Bedbugs and Pathogen Transmission
To determine a causal relationship between vector and disease researchers must decide whether a pest, such as a tick or bedbug, can contract, maintain, and transmit an infection. The way that this is done in the laboratory is by exposing the bedbug, for example, to an infected animal or infected blood and then testing to see if the bacteria (or other pathogen) has been maintained or amplified in the bug’s own body. The bug must then be seen to transmit the infection to a naive (uninfected) host animal.
Vector Competence Screening of Cimex spp.
Screening for vector competence in this way is a cornerstone of infectious disease research and scientists must also account for things such as location, climate, ethological, entomological, and epidemiological factors that can affect transmission. Some animals, for example, may not be natural hosts of a bacteria, or the bacteria may not survive at a given temperature or in animals living in a certain environment.
Evidence of Bedbugs as Disease Vector
The research into bedbugs as agents carrying disease has largely relied on association and logic rather than actual evidence. Epidemiological studies, for example have linked populations of bedbugs with human disease, as well as detecting infectious agents in bedbugs but without actually ascertaining the ability of the bedbugs to pass on the infection, or even acquire it in the first place. A review of the literature by Delauney, et al (2011), determined that bedbugs had the apparent capacity to act as vectors for transmitting forty-five pathogens but that the proof available to support such cases varied substantially in terms of quality and quantity.
Bedbugs and Infectious Disease
Those pathogens studied most in relation to transmission by bedbugs include Coxiella burnetii, Wolbachia spp., Aspergillus spp., T. cruzi, and both hepatitis B virus and human immunodeficiency virus, all of which appear to be good candidates for transmission by these pests. In the 1963 review by Burton, two species of Borrelia were found in bedbugs, namely Borrelia recurrentis and Borrelia duttoni and, although differences arise between subspecies of bacteria, this may indicate the potential for bedbugs to act as a vector for Lyme disease bacteria Borrelia burgdorferi sensu lato.
MRSA in Bedbugs in Vancouver
Lowe and Romney published a paper last year looking at the ability of bedbugs to spread drug-resistant bacterial infection. They found that bedbugs in the downtown eastside of Vancouver carried MRSA (methicillin-resistant Staphylococcus aureus) and vancomycin-resistant Enterococcus faecium (VRE). This is an area of the city whose population is marginalized, often transient, and closely linked with a nearby hospital and, like shelters in Toronto, and other marginalized populations in large urban centers, reported around a 30% incidence of bedbugs.
Bedbugs in North America and Europe
The apparent resurgence of bedbugs in North America and western Europe in the last decade has been attributed to changes in insect management, increased resistance of bedbugs to pesticides, and an increase in worldwide travel allowing Cimex lectularius and Cimex hemipterus to colonize new locales. Whilst there is currently no clear evidence linking Lyme disease infection with bites from bedbugs there does appear to be a strong possibility of a vector-disease relationship that could have significant consequences for urban populations often considered not to be at risk of Lyme disease.
Urban Lyme Disease
Borreliosis may no longer be a zoonosis isolated to mainly rural areas with large concentrations of deer and rodents, instead it could now, courtesy of bed bugs, afflict those who never travel outside the concrete jungle. With many doctors already resistant to the idea of diagnosing Lyme disease or reporting such cases the likelihood of a diagnosis in a patient with no tick exposure is extremely low. Without further testing of bedbugs as potential vectors for Lyme disease it is highly likely that many more cases arise in the coming years where the infection can be tied, at least circumstantially, to bedbugs. This would leave doctors in a quandary as to whether or not to go against guidelines and diagnose Lyme disease despite lack of tick exposure, based on symptoms alone and suspicion of bedbugs transmitting the infection. Lyme disease from bedbugs may not be proven to be possible as yet but, if it is, an urban epidemic could soon occur.
Delaunay P, Blanc V, Del Giudice P, Levy-Bencheton A, Chosidow O, Marty P, Brouqui P., Bedbugs and infectious diseases. Clin Infect Dis. 2011 Jan 15;52(2):200-10.
Burton GJ., Bedbugs in relation to transmission of human diseases. Review of the literature. Public Health Rep. 1963 Jun;78:513-24.
Christopher F. Lowe and Marc G. Romney, Bedbugs as Vectors for Drug-Resistant Bacteria, Emerg Infect Dis. 2011 June; 17(6): 1132–1134.
Goddard J, deShazo R., Bed bugs (Cimex lectularius) and clinical consequences of their bites. JAMA. 2009 Apr 1;301(13):1358-66.