The research is out and worth a close reading, not only because it is the anticipated report on the effectiveness of old dry residues of chlorfenapyr against bed bugs, a subject that sets off our collective anxieties about using pesticides preventatively, but it’s the first study of chlorfenapyr’s effectiveness against pyrethroid-resistant bed bugs.

Romero, Alvaro, Michael F Potter, and Kenneth F Haynes. 2010. Evaluation of chlorfenapyr for control of the bed bug, Cimex lectularius L. Pest Management Science. doi:10.1002/ps.2002

Chlorfenapyr is what is called a pro-insecticide in that it does not become active (toxic) until it is metabolized by the bed bug itself after absorption. It belongs to a class of pesticides called pyrroles.

It works on bed bugs as follows:

The active metabolite of chlorfenapyr (AC 303,268) inhibits the ion transport system of the respiratory chain in mitochondria, preventing the production of the energy molecule adenosine triphosphate (ATP), so leading to insect death.

Yes, but let’s not be deterred.

Cell energy being the operative concept, if one wanted a handy simplification (and one does!), it seems to me they get tired and then they die:

Typical symptoms of chlorfenapyr intoxication in bed bugs include sluggish movements, prostration and limited responses upon contact stimulus (Romero A, personal observation). Such symptoms may be less apparent in commercial practice, and users should understand that bed bugs treated with chlorfenapyr succumb more slowly compared with some other insecticides.

Thank you for that image, Dr. Romero.

This is unlike the nerve-acting pyrethroids which make bed bugs hyperactive.¹ Here let’s note for those who are just joining us that pyrethroid resistance is depressingly widespread (also see) and so much at the center of our troubles.

On this note, the authors raise our interest a bit:

It has been suggested that resistant arthropod populations with enhanced monooxygenase activity might have increased sensitivity to chlorfenapyr (a case of a phenomenon known as negative resistance), because pyrethroid resistance can be caused by detoxification by the same enzymes (P450 monooxygenases) that activate the pro-insecticide chlorfenapyr.

Only to pour cold water a sentence later:

In the present study, the similar rate of mortality caused by chlorfenapyr to all strains, regardless of their pyrethroid susceptibility status, suggests that the presence of pyrethroid resistance in bed bugs might not limit (or enhance) the effectiveness of chlorfenapyr.

If only pyrethroid resistance were good for something. But they found no evidence of this negative resistance (because it would be too cool for words and we should know by now such gifts are not allowed us in this great contest with our enemy).

Let’s get back to insect death, by all means.

Comparison of two chlorfenapyr formulations

Phantom is formulated chlorfenapyr and there is an aerosol and a liquid concentrate:²

Toxicity of chlorfenapyr formulations (Phantom aerosol and Phantom SC), Romero et al. (2010), Pest Management Science

Yes, the obnoxious CIN-1 strain.

It’s very interesting that the aerosol is faster as a dry residue as well.

Directly sprayed bed bugs (aerosol formulation)

Direct sprays with the aerosol caused 30% mortality to both pyrethroid-resistant strains within 4 h (data not shown) and about 50% mortality in 24 h. In contrast, direct sprays of the water-based formulation took at least 3 days (WOR-1) or 5 days (CIN-1) to cause 50% mortality. Direct sprays of the blank aerosol (formulation without chlorfenapyr) killed 25% of individuals within 4 h, which indicates that some formulation ingredients also have some contact activity. Insecticides that kill bed bugs upon contact are widely used by pest control companies because they can quickly suppress populations and provide some relief to their customers.

And:

Bed bugs from strains CIN-1 and WOR-1 showed no avoidance of surfaces treated with the chlorfenapyr aerosol.

No avoidance “presumably lessens the potential spread of bed bugs to adjoining areas.”

Dry residues (of liquid formulation)

The LT₅₀ of (time necessary to kill 50% of individuals) for CIN-1 bed bugs exposed to a 4-month-old dry residue deposit of Phantom (liquid formulation) was 4.6 days (and it was 4.8 days for fresh deposits), which means that the 4-month-old dry residue was just as toxic as a fresh deposit. The LT₉₀ was 8.8 days.

In other words, chlorfenapyr is that rare thing, an effective (if slower) residual pesticide against bed bugs. What challenges are tied to its slow action (continued feeding and egg-laying?) have to be set against, well, that it works.

The authors note the potential preventive value of these findings:

The ability of chlorfenapyr to remain effective over an extended period of time is encouraging because bed bugs that are not sprayed directly may still succumb after residing on treated surfaces. Most insecticides available today have limited potency as a dry deposit against pyrethroid-resistant bed bugs. Dry residual action of chlorfenapyr might also aid in preventing new infestations if likely areas of infestation are previously treated.

…but recommend further study of chlorfenapyr’s residual effectiveness on various surfaces³ and the “suitability of prophylactic applications” — which I’m afraid leaves us where we were, with the manufacturer recommending just such a course (PDF) and prudent people urging caution.

More research please.⁴

_____________________

This was almost the last planned post here but there will be one more. Thanks for reading. I keep a bed bug-related reading list you are welcome to follow if you are interested. Best wishes.

1. This (PDF, University of Maryland) is very useful to understand modes of action.
2. Labels and MSDS sheets here.
3. In my limited experience I can recall one article, Fletcher & Axtell 1993 (PDF), that examines the variability of performance of bed bug pesticides on different surfaces — we discussed it briefly here. One PMP I’ve talked to dismissed the need for this kind of study. Puzzling.
4. Interestingly, The Columbus Dispatch reported yesterday that researchers were conducting a four-house field trial of Phantom and Alpine dust in central Ohio.

Related posts:

1. More tales of CIN-1: PBO and deltamethrin
2. Finally, researchers on the efficacy of dusts
3. DE vs chlorfenapyr
4. kdr pyrethroid resistance widespread in U.S. bed bug populations
5. An interview with bed bug researcher Alvaro Romero

But two years earlier Girault had published a major article about bed bugs followed by an extensive critical bibliography, likely the entire literature of bed bugs until that time, which unfortunately I haven’t found, though surely much of it is in Usinger… but I wonder if only the useful bits and not the outlandish stuff that one really wants to find. In any case, Girault wrote several articles on the bed bug. We have time for only one.

There is this remarkable passage you should see about his “very unpleasant experiences” during a summer spent in “a small town in Virginia” (Girault studied at Virginia Polytechnic):

The whole place was thoroughly infested, and it was not an uncommon thing to see mattresses and bed-slats turned out to air, which were literally white with the insect’s eggs. The writer’s room was as bad as the rest; the old-fashioned bedstead was full of them, while during the day scores of them could be detected hiding in the walls. The place was almost unbearable, for the insects were not satisfied in staying indoors, but were frequently found secreted in one’s clothes. One night, returning to the room from outside, two were found beneath the collar, while occasionally, one would be found hiding within a pamphlet which was carried in my pocket. Wherever they were very numerous, many could be found frequenting privy-houses or other similar places, where they would be sure to obtain an occasional meal, visiting the host at every chance, night or day. That these insects are very active and freely move from place to place, that is to say, not necessarily confining themselves to certain rooms or houses, and hence not directly dependent upon any one host, is evidently true.

Remarkable, yes? Reminds me of WCW’s hat.

As if that were not vivid enough, Girault continues with this account of a colleague’s bed bug experience in an entomology lab:

Mr. William F. Fiske informed me that when stationed at Tryon, North Carolina, while working in the laboratory at night, bedbugs would crawl along the under sides of the edges of the table and stealthily approaching his bared arms, would attempt to feed.

Girault, A. A. 1905. The Bedbug, Clinocoris (=Cimex=Acanthia=Klinophilos) Lectularia Linnaeus. Psyche 12: 61-74. doi:10.1155/1905/10393

(What’s with Clinocoris… Acanthia? They couldn’t figure out what to call the bed bug at one time? Pity they didn’t ask us.)

I think Girault was having a bit of fun with the following, which he cited from an 1885 source, Lintner:

A correspondent wrote as follows: “ ‘Will you tell us something about the bed-bug, what its habits are, when it “spawns,” what it eats, how long it lives, and if it ever dies? I ask because I have moved into a house that I find was already occupied by several colonies of the pest. The room in which I have my library has the most. They are in my files of papers and periodicals. They seem to grow fatter every day, but for the life of me, I cannot tell what they live on. *******. Can it be that they live on the paste on the wall paper? As for remedies, ******. The latter (red pepper), I have sifted through my papers and books, and wherever I could get it; but instead of driving them off, they seem to fatten on it; ***************.****’ ” pp. 6-7.

And we may laugh at it too, for it is fantastic. What it eats!

Girault called bed bugs abominable. Actually, odious and abominable:

The trouble then is, that definitely stated facts are wanting concerning much of the life-history of this pest. This has doubtless been caused, partly on account of its being so common everywhere, and having an extensive literature, thus causing modern writers to believe it at first glance to be well studied, and partly because of its odious character and abominable nature. The last cause seems to have the most to do with it.

And:

It is the insect most directly affecting man, and the one, if any, which should be thoroughly studied, and yet, not until as late as 1896 (Marlatt, 1896 a) was its true life-history made known.

This is not scientific literature without personality. Girault could say of the body of a first instar that had just fed that it “became stained a very beautiful, deep, purplish red.” Nymphs are described as “sordid yellow.”

Like many, he fed bed bugs himself; except for 5th instars which caused “a distinct itching sensation,” he was not responsive to the bites. These are some of his notes on feeding bed bugs:

A single nymph or larva hatching during the morning of June 24th and isolated in a small glass vial, was fed at once. It was very active after hatching, and at first made attempts to escape, though in a few minutes readily took food. Just as soon as the least bit of blood entered the body it could be traced to its destination, and as more was sucked in, the body became stained a very beautiful, deep, purplish red. The abdomen, at first flt and round in outline, soon became distended, lengthened, and cylindric, and the nymph then measured 2.00 mm.a

On the afternoon of the next day (25th), the nymph was again fed, and the abdomen was much darker, not stained as previously. Again on the morning of July 6th, it was fed. It had not changed. On the morning of July 6th, it fed long and eagerly, until the abdomen became so large and distended that it was all out of proportion to the rest of the body; it was then stained purplish red, as after the first meal. The insect after this gluttonous meal did not lose its usual activity. The first molt then occurred about 7 P. M., 7th July. It had thus fed four (4) times during the first instar.

And his findings on feeding times for each instar:

The nymphs are very voracious, and at a single meal gorge themselves until unable to hold more. The time therefore given to each meal is limited by the capacity or size of the nymph at the time of any one meal, the capacity of course depending upon, or rather being more or less bounded by, the different instars. Hence, in each instar, the time taken for any single meal is more or less definite, shorter in the earlier, longer in the later instars, as the capacity is less in the earlier, greater in the later instars.

For its first meal after hatching, in instar I, it requires on the average, about three (3) minutes to glut itself, and if another meal is taken in this instar, a slightly longer period. In instar II, five (5) minutes; in instar III, six (6) minutes; in instar IV, eight (8) minutes; in instar V, ten (10) minutes, and when adult, from ten (10) to fifteen (15) minutes. These may be taken as averages, as the time for individuals varies somewhat.

He found that adults were unable to re-feed for at least 48 hours.

This is his table detailing the lifespan and the number of eggs deposited for two females, one fed and the other unfed:

oviposition and lifespan of fed and unfed female bed bugs - Girault 1905

I think of Girault sometimes. He pops into my head. I’m glad he was in the world. And wrote about bed bugs.

Related posts:

1. Girault and the bed bugs
2. Johnson’s hut, part 1.75
3. “They are also able to withstand chilling, thawing, rechilling and again thawing”
4. “The most useful application of the bed bug alarm pheromone may be to cause dispersal.”
5. Laundry and the motivating power of the bed bug web: Q&A with Richard Naylor

This is unprecedented stuff, so let’s take a very close look.

474 respondents, all with confirmed bed bug infestations, in Chicago, New York, Cincinnati, Louisville, Atlanta, LA and Miami. 66% living in apartments and 15% in single-family homes. All ages. 58% female, 42% male.

The breakdown for infestation level:

“Have you experienced any bites or skin reactions from the bed bugs in your dwelling?”

70% yes, 30% no.

Essentially the reverse of what was previously thought. Though there were also skeptics—see this note about last year’s article by Reinhardt and others.

The female/male differences were not statistically significant. And neither were ethnicity differences. The level of infestation was also not a factor.

Not so with age, however:

Significantly more people over the age of 65 reported no bites or skin reactions than those who were younger. Forty-two percent of the eldest individuals surveyed said they had no bites or reactions from bed bugs in their dwelling, whereas 26 percent of those aged 11 to 65 reportedly did not react.

This corresponds with an earlier survey where 76% of elderly tenants in one “severely infested” building did not react to bites (or reported not reacting). Possible reasons for this mentioned by the authors include reduced responsiveness to allergens in the elderly, medications that suppress the immune response (corticosteroids), and “diminished awareness due to other competing health issues.” For another discussion of a similar case, see the ASHES/Orkin white paper (PDF) from last year.

I think everyone is rightly worried about the elderly. Their infestations may go unreported, grow undetected, and then may be treated incorrectly.

Relationship to mosquito bites

The bed bug bite response reported in this survey corresponded with the level of mosquito bite response in the following way:

• “Barely visible” mosquito bite reactions = 53% reacted to bed bugs
• “Small (dime-size) welts” from mosquito bites = 77% reacted to bed bugs
• “Large (quarter-size)” / “severe (half-dollar size or larger)” mosquito bite reactions = 89% reacted to bed bugs

Characterizing the reactions of the 70%

• 72% had “itchy red welts”
• 50% had “redness or discoloration”
• 28% had “itching in the absence of welts”
• 21% had “a ‘pinprick’ or ‘stinging’ sensation”

Okay, let me pause here. On this last point the authors say: “which may or may not be symptomatic of bed bugs.”

Personally I have to say I can’t count the times people have reported this. Bed bugs!

There’s a lot more about the reported reactions.

The public health question, etc.

This is remarkable:

Other oft-mentioned symptoms from respondents living with bed bugs included nervousness, paranoia, anger, frustration, embarrassment, devastation and depression. Anxiety, stress, sleeplessness and depression are medically important symptoms that can lead to other conditions. Dismissing bed bugs as “not a public health pest” on the grounds that they are unproven disease vectors ignores the pain, suffering and emotional distress inflicted on their victims. When government agencies finally concede this point, additional resources may be allocated to combat the problem, as they were years ago.

I may have to put that on a post-it.

I hope they’re right.

Related posts:

1. New guidance for bed bugs in health care facilities
2. New study of bed bug bites suggests most people do react
3. New case report of severe anemia in a patient with an advanced infestation
4. Australian medical entomologists on what GPs should know
5. Bite sensitivity, ciao Johnson, post-feeding behavior, signals and more: ESA meeting abstracts

Naylor, R. A., and C. J. Boase. 2010. Practical Solutions for Treating Laundry Infested With Cimex lectularius (Hemiptera: Cimicidae). Journal of Economic Entomology 103 (February): 136-139. doi:10.1603/EC09288.

In keeping with our recent interest in the first line of these research abstracts, here is this one:

The common bed bug, Cimex lectularius (L.) (Hemiptera: Cimicidae) is known to become associated, from time to time, with clothing or linen.

From time to time…

The author surveyed 100 websites offering information on bed bug control in 2007, and found specific, practical information lacking.

Washing

3.2 kg dry weight of laundry, about 7 pounds, washed at 30°C/86°F, 40°C/104°F and 60°C/140°F in a 90-minute cycle wash (that’s the standard cycle in the UK) with a standard laundry detergent. Bed bugs (10 adults, 10 third instar nymphs, 10 eggs) were placed inside clothes pockets, in cotton pouches and sealed with a sandwich bag clip.

The 40°C/104°F cycle killed all adults and nymphs, but 75.6% of the eggs survived.

The 60°C/140°F cycle killed all stages.

Tumble drying

7 pounds of laundry (dry) in dryers set to “hot” and “cool” for 10 minutes and 30 minutes.

The temperature in the “cool” cycle never got above 30°C/86°F.

The 10-minute “hot” cycle did not kill all bed bugs, probably because it took more than 15 minutes to get above 40°C/104°F. (The authors reference the published thermal death point from previous work in the 1930s-40s in the range of 40-45°C/104-113°F.)

30 minutes in the “hot” cycle killed all life stages.

Here is a graph of the temperature logged during these drying cycles. The 40-45°C zone is the (previously published) dead zone, but it took more than 15 minutes.

temperature change over time, hot (A) and cool (B) drying cycles - Naylor & Boase 2010

Cold soaking

7 pounds of laundry in about 15°C/59°F tap water, without detergent.

Almost nothing dies if soaked for two hours. But, interestingly, all adults and nymphs died when soaked for 24 hours.

The eggs, however, survived. All of them.

Dry-cleaning

Professional dry cleaning with perchloroethylene.

100% kill of bed bugs and eggs.

Freezing

A laundry bag of 2.5 kg (about 5 and a half pounds) in a freezer drawer of a standard household freezer with a minimum temperature of -18°C/-0.4°F — a separate test was done with bed bugs placed in pouches in the freezer for two hours at -17°C/1.4°F.

2 hours at -17°C/1.4°F killed all bed bugs and eggs when placed directly (not in clothes) in the freezer. But when a bag of laundry was placed in the freezer, it took about 8 hours for the temperature at the center of the bag to reach -17°C.

The researchers advise caution about the regional differences in laundry equipment:

[T]here are regional differences in the operation and performance of domestic appliances that stress the importance of understanding the local situation when making recommendations. For example, washing machines in Europe typically heat their water to the user-selected temperature, whereas washing machines in the U.S. and Australia tend to use the household hot water supply and are therefore limited by the temperature of the water coming from the boiler. Furthermore, wash cycles in the U.K. typically last 90-120 min, whereas in the U.S., wash cycles of 20-30 min are much more common (Procter 2000). As Tables 1 and 2 demonstrate, differences in temperature and duration may make the difference between success and failure in terms of clothing disinfestation. These differences emphasize the need for caution when considering adopting advice generated in one country, for use in another.

For comparison of these results with some American laundering tests reported by Potter et al. in 2007, see this PCT article.

Q&A

Richard Naylor is a doctoral student at the University of Sheffield (UK). Take a look at his bed bug photographs here. I particularly like this one:

Bedbug. Copyright Richard Naylor.

He generously answered our questions via email.

New York vs Bed Bugs: Your group regularly produces some of the most fantastically interesting research about bed bugs and yet I have to say it is a joy to ask you about something as simple as laundry. Because in fact it is not so simple… so it is wonderful that you took an interest in this subject. I like that your study shows that people have options (e.g., you can disinfest clothing even if you don’t have access to a dryer), but you note that regional differences in laundry equipment are important to consider. So, with that in mind, if we were to make judgments based on temperature and time (in places where one doesn’t really know the temperature of washers and dryers but can use, say, a household thermometer for some limited testing), what would be a useful rule of thumb? Often people are confused by thermal death points, especially because they seem not to be stable in the literature and have much to do with method and duration of exposure.

Richard Naylor: The important thing does seem to be the temperature, whether washing or drying. 40 degrees [Celsius] seems to be the magic number. In simple terms this is about the temperature of a nice warm bath, so it doesn’t need to be scolding hot. Some washing machines don’t heat their own water and so the maximum temperature they can achieve is the temperature that the boiler is set to. If your hot tap produces water that is slightly too hot to hold your hands under for any length of time, it is probably fine for killing bedbugs. Unfortunately one can’t get round having to know something about their washing machine if they plan to use it for treating bugs. Perhaps it would be simpler to fill the bath with hot water. As long as it is a bit too hot to hold your hands in it should be fine. Hot water penetrates the fabric much quicker than hot air, so time isn’t really a factor as long as all the air is pummeled out of it.

New York vs Bed Bugs: Did you really read 100 bed bug fact sheets on the internet? I am honestly impressed by that diligence because that sounds like torture to me. Did you find great variability in the practical information on offer?

Richard Naylor: Yes I did. A lot of the sites offering advice were run by local councils. The advice wasn’t particularly variable because people just republish the same “knowledge” over and over again. I just kept a tally of every mention of “hot wash”, “tumble-dry” etc. and worked my way down a google search. Every now and then you stumble over a blinder, involving a bloody steak and a roll of sellotape, which keeps the motivation up! I keep a folder on my computer of all the best bedbug misinformation I can find on the web!

New York vs Bed Bugs: Can I ask you what you are working on? What are some of the interesting questions in need of answering?

Richard Naylor: I am currently interested in their ecology and dispersal. We actually know a lot more about the ecology of swallow bugs than we do of bedbugs, simply because when an infestation is discovered, it is normally treated straight away. People don’t want to wait a few weeks for studies to be made and experiments carried out. The solution I have come up with is to build about a dozen 3 meter long arenas complete with blood feeding station and around 200 bedbugs in each. I am trying to understand how they behave in an infestation and to figure out what factors are important in driving their dispersal.

New York vs Bed Bugs: I once saw what looked like a carved wood panel of mating bed bugs at your university’s website (can’t seem to find it again)—I am curious about just how old that is? Is it an artifact of the current interest in bed bugs or is it from much earlier? It is beautiful and I wonder if you’ve always had it.

Richard Naylor: Well spotted. We (though not me) started studying bedbugs at Sheffield University about 15 years ago. Mike [Siva-Jothy] used to be particularly interested in sexual conflict, which is the idea that males and females of a species are purely out to do the best for themselves as they can, often at the expense of the opposite sex. Bedbugs are a prime example, as males will mate with females much more often than the females require to stay fertile and as a result the females live about 25% less long than they would otherwise. We believe that traumatic insemination arose out of sexual conflict as a way of males preventing females from exerting choice over paternity.

Anyway, the carving was commissioned about 6-7 years ago and is made up of lots of images from old books and photographs around the department. The bedbugs are copied from an electron micrograph that we had done of some of our bugs at the time.

Related posts:

1. A tendency to synchronize feeding
2. Active dispersal, baby
3. Greater London bed bug infestation study
4. “We have formed a tenants committee”
5. Behavior of bed bugs in response to heat

The authors developed a method, with potential forensic applicability, to determine the time from the last bloodmeal based on measurements of the abdomen — actually a ratio of the abdomen size and width of the thorax, its average decrease over several hours with the process of digestion, at different temperatures:

The overall procedure for our method was as follows. Firstly, we quantified the decline in abdomen size of fully fed animals at different temperatures. Secondly, we tested whether the propensity to feed is temperature-dependent and, thirdly, we measured the shrinkage of the bugs’ bodies in the most commonly used preservation media, 60% and 96% ethanol. In a case study, we then applied this method to measure the digestion status of bedbugs in a naturally infested room and to calculate an average feeding rate for bedbugs in that room.

As for the room in question, I am grateful for the reserve of these researchers who describe the room simply like this:

Samples of bedbugs were collected from 21 harbourages in a heavily infested dwelling in London (Figs 1 and 2) in June 2007. The temperature in the infested room was maintained by a thermostat at a constant 26° C throughout night and day. The only tenant of this apartment was an elderly man who kept most of his newspapers, books and other belongings in stacked piles throughout his home (Fig. 2). Harbourages were mainly found in the stacks of newspapers, which were at most separated by a few centimetres (Figs 1 and 2).

Yes, there is a graphic photograph in the article, but what you really want to see is this drawing:

schematic drawing of an infested room - Reinhardt, Isaac, Naylor 2010

From this room, from all those harborages in newspaper stacks, they collected “a small proportion” of the total bed bug population. 3,750 bed bugs. (So this is how lab colonies are built…) Some were kept alive and some were preserved in ethanol, hence the need to figure out how much bed bugs shrink in ethanol.

The average time from the last bloodmeal for female bed bugs in this room was 2.5 days (at a temperature of 26dC/78.8dF), which is at the low end of a 2-4 day feeding interval estimate for this temperature. In lab conditions, the authors say that feeding rate increases as the temperature increases (1-3 days at 32dC/89.6dF vs 5-9 days at 18dC/64.4dF).

(Mellanby previously estimated that adults fed every 5-6 days at temperatures between 20-27dC/68-80.6dF. And by the way he had to paint individual bed bugs and recapture them on their feeding excursions… his “natural” infestation was in rat cages.)

One wonders if it’s not just temperature and if feeding intervals would be different in a lower-density infestation.

You might remember, Pfiester et al. observed that the percentage of female bed bugs grouped together rises with population density, especially in female-biased aggregations. Well, the sex-ratio in all those paper stacks in this study was definitely female-biased, 65.8% of adults collected.

The graphs in the drawing above show the mean number of days since the last bloodmeal for each harborage location they represent (these are female bed bugs in harborages that contained more than 10 adult females). Notice the difference between harborages immediately next to each other on the bed? The authors don’t know what accounts for this but, as ever, it may have to do with mating:

These differences between harbourages cannot be attributed to temperature differences because they were found in the same confined room. They are also unlikely to be caused by the switch of sleeping sites (between sofa and bed) of the inhabitant of the apartment because harbourages that were next to each other differed in feeding stage distribution (Fig. 1, Table 3). There is a possibility, however, that the tendency towards synchronous feeding may be related to the mating biology of bedbugs. Mating and feeding are closely linked in bedbugs because fed females cannot avoid mating (Reinhardt et al., 2009b). Males control the mating rate of females and frequent mating reduces female lifespan and egg production (Stutt & Siva-Jothy, 2001). As females cannot reduce feeding without ceasing reproduction, Reinhardt et al. (2009b) speculated that females might lower male attention by engaging in synchronized feeding.

Fascinating.

But all I can think about is that poor man, futilely alternating between the bed and the sofa, trying to find relief.

Related posts:

1. Compensation
2. Johnson’s hut, part 1.5
3. Caught in a situation trap
4. The wandering females
5. Girault, cont’d

Wang, C., K. Saltzmann, E. Chin, G. W. Bennett, T. Gibb. 2010. Characteristics of Cimex lectularius (Hemiptera: Cimicidae), Infestation and Dispersal in a High-Rise Apartment Building. Journal of Economic Entomology 103(1):172-177 DOI: 10.1603/EC09230

First let me get this out of the way. Check out this first sentence from the abstract:

Bed bugs, Cimex lectularius L. (Hemiptera: Cimicidae), are a fast-growing urban pest of significant public health importance in the United States and many other countries.

Significant public health importance. I think of this phrase every day. May it one day mean what it says, yes?

Dr. Wang and colleagues studied a bed bug infestation in a 233-unit building for low-income elderly and disabled tenants in Indianapolis. The infestation is believed to have started with one tenant moving in, but it had already spread to more than 10 apartments by the time building management learned about it. Bed bugs spread in this building between 2006-2008 and a variety of treatments were tried, including educational efforts and treatments by the researchers themselves in 24 apartments from 2007-2008.

From December 2008 to April 2009 the researchers conducted inspections of apartments with reported infestations and interviewed the tenants. Bed bugs were counted and removed and Climbup Interceptors were installed. Adjacent apartments were then inspected and, not surprisingly, there were a number of apartments that could not be inspected.  Apartments across the hall were also inspected:

After an apartment was identified as having bed bugs, the two adjoining units and the two units immediately across the hallway from the infested unit were also inspected. If no bed bugs were found, the apartments were inspected again 1-3 mo later to confirm the absence of bed bugs. Residents from ≈ 15% of the apartments declined the inspection services, citing their belief that bed bugs were not present.

Across the hall dispersal

The researchers found a way to test their across-the-hall dispersal hypothesis by placing two interceptors baited with a chemical lure outside five infested apartments. The article addresses the question of using lures in these traps thus:

Although chemical lures were used in the interceptors to detect bed bug dispersal, a separate study in nine apartments indicated that the presence of lures did not significantly increase the number of trapped bed bugs (our unpublished data). Thus, we considered the counts from interceptors placed at entry doors or in the hallways to be random catches of bed bugs that were passing through those areas.

bed bug interceptors outside apartment door - Wang et al. (2010)

In any case, management objected to the traps in the hallways and so they were removed after 7 days. They were then placed behind the front doors of eight infested apartments:

Three of the five pairs of interceptors placed in the hallways trapped two bed bugs per pair after 1 wk, supporting our hypothesis that bed bugs used hallways as a route for dispersal. The mean visual counts from these five apartments before placing the interceptors were 196.4 ± 58.7 per apartment. The average number of bed bugs detected at entry doors over 4 wk period was 6 ± 2 (n = 8 ) and the maximum was 42. Among the 138 bed bugs examined that were caught at entry doors (dispersing), 30% were nymphs, including first instars. Some of the first instars were from eggs laid by trapped adult females as evidenced by the presence of empty eggs in interceptors. The difference between the proportion of nymphs at entry doors versus under furniture indicates that adult bed bugs were 9 times more likely to disperse than nymphs.

It’s not all active dispersal though—who would have thought one could write that after all these years—because standard mechanisms of the spread were observed too, including an infested wheelchair used in common areas, the introduction of infested furniture, “not wrapping infested furniture in plastic before removal from the building” and visits by residents and “guests harboring bed bugs on their clothing or belongings.”

The characteristics of a building-wide infestation

The facts gleaned about this infestation in this building:

• three years after the first suspected introduction, 45% of the building’s apartments were known to be infested, 101 apartments as of April 2009
• in the apartments visually inspected, there were 53 identified infestations; of these, 53% were adjacent apartments on the same floor and 45% were apartments across the hall
• in 40 apartments with a history of reported infestations, only 12 residents were aware of bed bugs; of these 40 apartments, 24 were still infested
• of 40 residents surveyed, 50% received bed bug treatments provided by the building management, 40% tried to control the infestation on their own with chemicals, 35% threw away furniture and 20% used store- or internet-bought pyrethroid-based sprays or foggers. Otherwise, alcohol, bleach and boric acid were used—as well as laundering, covering cracks with tape, placing blankets under doors and using mattress encasements

Information gleaned from interceptor traps in 20 infested apartments:

• while there was a 77% reduction in bed bug counts, after 12 weeks there were still bed bugs in 11 of 20 apartments
• 78% of the trapped bed bugs were nymphs
• 89% of trapped bed bugs were in the outer well of the interceptor “suggesting movement into the trap from the room” and that “most of the bed bugs missed by visual inspections were not on the furniture”
• more than 98% of trapped bed bugs were already dead when counted

This last item is interesting but I’m not sure what to make of it because, in fact, one of the conclusions of this study is that pest control efforts in this building were ineffective at eradicating the bed bugs. This may simply be that elusive line between mitigation and eradication. Unless they’re dying of fright? (Sort of joking but sort of serious—is there any possibility that being trapped makes them, well, not spry let’s say.)

Prospects

The researchers underscore what to me is an astonishing fact, that 50% of residents in infested apartments were unaware of their own infestations, this despite each tenant receiving a bed bug educational brochure and having the opportunity to attend a seminar.

This is in part what I believe this means: education alone will not solve the problem of bed bugs in our cities. Even assuming a significant investment in educational resources (an insurmountable if at present), there will not be a way to reach everyone.

At some point, you have to have access to all infested locations and then you have to kill all the bed bugs, with something—whatever it is, it must be inexpensive and widely deployable.

Impossible?

What else does this study show us?

This is what the researchers say:

Several of the surveyed apartments in this study were infested for more than two years. The active and passive bed bug dispersal mechanisms observed during this study and the rapid spread of bed bug infestations suggest an urgent need for more effective bed bug monitoring and intervention programs to curb the exploding problem of bed bug infestations. Without such efforts, bed bug infestations will continue to spread in our society and likely become much more widespread in low-income housing in the years to come. Bed bugs cause more than discomfort and pain. Bed bug infestations have economic, social, and legal ramifications (Potter 2006). Thus, it is critical to act early to prevent bed bug infestations from becoming chronic and incurring much greater health and economic consequences.

These are the facts on the ground. From people who know what they’re talking about, not wishful thinkers or would be social engineers.

Clearly, I believe that while many are beginning to recognize the need to act, no one really wants to. It will just take too much money.

But what happens then if we continue on this particular bed bug road?

_______________________

Active dispersal is an intriguing topic that is near to my heart. Here are some other posts on this subject:

• Where does it say…? 6 essential documents to survive an argument about bed bug dispersal
• Walking bed bugs
• Johnson’s hut, part 1.5
• Across the hall
• Active dispersal, baby
• The wandering females

And here are previous posts about the research of Dr. Wang and colleagues:

• DE vs chlorfenapyr (sorry, an unfortunate title)
• Baited pitfall traps for bed bugs
• Detecting bed bugs using bed bug monitors, Rutgers Cooperative Extension

Related posts:

1. DE vs chlorfenapyr
2. Walking bed bugs
3. NYC Health Code, Pest Prevention and Management
4. Baited pitfall traps for bed bugs
5. Where does it say…? 6 essential documents to survive an argument about bed bug dispersal

Please heed the caution advice about dry ice. It is probably unlikely that a professional pest manager will use a dry ice trap in your home, for liability reasons, but you now have several options to consider if, like so many, you are on your own when it comes to inspecting for bed bugs in your home:

There are some inherent safety risks that are associated with dry ice, and it is always advisable to contract the services of a pest management professional that uses devices that have been designed and tested to monitor and detect bed bugs. However, the dry ice trap, when designed and used correctly, offers an effective method for individuals that cannot afford professional pest management services.

It is impossible to overstate how important it is for affordable solutions to be developed and shared with the public. I am so grateful for Dr. Wang’s and his colleagues’ efforts.

The fact sheet has a brief comparative discussion of other bed bug monitoring solutions. Solutions need to be fitted to the circumstances. On the very effective passive monitor, Climbup Insect Interceptor, for example:

Interceptors are not intended for use in vacant rooms and cannot be used when furniture legs are absent or the furniture legs do not fit into the interceptor. Interceptors need to be placed for at least a week or longer to detect bed bugs at very low numbers.

The vacant room problem is an interesting one. I hope we will see more knowledge develop in this area.

For our note about the previously published research, see Baited pitfall traps for bed bugs.

Related posts:

1. Baited pitfall traps for bed bugs
2. The active spread of bed bugs in buildings: the stakes for cities
3. DE vs chlorfenapyr
4. NYT neediest: a Bronx mother, disabled child and bed bugs
5. Walking bed bugs

From the press release:

Fang Zhu, a post-doctoral fellow at UK along with fellow UK entomologists Mike Potter, Ken Haynes and Reddy Palli and several students, analyzed 110 bed bug populations from across the United States and found 88 percent of them had one or two genetic mutations. These mutations produce what is known as knockdown resistance, meaning the insecticide is not able to kill bed bugs.

[...]

“We need alternative insecticides to fight this bug,” Potter said, “Unfortunately today’s products are not as effective as ones we had previously. Non-chemical measures are important but are seldom completely effective and can be laborious and expensive. History has taught us insecticides are a crucial part of the bed bug solution.”

Data from this study will help pest management professionals make future decisions.

“The methods and primers developed by this group could be used to tell pest control professionals whether or not pyrethroids work on certain bed bugs by looking for these genetic mutations in the bugs’ DNA,” Palli said. “If it’s a target-site mutation, like the majority of these, spraying probably would be ineffective, but if it has another type of resistance, we could possibly add synergists to the current insecticide to help fight them.”

kdr-type mutations cause resistance at the pesticide target site via a mechanism of nerve insensitivity. (For an accessible explanation of pesticide resistance, I refer you to our interview with Dr. Alvaro Romero last year.)

For organochlorines and pyrethroids, these target sites are nerve sodium channels. Thus, DDT resistance can lead to pyrethroid resistance, as both pesticide classes act on the same target site.

As this study is not yet available, I reached out to the University of Kentucky researchers for clarification of the potential meanings of these findings.

New York vs Bed Bugs: Your study shows that the two mutations identified by Yoon et al. (2008) in a NYC population are actually widely prevalent in the United States?

Reddy Palli: Correct, more than 80% of populations showed the presence of one of these mutations.

New York vs Bed Bugs: In the press release you indicate that pest management professionals might use this information to determine a course of action. Can you confirm if UKY’s NYC and Cincinnati bed bug populations are among those with kdr mutations in your study?

Mike Potter: Some of the populations we tested from Cincinnati had one or both mutations while a few others did not (both of the latter still showed high resistance to pyrethroids in bioassays, however, suggesting that other resistance mechanisms may be involved). As far as the NYC populations we tested, all (12) had one or both mutations for pyrethroid resistance.

New York vs Bed Bugs: Are kdr mutations predictive of cross-resistance with other pesticide classes? I note that DDT conferring resistance on modern populations is stated as a possibility (but does this require further investigation?), but what of other possible cross-resistance possibilities?

Reddy Palli: Insecticides (eg. DTT, BHC) that use sodium channel as a target site likely show resistance. As you say, this requires further investigation. Insecticides (eg. Phantom and Propoxur) that work through target sites other than sodium channels may work fine on these resistant populations.

Mike Potter: Unfortunately, we just don’t have too many of these presently that have residual activity as a dry deposit other than products like Phantom (chlorfenapyr), desiccant dusts (e.g., silica gel, DE), and to a degree, the IGRs. Propoxur would be another but the decision to grant it a Section 18 emergency exemption is up to EPA.

New York vs Bed Bugs: I think the public may misinterpret this study as confirmation that “pesticides don’t work” — which is not really the case.

Mike Potter: I think it may be a bit too strong of a statement to conclude that pyrethroids “don’t work” on most of the bed bug populations in US, as we often do kill a percentage of the individuals we test in the laboratory, especially when they are contacted directly with the wet spray deposit. Dry residues typically kill far fewer and we know this to be important for optimal performance of products in the field. Reports from many pest control firms further indicate the pyrethroid products are not performing as well as they would like. Some companies continue to believe that they are working ok, but generally these companies are also incorporating additional treatment measures such as the use of contact killers (Sterifab, Bedlam, Phantom aerosol, etc.), steam, encasement of beds, etc., making it hard to know what specifically is working.

__________________________________________

I thank Dr. Palli and Dr. Potter for so kindly taking the time to answer my questions.

This is most definitely bad news; however, we have been expecting as much and indeed researchers at the University of Kentucky have been warning of widespread pyrethroid resistance for years. Having this confirmed, on this scale, is still a blow. The urgency of having options to enable the most basic resistance management countermeasures should be obvious.

Perhaps I should remind you that today is the last day of the public comment period for Ohio’s Section 18 propoxur exemption request under consideration by EPA.

1. 4/10 – the article has been published: Zhu, Fang, John Wigginton, Alvaro Romero, Ali Moore, Kimberly Ferguson, Roshan Palli, Michael F. Potter, Kenneth F. Haynes, and Subba R. Palli. 2010. Widespread distribution of knockdown resistance mutations in the bed bug, Cimex lectularius (Hemiptera: Cimicidae), populations in the United States. Archives of Insect Biochemistry and Physiology 73, no. 4: 245-257. doi:10.1002/arch.20355.

Related posts:

1. NY-BB
2. DDT resistance: once more, with tables and sources
3. An interview with bed bug researcher Alvaro Romero
4. More tales of CIN-1: PBO and deltamethrin
5. The workmanlike chlorfenapyr

The females were repeatedly fertilized, and dissections showed immense quantities of sperm inside their bodies. It appeared, however, that 12 males were too many, as some of the females died.

6 males to 1 female did finally allow the female subjects to survive the experimental conditions and the experiment to proceed. There was still “a great deal more of sperm.”¹

We hear a lot about the costs of mating—and indeed the culture is awash in references to “nasty” bed bug sex—and about the risk that female mating avoidance may cause the spread of infestations. But as we should now expect, things are more interesting and complex. An article published last month in the Proceedings of the National Academy of Science shows that, controlling for mating frequency, bed bug semen, which contains potentially beneficial antioxidant and antibacterial substances, elicits female reproductive benefits.

Reinhardt, K., Naylor, R.A. & Siva-Jothy, M.T., 2009. Ejaculate components delay reproductive senescence while elevating female reproductive rate in an insect. Proceedings of the National Academy of Sciences, 106(51), 21743-21747. doi:10.1073/pnas.0905347106

Females in this study either received 1 ejaculate unit (low exposure rate, n = 79) or 3 units (high exposure rate, n = 80) every week of their adult life. Even our low treatment rate exceeds the ejaculate provision rate required to maintain female fecundity, because 1 ejaculate unit sustains female fecundity and fertility for 4–8 weeks (20, 36). Females in both treatments received 3 copulatory intromissions per week, thus experimentally controlling for the 2 processes that have been implicated in reducing female fitness: the wounding of the female (38), which occurs at every mating in bedbugs (traumatic insemination; ref. 20), and infection from male genital contamination with microbes (39, 40). Although all females were fully fed and did not experience macronutrient limitation, females receiving the high ejaculate dose showed a significant increase in reproductive rate compared with females receiving the low ejaculate dose (Fig. 1A and B).

Emphasis added.

The age at which female reproductive rate declined was delayed by 11.4% (0.9 to 3.6 weeks) in the high ejaculate exposure females.

I’m not sure I understand what this may mean for the mortality of females, yet to be explored if I understand correctly. High ejaculate exposure increased mortality in only one of the populations tested.

1. This strong image that I guess I’ve now burdened you with is from Mellanby, K. 1939. Fertilization and egg production in the bed-bug, Cimex lectularius L. Parasitology 31, 193-199 doi:10.1017/S0031182000012750

Related posts:

1. Caught in a situation trap
2. Johnson’s hut, part 1.5
3. The wandering females
4. A tendency to synchronize feeding
5. “The most useful application of the bed bug alarm pheromone may be to cause dispersal.”

It is a report produced by Stephen Doggett and colleagues on behalf of diatomaceous earth manufacturer Mount Sylvia Diatomite.

Stephen L. Doggett, Merilyn J. Geary, David Lilly, Richard C. Russell. 2008. The Efficacy of Diatomaceous Earth against the Common Bed Bug, Cimex lectularius: a report for Mount Sylvia Diatomite. (PDF) Department of Medical Entomology, ICPMR and University of Sydney, Westmead Hospital.

In the laboratory investigations, DED [diatomaceous earth] produced a complete kill of adult bed bugs with all dose rates. At the dose rate equivalent to 1g of product/m2 this took 15 days; 2g/m2 – 10d; 4g/m2 – 13d; 8g/m2 – 9d.

The researchers also tested DE in conditions of higher humidity (70% RH) and also in a simulated environment.

(Lab investigations were of bed bugs confined to DE-treated filter paper in covered petri dishes. The bed bugs are from the Department of Medical Entomology’s colony, established in 2004, and have “a degree of insecticide resistance to both the synthetic pyrethroids and the carbamates.”)

On humidity:

It is well known that DED is less effective at higher humidities (Quarles & Winn 1996, Fields & Korunic 2000). As bed bugs are particularly problematic in tropical regions, it was thus important that testing was undertaken at a high relative humidity to examine if the product was still insecticidal. The longer time taken to achieve a complete kill was not unexpected in Experiment 3, however 100% mortality was still obtained with all treatment rates. The higher humidity however, does not affect the insecticide dust itself, rather the insect takes longer to die from desiccation. In Australia, humidity levels tend to be greater in the north of the country and it thus may be expected that DED would be less efficacious in these regions, however it is well known that DED is more effective at higher temperatures and this may counteract the higher humidities (Quarles & Winn 1996).

At 70% RH, 100% mortality occurred on Day 11 of exposure for the highest dose of 8g/m2.

The trial with simulated environments (new to me: mesocosms) used bulb dusters:

Mesocosms (Fig. 9) were constructed out of materials that are often typically encountered in dwellings; notably gyprock and pine, and were designed to simulate a bed bug infestation in a cavity such as a wall void. The lid of the mesocosm consisted of clear Perspex sheeting, which was fixed into position with removable screws. Perspex was used so that the flow of the DED into the mesocosm cavity could be observed, to facilitate the introduction of living bed bugs, to aid in experimental observation, and the removal of dead insects.

You should check out the cool photographs in the article, starting on page 40.

One mesocosm received 16 puffs of DE (the target dose rate was 2g/m2). A second mesocosm received 8 puffs.

100% mortality in the simulated environments by Day 9.

It’s a shame that no identifying information for the diatomaceous earth used in this study is provided.

I’ll leave you with this quote, an essential caveat about DE:

It is worth noting that there are many different types of DED and not all have insecticidal properties. A study undertaken in South Africa against a wide range of pests including the Common bed bug, found that the DED tested had little to no efficacy (Martindale & Newlands 1981). In contrast, the DED supplied by Mount Sylvia Diatomite Mines was highly efficacious. This implies that any Diatomaceous Earth that is submitted for registration should be accessed for its efficacy.

Related posts:

1. Finally, researchers on the efficacy of dusts
2. “The most useful application of the bed bug alarm pheromone may be to cause dispersal.”
3. DE vs chlorfenapyr
4. “They are also able to withstand chilling, thawing, rechilling and again thawing”
5. Behavior of bed bugs in response to heat