Special Issue "Bed Bugs: An Emerging Pandemic"

Abstract: The reemergence of the bed bug, Cimex lectularius Linnaeus, has recently spawned a frenzy of public, media, and academic attention. In response to the growing rate of infestation, considerable work has been focused on identifying the various host cues utilized by the bed bug in search of a meal. Most of these behavioral studies examine movement within a confined environment, such as a Petri dish. This has prevented a more complete understanding of the insect’s host-seeking process. This work describes a novel method for studying host-seeking behavior, using various movement parameters, in a time-lapse photography system. With the use of human breath as an attractant, we qualitatively and quantitatively assessed how bed bugs navigate their environment between its harborage and the host. Levels of behavioral activity varied dramatically between bed bugs in the presence and absence of host odor. Bed bugs demonstrated not simply activation, but attraction to the chemical components of breath. Localized, stop-start host-seeking behavior or alternating periods of movement and pause were observed among bed bugs placed in the environment void of human breath, while those exposed to human breath demonstrated long range, stop-start host-seeking behavior. A more comprehensive understanding of bed bug host-seeking can lead to the development of traps and monitors that account for unique subtleties in their behavior. The time-lapse photography system uses a large, artificial environment and could also be employed to study other aspects of the insect’s behavioral patterns.

Abstract: Blood-feeding insects have evolved resistance to various insecticides (organochlorines, pyrethroids, carbamates, etc.) through gene mutations and increased metabolism. Bed bugs (Cimex lectularius) are hematophagous ectoparasites that are poised to become one of the major pests in households throughout the United States. Currently, C. lectularius has attained a high global impact status due to its sudden and rampant resurgence. Resistance to pesticides is one factor implicated in this phenomenon. Although much emphasis has been placed on target sensitivity, little to no knowledge is available on the role of key metabolic players (e.g., cytochrome P450s and glutathione S-transferases) towards pesticide resistance in C. lectularius. In this review, we discuss different modes of resistance (target sensitivity, penetration resistance, behavioral resistance, and metabolic resistance) with more emphasis on metabolic resistance.

Abstract: The bed bug resurgence in North America, Europe, and Australia has elicited interest in investigating the causes of the widespread and increasing infestations and in developing more effective control strategies. In order to extend global perspectives on bed bug management, we reviewed bed bug literature in China by searching five Chinese language electronic databases. We conducted telephone interviews of staff from 77 Health and Epidemic Prevention Stations in six Chinese cities in November 2010. We also conducted telephone interviews of 68 pest control firms in two cities during March 2011. Two species of bed bugs (Cimex lectularius L. and Cimex hemipterus (F.)) are known to occur in China. These were common urban pests before the early1980s. Nationwide “Four-Pest Elimination” campaigns (bed bugs being one of the targeted pests) were implemented in China from 1960 to the early 1980s. These campaigns succeeded in the elimination of bed bug infestations in most communities. Commonly used bed bug control methods included applications of hot water, sealing of bed bug harborages, physical removal, and applications of residual insecticides (mainly organophosphate sprays or dusts). Although international and domestic travel has increased rapidly in China over the past decade (2000–2010), there have only been sporadic new infestations reported in recent years. During 1999–2009, all documented bed bug infestations were found in group living facilities (military dormitories, worker dormitories, and prisons), hotels, or trains. One city (Shenzhen city near Hong Kong) experienced significantly higher number of bed bug infestations. This city is characterized by a high concentration of migratory factory workers. Current bed bug control practices include educating residents, washing, reducing clutter, putting items under the hot sun in summer, and applying insecticides (pyrethroids or organophosphates). There have not been any studies or reports on bed bug insecticide resistance. Difficulties of control were noted in our surveys of dormitories in which crowded living, seasonal worker migration, and financial constraints contributed to control failures. This study supports the following conclusions: (1) the bed bug infestation in China dramatically decreased following the campaigns from 1960 to the early 1980s; (2) In our survey of Health and Epidemics Prevention Stations, no bed bug cases were reported in Beijing and Shanghai for the past 12 months, but complaints were reported in Guangzhou, Lanzhou, Urumqi, and Shenzhen; (3) Current bed bug infestations primarily are reported in crowded living environments or transient environments such as worker dormitories and military dormitories. These findings suggest that community-wide bed bug monitoring and control campaigns are necessary for effective control of bed bug infestations as a societal response.

Abstract: Australia has experienced a sudden and unexpected resurgence in bed bug infestations from both Cimex lectularius L. and Cimex hemipterus F. A survey in 2006 revealed that infestations had increased across the nation by an average of 4,500% since the start of the decade. In response, a multi-disciplinary approach to combat the rise of this public health pest was implemented and involved the coordinated efforts of several organizations. The key components of the strategy included the introduction of a pest management standard ‘A Code of Practice for the Control of Bed Bug Infestations in Australia’ that defines and promotes ‘best practice’ in bed bug eradication, the development of a policy and procedural guide for accommodation providers, education of stakeholders in best management practices, and research. These strategies continue to evolve with developments that lead to improvements in ‘best practice’ while bed bugs remain problematic in Australia.

Abstract: Recent emergence of bed bugs (Cimex spp.) has prompted a significant expansion of research devoted to this pest. The ability to survive and recover from stress has significant implications on the distribution and survival of insects, and bed bugs are no exception. Research on bed bug stress tolerance has shown considerable progress and necessitates a review on this topic. Bed bugs have an extraordinary ability to resist dehydration between bloodmeals, and this represents a critical factor allowing their prolonged survival when no host is available. High relative humidities are detrimental to bed bugs, leading to reduced survival in comparison to those held at lower relative humidities. Continual exposure of bed bugs, eggs and mobile stages, to temperatures below freezing and short term exposure (=1 h) to temperatures below −16 to −18 °C results in mortality. The upper thermal limit for short term exposure of eggs, nymphs and adults is between 40–45 °C for the common (Cimex lectularius) and tropical (C. hemipterus) bed bugs. Long-term exposure to temperatures above 35 °C results in significant reduction in survival of mobile bed bugs. Eggs for C. lectularius and C. hemipterus are no longer viable when held below 10 °C or above 37 °C throughout embryogenesis. Blood feeding, although necessary for survival and reproduction, is discussed as a stress due to thermal and osmotic fluctuations that result from ingesting a warm bloodmeal from a vertebrate host. Cold, heat, water stress and blood feeding prompted the expression of heat shock proteins (Hsps). Pesticide application is a common human-induced stress for urban pests, and recent studies have documented pesticide resistance in many bed bug populations. High levels of traumatic insemination (mating) of bed bugs has been linked to reduced survival and fecundity along with possibly exposing individuals to microbial infections after cuticular penetration by the paramere (=male reproductive organ), thus represents a form of sexual stress. Additionally, less common stress types such as microbial infections that have been documented in bed bugs will be discussed. Overall, this review provides a current update of research related to bed bug stress tolerance and how their ability to resist stressful conditions has lead to their expansion and proliferation.

Abstract: Experimental life tables were constructed and analyzed for three strains of the common bed bug: a pyrethroid-susceptible laboratory strain (HS), a highly resistant field strain (RR), and a field strain with a declining level of resistance (KR). Egg to adult survival in the RR strain was 94% compared with 79% and 69% in the HS and KR strains, respectively. The RR strain also developed significantly faster from egg to adult (~35 days) than the other two strains (~40 days). Analysis of a survivorship and fecundity life table for the RR strain produced the following results. The average life expectancy for a newly laid egg was ~143 days, and that of a newly molted adult was ~127 days. Females produced an average of 0.64 daughter eggs/day with the highest weekly production during the fifth week of adult life. Analysis of daily reproductive parity showed that females produced 1–3 and 4–6 eggs on 79 and 21% of the days, respectively, when egg laying occurred. The net reproductive rate (R₀) of the RR strain was ~35, which represents a 35-fold increase in the population per generation (~92 days). The intrinsic rate of increase, r, was 0.054 indicating that the population multiplies 1.1 times/female/day (λ) and doubles in size every 13 days. The stable age distribution (c_x) was dominated by nymphs (54%), followed by eggs (34%) and adults (12%). Reproductive values (v_x) for the strain increased from egg to the adult stage.

Abstract: Groups of starved, virgin adult male or female bed bugs were stimulated to search for a host by the presence of a heated artificial feeder. Some of the bed bug groups were allowed to obtain a blood meal and some were not. After the removal of the feeder, bed bugs were observed throughout the scotophase to record their searching and aggregation behavior. Groups of male and female bed bugs that were unable to obtain a blood meal continued to search in the arena for the majority of the scotophase. Bed bugs that were able to obtain a blood meal returned to their shelter to aggregate 30 min after feeding. Overall, the proportion of bed bugs aggregating in shelters during the scotophase was significantly greater for those that had fed successfully than those that had not. However, all bed bugs, regardless of feeding status, began to return to shelters to aggregate 2 h prior to the photophase.

Abstract: The scarcity of bed bugs in many countries over the last 50 years has resulted in a lack of modern research into the toxicology of this pest. Although bed bugs resurged in the late 1990s, published research related to insecticides has lagged behind and only began to appear in 2006. The difficulty in controlling bed bugs triggered the interest of both private and academic sectors to determine the value of currently available insecticides. What follows, is updated information on effectiveness of products, studies on insecticide susceptibility, identification of mechanisms of insecticide resistance and chemical strategies proposed to overcome resistance in modern bed bug populations.

Abstract: Four bed bug strains (Cimex lectularius) with different levels of pyrethroid resistance were evaluated to determine their ability to survive extended periods of starvation. First instar bed bugs of all strains were the most vulnerable to starvation (13.8–36.3 days mean survival time). Fifth instars and adults survived the longest during starvation (41.5–142.6 days). Significant differences in survivorship during starvation were observed between resistant and susceptible strains of bed bugs. Overall, all immature and adult stages of the resistant bed bug strains had significantly shorter survival times than those of the susceptible strains (P < 0.05).

Abstract: Egg production was compared among three field-collected bed bug strains over the course of 13 feeding/oviposition cycles, each of which lasted ~10 days. No significant differences were found among bed bug strains in the mean number of eggs/female/day (~1.0 egg). However, significant differences were found among strains in their patterns of egg production throughout the study period. Specifically, differences were observed in the timing of peak egg production and the rapidity of egg production decline among the three strains. Egg production was also quantified for female bed bugs that were subjected to single or multiple traumatic insemination events over a period of six feeding/oviposition cycles. Significant differences were found in egg production between females exposed to single and multiple inseminations. Females mated only once produced 83.8 ± 4.5 (mean ± SE) eggs over six feeding cycles. Females exposed to multiple inseminations produced 61.0 ± 3.1 eggs, indicating that multiple traumatic inseminations may reduce female fecundity by as much as 27%. This study is the first to suggest that, in a new infestation (first ~6 weeks), a solitary, singly-mated female with access to regular blood meals is capable of producing greater numbers of offspring than the same female in the presence of a male.