Up in the Air

Editor’s note: This article is an excerpt from “Advances in the Biology and Management of Modern Bed Bugs,” a 472-page reference book that was released last year. The book was co-edited by Stephen L. Doggett, Department of Medical Entomology, NSW Health Pathology, Westmead Hospital, Westmead, Australia; Dini M. Miller, Department of Entomology, Virginia Tech, Blacksburg, Va.; and Chow-Yang Lee, formerly with School of Biological Sciences, Universiti Sains Malaysia, Penang, Malaysia, but now with University of California, Riverside.

The management of bed bugs onboard aircraft is one of the most challenging issues facing pest management professionals around the world. Bed bugs can easily be introduced onto aircraft by passengers, luggage, crew and ground personnel. Both the common bed bug, Cimex lectularius L., and the tropical bed bug, Cimex hemipterus (F.), have been detected on commercial aircraft, although C. lectularius is by far the most prevalent species (Adam Juson, unpublished results). PMPs face a diverse range of infested environments that have little in common except their vulnerability to bed bugs. The body of an aircraft presents a unique challenge to any PMP charged with eradicating an infestation. This article focuses on bed bug management on aircraft and reviews the challenges unique to this situation, as well as the protocols required to achieve successful eradication.

AVIATION ENTOMOLOGY HISTORY. Kisluik (1929) initiated the field of research investigating insect transport and infestation potential on aircraft, when he inspected the Graf Zeppelin in 1928. He found 10 species of insect pests onboard, including one “bug.” Since that time, concerns have been raised regarding various biting insects being transported on aircraft (Griffitts and Griffitts, 1931). Swain (1952) predicted that aircraft would be a major distributor of insect species, and Sullivan et al. (1958) reported on how insects might survive on aircraft. Public health pests have received the most attention due to their potential to spread agents of disease (Evans et al., 1963; Basio et al., 1970; Otaga et al., 1974; Russell et al., 1984; Goh et al., 1985). Disinsection (a term indicating the process of treating of an aircraft so as to eliminate insects) of aircraft cabin environments to control mosquito species on international flights is now required under the World Health Organization, International Health Regulations (WHO, 2005).

The resurgence of bed bugs around the world (Robinson and Boase, 2011) has included their introduction onto commercial aircraft (Haiken, 2011). The efficacy of a limited number of detection and control devices for bed bug management on commercial aircraft was reviewed by Juson (2014). Little is known about the prevalence of bed bugs or their control on private, medical or military aircraft. However, NATO’s advisory group for aerospace research and development acknowledges that bed bugs are carried onto aircraft, and are known to be exchanged between passengers (Ellis, 1996).

CHALLENGES. One of the challenges facing PMPs when working on aircraft is access. An aircraft’s duty cycle limits opportunities for non-critical inputs, such as bed bug inspections. Long-haul aircraft spend approximately 16 hours a day in flight, giving bed bug populations virtually unrestricted feeding opportunities. The presence of sedentary hosts, coupled with a warm and stable air temperature, provide near optimal conditions for bed bug population establishment and growth.

The cost of bed bug management on aircraft is quite variable depending on how the aircraft is employed. Private (luxury) aircraft, commercial aircraft and military aircraft have very few financial restrictions with regards to the cost of bed bug control. This is because the cost of bed bug management in these aircraft is minimal when compared to the expense associated with even a short flight delay. However, domestic medical aviation is often charitably funded and, as a result, very cost conscious. Air ambulance infestations are not common, but they are among the most time-consuming and costly to resolve. This is due to the complex interior structure of the aircraft, which is designed to house medical equipment (Adam Juson, unpublished results).

The complex nature of the aircraft interior limits both visual inspection and treatment ability. In many cases it is not possible to access deep harborages on the airframe without dismantling the aircraft interior. The widespread use of light honeycomb structures in both aircraft seating and cabin construction allows bed bugs to harbor in protected microclimates that are in close proximity to the hosts. These ideal harborages allow infestations to go unnoticed for considerable periods of time and make treatment efforts very challenging.

Aircraft engineers and other aircraft employees are typically reluctant to work alongside PMPs onboard an infested aircraft. Widespread fear of bed bug exposure, coupled with the perceived risk of infesting their own homes, limits employee cooperation and leaves the PMP to inspect and locate sites of infestation on their own.

Another challenge for PMPs is that aviation is one of the world’s most highly regulated industries. Not surprisingly, the pest management options that are acceptable for use on an aircraft are quite limited and these options must fit within the aviation regulatory framework. In addition, all pesticides used for insect control must meet the AMS1450a specifications (SAE International, 1995) and carry cabin approval (further local restrictions also may apply). This limits the currently available actives to a few pyrethroids and carbamates. Consequently, any new or innovative control technologies that might be of use on aircraft must be reviewed, evaluated and go through an often lengthy approval process before they can be applied.

Another challenge for aircraft disinfestation is that any work carried out on board the aircraft, including pest control, has to be overseen by a licensed aircraft engineer. This necessitates that engineers be present during the strip-down and re- cover of passenger seating before and after chemical treatment. Engineers also must be present for the removal and reinstatement of heat-sensitive items, such as life vests and emergency exit slides, during thermal disinsection (heat treatment). The requirement that an engineer be present increases the cost of bed bug remediation and often puts pressure on the pest management crew to complete their treatment as quickly as possible.

As is often the case in any insect infestation, a small number of unauthorized (and unproven) treatments may be undertaken by the cabin crew. Crew members will often use disinsection aerosols (pyrethroid-based insecticides intended to control mosquitoes and agricultural pests that may pose a health or economic threat to various nations) when bed bugs are detected in flight. This application often results in flushing the population from the harborages into the passenger cabin. Passengers are often moved from infested seats to open seats elsewhere in the aircraft, potentially spreading the infestation.

Few academic studies have focused on evaluating best practices for bed bug remediation on aircraft. Those methods that have proved successful in aviation have come from research studies conducted in other environments.

BED BUG MANAGEMENT. Bed bug management techniques focus on detection first, and then eradication. The application of these techniques must fit into the airlines’ flying schedules. The severity and spread of bed bug activity is obviously directly correlated with the elapsed time since the inoculating event, or the failure of the previous treatment to eradicate the problem. As preventing a bed bug introduction is not possible, the early detection of infestations is vital. The complex nature of aircraft seating products severely limits the detection systems that can be used on board aircraft.

Refuge monitors, lure monitors, electronic air sampling detectors and scent detection dogs all have been evaluated on aircraft to determine their utility and practicality (Juson, 2014). Harborage and lure-based monitors were determined to be unviable, as these products require not only an initial set up, but regular follow-up visits to check for activity. The monitor maintenance alone made them unfavorable with airline operators. Also, these monitoring devices could not compete with the attractiveness of the airline seats for bed bug harborage.

Alternative monitoring methods, such as the use of air sampling devices, were promoted extensively by some commercial operators. One particular device contained an infrared absorption cell calibrated to recognize the spectrum of gases resulting from bed bug respiration. However, this device was found to be very time consuming to use, and resulted in a large number of false positives, due to warm air pockets in the airline seats.

Although somewhat controversial, the most accurate and time-efficient method of bed bug detection on aircraft was the use of scent detection dogs. The ability of scent detection dogs to locate live bed bug infestations in a confined environment is well- documented (Pfiester et al., 2008). However, the reported accuracy among different dog teams (inspecting multi-unit housing) has been shown to be quite variable (accuracy ranging from 15-98 percent, and a mean false positive rate of 15 percent; Cooper et al., 2014). However, the two studies that have been conducted onboard commercial aircraft found the canine accuracy to be 95 percent (Juson, 2014), with a mean false positive rate of 16 percent (Adam Juson, unpublished results). In heavily infested aircraft, dogs have difficulty detecting the periphery of the infestation, and will display scent saturation behavior in a closed, infested aircraft.

Many bed bug control methods have been attempted to manage active infestations. Some airlines attempted to use modified methods based around the WHO guidelines for aircraft disinsection (WHO, 2013). In essence, disinsection treatments involve either the application of “residual” pyrethroids every six to eight weeks, or the use of pyrethroid-based total release aerosols. Both of these pyrethroid applications have been observed to agitate and disperse bed bug populations. This complicates control efforts further by spreading the infestation. In addition, it has been well documented that total release aerosols are ineffective for controlling bed bugs. This is because the chemical droplets do not penetrate harborages, and the bed bugs that contact the treated surfaces are highly resistant (Romero et al., 2007) so the product has no residual activity (Jones and Bryant, 2012). In summary, the chemical treatments currently applied by PMPs on aircraft have produced disappointing results (Juson, 2014). The complex construction of aircraft seating and the restrictions on dismantling seats does not allow PMPs enough access to make an adequate insecticide application. Additionally, the aircraft cabin environment rapidly degrades chemical insecticides so that the products have no residual activity for controlling resistant bed bugs.

IMPROVING PROTOCOLS. Current pest management methods on aircraft need to be improved. As bed bug populations continue to proliferate throughout the world, consumer complaints will no doubt drive efforts toward improving eradication methods. Thorough inspections of the aircraft will be necessary to locate the areas of infestation in the cabin. Insecticide applications, and other treatment methods, will need to be applied and evaluated for efficiency. The treatment processes will need to be flexible so that they can be scaled to adequately address the size and distribution of the infestation on the type of air frame being treated.

Most recently, a four-phase approach has proven to be the most effective for treating bed bugs on a variety of aircraft. This sequential protocol involves using a vacuum to reduce the number of bed bugs immediately, then using steaming to kill additional bed bugs and their eggs. Steaming is followed by the application of a desiccant dust to provide residual activity. The success of these control measures is determined by re-inspection of the aircraft for survivors at weekly intervals following the initial treatment (Adam Juson, unpublished results). The specific elements of this treatment protocol are described later in the article.

The information gathered from the initial inspection (the relative number of bed bugs and their specific locations) is used to inform the PMP where to vacuum. The vacuuming physically removes both live and dead bed bugs, and their cast skins. This initial removal of bed bugs and their debris does a lot to improve the efficacy of subsequent treatments. Vacuuming the major bed bug harborages found within aircraft seating has been found to reduce living bed bug biomass by about 70 percent.

Topical heat treatment using steam is highly effective at killing bed bug eggs left behind after vacuuming. Steam is also good for penetrating the airline seating. Steam has been found most effective for treating light- to moderate infestations. Treating airline seating with steam requires the removal of the seat cover by airline personnel. The cover is then thoroughly vacuumed, and steam applied to all seams. The steamer is used to treat the seat structure and cushioning. Steam should be applied methodically, starting at the head rest, moving down the seat back, and finally onto the base of the seat and the foot rests. The treatment should be focused on, but not limited to, bed bug harborages that would be located near the passenger’s shoulders and waist. It is very important that the steam velocity exiting the steamer head be limited to minimize the risk of blowing live bed bugs around inside the aircraft.

In the rare case of a high-level infestation, localized or full cabin heat treatment should be considered. If the infestation is restricted to the seating cabin, the use of a tented heat treatment will provide satisfactory results, providing that all potential harborage locations reach 131°F (55°C), and there are no cold spots. If the infestation extends behind the cabin wall paneling, or into the floor runners or electrical runs, it will be necessary to pre-heat the exterior of passenger aircraft before heating the interior cabin. The exterior heating will prevent bed bugs from migrating behind the aircraft’s thermal blanketing.

Residual treatment is applied to key bed bug harborage locations using a desiccant dust (which must have AMS1450a approval). This application will prevent re-infestation of harborages in passenger seating and other hard-to-treat locations. Desiccant dusts will not only kill bed bugs exposed to the dust but will act in a prophylactic manner to reduce the ability of newly introduced bed bugs from establishing an infestation.

As with any bed bug treatment, the infested treated area needs to be inspected post-treatment to evaluate the results. Re-inspection should be undertaken at weekly intervals to determine treatment efficacy. Any remaining bed bugs should receive focused remedial treatment until complete control is achieved.

In summary, the management of bed bugs on aircraft poses many logistical and engineering challenges. Furthermore, the industry is so highly regulated that significant constraints are imposed as to the range of control options that are available to the PMP. Similar to managing bed bug infestations in other locations, only an integrated and sustained approach will ensure bed bug eradication on aircraft.