In the third in a series of articles looking at the effects of the changes in Human behaviour caused by the Covid-19 restrictions on pest specie populations and behaviour, we look at the bed bug. At the tail end of March 2020 the UK was plunged into conditions none of us have seen in our lifetime, it has also allowed those of us who study pest activity to observe survival behaviours and the true resilience of these amazing animals.
With the aims of reducing transmission of the Sars-Cov2 virus, governments around the globe restricted the movement of people and closed non-essential businesses to the public now as we face a second national lockdown we will test the resilience of these insects.
Bed bugs are one of mans’ closest and longest established ectoparasites. Bed bugs have been biting us pretty much since our evolutionary origins. Evidence suggests the parasites first fed on bats, turning their attention to humans after we began inhabiting the same caves. As our species moved from caves to built structures the bed bug diverged into a distinct specie leaving the bat bug (Cimex adjunctus) to feed on the bats. Although now called bed bugs this is a greatly misleading name as they can be found in cars, busses, aircraft, bars of anywhere else people come to rest for any period of time. The Ancient Chinese cultures called them “stinking bug,” and prompted a similar name punaise, “to stink” in medieval France the name they still hold there. The Japanese once called bed bugs, insects from Nanjing (China), However, this term is considered derogatory in much the same way as the English called syphilis “the French disease”. Interestingly there is no indigenous American word for bed bug inferring that they did not occur in North America before the arrival of European settlers. However, the high population density and poor construction practices north America have allowed bed bugs to more than make up for the late introduction and thrive, much to the annoyance of our American cousins.
Bed bugs have survived every technological and pharmaceutical advance that man has taken to control this pest and they remain our closest ectoparasite. As our understanding develops the resilience of this insect never fails to stagger all who work with them. The covid-19 lockdowns and alterations to human behaviour caused by the risk of infection may pose the greatest threat to the success of this insect. It is logical to assume that no animal will just wait to starve to death. So will employ a number of survival tactics to ensure their population is ready to maximise all opportunities that present themselves in the short term but also to ensure genetic diversity to ensure the long term survival of the specie.
Planes, trains and automobiles
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. The first case of bed bugs on an aircraft was reported in 1929 on a Graf Zeppelin and they have plagued the aviation industry since. In Q2 of 2020 international air travel reduced by 92% due to the Covid lockdown restrictions, airlines around the world mothballed their fleets of converted the airframes for cargo transport. Bed bugs were always very adept at exploiting the high occupancy of airline seats however for the past 6 months most have been empty. It would appear that bugs on aircraft during this period have entered a state of diapause, a starvation induced hibernation. The regular maintenance needed to keep aircraft compliant however, will have caused an increase in atmospheric CO2 in the aircraft cabin, this caused bugs to reawaken and start to quest for a feed. Some reports have been received of questing bugs found by cabin cleaners or maintenance teams. This regular short stimulus in an otherwise barren environment causes the bugs to initiate questing with no chance of a feed. It is unclear how long bugs will survive the repeated energy wastage, but it is apparent that this will have a negative impact on the survival of the population and that aircraft bound insects will fair far worse than their land based counterparts. It will be interesting to see what effect the removal of this potential conduit of infestation, even for a short period, will have on the hospitality sectors infestation frequency but only time will allow us to assess this.
Although relatively rare in the road and rail passenger transport sectors bed bugs have seen a similar reduction in feeding opportunities in buses, coaches and train carriages and the frequency of bed bug activity appears to be on the rise. The passenger reduction is just as marked as seen in the aviation sector but with an added change in user groups and a strong proportionate swing towards care and other essential workers using public transport has also been seen. We must ask if there could be links between the increase in infestations in the care sector and the transport infrastructure.
Broadly speaking, all bed bug populations in hotels and holiday lets have seen similar population dynamics through the Covid restrictions. During the first month of the travel bans populations stayed fairly stable. Egg clutch size and frequency declined towards the end of the first month. Egg hatching continued as normal however with no access to a blood meal of stimulus to start feeding these early unfed first instar nymphs did not have energy reserves to allow them to survive for any protracted period. Later nymphal instars and adults were not adversely affected. During the Second and third month of lockdown early instar insects started to die out from starvation. Later instars show very little mobility. Gravid females started to show some unusual behaviour. In most insect species, females oviposit close to food sources and select egg laying sites that maximise nymphal survival but lockdown caused unpredictability of feeding opportunities and led to reports of females making suboptimal decisions in egg laying with clutches being found a long way from possible feeding opportunities. This could, however, easily be argued as actually being a sound survival tactic. Many insects will, under unfavourable conditions, lay eggs in a dispersed and apparently haphazard fashion, this is in the hope that at the time of hatching at least some will be in more favourable conditions. As we moved beyond the first few months of Covid restrictions we started see hotels beginning to reopen. The first 1000 or so that we look after were open by the end of month 4. During this period, we started to find extensive questing behaviour from infestations that were left untreated through lockdown. With single insects being found in areas with no history of activity, bugs found walking in corridors or in linen rooms. This has resulted in some unusual infestation locations in hotels like back offices and restaurants.
Sites operating partial lockdown like hotels supporting care or social service contracts continued to have infestations introduced and developing at the expected rate.
The unstable overseas travel opportunities caused by the unpredictability of the travel corridor scheme caused a behavioural shift in the UK towards the “staycation”. Many coastal and rural hotels were operating at full capacity, but the traditional business hubs were operating at less than 10%. This has caused a disparity in infestations away from the traditional hot spots of activity. The rapid increase in activity in these hotels suggests that the bed bug numbers in domestic settings have increased during the period we were confined to our homes. It is logical that their numbers should boom in areas with increased human activity but unfortunately for humans this is our homes.
Only time will tell how the bed bug population will fair in the long term, but it is likely that as our lives and habits return to normal so will those of bed bugs.
