Pyrethroid resistance and bed bugs in Winnipeg

In 2006 I noted an apartment block beside my building had numerous suites with bed bugs which were successfully treated with a single course of Permethrin. Each suite required about 10 minutes of work. Impressive!!


In 2007 when i began my own bed bug work I noted similar patterns. Some cases of bed bugs were easily treated with a single course of Permethrin – even in cases where cooperation was poor. Other cases were much more difficult.


It is now 2014 and I have noted that it is exceedingly rare to find those easy cases. Almost all the cases require multiple treatments. Many exterminators have also shifted to Cyfluthrin to avoid the resistance issues with Permethrin.


I have noted in cases where there are beds on the floor that bed bugs can traverse a treated box spring and baseboard with impunity. I now rely in bed leg traps and chemical treatments under the bed to increase the pesticide load onto the bugs. Most recently I had a case where the tenant refused to cooperate with bed isolation and laundry protocols and we could not get rid of the bugs. I evicted the tenant after the 9th treatment. I did note that some of the bugs in this case abandoned the treated baseboards and harboured on the ceiling in plain view to avoid the treated baseboards. But they survived quite nicely despite repeated crossings of treated box springs and baseboards.


In other cases I have noted bed bugs harbouring (apparently quite happily) in cloth folds treated with Permethrin two weeks earlier. In another case I noted a bug happily harbouring on a block of wood that had been treated with Cyfluthrin. When prodded the bug ran for cover elsewhere. I don’t know if these bugs would have survived long term but the sight of bugs quietly harbouring on treated surfaces was quite disturbing.


Currently pyrethroids are being reviewed for safety and there is some concern that their label directions might become more restrictive. Given the pace of growing pyrethroid resistance I don’t think it really matters. It is only a matter of time before we are simply forced to abandon pyrethroids altogether because they are ineffective. We will have to start thinking differently.


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