ABERDEEN PROVING GROUND, Maryland –
Entomologists with the Army Public Health Center say concerns about blood-sucking "kissing bugs," which can transmit Chagas disease, spreading north from southernmost states may fuel social media rumors, but the reality is there is no cause for alarm.
The eastern bloodsucking conenose, Triatoma sanguisuga, a species of kissing bug, feeds on animals and humans and has a habit of biting humans in the face, according to the U.S. Centers for Disease Control and Prevention, which recently confirmed a July 2018 bug bite incident in Delaware.
"There are two major reasons we don't see more cases of locally-transmitted Chagas disease in the United States," said Kevin Harkins, an APHC entomologist. "First, our local kissing bugs aren't great disease vectors, and second, most people live in tightly constructed housing that won't let in a tiny mosquito, much less a large insect like a kissing bug."
Harkins explains that insect-borne diseases usually need three connected "pieces" to happen, and if you remove one of these pieces, there is no disease transmission. These pieces are:
1. A susceptible host (people)
2. A good disease vector (kissing bugs)
3. The pathogen (Trypanosoma cruzi)
It turns out that U.S. kissing bugs may not be "good" vectors. Kissing bugs pick up the pathogen T. cruzi by feeding on infected animals (called "reservoir animals"), which may include domestic dogs, raccoons, opossums and other wildlife. Infected kissing bugs feeding on humans take in blood, and defecate infected feces. If someone rubs the kissing bug's feces into the itchy bite, or into their eyes, nose or mouth, they can become infected.
Kissing bugs in Mexico, Central America and South America usually defecate while they are feeding, and it's easy to accidentally infect yourself by rubbing or scratching without even waking up, said Harkins. Kissing bugs in the U.S. tend to defecate after they are done feeding and have climbed off the host, which means that even if the kissing bug bites, people are not exposed to the infectious feces, and don't contract the disease.
Kissing bugs are currently found in the 28 southernmost states and Hawaii, though they are most commonly reported in Arizona, California, New Mexico and Texas, Harkins said.
It is very rare to get Chagas disease from a kissing bug in the U.S., said Zia Mehr, a colleague of Harkins and also an APHC entomologist. For example, Texas had 22 locally transmitted cases from 2013-2017, Oklahoma is investigating two possible cases from 2018, and Louisiana reports a total of eight locally transmitted cases to date. According to the Maryland State Department of Health, there have been no locally acquired cases of Chagas diseases in the state. However, one kissing bug tested positive for T. cruzi in Charles County, Maryland, back in 2014.
Far from an invading species, Mehr says there are actually 11 different naturally occurring species of kissing bug in the U.S., though they do best in the warmer climates of the southern states. Despite the recent media attention, kissing bugs are not a new or "invading" insect in the U.S. and have been documented here since the mid-1800s.
Recent media reports about the Delaware kissing bug incident have increased awareness of Chagas disease and the kissing bugs that transmit it, but there is no evidence of an increase in Chagas cases acquired in the U.S.
"Most reported cases of Chagas disease are identified through programs like blood donation, where blood is screened for Chagas before being used," Mehr said.
Doctors follow up with donors who have positive tests to identify where they acquired the disease, said Mehr. Based on data from these tests and the follow-up questions, the vast majority of people in the U.S. diagnosed with Chagas disease contracted it while living in or traveling to other countries, particularly Mexico and Central or South America.
About 300,000 people in the U.S. and 8 million people in Central and South America are living with Chagas disease, but only a few contracted the disease through bites in the U.S., according to the CDC. The rare parasitic disease can lead to heart failure or stroke, but the parasite can hide in the body for decades and most people who are infected do not develop any signs or symptoms.
While overall risk is of contracting Chagas disease from an infected kissing bug is low, APHC public health experts say your greatest risk of exposure is by camping or sleeping outdoors in known kissing bugs endemic locations. Thus, it is necessary to protect yourself by using the Department of Defense Insect Repellent System, especially sleeping under a permethrin-treated bed net.
"Most people will never encounter a kissing bug, but we always recommend sleeping under a bed net if you plan to sleep outside or in rough structures like cabins and camping shelters in these states," Harkins said.
For more APHC information about kissing bugs, visit: https://phc.amedd.army.mil/PHCResourceLibrary/ChagasDisease_FS_18-045-0317.pdf