There are plenty of examples of blood-sucking insects passing on diseases to their hosts. Mosquitoes, ticks, fleas, and several different species of flies are just a few insects that pass on human pathogens while getting a meal. However, bed bugs, one of the most prevalent blood-sucking insects, are talked about more for being annoying pests that are difficult to get rid of and less as deadly killers.
Bedbugs belong to the Cimicidae family, which contains over 100 species. While all members of the family suck blood, only two species feed almost exclusively on humans—most of the species belonging to the Cimicidae family prey on bats. Since bed bugs fed on bats, they were often in caves, infesting bat nesting areas. Once humans moved into caves to seek shelter, the bed bugs had a new meal source. After that, wherever humans went, the bed bugs followed. Bed bugs were found to associate with humans as early as 400 B.C. in Greece and 600 B.C. in China.
Although bed bugs were previously isolated to specific geographical ranges, they have experienced substantial population increases since the 1990s, likely due to the rise in global travel and trade. Cimicidae species previously isolated to tropical and subtropical regions are now in the United Kingdom.
Bed bugs have been reported to carry 45 different human pathogens, but can they make humans sick? When an insect takes a blood meal, it often ingests pathogens. However, just taking in a pathogen doesn’t mean it can replicate within the host and spread to future hosts. Both ticks and mosquitoes have been found to have HIV after taking a blood meal from an infected person but cannot spread it to humans.
As of 2023, no disease outbreaks due to bed bugs have been reported. In fact, there have been no confirmed cases of humans contracting any diseases transmitted by bed bugs. However, other species of the Cimicidae family that prey on birds transmit bird-specific viruses. Additionally, there is evidence that bed bugs are competent vectors, meaning they can spread a pathogen from person to person for some diseases. For a blood-sucking bug to transmit pathogens, the pathogen must be able to replicate both in the host and the bug, meaning the pathogen has to overcome two very different immune systems. Once a pathogen has reached sufficient replication levels, it can be passed on to a new host during a blood meal. Most pathogens are species-specific due to the diversity of animal tissues and immune systems.
In 1970-1971, workers in Thailand who mined for bat guano began to complain of illness after entering the caves. Many of the bats in those caves carried the Kaeng Khoi virus; also in the caves were Cimex insuetus members of the Cimicidae family that fed on the bats in the cave. However, Cimex insuetus is opportunistic and would feed on the cave workers. Cimex insuetus tested positive for the Kaeng Khoi virus, and so did several cave workers. However, the Kaeng Khoi virus transmission by Cimex insuetus has yet to be demonstrated experimentally.
Bugs can also spread diseases without direct bites through feces. Open wound contact with feces can cause infections. Kissing bugs, which carry the causative pathogen of Chagas disease, Trypanosoma cruzi, are strikingly similar to bed bugs. Kissing bugs are bloodsuckers, and Trypanosoma cruzi can enter the human body through the open wound caused by bites. Common bed bugs have been shown to carry Trypanosoma cruzi, and infected bed bugs that fed on mice transmitted the disease, likely through bed bug feces. However, there have not been any confirmed cases of a human contracting Chagas disease from a bed bug.
Although there is emerging evidence that bed bugs can spread disease, they are far less prevalent as pathogen spreaders than other blood-sucking insects. While it is still poorly understood why bed bugs do not carry diseases, some hypotheses exist. Bed bugs mate through traumatic insemination, where the male bypasses the female’s genital tract and instead ejaculates into her bloodstream. This mating method causes damage to females and results in shorter lifespans. Still, it also means there are frequent introductions of pathogens directly into the bloodstream, which can cause repeated immune stimulation. Bed bugs may just be better at clearing pathogens than other bugs. They also have compounds that destroy bacteria in their ejaculate, hemolymph (the blood equivalent in bugs), and antimicrobial peptides in their saliva.
Given the dramatic increase in bed bug populations each year and their frequent contact with human pathogens, it is not out of the realm of possibility that pathogens will adapt to being spread by bed bugs. Either way, they are annoying pests that everyone hopes never to encounter.
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