A report published on 28th January 2016 is a major setback to those trying to control the explosive spread of bed bugs. Neonicotinoids, the latest group of insecticides used by eradication professionals are proving ineffective due to a dramatic surge in resistance. Other reports imply that bed bugs may transmit Arboviruses. The Zika virus epidemic, recently linked to microcephaly, is an arbovirus.
Bed bugs (Cimex lectularius) have accompanied humans probably since we lived in caves. In fact they have several close relatives that are parasites of bats but will feed off humans who disturb the bat habitats. When humans left their cave environment and started sleeping in bedrooms the bed bugs moved in with them and have been a common inhabitant of most homes until the 1940s.
In the 1940s broad spectrum pesticides like DDT started to be used which together with a greater awareness of public hygiene effectively eradicated bed bugs from the developed world. This separation lasted until 1995 when increasing pesticide resistance and governmental bans of the most effective pesticides led to a resurgence in the spread of these blood sucking animals throughout society.
Although the after-effects of the feeding sessions, as shown in the photo above, can be rather unpleasant – a hundred years of research into bed bugs has not found them to transmit any particularly dangerous human diseases. They feed, usually when a person is sleeping, about once every 5-10 days and then retire to digest the blood and have sex (which sadly can be rather traumatic because their exoskeletons are not really designed for sensuous passion).
An adult can survive many months without a feed (even up-to a year if it is cool)
Until a few years ago most professional bed bug eradicators used pyrethroid insecticides to try and control the new epidemic. Then in 2013 a report was published in the journal Nature‘s ‘Scientific Reports’ (link here) which described that the bugs had evolved multiple ways of resisting these insecticides. This, together with increased travel, and population mobility, went a long way to explaining why the expansion in bed bug infestations was booming again. Their resistance was based on a variety of mechanisms like ‘strengthening’ the bug’s exoskeletons, neutralising the chemical effects of the insecticides or making the bugs metabolism less susceptible to these effects.
A new family of insecticides, the neonicotinoids, was introduced to try and combat this rapidly growing bed bug resistance. On January 28th 2016 a report was published in the Journal of Medical Entomology (link here) demonstrating that resistance to these newer insecticides was already so widespread that their application was becoming useless. In fact they may be harmful to nature due to their linkage to the drastic reduction in the bee population. As a result the currently available insecticides will be of little use as the bed bug epidemic spreads.
Although life with bed bugs is far from comfortable – years of research has failed to associate them with any nasty pathogens. However much of this research was during the period in which the bed bugs had been effectively eradicated in the developed world. The development of pesticide resistance has demonstrated how quickly they can mutate and evolve. What’s more – the scientific studies focused on diseases like HIV, MRSA and Hepatitus but little serious research had been done in relation to Arboviruses.
Arboviruses are viruses that are transmitted between humans via insect vectors (carriers) like mosquitos. A 2013 report in the scientific journal Plos (‘Bed Bugs and Infectious Disease: A Case for the Arboviruses‘ – link here) pointed out:
“Blood feeding arthropods such as mosquitoes, ticks, fleas, kissing bugs, biting flies, and lice serve as biological vectors for human pathogens. Thus, it seems natural that bed bugs would also transmit infectious agents……Surprisingly, previous attempts to link bed bugs with disease transmission have largely omitted those viral pathogens known to have transmission cycles involving insect vectors.”
The report describes the close relationship between human bed bugs and similar bugs which are parasites of bats and birds. It also explained how humans collecting guano from caves in Thailand were aggressively fed upon by local bat bugs. These people developed disease symptoms and antibodies to viruses (Kaeng Khoi virus) which are known to be transmitted by the bugs living with the bats (bat bugs).
With regard to any disease that might be transmitted by human bed bugs the authors suggest:
“Human populations most at risk would be those coexisting with long-term bed bug infestations such as those living in refugee camps, homeless shelters, migrant worker camps, or similar situations; particularly those located in proximity to large bat/bird populations. While some dramatic exceptions exist, arbovirus infection typically presents with generic symptoms such as fever, rash, or joint pain. These nonspecific symptoms severely complicate accurate diagnosis, particularly in geographic locations where diseases like malaria and dengue are common.” (and now of course Zika – CD comment)
I believe the current investigations concerning the Zika outbreak in several countries of the World should also not overlook the bed bug as a potential alternative vector for this disease. Zika’s normal vector is the Aedes mosquito and until the recent explosion in cases of child brain deformities (Microcephaly) this was thought to be a relatively mild illness with only 20% of those infected showing symtoms. The risk of foetal deformities has led to considerable interest in maps of the countries affected and the regions where the Aedes mosquito is present (both maps are in my report on Zika here).
If the human bed bug is found to be capable of transmitting the Zika virus (or any other dangerous arbovirus for that matter) the current explosion in the bed bug population across the world could broaden the geographical potential of such diseases way beyond the areas currently frequented by their mosquito vectors. As we prepare for the next pandemic (and there will surely be more pandemics) we should keep an open mind as to the source of the disease and any vector involved. Even Bubonic Plague may have used the human louse to lie dormant between epidemics in the middle ages (see my report here).
Diseases like SARS, MERS and HIV/Aids could not easily have been predicted but generally the worst pandemics have been due to viruses from other host animals that have mutated to become deadly to humans. Bed bugs, which have not been around for nearly a century, may turn out to be useful vectors of such microbes.
Time to go and vacuum the bed!
If you are interested in reading my other health focused articles try the following