The Bug with a Dangerous Kiss

Kissing Bug

The CDC Has Reported A Potentially Dangerous Insect in North Carolina, But Is There Cause for Concern?
November 25, 2015

Blown up, and looked at from afar, the triatomine bug — or as it is more commonly known, the “kissing bug” — could be considered almost beautiful. Dark wings and legs and a vibrant striped body set this penny-sized insect apart from many beetles or mosquitos North Carolinians see every day.

Kissing BugInside the beauty, however, resides a sinister passenger: a single-celled swimming parasite called Trypanosomiasis cruzi (T. cruzi for short) that causes the potentially deadly Chagas disease.

Experts for a long time considered Chagas and the kissing bugs themselves a problem mainly in Latin American countries, occasionally jumping northward into Texas or Arizona. According to the CDC, however, reports of kissing bugs have been coming in from most of the southern U.S., including Georgia, South Carolina and North Carolina.

Kissing bugs, like mosquitos, some species of flies and ticks, are blood feeders. They come out at night and bite sleeping animals — generally on the face, hence the “kiss”. They are not picky, either. Kissing bugs will feed off humans, domestic and wild mammals, birds and even snakes.

Also like mosquitos, flies and ticks, the kissing bugs themselves are not the real danger. Anyone who has had a bug bite knows it can itch and swell and hurt, but the real threats are the parasites, bacteria and viruses that live inside these insects. Epidemiologists call these insects “vectors:” a means of spreading an infection from a reservoir where a disease normally exists, often without causing harm, to a host where it can wreak havoc.

Malaria, Lyme disease, Dengue fever and Chagas disease are just a few of the infections that use insects to infect humans. Many, like Dengue, malaria and African sleeping sickness are saliva-borne. They live in the mouths of the insects and enter a host’s body directly through a bite.

T. cruzi, the kissing bug parasite that causes Chagas, takes a different and markedly more stomach-churning path. Unlike malaria or Dengue, T. cruzi  is an intestinal parasite so it lives in the kissing bug’s intestines and passes through its feces. Kissing bugs will feed as much as they can off a single host and while they are sitting around and drinking up blood, they will defecate. If a host scratches near the bite or brushes against it, the kissing bug feces and the T. cruzi parasites get rubbed into the open bite wound. Also, if the kissing bug defecates on a mucous membrane (usually the eyes, nose or mouth), the parasites can seep in through the membrane.

T. cruzi in Red Blood CellsOnce inside the body, T. cruzi gets right to work at creating Chagas disease. The acute form of Chagas occurs immediately after infection and can cause swelling, fever, rash, and a few other symptoms that tend to go away on their own in a few weeks or months.

More troubling, however, is the chronic form of Chagas. After the acute infection dies down, the parasites remain in the body, just going about their business and for about 70% of Chagas patients, that’s the last they ever hear of it. But about 30% of people with Chagas develop dangerous swelling of the intestines or heart. These complications can pop up decades later without symptoms and the heart issues can even be deadly.

Chagas is treatable, and can even be curable if it is detected quickly enough. The trouble is its acute form is somewhat generic — that is, it doesn't have a collection of symptoms that screams "I'm Chagas" — and is relatively rare in most of the United States so it is not generally a doctor's first thought, and both the acute and chronic forms can be symptomless. As a result Chagas often goes undetected until the big heart and intestinal symptoms hit.

So if kissing bugs are flying around the southern half of the United States and spreading potentially deadly Chagas disease, the next logical question is, “Why aren’t people dropping dead right and left?”

Well according to the CDC, getting Chagas from an insect bite, especially in southeastern states like North Carolina is very rare and very difficult for a number of reasons. The first reason is that the mode of transmission (the kissing bug feces getting into a wound or the eye or mouth) requires a lot of steps to go exactly right (or wrong). The bug has to defecate near the wound, which is common but not guaranteed, and then by (un)lucky chance it has to roll into the bite wound, eyes or mouth or the bitten animal has to move it there, which is also not a guarantee.

In fact, a 2013 study by Mexican and French scientists estimated — based on modelling and field data of Chagas disease from the last 10 to 15 years — that the chance of contracting Chagas from a kissing bug bite, in an area where T. cruziChagas disease is prevalent (discussed below) is about 58 thousandths of a percent. Put another way, if infected kissing bugs bit the same person somewhere between 900 and 4000 times, he would contract Chagas once.

The way we live also makes insect transmission unlikely. Kissing bugs come out at night to feed while we are sleeping, but they can’t burrow through plaster walls or melt a screen door so by the virtue of just being inside and taking normal bug prevention steps, we can keep most, if not all of the kissing bugs away.

Not just how we live but where we live also pushes down the likelihood of getting Chagas from a kissing bug. Chagas is not what epidemiologists call “endemic” to this region. What that means is that we do not have a high enough population of people with Chagas for the disease to keep surviving and spreading without help from other places.

Endemism is important, especially with Chagas, because of how it spreads. Once a bug infects one animal, then another bug feeds on that animal and is infected before moving on to infect more animals and on and on it goes. Not all kissing bugs carry T. cruzi, and in a place that is not endemic, like North Carolina, there are not as many places for the kissing bugs to pick up the parasites and reload on parasite to pass to other animals. Combine that with an already low transmission rate and T. cruzi has a hard time moving around in the United States.

The CDC estimates there are roughly 300,000 people in the United States who are infected with Chagas, most of who either immigrated to the United States from or frequently travel to Central or South America. That may sound like a lot, but at one tenth of a percent of the U.S. population, that’s not enough to really consider Chagas endemic to the point where insect transmission is a problem for most of the country. States like Texas, however, where there is a comparatively high rate of Chagas are stepping up efforts to curb the disease and monitor kissing bugs.

For now, though, the CDC is primarily focused on stopping human-to-human transmissions. Humans can pass Chagas on to other humans, but that is also much more difficult than passing on a cold or the flu. Blood and tissue are generally how Chagas gets from one person to another, so the CDC watches for blood transfusions, organ transplants and pregnant mothers, who could pass Chagas to their babies. The Red Cross now screens blood donations for Chagas, which is one way people find out they have it.

All in all, getting Chagas from a kissing bug is unlikely in the United States. Still Chagas disease is no joke, and with the CDC finding kissing bugs throughout the southeast and entomologists in Texas finding more and more kissing bugs with Chagas, the insect and the disease should be on the radar. Luckily, there are things anyone can do in and around their home to keep their risk for Chagas low.

Kissing BugThe World Health Organization, which constantly fights Chagas in its endemic regions, says the best way to deal with the disease is to control the kissing bugs. For North Carolinians, that means keeping them out of your house and watching for them on your property.

Making sure you have good screens, sealing any cracks around doors and windows, and preventing access to attics and crawlspaces can prevent the bugs from getting in. Outside, they like to live in wood piles, rock piles, under concrete and under porches, so periodically checking these locations, and removing whichever ones you can, can cut down on the possibility of kissing bugs.

Kissing bugs also like to live near their food, where animals sleep. Doghouses, chicken coops and areas where rodents have made their homes are big nest spots for kissing bugs. Keeping pets inside at night can keep them safe and keep kissing bugs away.

If they do manage to get into the house, they will probably make their home near food. Under mattresses, near pet beds, under nightstands and in bathrooms are all likely spots.

If you do happen to see a kissing bug in your house, don’t crush it, as that can spread the parasites. Instead, try to trap it in a small container, then either fill the container with rubbing alcohol or freeze it to kill the bug. You should also clean any surface the kissing bug has touched with bleach (1 part bleach to 9 parts water) or ethanol (7 parts ethanol to 3 parts water). If you see them in your home repeatedly, or find kissing bug eggs, your best bet is to call an exterminator and if you suspect for any reason that you may have Chagas disease, talk to your doctor. Your doctor can do a blood test and if it comes back positive, your doctor can work with you on treating it. As the CDC reports though, getting Chagas from an insect bite would be very rare in North Carolina.

As the CDC continues to monitor kissing bugs and Chagas in the United States, knowing that you found one could be helpful. You can help put yourself at ease and help the CDC by having the bug identified and tested for T. cruzi parasites. You can do this at a local extension service, health department or a university laboratory. If you don’t have any of those near you, you can contact the CDC Division of Parasitic Diseases and MalariaFor more information of kissing bugs and Chagas disease from the CDC, click here.

All in all though, the last word on the kissing bug in North Carolina is awareness. While the consquences of a kissing bug bite can be severe, North Carolinians deal with similar threats on a daily basis. Just like we wear long pants and check for ticks when in tall grass, steer clear of beehives and keep an eye out for snakes when we're out in the woods, staying safe from kissing bugs and Chagas disease is a matter of knowing and following the rules and being aware of your surroundings. That is the best way to protect yourself, your pets and your family. Kissing bugs don't have to be the kiss of death.

— Daniel Lane

Daniel Lane covers science, engineering, medicine and the environment in North Carolina.