Valentines Day. A day for love! So surely the kissing bug should be a suitable subject for today’s blog?
Well, maybe not. These bugs (scientifically known as Triatomine bugs) are almost all haematophagous, meaning they feed on the blood of other animals. And though a few species of kissing bug feed on other insects, the majority have evolved to feed upon the vast reserves of blood found in vertebrate bodies. The name ‘kissing bug’ comes from their propensity for feeding on people’s faces, usually near to the mouth, as they are attracted to the odours exhaled during sleep. Some species of these tropical insects are found in Asia, Africa and Australia, but the majority are found in the Americas. One of the first published accounts of these insects was in Charles Darwin’s Journal and Remarks (better known as The Voyage of the Beagle) where he described being bitten by them whilst in South America:
“At night I experienced an attack (for it deserves no less a name) of the Benchuca (a species of Reduvius) the great black bug of the Pampas. It is most disgusting to feel soft wingless insects, about an inch long, crawling over one’s body. Before sucking they are quite thin, but afterwards they become round and bloated with blood, and in this state are easily crushed. They are also found in the northern parts of Chile and in Peru. One which I caught at Iquique, was very empty. When placed on the table, and though surrounded by people, if a finger was presented, the bold insect would immediately draw its sucker, make a charge, and if allowed, draw blood. No pain was caused by the wound. It was curious to watch its body during the act of sucking, as it changed in less than ten minutes, from being as flat as a wafer to a globular form. This one feast, for which the benchuca was indebted to one of the officers, kept it fat during four whole months; but, after the first fortnight, the insect was quite ready to have another suck.”
This behavior may be what gives these bugs one of their other common names – assassin bugs.
The Triatomine bugs are also a medically significant insect as they carry the parasite Trypanosoma cruzi. This parasite is the cause of Chagas Disease, which in the early stages cause localised swelling but without treatment goes on to cause life threatening damage to the heart and digestive system. Unlike malaria, the parasite is not passed from insect to human via the bite but rather from the insect defecating on the skin and the parasite making its way into the bloodstream via the bite wound.
These insects tend to congregate in dark crevices and hiding spaces in poorly maintained properties, waiting until night to come out and feed on the occupants of the building. As such the disease was historically found in poorer areas in South and Central America. The disease is now a major health concern for the region, with an estimated 18 million people infected, and around 14,000 deaths a year attributed to the disease. This is despite only 10% of those infected developing symptoms in the first 30 years following infection. With population booms and greater migration, in particular economic migration, the disease is beginning to spread into the USA. Around 30,000 cases have been reported in the US, and the CDC has listed it as one of the 5 main neglected parasitic infections in the country. This is because it tends to be confined to economic migrants, and groups less likely to seek out or afford medical treatment.
Whilst most species of kissing bug are confined to a fairly small geographic range, the species Triatoma rubrofasciata has a global tropical range. This is a recent phenomenon and has been driven by their close relationship with rats, which has seen them spread to ports around the world with international trade. Luckily this particular species rarely bites humans, and therefore tend not to spread the parasite easily. They also do not survive in cold temperatures, allowing the UK to remain free of them despite being a trade hub for many shipping lanes.
However, in 1999 one example was found in a sleeping bag in Hastings. This insect was already dead when found and the owner of the sleeping bag had never travelled outside the UK. It was sent to the Booth Museum for identification, where it was identified as a kissing bug, and samples were sent to the London School of Tropical Medicine. They confirmed the species, felt there was minimal chance of infection and stated that it likely died in the sleeping bag during manufacture or shipping in Asia (disappointing a few journalists who’d thought they’d found a juicy story). So avoid kissing bugs this Valentines Day (or any other day, for that matter!)
Lee Ismail, Curator of Natural Sciences