Kissing Bugs

"Beware of kissing bugs!" Recent news headlines suggest that deadly insects are invading the U.S., inflicting lethal bites on people. These misleading headlines were shared widely on social media, and health departments across the U.S. have subsequently been inundated with calls and emails from concerned residents.

Kissing Bugs

Kissing bugs are true bugs in the assassin bug family (Reduviidae), but don't let that frighten you. This insect order, Hemiptera, includes everything from aphids to leafhoppers, all of which have piercing, sucking mouthparts. Within this large order, the assassin bugs are a smaller group of predators and parasitic insects, some of which use remarkable cunning and skill to catch and eat other insects.

The family of assassin bugs is further divided into subfamilies, one of which is the subfamily Triatomina, the kissing bugs. They're known by a variety of nicknames, including the equally ominous "bloodsucking conenoses." Although they look nothing like them, triatomine bugs are related to bedbugs (also in the order Hemiptera) and share their bloodsucking habit. Triatomine bugs feed on the blood of birds, reptiles, and mammals, including humans. They are mainly nocturnal and are attracted to lights at night.
Triatomine bugs earned the nickname kissing bugs because they tend to bite humans on the face, particularly around the mouth. Kissing bugs are guided by the smell of the carbon dioxide we exhale, which leads them to our faces. And because they feed at night, they tend to find us while we're in bed, with only our faces exposed outside our bedding.

How Kissing Bugs Cause Chagas Disease

Kissing bugs don't actually cause Chagas disease, but some kissing bugs carry a protozoan parasite in their guts that does transmit Chagas disease. The parasite, Trypanosoma cruzi, is not transmitted when the kissing bug bites you. It isn't present in the kissing bug's saliva and isn't introduced into the bite wound while the bug is drinking your blood.

Instead, while feeding on your blood, the kissing bug may also defecate on your skin, and that feces may contain the parasite. If you scratch the bite or otherwise rub that area of your skin, you can move the parasite into the open wound. The parasite may also enter your body in other ways, such as if you touch your skin and then rub your eye.

A person infected with the T. cruzi parasite can transmit Chagas disease to others, but only in very limited ways. It can't be spread through casual contact. According to the Centers for Disease Control and Prevention (CDC), it can be transmitted from mother to infant congenitally, and through blood transfusions or organ transplantation.

A Brazilian doctor, Carlos Chagas, discovered Chagas disease in 1909. The disease is also called American trypanosomiasis.

Where Kissing Bugs Live

Contrary to the headlines you've seen, kissing bugs are not new to the U.S., nor are they invading North America. Nearly all of the estimated 120 species of kissing bugs live in the Americas, and of these, just 12 species of kissing bugs live north of Mexico. Kissing bugs have lived here for thousands of years, long before the U.S. even existed, and are established in 28 states. Within the U.S., kissing bugs are most abundant and diverse in Texas, New Mexico, and Arizona.

Even within the states where kissing bugs are known to live, people often misidentify kissing bugs and believe they are more common than they actually are. Researchers running a citizen science project at Texas A&M University asked the public to send them kissing bugs for analysis. They reported that over 99% of the public's inquiries about insects they believed to be kissing bugs were actually not kissing bugs. There are a lot of other bugs that look similar to kissing bugs.

It's also important to understand that kissing bugs rarely infest modern homes. Triatomine bugs are associated with impoverished areas, where homes have dirt floors and lack window screens. In the U.S., kissing bugs generally live in rodent burrows or chicken coops, and can be a problem in dog kennels and shelters. Unlike the box elder bug, another Hemipteran insect that has a bad habit of finding its way into people's houses, the kissing bug tends to stay outdoors.

Chagas Disease Is Rare in the U.S.

Despite the recent hype about "deadly" kissing bugs, Chagas disease is a very rare diagnosis in the U.S. The CDC estimates there may be 300,000 people carrying the T. cruzi infection in the U.S., but that the majority of these are immigrants who contracted the infection in countries where Chagas disease is endemic (Mexico, Central America, and South America). The University of Arizona's Department of Neuroscience reports that only 6 cases of locally transmitted Chagas disease have been reported in the southern U.S., where Triatomine bugs are well established.

Besides the fact that U.S. homes tend to be inhospitable to kissing bugs, there's another key reason why infection rates are so low in the U.S. The kissing bug species that live north of Mexico tend to wait to poop for a good 30 minutes or so after they indulge in a blood meal. By the time the kissing bug defecates, it's usually a good distance from your skin, so it's parasite-laden feces doesn't come in contact with you.

Sources

• _{Subfamily Triatominae – Kissing Bugs, Bugguide.net. Accessed online December 7, 2015.}
• _{Chagas Disease, University of Arizona Department of Neuroscience. Accessed online December 7, 2015.}
• _{Triatomine Bug FAQs, Centers for Disease Control and Prevention. Accessed online December 7, 2015.}
• _{Epidemiology & Risk Factors (Chagas Disease), Centers for Disease Control and Prevention. Accessed online December 7, 2015.}
• _{Kissing Bugs & Chagas Disease in the United States, Texas A&M University. Accessed online December 7, 2015.}
• _{"Kissing bugs (Triatoma) and the skin," by Rick Vetter MS, Dermatology Online Journal 7(1):6. Accessed online December 7, 2015.}
• _{"Remain Calm: Kissing Bugs Are Not Invading the U.S.," by Gwen Pearson, Wired.com, December 3, 2015. Accessed online December 7, 2015.}
• _{Developing a Clearer Picture of How Assassin Bugs Evolved, by Iqbal Pittalwala, by October 25, 2012, University of California Riverside news release. Accessed online December 8, 2015.}