Histamine is involved in allergic reactions. It’s a biogenic amine and for our purposes the important thing to know is that it modulates the immune response in mammals, like us. Histamine is in many things including foods we eat, and when it comes into contact with certain receptors, it can cause allergic reactions.  

So what does that have to do with bed bugs? Bed bugs excrete histamine in their feces and it serves them as part of their aggregation pheromone as a “stop here” sign for fellow bed bugs. We call that an arrestant. What we didn’t know is if other household pests or blood feeding insects also produce histamine or if just closely related insects to bed bugs produce histamine. The researchers wanted to know if histamine production was related to blood feeding, hematophagy.

 

 

In this study, they looked at 22 species of arthropods to determine presence and production of histamine in excreta. These species were grouped into three categories, common indoor pests, which included several cockroaches, termite, flies, beetles, moths, and mites. Then blood feeding species which was mosquito, flea, and tick, and finally specifically blood feeding hemipterans like bat bugs, kissing bugs, and of course our star, the bed bug. Also a non-blood feeding hemipteran, the stink bug, was tested.   

They reared all the species in laboratory conditions according to individual best practices. They fed the blood feeding species on either lab alternatives or animal blood, don’t worry they didn’t sacrifice themselves. After rearing up enough adults or nymphs, they went to determine histamine presence. They took swabs and sampled the substrate in the rearing containers of the pests.  After swabbing, they tested the samples using gas chromatography and mass spectrometry commonly referred to as GCMS which is used to determine the chemical makeup of a sample. Its quite a process that is beyond the basics of what I remember from organic chemistry but the important part is what they found.  

If histamine was detected at all, they continued further testing with that species. Histamine was only found in 5 of the 22 species which were the bed bug, tropical bed bug, bat bug, and two kissing bugs. Two species, not two individual bugs that were kissing. These are all blood feeding hemipterans. No other blood feeders were found to have histamines.  

Further testing consisted of starving the arthropods then separating them into individual tubes and feeding them afresh. They were able to then weigh them to see how much blood was being consumed. They sampled the tubes again to collect the insect feces and then prepped the samples for analysis. The analysis showed them how much histamine was being produced per bug per day. They saw that there was a strong positive linear correlation between amount of blood consumed and amount of histamines excreted. Blood alone was not cause for histamines since other blood feeding insects didn’t have any. Hemipterans in general didn’t have it because the stink bug which is a non blood feeding hemipteran, didn’t produce any.  

They hypothesized that histamine was introduced to the bugs by blood but that hemipterans didn’t have a certain enzyme to break it down so they ended up excreting it, making bed bugs as major indoors pests compared to the other bugs tested, are the main arthropod source for histamines in a household. Bed bugs proportionately produce more histamines than other hematophagous hemipterans, making them the top concern for household histamines. Household hematophagous hemipteran histamines, try to say that five times fast.   

Article by Ellie Lane

References

Simona Principato, Alvaro Romero, Chow-Yang Lee, Kathleen Campbell, Dong-Hwan Choe, Coby Schal, Zachary DeVries, Histamine excretion in common indoor and hematophagous arthropods, Journal of Medical Entomology, Volume 60, Issue 6, November 2023, Pages 1269–1277, https://doi.org/10.1093/jme/tjad103

Podcast