Everything You Need to Know About the Biology, Clinical Significance
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CMN Clinical Stay Current... Microbiology Stay Informed. Newsletter Vol. 43, No. 1 January 1, 2021 Sleeping with the Enemy: Everything You Need www.cmnewsletter.com to Know about the Biology, Clinical Significance, IN THIS ISSUE and Laboratory Identification of Bed Bugs 1 Sleeping with the Enemy: Blaine A. Mathison, B.S., M(ASCP), Institute for Clinical and Experimental Pathology, ARUP Everything You Need to Laboratories, Salt Lake City, Utah, and Bobbi S. Pritt, M.D., M.Sc., DTM&H, Division of Clinical Know about the Biology, Microbiology, Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, Minnesota Clinical Significance, and Laboratory Identification Abstract of Bed Bugs The world has experienced a major global resurgence of bed bug infestations over the past 2 decades. 7 CMN Q & A: While bed bugs do not serve as vectors of disease, their bites and household infestations result in sig- A Bloody Problem nificant psychological distress, clinical manifestations, and economic costs. Most human bed bug infes- tations are caused by the “common bed bug,” Cimex lectularius, or the “tropical bed bug,” C. hemipterus. Zoonotic cimicids also occasionally feed on humans. Bites are the most commonly reported manifesta- tion of infestations, although findings may be subtle and overlooked for some time. The bugs can be submitted to the laboratory for identification, and therefore, clinical microbiologists should be familiar with their key identifying features and how they can be differentiated from similar-appearing arthro- pods. This review covers the biology and epidemiology of bed bugs; aspects of laboratory collection, identification, and reporting; and the clinical implications of bed bug infestations. Introduction affected those living in poor, crowded neighbor- hoods. While bed bugs do not serve as vectors “Good night, sleep tight; don’t let the bed bugs of disease, their bites and household infesta- bite.” This version of the well-known rhyme was tions result in psychological distress, a range of first published in 1896 in the bookWhat They Say unpleasant clinical manifestations, property loss, in New England by Clifton Johnson, but variations and other substantial economic costs [4-6]. It of this verse can be found in the literature in the was only with the widespread household use of decades before [1]. While a seemingly innocent dichloro-diphenyl-trichloroethane (DDT) and bedtime rhyme, it reflects the reality of life in other potent long-lasting pesticides throughout colonial New England, in which residents went the 1940s to 1960s that the prevalence of bed bug to bed hoping not to be bitten by these blood- infestations significantly decreased worldwide [3]. sucking pests while they were sleeping. We now know that bed bugs have long been associated Unfortunately, the world is now experiencing a Corresponding author: Blaine with human habitats, being found in references major resurgence in bed bug infestations, with A. Mathison, B.S., M(ASCP), Institute for Clinical and throughout history and from archaeological an explosion of reports beginning around the Experimental Pathology, sites dating back 3,500 years [2]. Bed bugs were turn of the century [4, 7]. Although the exact ARUP Laboratories, Salt Lake thought to have spread throughout Asia and cause of this resurgence is unknown, it is thought City, UT 84108. Tel.: 801-5 Europe in the early centuries of the Common to be due to multiple factors, including wide- 83-2787. ext. 2804. E-mail: Era, and later traveled to the Americas aboard spread resistance to commonly used pesticides, [email protected] ships of early European sailors [3]. By the 1900s, increased domestic and international travel, and 0196-4399/©2021 Elsevier Inc. bed bugs were estimated to be in 1/3 of the dwell- the decline in public health pest control programs All rights reserved ings in European cities and disproportionately that occurred in the latter half of the 1900s [8]. Clinical Microbiology Newsletter 43:1,2021 | ©2021 Elsevier 1 Bed bugs can be submitted to the clinical laboratory for identifica- In addition to C. hemipterus and C. lectularius, a few other mem- tion, and thus, clinical microbiologists should be familiar with their bers of the Cimicidae (cimicids) have been documented to feed on key morphologic features and how they can be differentiated from humans. Most of these zoonotic cimicids are parasites of bats or similar-appearing arthropods. Accurate identification is necessary birds but will feed on humans in the absence of their natural hosts for determining the cause of a patient’s clinical manifestations and or when humans live in close proximity to, or have frequent con- is also used to guide control efforts. This review addresses the tact with, the natural host (such as poultry farmers or when human aspects of laboratory collection, identification, and reporting of habitations become colonized by anthropophilic bats and birds). bed bugs, as well as their biology and epidemiology and the clini- Some examples are the bat bugs C. pipistrelli in Europe, C. pilosellus cal implications associated with infestations. and C. adjunctus in North America [11,12], and Leptocimex boueti in Africa [13] and bird parasites, such as the “Mexican chicken bug,” Haematosiphon inodora; the “swallow bug,” Oeciacus vicarious; the Species Implicated in Human Infestations “chimney swift bug,” Comexopsis nyctalis; and the “Colorado bed bug,” Hesperocimex coloradensis, in North America [12]. Bed bugs are obligatory hematophagous (blood-feeding) insects in the family Cimicidae of the order Hemiptera (the “true bugs”). Biology and Life Cycle Most human infestations with bed bugs are caused by the “com- Like all members of the order Hemiptera, bed bugs are hemi- mon bed bug,” Cimex lectularius, or the “tropical bed bug,” C. metabolous, meaning that immature stages (nymphs) resemble hemipterus. C. lectularius (from the Latin cimex, bug, and lectu- smaller versions of the adult and there is no dormant stage (pupa) larius, couch or bed) has a cosmopolitan distribution and feeds between immature stages and adults. All bed bugs that have been on humans, bats, and birds. Bed bugs probably originated as a implicated in human infestations have seven developmental stages: bat parasite and adapted to humans very early on, possibly when egg, five nymphal instars, and adult [4], with the exception of humans were still cave dwellers [9]. C. hemipterus (Latin hemipterus, H. inodora, which has only four nymphal instars [9] (Fig. 1). All half winged) also feeds on bats and birds, in addition to humans, nymphal instars and adults of both sexes require a blood meal [4]. but have a more tropical and subtropical distribution, primarily limited to within 30° north and south of the equator [10] (see “Epi- The duration of the life cycle of beg bugs is variable based on tem- demiology of C. lectularius and C. hemipterus” below). perature and humidity. Under average conditions in a controlled Figure 1. Life cycle of bed bugs. (Image courtesy of the CDC-DPDx.) 2 Clinical Microbiology Newsletter 43:1,2021 | ©2021 Elsevier environment (such as in a home or hotel), eggs take 1 to 2 weeks marked contrast to surveys conducted prior to 2000, in which to hatch and then about two months for nymphs to become adults only 25% of respondents had encountered a bed bug infestation. [14]. Adults usually live up to about 4.5 months [14], but under Their accompanying survey of 429 international pest management cooler conditions, a well-fed adult can live for up to one year or companies found similarly high frequencies for encountering a bed so [15]. bug infestation in Mexico/Central America (80%), Canada (98%), and Europe (92%) [19]. Similar findings have been reported by Bed bugs are primarily nocturnal feeders, while spending the day independent country and regional surveys [4]. hidden away from direct light in secluded areas called harborage areas. The peak feeding time is between 1 and 5 AM [4]. They Over subsequent NPMA surveys, U.S. pest control companies usually spend about 5 to 15 minutes feeding and feed once every reported increasing incidences of bed bug infestations and noted few days based on host availability, returning to their harborage that bed bugs were more difficult to control than infestations with areas, where molting, breeding, and oviposition take place. Bed ants, termites, and cockroaches [20,21]. Summer was noted to be bugs are positively thigmotactic (seeking contact with objects) and the season for receiving frequent complaints about bed bugs, and specifically prefer habitats where they can be in contact with rough 91% were found in single-family homes, followed by apartments/ substrates. In cases of heavy infestations, large quantities of bugs condominiums (89%), hotels/motels (68%), nursing homes (59%), congregate together, forming brood centers where their empty egg daycare centers and schools (47%), and offices (46%). Interest- shells, nymphal exuviae (shed cuticle), and feces accumulate [9]. ingly, hospitals accounted for 36% of bed bug infestations reported It is still not completely understood how bed bugs find a host. Sev- by survey participants, and public transportation accounted for eral external factors may play a role, including light, temperature, 19% [22]. and host stimuli, such as breath or carbon dioxide production. More details regarding bed bug infestation rates can be found in Under experimental conditions, bed bugs seemed less likely to a number of smaller regional studies. For example, a 2014 survey leave harborage areas in the absence of host stimuli, such as breath by the New York City Department of Health and Mental Hygiene [16]. When bed bugs do hone in on a host stimulus, the pathway to revealed that 5.1% of all respondents had a bed bug infestation in the host is not necessarily a direct line, and the insects exhibit stop- the past 12 months, with rates as high as 12% in some areas [23].