{"id":4355,"date":"2016-09-01T14:36:56","date_gmt":"2016-09-01T04:36:56","guid":{"rendered":"https:\/\/ppmmagazine.com.au\/?p=4355"},"modified":"2025-03-31T20:01:57","modified_gmt":"2025-03-31T09:01:57","slug":"bed-bugs-still-a-tough-nut-to-crack","status":"publish","type":"post","link":"https:\/\/professionalpestmanager.com\/nz\/bed-bug-treatments\/bed-bugs-still-a-tough-nut-to-crack\/","title":{"rendered":"Bed Bugs \u2013 Still a Tough Nut to Crack"},"content":{"rendered":"<p><em>Researchers from the Department of Medical Entomology at Sydney&#8217;s Westmead Hospital share some of their latest research into bed bug resistance.\u00a0<\/em><br \/>\n<!--more--><\/p>\n<div class=\"hr-thick\"><\/div>\n<div class=\"page\" title=\"Page 17\">\n<div class=\"section\">\n<div class=\"layoutArea\">\n<div class=\"column\">\n<p>If you\u2019re still finding bed bugs a difficult pest to control, or you\u2019ve got a few hardy survivors that refuse to die, you\u2019re certainly not alone. Recent research is shedding a light on exactly why this might be.<\/p>\n<p>You will have no doubt heard of insecticide resistance being a key reason for the bed bugs\u2019 resurgence, with\u00a0the modern bugs able to withstand significantly higher doses of insecticide that would normally kill a susceptible population. This is particularly well established around the world with the pyrethroids (the most widely available group of insecticides), and has also recently been confirmed\u00a0in the US with the neonicotinoids (a group that includes compounds such as imidacloprid and acetamiprid).<\/p>\n<p>However, when we talk about \u2018insecticide resistance\u2019, what might be causing that resistance \u2013 the \u2018mechanism\u2019 \u2013 could actually be one of several different biological processes within the insect. In bed bugs, insecticide resistance is likely to result from a combination of up to three resistance mechanisms:<\/p>\n<ul>\n<li>kdr-type target site insensitivity<\/li>\n<li>metabolic detoxification<\/li>\n<li>or reduced penetration.<\/li>\n<\/ul>\n<p>So, why does this matter? Primarily, it\u2019s because we have\u00a0so few insecticides left today that are reliably effective, and we want to protect them for as long as we can. But to do\u00a0so, we have to understand what mechanisms of insecticide resistance are present within the bed bug populations we\u2019re dealing with today.<\/p>\n<div class=\"page\" title=\"Page 17\">\n<div class=\"section\">\n<div class=\"layoutArea\">\n<div class=\"column\">\n<p>This was a challenge we faced in Australia recently when, after collecting a field strain of bed bugs from the suburb\u00a0of Parramatta (within Sydney), we found it to be the most insecticide resistant strain we\u2019d ever encountered. However, we also noticed that when we forcibly kept the bugs on a recently insecticide-treated surface, some of the bugs would succumb after a relatively short time, some would die after a few hours, and some simply wouldn\u2019t die at all.<\/p>\n<p>Knowing this, our lab set about investigating what mechanisms may be contributing to the observed resistance. Firstly, Dr <strong>Kai Dang<\/strong> determined that the strain uniformly possessed kdr-type mutations that meant that pyrethroids wouldn\u2019t bind to their target site correctly. However, we also had other strains that possessed the same mutation that weren\u2019t as highly resistant, so something more had to be going on.<\/p>\n<p>The next step was to examine for metabolic detoxification and, in particular, two types of enzymes that might be breaking down the insecticide before it has a chance\u00a0to work. These enzymes are broadly called \u2018oxidases\u2019\u00a0and \u2018esterases\u2019. Beyond knowing that a strain possesses metabolic detoxification, it is useful to know what type of enzyme might be present as each type has the potential\u00a0to confer cross-resistance to more than one insecticide group. For instance, oxidases detoxify pyrethroids, but may also have the potential to work against neonicotinoids and could explain why resistance to that group has developed so quickly.<\/p>\n<p>One way to test for enzyme activity is to use chemicals called \u2018synergists\u2019. Synergists can inhibit, or lower, the levels of enzymes and by using different types of synergists we can understand which enzymes type is present. One of\u00a0the best-known synergists is a chemical called piperonyl butoxide, or \u2018PBO\u2019. PBO is very useful as it can inhibit both esterases and oxidases, but that ability in turn makes it hard to determine which enzyme type is contributing to any perceived resistance. However, a new synergist known as \u2018EN16\/5-1\u2019 had recently been developed that only inhibits esterases (as opposed to oxidases). This meant that by using both synergists in combination, there was a unique opportunity to investigate the role of metabolic resistance and to determine which enzyme type was responsible.<\/p>\n<div class=\"page\" title=\"Page 17\">\n<div class=\"section\">\n<div class=\"layoutArea\">\n<div class=\"column\">\n<p>Our studies investigated the Parramatta strain, as well as\u00a0a range of bed bug strains originating from cities across Australia. This included an additional strain from Sydney (New South Wales), two from Melbourne (Victoria) and one from Alice Springs (Northern Territory).<\/p>\n<p>The results indicated that metabolic detoxification played a major part in conferring resistance to our field strains, but also that there appeared to be a mix of both oxidase and esterase dominated strains (two strains each). The Parramatta strain\u2019s resistance could almost (almost&#8230;) be \u2018turned off\u2019 by the addition of the synergists \u2013 the use of the both PBO and EN16\/5-1 indicated that esterases were likely to be playing a major part in that strain. However, there still remained the problem of some bugs that we just couldn\u2019t kill \u2013 these were the best of the best at resisting insecticides, and we needed to know why!<\/p>\n<p>So the final part of our study was to look at the cuticle thickness, and examine it for any differences between bugs that died early versus those that were the hardy survivors within the same strain. Interestingly, older bed bugs have thicker cuticles \u2013 the cuticle is laid down much in the same way a tree ring is, except on a daily basis.<\/p>\n<p>As such, we had to carefully age the bed bugs, to ensure no bias was introduced.<\/p>\n<p>We then repeated the earlier insecticide forced exposure experiment, monitored how quickly they were affected, and then separated them into respective groups of \u2018intolerant\u2019 (died within 2 hours), \u2018tolerant\u2019 (still alive at 4 hours), and \u2018resistant\u2019 (still alive at 24 hours). Some careful manipulating under an electron microscope then enabled us to measure the cuticle thickness in the bed bugs\u2019 legs (Figure 1).<\/p>\n<div class=\"page\" title=\"Page 17\">\n<div class=\"section\">\n<div class=\"layoutArea\">\n<div class=\"column\">\n<figure id=\"attachment_8457\" aria-describedby=\"caption-attachment-8457\" style=\"width: 450px\" class=\"wp-caption alignnone\"><img fetchpriority=\"high\" decoding=\"async\" class=\"wp-image-8457\" src=\"https:\/\/professionalpestmanager.com\/nz\/wp-content\/uploads\/2016\/09\/Figure-1-300x208.png\" alt=\"Chart showing increasing bed bug cuticle thickness leads to increased tolerance to insecticide\" width=\"450\" height=\"312\" srcset=\"https:\/\/professionalpestmanager.com\/nz\/wp-content\/uploads\/2016\/09\/Figure-1-300x208.png 300w, https:\/\/professionalpestmanager.com\/nz\/wp-content\/uploads\/2016\/09\/Figure-1-768x533.png 768w, https:\/\/professionalpestmanager.com\/nz\/wp-content\/uploads\/2016\/09\/Figure-1-288x200.png 288w, https:\/\/professionalpestmanager.com\/nz\/wp-content\/uploads\/2016\/09\/Figure-1-274x190.png 274w, https:\/\/professionalpestmanager.com\/nz\/wp-content\/uploads\/2016\/09\/Figure-1-150x105.png 150w, https:\/\/professionalpestmanager.com\/nz\/wp-content\/uploads\/2016\/09\/Figure-1.png 905w\" sizes=\"(max-width: 450px) 100vw, 450px\" \/><figcaption id=\"caption-attachment-8457\" class=\"wp-caption-text\">Figure 1: Increasing cuticle thickness leads to increased tolerance to insecticide<\/figcaption><\/figure>\n<p>The results clearly indicated that the susceptibility to insecticide decreased as thickness of the cuticle increased, with bed bugs with the thickest cuticles showing the highest level of resistance. When this finding is combined with our knowledge about the presence of target-site and metabolic detoxification in this strain, it means that these \u2018super-resistant\u2019 bugs are perfectly evolved to resist most pyrethroid insecticides available to pest managers (Figure 2).<\/p>\n<figure id=\"attachment_8458\" aria-describedby=\"caption-attachment-8458\" style=\"width: 450px\" class=\"wp-caption alignnone\"><img decoding=\"async\" class=\"wp-image-8458\" src=\"https:\/\/professionalpestmanager.com\/nz\/wp-content\/uploads\/2016\/09\/Figure-2-300x209.png\" alt=\"Chart showing that the resistant Parramatta bed bug strain had a significantly thicker cuticle than the susceptible Monheim bed bug strain\" width=\"450\" height=\"313\" srcset=\"https:\/\/professionalpestmanager.com\/nz\/wp-content\/uploads\/2016\/09\/Figure-2-300x209.png 300w, https:\/\/professionalpestmanager.com\/nz\/wp-content\/uploads\/2016\/09\/Figure-2-768x534.png 768w, https:\/\/professionalpestmanager.com\/nz\/wp-content\/uploads\/2016\/09\/Figure-2-288x200.png 288w, https:\/\/professionalpestmanager.com\/nz\/wp-content\/uploads\/2016\/09\/Figure-2-273x190.png 273w, https:\/\/professionalpestmanager.com\/nz\/wp-content\/uploads\/2016\/09\/Figure-2-150x105.png 150w, https:\/\/professionalpestmanager.com\/nz\/wp-content\/uploads\/2016\/09\/Figure-2.png 902w\" sizes=\"(max-width: 450px) 100vw, 450px\" \/><figcaption id=\"caption-attachment-8458\" class=\"wp-caption-text\">Figure 2: The resistant Parramatta strain had a significantly thicker cuticle than the susceptible Monheim strain<\/figcaption><\/figure>\n<p>The important implication of this is that when attempting control of bed bugs in a field situation, you\u2019re likely to be\u00a0up against some bugs that are just naturally \u2018super-resistant\u2019 compared to all the other bugs in the infestation. Miss\u00a0those bugs and they\u2019ll either start the infestation anew, or potentially spread it to a new location. Either way, these will be even more difficult to control as you have selected the \u2018super-duper\u2019 bugs!<\/p>\n<p>Fortunately, there are two main ways to partially overcome this super-resistance. The first would be to use non- chemical means (no matter how resistant these bugs are they can\u2019t withstand a vacuum!), and the second is to ensure you\u2019re using an insecticide either with piperonyl butoxide (PBO) or one that is a combination product with pyrethroid and neonicotinoid (such a imidacloprid), or use a silicate based product as resistance does not occur to this group. Both methods significantly improve the effectiveness of control methods, and thus reduce the likelihood of call-backs.<\/p>\n<p>Back to <a href=\"https:\/\/professionalpestmanager.com\/nz\/bed-bug-treatments\/\" data-wplink-edit=\"true\">bed bug treatment<\/a> landing page.<\/p>\n<p>More information on <a href=\"https:\/\/professionalpestmanager.com\/nz\/bed-bugs\/\">bed bugs<\/a>.<\/p>\n<p><strong>David Lilly<\/strong>, <strong>Cameron Webb<\/strong> and <strong>Stephen Doggett<\/strong>, <em>Department of Medical Entomology, Westmead Hospital, Sydney<\/em><\/p>\n<div class=\"thin\"><\/div>\n<p><strong>David Lilly<\/strong> is a PhD Student at the University of Sydney based at the Department of Medical Entomology, Westmead Hospital, Westmead. He is a recipient of an Australian Postgraduate Award that is generously supported by an Industry Top-Up Grant from Bayer CropScience, Australia.<\/p>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"<p>Researchers from the Department of Medical Entomology at Sydney&#8217;s Westmead Hospital share some of their latest research into bed bug resistance.\u00a0<\/p>\n","protected":false},"author":133,"featured_media":8455,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"_seopress_robots_primary_cat":"","_seopress_titles_title":"Bed Bugs \u2013 Still a Tough Nut to Crack! 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