Bat mites and bat ticks...really?

Bat mite bites to humans are rare, most commonly occurring
when biologists handle infested bats or work in caves among
mite-infested colonies. Photo: Elaine Miller Bond

For me it's not uncommon to get questions about biting mites in homes. While some cases can be traced to actual infestations of rodent or bird mites, most do not. In cases where I cannot detect a valid pest, and the pest physical description or behavior doesn't reasonably match any known pest, I consider the case to likely be a non-pest problem.

However a recent email begged for help with some sort of biting bug in their home.  The bug could not be seen, the writer said, but two pest management companies suggested the problem could be either bird mites or "bat mites". According to the email, both companies treated the home with insecticide but (surprise!) the treatments did not solve the problem.

It being winter, and the client not mentioning anything about birds nesting in the home, bird mites did not seem likely. But the claim about bat mites caught me off guard.  Over the past few years I've had many callers ask about bird mites, but never bat mites. I wondered if there even was such a thing?  I could conceive of bats possibly overwintering in a chimney or attic of a home, so perhaps a winter infestation of mites is possible?  In searching my medical entomology and structural pest control books, the only reference to bat mites was Mallis' Handbook of Pest Control.

Mallis cites a single report of bat mite dermatitis published in a 1973 Journal of Medical Entomology. The report described an old rural home in northern California infested with bats. A baby in the home suffered from a chronic dermatitis on the face and abdomen.  Investigators found the child was being bathed on a sink where mites were visibly evident, next to a wall infested with Mexican free-tailed bats. Adults and an older child in the house were not bitten. Once the child's bathing site was changed, and bats eliminated from the home, the biting problem stopped. The mite species was Chiroptonyssus robustipes, whose sole host appears to be the Mexican free-tailed bat.  This was clearly an unusual situation, and one never since reported in the medical or pest control literature that I can discover. My medical entomology textbook notes that bat mites rarely bite humans, and when they do it is usually zoologists handling infested bats or otherwise working in caves among mite-infested bat colonies.

Bat ticks are not uncommon in homes where bats are active or
have recently left the structure after breeding. (Courtesy Iowa
State University)

Complicating things a bit, a colleague pointed out to me that ticks are also associated with bats. Ticks are related to mites, but larger and always parasitic. The bat tick, Carios kelleyi, is a soft tick (1/8-3/8 inch-long) and, according to an Iowa State University publication, is routinely found in bat-infested homes in that state. It is found throughout the U.S.

Ticks in the U.S. are classified as either hard ticks (family Ixodidae) or soft ticks (family Argasidae).  By far the most common human biting ticks are hard ticks, like the deer tick and brown dog tick. Soft ticks are less commonly encountered by humans and are mostly parasites of birds and bats.  They have a leathery, folded cuticle that resembles a crushed felt hat when seen from above. Carios kelleyi is of some medical concern as it has been reported to bite humans and is known to carry at least three types of pathogens, including Borrelia species, the causative agents of tick-borne relapsing fever.

I've never had a bat tick sent to me for identification, nor heard of a human bitten by a bat tick. My colleague Richard Pollack with Identify.us.com commented that each bat tick he has received was misidentified by a professional who "should have known better". Several were PMPs, but one was a veterinarian (who thought the tick was a tapeworm segment), and a doctor who thought "it was some kind of alien being".  I hope readers of this blog will be better equipped when one of these strange critters shows up.

According to a review by Loftis et. al (2005), documented cases of bat ticks biting humans are rare with only one verified U.S. case, in Iowa--and probably the reason that the only state with an extension publication on these ticks. The solution for a bat tick infestation is removal and exclusion of the bats, along with application of residual dusts and/or sprays in suspected roosts and points of entry into the home.

Which brings me back to my email query from the worried Texas homeowner.  Given the rarity of bat mite or tick infestations throughout the country, and even greater rarity of human bites from these arachnids, its doubtful that this case was correctly identified by the PMPs involved. Because no mite or tick could be produced, it's more likely that this was not a true pest problem, and no pesticides should have been applied.  However, when called out on cases like this, it's especially important for the PMP to eliminate all possibilities, including nest parasites (mites and ticks) of birds, rodents and other mammals, including bats.

When faced with mystery bugs in a home or office situation, keep the following in mind:

• Sticky traps can capture mites and ticks and should be used in all areas of the house where the customer believes that suspected "bites" are occurring.
• Take the possibility of mites seriously by inspecting the structure for signs of wildlife or rodent entry. Recommend closing, or using one way doors, any suspected entry points.
• If no evidence of wildlife is present, and no specimens of mites, ticks, fleas, bed bugs or other biting pests can be found, it's generally best to not apply pesticides.  Explain that your company follows IPM principles and that you try to avoid unnecessary applications of insecticides for the sake of your customers and the environment.

A professional knows how to deal with both the common scenarios, and understands something about the uncommon possibilities, like bat mites and bat ticks.

Biting mite makes a fall appearance

Gravid female (left) and two more oak leaf itch mites (top and
lower center) feeding on the (brownish) larvae of a gall-making fly,
Macrodiplosis erubescens. The balloon-like structure on the female
is the swollen abdomen full of eggs. Photo by Rick Grantham,
OK State University.

It's a wise PMP who can diagnose what's biting himself and his customers. But given that some biting pests are obscure this is no easy skill to develop.  In the latest issue of Pest Alerts from the Entomology Department at Oklahoma State University, entomologist Justin Talley reports finding evidence of a biting pest that has not been seen in Oklahoma or Texas for over ten years.

The oak leaf itch mite, Pyemotes herfsi, is cousin to the straw itch mite--a predatory mite often associated with stored grain and stored grain insects, and known to bite people who come in contact with infested grain (if you've never heard of this or straw itch mite, check out the Mallis Handbook of Pest Control). It was first reported in the U.S. from Kansas in 2004, a year when the mite was unusually abundant and resulted in thousands of biting complaints from people working and playing outdoors. That same year the mite was found in Nebraska, Missouri and here in Texas.

The mite's normal home is inside of leaf galls found on trees, and it is best known from marginal leaf curl galls caused by a midge (Macrodiplosis erubescens) on oaks. It may be equally at home in other types of galls on different trees.  The problem with this mite seems to occur mostly in late summer and fall, when mites are prone to dropping from trees.  Although the mites are principally predators on insects, if they come in contact with skin they will bite, leaving a painful, itchy welt. For more information on the mites click here for a Nebraska fact sheet.

Bites from the oak leaf itch mite are typically seen on the neck
or shoulder region of people who have been outdoors under
trees with galls.

This little mite has a history in Texas too.  In October, 2004 the Dallas area had what was believed to be a mini-outbreak of these mites, when Dallas County Health and Human Services received a number of complaints from schools concerning "bug bites" among students and staff--apparently from playgrounds.  At that time DCHHS staff and I sampled leaves from a number of school campus trees and isolated a single oak leaf itch mite, confirming at least the presence of these mites in north Texas. The rash of bite cases was assumed due to this mite by DCHHS in its December 2004 monthly report of epidemiology activity.  No remarkable incidents of these bite complaints have recurred since 2004, although a few suspect calls have been received this year.

These mites are very small (0.2 mm-long) and difficult to find.  Bites, when they occur, tend to be around necks and shoulders, implying that the mites bite when they land, and do not crawl much on the skin before biting, like ticks or chiggers.

Complaints about mystery bites are one of the most common and frustrating calls for PMPs.  But if the complaints come from a client who has been spending time outdoors, and especially under trees that are shedding their leaves, this is one critter to keep in mind.

Concrete mites

Mites are among the tiniest arthropod pests to challenge the pest management professional. Tiny relatives of ticks (Class Acarina), mites play many roles in their microscopic world.  Some are predators of insects, insect eggs or other mites. Others are plant feeders, weakening plants and spreading disease.  Some mites feed exclusively on decaying plant material.  And still others are parasites, hitching rides on spiders or beetles, feeding on birds and mammals and even humans.

Insects are hard enough to identify because of their small size. But most insects are huge compared to mites. Larger mites may reach 1-2 mm in length; most are much smaller.  Scabies mite, one of the only mite parasites to exclusively feed on humans, are among the smallest of mites (0.18-0.45 mm-long) and visible only through magnification. Most mites are less than 1 mm-long, though velvet mites (the largest of the mites) can reach lengths of 4 mm, as long as a termite worker.

Clover mites are distinguished by their long front legs. Photo
by Rayanne Lehman.

For size reasons, I'll admit that I groan a little inwardly when I receive a mite specimen to identify. Mounting mites on glass slides is not one of my strong skills, and takes extra time.  So I was pleasantly surprised this week when a promised mite sample arrived and it was actually on the big size, at least for a mite.

I was initially ready to identify my client's mite as a clover mite, one of the common springtime mite pests in Texas. The clover mite, Bryobia praetiosa, is a reddish brown mite with very long pair of front legs, about 2X the length of the other legs. Though mostly harmless, the clover mite is an occasional nuisance pest indoors when it migrates from its normal feeding sites in grass and weeds outdoors through windows and under doors.  But there was something about these mites that didn't quite fit the clover mite profile.  

Balaustium (or concrete) mite. Photograph
by Lyle J. Buss, University of Florida

The one-millimeter-long, bright red mites were being found all over decorative stone and concrete in a Tyler, Texas backyard.  The homeowner thought he was being bitten, perhaps by mutant chiggers from you-know-where. But although chigger mites are also bright red, they are tiny (.3 mm) and barely visible to the naked eye. These were not chiggers.

An online search led me to one of my favorite online resources, Bugguide.net. There I discovered a mite genus I had never heard of before.  Concrete mites, Balaustium species, were a dead ringer for the specimens I had under the microscope.  So called, because certain species in this genus are commonly found wandering on concrete sidewalks, foundations and walls, and stonework, Balaustium mites are apparently common throughout the U.S.; but I had never heard of them before.

The University of Florida Entomology Circular Series (also an excellent source of detailed information about urban insects, especially plant-feeding pests) had a 1995 publication by W. C. Welbourn on Balaustium mites in Florida. According to the circular, at least one species of Balaustium is "commonly found in urban areas where they appear in large numbers on sidewalks and walls for a brief period during the spring and early summer. It is during this time that they sometimes enter homes and buildings and become pests."  

One of, if not the only, food source of these urban mites appears to be pollen. Balaustium mites have been found clustered in large numbers on anthers of flowers.  And based on the numbers of times I've had to wash my car and BBQ grill of oak pollen in the past month, I'm imaging that these mites have been having a good time of it lately.  This would also explain why the mites can be found on nearly any outdoor surface, including sidewalks and roofs--because pollen is everywhere.

Some species of Balaustium are predators on other insects, others feed on plants.  I was surprised, however, to read that there may be some association between our otherwise peaceful, pollen feeding, house-invading concrete mites and bites on people.  An entomologist named Irwin Newell in 1963 reported four cases of human "biting" involving Balaustium, three of which were associated with structures. The evidence for the bites was very strong, including a sample submitted by entomologist who was bitten on the arm while working in an entomology museum (how dare they!). 

The curious thing about the story is that while Dr. Newell stumbled across several cases in a relatively short period of time, prompting him to predict this mite was a growing problem, it's been crickets (silence) since then.  None of the major texts or reference books I scanned have even a mention of this family of mites, in spite of being common in the landscape. Even Ed Riley, Texas A&M University's crack assistant museum curator, was not familiar with these mites--though he admits, like me, to not paying too close attention to red mites he sees outdoors.  

Newell admits in his paper that he had no idea what species of Balaustium he was dealing with in his biting cases. And I don't believe anyone know what species are common in Texas. But I will be more interested and paying closer attention the next time I see my brick mailbox covered with red mites. 

[Request: I have little doubt that some of you get questions from customers about little red mites crawling on the sides of homes and sidewalks this time of year.  I would be interested to know if you or anyone you meet believes they have experienced bites from these little critters.] 

Rats in the news

Norway rats scavenge left-over people food
in a New York city park. Photo by Mailman
School of Public Health, Columbia University.

Perhaps appropriate for the Halloween season, rats and rat mites have been in the news recently. It was reported last week that a study conducted on New York City rats found that rats carry even more diseases than we previously thought.  Scientists at the Center for Infection and Immunity at Columbia University’s Mailman School of Public Health identified several bacterial pathogens, including an E. coli, Salmonella, and Clostridium difficile, that cause mild to life-threatening gastroenteritis in people; Bartonella bacteria; and Seoul hantavirus, which causes Ebola-like hemorrhagic fever and kidney failure in humans. The study highlights the prevalence of these diseases in wild urban rodent populations, and the real risk of acute stomach and febrile illnesses carried to people from rodents.

The authors state that the study shows a need for improved pathogen surveillance and disease monitoring in urban environments.  I would add that these results also show the importance of rodent control to human health, as well as the need for pest management professionals to take precautions when handling dead rodents.

Along with the NYC rat report, came coverage last week of rat mites.  One reporter called them a worse scourge than bed bugs... something I disagree with, but a story that is sure to resonate with some of your customers with suspected mite problems.

Rat mites are tiny parasites that principally attack rodents.  The primary homes of rat mites are in the nests of rats and mice; but when the rodents are trapped or exterminated, the resident mite population may abandon the nest in search of other hosts.  Though rat mites cannot live on human blood, they will bite people, often leaving a red mark and blister.

The reason I don't consider rat mites to be as troublesome a pest as bed bugs is that rodent control will ultimately eliminate a rat mite problem--though mite control in a structure may still be needed to clean up residual mites that can linger in a home for several months.

The other, more scholarly story in the news this week is a study that appears to show a connection between rat mites and Bartonella infections in two dogs and a human.  In a study reported by researchers from North Carolina State University, several raccoons were trapped and removed from a New York home.  After removal, the house living area became infested with rat mites, Ornithonyssus bacoti, many of which were removed from the animals and some of which were collected by the homeowner.  Both the dogs and the homeowner subsequently became ill, and blood tests revealed the presence of Bartonella henselea, a bacterial pathogen best known for causing "cat scratch disease".

Bartonella is known to be transmitted from cats and dogs via fleas and ticks, but this was the first time rat mites have been implicated in transmission (It's important to note that the researchers couldn't conclusively prove that the mites transmitted the disease, as ticks were also found on one dog. Also they did not rule out the presence of rodents or fleas in the home, but the timing and series of the events, along with the large number of mites and visible bites on both dogs and the person in the house provide good circumstantial evidence of the mite's role).

I gleaned a couple of points from this paper.  First, although the paper did not in my mind conclusively prove the raccoon as host and source of the mites, the close association of the raccoon removal and mite infestation seem to suggest that rat mites could infest raccoons. Raccoons are a relatively common wildlife invader of homes in Texas and throughout the U.S., and these results potentially impact many pest control jobs.  Second, I was unaware of the potential disease problem associated with rat mites.  The potential for rat mites to transmit disease appears to be low, or else there would be many more instances in the literature; nevertheless, this paper is something we in the pest control industry should be aware of--not only for our customers, but also when treating for rodent or bird mites. If a technician is going into a situation with lots of biting mites, it would be prudent to provide protective gear, including gloves and protective overalls sealed at ankles and wrists.

Lastly, I was reminded that when a real rodent mite problem exists, it is normally not too difficult to collect mites.  In this case the homeowner had no problem seeing and collecting mites for the pest control company and researchers.  This is not the case with many submitters of "mites" to my office. This year I've received dozens of samples of suspected mites from people who are convinced they are being attacked by mites. In most of these cases the sample submitters have been unable to provide an actual mite specimen. This is often a case of a misinformed customer who has been led astray by poor information on the Internet, or from poorly informed friends. For customers who will not take a diagnosis of no mites, regardless of repeated efforts to get samples, the situation may be one of delusions.

Once again the importance of pest control is supported by scientific research. It's important for you and your employees to remember every day that the service your pest control company provides is important. Rodents simply cannot be tolerated in homes, schools, food plants, businesses or multifamily apartments.  And it's not just a matter of aesthetics. Even when rodents are present but out of sight, remember that many rodent diseases are transmitted by airborne dust from rodent urine and droppings.  It's critical that we are protected not just from seeing rodents, but from being exposed in any form to rodents in our buildings.

If we're talking scary, forget the zombie costumes or Ebola scare stories this Halloween.  A much more real risk is that of unwanted contact with rodents and their mites and diseases.

Brits have mystery bugs too

Mites, like this rodent mite, are often blamed for mysterious
"bites" by sufferers of delusions of parasitosis.  But real mites
are rarely found in such cases.

A British weekly cultural and current affairs magazine, The New Statesman, yesterday published an article by a physician, Phil Whitaker, on his encounter with a delusional parasitosis patient.  I found it interesting because the description of how he handled a sufferer of delusions of parasitosis, a not-uncommon condition encountered by PMPs here "across the water" in the U.S.

Delusions of parasitosis is a mental illness in which the sufferer complains of non-existent insects or mites crawling on their skin, biting, or burrowing into their bodies.  In the past a clinical symptom of the condition was frequently referred to as "the matchbox sign". This came from the observation that sufferers often carried to the pest control professional, or physician, a small matchbox supposedly containing samples of a parasitic insect that was making life miserable.  Today, it's more likely to be a ziploc bag or plastic pill jar, or pieces of tape on a sheet of paper carrying the mystery samples.

The only point in his article on which I would disagree with Dr. Whitaker is the frequency, at least here in the States, of delusional parasitosis. He calls it rare. Based on stories I hear from likely delusional patients, I don't think it is. If I can believe half of the stories, doctors--at least here in the big city, Dallas--seem to be pretty aware, and a little gun shy, of anyone coming into their office complaining of "invisible bugs".  From my perspective it seems like the medical community could better help these patients by being better informed of the illness and of the available treatments.  This is a serious and highly disruptive mental illness, and one that often leaves pest management professionals confused and frustrated.

Our role in the pest management field is, of course, to take all complaints of biting pests seriously.  After all, our expertise is, or should be, to be very familiar with all biting pests likely to be in a home. Bird and rodent mite calls seem to be more common this year than ever before, a situation I blame on some very bad information being promoted on the Internet.  To learn more about biting mites, what they can and can't do, check out my biting mites in homes fact sheet.  And for a more general publication to share with customers who complain of mystery bugs, click here.