's make sure all our sensitive accounts, like nursing homes, get the good service they deserve.

For more information about fire ant control in nursing homes, see Extension factsheet ENTO-022.

Friday, August 9, 2019

Where is West Nile virus this year?

If it seems you're hearing less about West Nile virus (WNV) this summer, you may not be imagining it.  Although mosquitoes have been abundant in north Texas this year, for some reason the virus has remained relatively quiet.

Where has WNV gone?

A paper written by epidemiologist Dr. Wendy Chung and colleagues in 2013 may offer some insights on the absence of the virus this summer. Those of us who lived in Dallas in 2012 may remember that summer as the worst human outbreak of WNV ever.  Nearly 400 cases were reported in Dallas County alone, and 19 people died of the disease. The epidemic was so bad that Dallas county resorted to spraying the entire county for mosquitoes by plane--something not seen in north Texas since an encephalitis outbreak in 1966.

Chung and colleagues charted the course of the disease during 2012 and saw high infection rates of mosquitoes early in the summer, followed by a rapid increase in human cases. Looking back over previous years and case numbers, the researchers concluded that an unusually mild winter followed by rainfall patterns ideal for mosquito breeding in the spring (and a very hot summer--West Nile virus multiplies quickly in mosquitoes at higher temperatures) created ideal conditions for an outbreak.

So what's different about 2019? We had a relatively mild winter, with only three days at or below 28° F, and a wet spring--both conditions mosquitoes love. But the summer, at least by Dallas standards, has so far been cool.  Until this week, the DFW Airport weather station saw only two days over 100° F. By the end of July the area usually has experienced more than seven days over 100° F.

These graphs show 2019 mosquito abundance and Vector Index (V.I.) estimates compared to previous years. Although mosquito numbers are high this year, the V.I. has remained low for both Tarrant (=Fort Worth-top) and Dallas counties (bottom). In 2012 the V.I. exceeded the danger level of 0.5 for multiple weeks (blue dotted line). Source: Tarrant County Public Health and Dallas County Health and Human Services.

Predicting WNV

One of the tools used by health departments to predict disease risk for WNV is a statistic called the vector index (V.I.).  The V.I. is calculated weekly from mosquito trap data, and combines information on both average abundance of Culex quinquefasciatus (the main carrier of WNV) and disease incidence in the trapped mosquitoes.  A V.I. of 0.5 or higher for two or more weeks is considered a crisis indicator by some health officials.

The graphs shown here are provided by epidemiologists in Dallas and Fort Worth, and show both mosquito abundance and V.I. estimates for both counties. Despite higher mosquito numbers, the V.I. hasn't ventured above 0.1 for either Dallas or Tarrant counties this summer. Most of the season the V.I. has been closer to zero, hence less need for mosquito spraying and fewer people getting sick. In Dallas county this year there have been no human cases of WNV. Tarrant County (Fort Worth) reports only one case this year with a very low V.I., near zero most weeks (top graph).

According to statistics from the Texas Department of State Health Services, low WNV incidence seems to be true for the whole state this year with no reported human cases as of the end of July.  Harris County (Houston) also reports a light year for WNV, according to the acting director of Mosquito and Vector Control, Chris Fredregill.

Looking Ahead

With this week's string of 100° days in many areas will risk go up?  Certainly West Nile virus remains a threat to all of us through the end of the summer and into the fall; but this late in the season the chance of a major outbreak is probably low. On the other hand, hot weather favors the virus. It's no time to forget about mosquitoes. I expect Aedes mosquitoes (yellow fever mosquito and Asian tiger mosquito) to become more abundant after last weekend's rains.  This week is a good time to get out and dump standing water.  Although Aedes mosquitoes are not major disease risks, they cause most of the itchy mosquito bites we get during the day--and we don't want that.

Why Surveillance Reports?

Integrated pest management is just as relevant for mosquito control as it is for all other forms of pest control.  One of the principles of IPM is to base treatments on pest numbers.  Because mosquito monitoring is expensive and requires special expertise beyond what most PMPs possess, few companies monitor mosquito numbers or disease. However, high quality data may be available from your local health authorities, depending where you live. A pest management company can use this data to alert customers to times of higher disease risk and changes in mosquito abundance.

Every community's mosquito situation will be different.  If you are doing business in a larger metropolitan area, or a mosquito control district, you may have access to the kind of data shown here. To find out, contact your local or regional health department and ask if they provide reports of mosquito abundance and disease prevalence.

In Dallas, weekly reports may be obtained by emailing and requesting to subscribe to the weekly Arbovirus Surveillance Report. For Tarrant County, email and request to receive the Arbovirus Surveillance Report Weekly.  Unfortunately, not all counties have equivalent reporting systems. Harris County provides mapping of areas with virus detection.  And the Texas Department of State Health Services provides weekly reports throughout the summer for the whole state.

An additional source of information for both PMPs and your customers is the Mosquito Safari website. At the Safari you can take a virtual tour of a field and a backyard and learn important facts about mosquitoes. 

If you need more intensive training, our Extension medical entomologist, Dr. Sonja Swiger, is offering classes this year for pesticide applicators wanting to prepare for their Public Health (Category 12) license.  In the fall she also offers several 3-day Master Vector Borne Disease Management Courses around the state.  To learn more, or to register, go to .

Monday, August 5, 2019

Getting to know the Turkestan cockroach

Cockroaches have historically been a top pest and reliable source of business for PMPs.  Indeed, from day one most new technicians are taught to recognize the four most commonly encountered species:
  • the German cockroach--one of our smaller cockroaches, bane of restaurants and homes
  • the American cockroach (a fast and intimidating insect that looks twice as big as it really is when running across a floor or flying)
  • the black, rather nasty Oriental cockroach--pest of sewers and the grounds around buildings
  • the smoky brown cockroach, an outdoor cockroach unafraid to venture into homes. 
Other common species, depending on your part of the country, include the Australian, brown, brown-banded, Asian and field cockroaches.

Figure 1. The adult female S. lateralis (A) and adult female Oriental
cockroach (B) are similar in size and color. Arrow points
to the distinguishing light marking on the forewing margin
of the Turkestan cockroach. Photo modified from Kim and
Rust (2013).
In many parts of the country pest management professionals need to add the invasive Turkestan cockroach (Shelfordella lateralis Walker) to their watch list. This Asian invader is quickly making a name for itself and moving through Texas and other states.

Because the Turkestan cockroach looks similar to other species, you may already have seen it and not realized it was something new. Female Turkestans look like Oriental cockroaches. Male Turkestans look like small American cockroaches or perhaps an innocuous field roach.


The Turkestan cockroach has becoming a significant new pest since it was first reported in Shelford, California in 1978 and El Paso, Texas in 1979.  It has since spread through Arizona and New Mexico, across Texas and even to Georgia.  This week I got my first north Texas specimen, and tentatively identified an emailed photo from Tennessee as a Turkestan cockroach.

Figure 2. To my knowledge, this is the first Turkestan cockroach
recorded from north Texas. Collected from a hotel in Frisco,
TX (VII-29-2019). Note the pale, almost transparent border
at the margin of the forewing, and the size (28 mm/one inch),
which is smaller than a typical American cockroach. Photo
M. Merchant.
If you think this pest won't reach your area soon, think again. Internet commerce is also at work. Turkestan cockroaches are commonly sold online where they are well known in the pet trade as "red runners." They provide food for reptile, amphibian and small mammals. Pet owners like the fact that Turkestan cockroaches breed quickly, do well in captivity and don't climb glass (so are easy to keep in aquaria).

My first North Texas specimen of a Turkestan cockroach came this week courtesy of Emory Matts, with Rentokil Steritech.  Guests at a local hotel recently started complaining of roaches on several floors. Whether this was an invasion from outdoors (males can fly and are attracted to lights at night), or represented an indoor infestation could not be determined.  Though it's often referred to as an "outdoor" insect, the Turkestan is capable of establishing itself indoors, similar to Oriental and American cockroaches.


Figure 3. Turkestan (A) and Oriental cockroach nymphs.
Notice the reddish-brown thorax and dark abdomen of
the Turkestan nymph compared to the uniform brown color
of the Oriental. Photo from Kim and Rust (2013).
According to Kim and Rust (2013), the Turkestan is replacing the Oriental cockroach throughout much of the Southwest as the most important cockroach pest around the outsides of structures.  Common breeding sites are similar to those of Oriental cockroaches, including water meter and irrigation boxes, electrical boxes, hollow block walls, cracks and crevices in concrete, compost piles and potted plants.  However, it appears that in the warm climates of the Southwest, Turkestan cockroaches rush through their 5 nymph stages faster than the Oriental with its 7-10 nymph stages.  A female Turkestan cockroach will produce about 25 oothecae (egg cases) in her lifetime compared to 5-10 oothecae for an Oriental cockroach.  The numbers tell the story as to why Turkestan cockroaches are taking over.

Distinguishing Turkestan cockroaches

The immature Turkestan roach resembles both Oriental and American nymphs in general appearance (Fig. 3).  The Oriental cockroach, however, is uniformly dark-brown and the American cockroach is uniformly reddish brown.  The Turkestan, in contrast, is reddish-brown on the head and  thorax (pro- and meso-thorax) and dark-brown only on the rear of the body.

Figure 4. American (top) and Australian cockroaches. 
Note the bold markings on pronotum and the
forewings of the Australian cockroach, in contrast
with the American, which lacks forewing markings.
Photos, M. Merchant.
Besides size (the male Turkestan cockroach is smaller), American and Australian cockroaches can be distinguished by both the wing borders and markings on the prothorax (shield behind the head)(Fig. 4).  Forewing margins of the Turkestan cockroach are pale and almost transparent compared to the uniform-colored wings of the American, and the bold yellow margins of the Australian. Click here for another image of male and female Turkestans.


Research on control methods for the Turkestan cockroach is still limited; however control methods should be similar as for the Oriental cockroach. Granular cockroach baits can be effective; however, Kim and Rust suggest that higher reproductive and growth rates for the Turkestan cockroach could mean that technicians should need more bait when treating.  Special attention should be paid to pest proofing doors and other building entry points to keep cockroaches outdoors where they pose the least trouble.


Kim, T. and M. Rust. 2013. Life history and biology of the invasive Turkestan cockroach (Dictyoptera: Blattidae). J. Econ. Entomol. 106(6): 2428-2432.

Friday, March 8, 2019

When a bed bug isn't a bed bug

Entomologists get excited over the strangest things. This morning I got my first bat bug sample ever, and I'm still all aflutter.

The pronotal fringe hairs on these common bed bugs
(see arrow) are short, no longer than the width of
the bed bug's eye. This feature is visible with a
hand-lens even through a plastic zip-loc bag, as in
this photo. Image by Mike Merchant.
Bat bugs and swallow bugs are relatives of the common bed bug, Cimex lectularius--the species you are most likely to encounter on a daily basis in the pest control business. There are approximately 100 species in the bed bug family, referred to as cimicids (sigh MISS ids).  Most are specialists on certain types of birds and bats. Generally, these bird and bat feeders have little interest in human blood, and cannot survive without their normal winged hosts.

Most of these other species of cimicid bugs look much like our common bed bug.  They will be flat, oval-shaped and reddish-brown, with adult forms about the size of an apple seed.

Current thinking among biologists is that cimicids that specialize in birds and people are spin-offs from ancestral, bat-loving bed bugs. The data suggest that the switch-over from bat feeding to human feeding may not have been that long ago in evolutionary time. It's not difficult to imagine our ancient ancestors scratching from the first hungry bat bugs checking out other food choices in dark caves.

Today, it's rare to find our common bed bug feeding on bats, though it seems this species is less choosy about hosts than most other cimicids. Cimex lectularius has been found feeding on chickens, pigeons, swallows and even pets (though its clearly preferred host seems to be humans). 

Distinguishing common bed bugs

Though bed bug identification is definitely a job for specialists, fortunately it's not difficult for any PMP to tell the difference between bat bugs and the common bed bug with a hand lens or office microscope.  It has to do with the haircut. 

Common bed bugs, our main human bed bug pest, have a fringe of short hairs on the edges of the pronotum, that "shield-like" plate behind the head (see first picture).  

The pronotal fringe hairs of bat bugs and most
bird bugs (see arrow) are longer than the eye is
wide. Image of an eastern bat bug, Cimex adjunctus,
by Mike Merchant.
Bat and swallow bug fringe hairs are longer (see lower picture). This shouldn't be hard to remember if you think of bats as being hairier than people.  Though this character won't necessarily help you tell a bat bug from a swallow bug or pigeon bug, it is a reliable way to tell one of these non-people feeders from the common bed bug.

Don't walk away

Just because your customer has bat bugs instead of bed bugs, it doesn't mean your job is done. While treating bedrooms with a conventional bed bug treatment is unnecessary (bat bugs do not aggregate around beds, nor reproduce on people), there is still pest control to be done. Bat and bird bugs are best controlled by eliminating their preferred hosts from the structure and possibly treating the roosting/nesting sites for bed bugs.

Host elimination is not as simple as closing entry points for bats or birds. Most birds and all bats are federally protected and cannot be killed, nor active nests destroyed.  Instead, they must be excluded at the end of nesting season.  If you have questions about bird and bat exclusion, it's best to check with your state wildlife department. Nesting season for protected birds and bats varies from one area to another.

Unlike common bed bugs, it's unlikely that bat bugs and the various bird bugs will exhibit high levels of insecticide resistance. Any of the pyrethroid or pyrethroid-combination insecticides for common bed bugs should provide good control of bat and bird bugs around suspected harborages and entry points into living areas.

Bat bug and swallow bugs are not that common in our business. The sample I received today was, I learned later, collected from a home in Indiana.  But if bed bugs are being found in unusual places, especially away from bedrooms, keep in mind that other bed bug species are out there. Remember that pest identification is always the starting point for good pest control. And it can be fun too; ask any entomologist.

Monday, December 17, 2018

Two chances to prepare for the ACE exam

If you've been thinking you'd like take the Associate Certified Entomologist (ACE) exam, two opportunities are coming up soon.  The IPM Experience House will be sponsoring an ACE prep class and exam on Dec. 20, 21.  And the Annual Texas A&M University Urban Pest Management Conference and Workshop will also host a class on Jan. 16, with exam on Jan. 17.

Prep classes provide a format for a condensed review of materials covered by the ACE Exam.  Topics included in the two day course include:

  • Intro to the ACE program
  • Insect biology and morphology
  • IPM
  • Toxicology, Safety and Laws
  • Wood destroying insects
  • Biting and stinging arthropods
  • Cockroaches
  • Flies
  • Occasional invaders
  • Stored product pests
  • The science of insecticides
The Dec. class will be offered over one-and-a-half days and will include some lab activities to supplement the traditional classroom review.  This class will be held at the Texas A&M AgriLife Center at Dallas campus, located in north Dallas, on Coit Road.  Class will start at 8:30 and go until 5 pm.  Microscopes will be provided to look at stored product pests and ants.  Click here if you would like to learn more or to register.  Time is running out.

Size of the prep class is limited to 30 students. Up to 4 CEU credits will be available for those providing license numbers. In addition, you have the option to purchase the highly recommended: ACE Study Guide “IPM for the Urban Professional: A Study Guide for the Associate Certified Entomologist.” Entomological Society of America -$49

Rodent mites: They're a Thing

Several years ago, a nice lady left a “bug” sample for me to identify. It consisted of an electric alarm clock in a Ziploc bag. The accompanying note read: “Help! We’re being bitten by tiny bugs that come out of this clock when it’s plugged in.”

It’s not uncommon for our office to be visited by folks who for a variety of reasons are convinced they are being attacked by invisible [often non-existent] bugs. The descriptions often range into the fantastical, but most often there are simply no bugs. I figured this sample would fall into the imaginary bug category. For that reason, the sample sat on my desk for a few days before I reluctantly examined it. The clock was ordinary enough--no insects in sight. To be fair, I figured I would humor my client and plug in the clock.

A minute later I gazed at the clock. To my surprise I saw a half dozen (what turned out to be) rodent mites exiting and entering the holes in the back of the clock. The homeowner, I later learned, had just had the home cleared of roof rats by a pest control company. Upon losing their hosts, the now-lonely rat mites had apparently discovered the next best thing to a warm rodent nest was a warm electric clock.

This experience taught me two things. Rodent mites are attracted to warm places, and I should take every sample (goofy or not) seriously.

Rodent mites are one of the most poorly known biting arthropods. Yet as rodents grab headlines from New York City and Chicago, even the media is beginning to take notice of these tiny pests. One recent New York periodical recently proclaimed: "Rat mites. They're a thing, and they're worse than bed bugs." Like bed bugs, rodent mites are active at night and can leave you with an itch. But their tiny size and painful bites make them scarier than bed bugs to many.

Still, many PMPs get caught off-guard when asked by a customer about mites; or when customers complain about mystery bites after a successful rodent control job. It pays, therefore, to know something about these tiny pests.

Not insects

This is what a  rat mite caught in a sticky trap will  look like
with a hand lens. In size they will be little larger than a period
at the end of a sentence.
Mites are arachnids, more closely akin to spiders than insects. They belong to the taxonomically-complex sub-Class Acari, which includes mites and ticks. Like all arachnids, adult mites have four pairs of legs. They mainly differ from ticks in being smaller (almost microscopic), often having long body hairs and mouth-parts without teeth.

Mites include species that feed on stored products like flour and cheese, species that are predatory, species that are parasites, plant feeders and scavengers. In all, over 250 species of mites cause problems for humans including allergies, dermatitis, serving as bridge hosts for parasites. Some species even infest skin and transmit disease. If mites are so bad, why don't we talk more about them?

The answer may have something to do with size. Mites are crazy small! Their tiny size means that they often get overlooked, and few people feel compelled to study them (yes, even scientists are sometimes drawn to larger, easier subjects of study).

Secret lives of mites 

So what do we know about the secret lives of mites? All rodent mites are ectoparasites, meaning they live externally on their hosts, not internally like a tapeworm. They reproduce quickly, usually going through their life cycle (egg to egg) in about two weeks. There are several species of rodent mites, including the tropical rat mite, Ornithonyssus bacoti, the spiny rat mite, Laelaps echidnina, and the house mouse mite, Liponyssoides sanguineus. All of these mites, if you take time to look, can be found in rodent nests or in the fur of their hosts. According to rodentologist Dr. Bobby Corrigan, one of the few people I know who literally combs dead rats for science, mites can be found on most Norway and roof rats. Less is known about the prevalence of house mouse mite on house mice.

In structures, rodent mites will usually be found in walls or attics close to their hosts’ nests. Baby rodents are likely a favored blood meal during breeding season. When they become too numerous for the nest, or when the baby and adult rodents die or leave, rodent mites will wander in search of another host. These homeless mites are most likely to bite people; but luckily, we humans make poor hosts. Our lack of fur combined with fastidious grooming (think scratching) means that rat and mouse mites don’t last long when people are the only hosts around. Even dogs and cats do not appear to be suitable hosts for rodent mites.

Case studies 

Rodent mites can also infest the cages of captive rodents, and are occasional
pests in animal rearing facilities. From Beck and Folster-Holst, 2009.
In the absence of their preferred hosts, rodent mite infestations generally go away naturally within one or two weeks. One European case study (Beck 2008) involved three children with rat mite-caused dermatitis. The children lived in the same room with a pair of mite-infested gerbils. Once the gerbils were treated (selamectin) and cages cleaned and treated (permethrin + pyriproxyfen), the dermatitis ceased within seven days.

In another case a German medical student lived above a bakery with a rat infestation. The student was bitten repeatedly at night by mites that had apparently moved upstairs through the walls from the infested bakery. One week after professional treatment with permethrin, the hundreds of mites present in the home had disappeared and dermatitis ceased (Beck 2008, Beck and Folster-Holst 2009).

In Houston, a 60-year-old woman living in a dilapidated home infested with rats went to her physician complaining of itching and red bumps scattered on her upper body and arms (Hetherington et al 1971). Rats in the house were trapped and examined and found to be infested with the mites. The rashes and bites stopped when the woman left the house but resumed when she returned. Unlike bed bugs, rodent mites are not hitchhikers and not likely to be carried from one place to another by human transport.

The well-known urban entomologist, Walter Ebeling (1960), reported successful treatment of rodent mites with fluoridated silica aerogel, a type of desiccant dust, applied to the attics and bedding of severely infested homes. He reported that bites stopped immediately after treatment.

In another case involving an old house and six medical students (Engel et al. 1998), rodent mites were found to be the cause of severe itching and red bumps. Noises in the attic suggested an active rat problem, so a professional was called. During extermination the bites became so severe that the students had to leave the house temporarily. After the rooms were sprayed repeatedly with a miticide (benzyl benzoate + tannic acid) the students returned in a few days with no more cases of dermatitis or sighting of mites. This case demonstrated how rodent mite infestations can become worse after rodents are eliminated, as the mites seek new hosts.

In all cases, the use of creams and medications without addressing the rodent problem was ineffective. Once rodents were eliminated, and appropriate miticides applied, bites stopped within a week, or immediately in some cases.

Rodent mites and mystery bugs 

Because of their small size, rodent mites can be difficult to diagnose. Many cases of supposed mite bites turn out to have a medical or psychological explanation. For this reason, inspections are important. Use your flashlight to look for tiny arthropods little larger the the period at the end of this sentence. Look on solid colored surfaces in areas where your customer is reporting bites. To see a short video of rodent mites crawling on a person's hand, click here

Sticky cards are effective mite collecting devices. Place them in suspected hot spots. If your customer claims they are getting bites everywhere in the house, or even in their car, or place of work, rodent mites may not be the problem.

If you cannot find mites during an inspection, instruct your customer how to collect a sample. A piece of Scotch tape, or a hobby paint brush moistened with a bit of gel hand sanitizer or rubbing alcohol is an easy way to pick up small arthropods like mites. Bring the sample back to the office and have it checked by a certified entomologist or Extension entomology specialist.

Wrapping up

Some key points to communicate to your rodent control customers:
  • Rodent mites may appear during or after rodent extermination. 
  • If customer thinks they have mites, ask them to collect a sample so you can confirm the problem. Mites should be large enough for most people to see--they are not invisible.
  • Rodent mites can bite us; but they do not infest people, dogs or cats. 
  • Pet rodents can become infested with rodent mites. If so, a veterinarian should treat the pet and the customer clean and (optionally) treat the pet cage. 
  • Bird and rodent mites do not hitchhike on people (though “mouser” cats may serve as temporary transport for rodent mice to people) 
  • Rodent mite bites almost never cause disease (house mouse mites may rarely carry rickettsial pox)
Rodent mites may be the smallest pest your technicians are likely to ever encounter, but their impact can be big. Anticipate problems with mites when doing rodent control, especially in offices or residential accounts. Use sticky cards and consider treating any discovered rodent nests or room perimeters with a proven insecticide like permethrin or bifenthrin. Void areas can be treated with a desiccant dust like diatomaceous earth or silica aerogel.

Rodent mite infestations are not uncommon. You owe it to your customer to take all reports of biting insects seriously, even when they are difficult to see. And if your customer hands you a clock, try plugging it in.