‘Kissing Bugs’ Not the Only Hosts for Potentially Deadly Chagas Disease

chagas disease

Story at-a-glance -

  • Chagas disease, caused by a protozoan parasite typically found in Mexico, Central and regions of South America, is a deadly infection that currently affects 8 to 9 million people. The disease can also infect many other animals, including dogs
  • The infection spreads via a parasite known as Trypanosoma cruzi (T. cruzi) which is transmitted to animals and humans via “kissing bugs,” and can cause heart failure and colon complications (among other problems) in humans and dogs
  • Chagas disease can be spread to people through blood transfusions, organ transplantation, congenital transmission and eating uncooked food contaminated with feces from infected bugs
  • Several new animals native to Latin America can host kissing bugs, including tayras, New World monkeys, porcupines, sloths and coatis, but the infection is also showing up in areas of the southern U.S.
  • There are not consistently effective, readily available treatments to cure Chagas without side effects in the myriad of animals that can contract the disease, so avoiding contact with the insect is recommended

By Dr. Karen Shaw Becker

Chagas disease, aka American trypanosomiasis, a potentially deadly infection that can have lifelong effects if not treated, is caused by a protozoan parasite typically found in Mexico, Central and most of South America. The disease can cause heart failure as well as chronic esophagus or colon complications, among other problems.

While it affects 8 to 9 million people, according to the Centers of Disease Control and Prevention (CDC),1 most aren’t even aware of it; however, it can also affect animals. The infection comes from a parasite known as Trypanosoma cruzi (T. cruzi) which is transmitted to animals and humans via triatomine vectors, aka “kissing bugs.” The mode of transfer is enough to make the stoutest heart cringe, as the CDC explains in detail:

“These blood-sucking bugs get infected by biting an infected animal or person. Once infected, the bugs pass T. cruzi parasites in their feces. The bugs are found in houses made from materials such as mud, adobe, straw, and palm thatch. During the day, the bugs hide in crevices in the walls and roofs. During the night, when the inhabitants are sleeping, the bugs emerge.

Because they tend to feed on people’s faces, triatomine bugs are also known as ‘kissing bugs.’ After they bite and ingest blood, they defecate on the person. The person can become infected if T. cruzi parasites in the bug feces enter the body through mucous membranes or breaks in the skin. The unsuspecting, sleeping person may accidentally scratch or rub the feces into the bite wound, eyes, or mouth.”2

In the latter part of 2017, scientists from the University of California, Riverside (UCR)3 revealed the disease may spread easier than they once thought, as four animals native to Latin America can host kissing bugs: weasel-like mammals called tayras; New World monkeys, of which there are about 100 species, including marmosets and tamarins;4 porcupines, found in temperate areas of both North and South America; sloths; and coatimundis, aka coatis, including the white-nosed species, which can also be found in the southernmost portions of the U.S.5

Divide the U.S. horizontally, and roughly the bottom half is also home to one or more of the 152 species of kissing bugs. Texas A&M University (TAMU) notes that 55 percent of those collected and submitted by the public for its research were infected with T. cruzi.6

Where Kissing Bugs and Chagas Disease Are Found

In the U.S. and other areas where Chagas disease is not common, but can still be found, strategies for controlling it focus on prevention. The CDC notes that while it’s not spread through casual contact with infected people or animals, there are other ways this disease can be passed to — or contracted from — others:

  • Congenital transmission (from a pregnant woman to her baby)
  • Blood transfusion
  • Organ transplantation
  • Consumption of uncooked food contaminated with feces from infected bugs
  • Accidental laboratory exposure

Chagas disease, largely overlooked as a deadly infection, is at least now on the priority list (along with other parasitical diseases cysticercosis, toxocariasis, toxoplasmosis and trichomoniasis) for intervention for the sake of public health. As such, Chagas disease is called an NTD — a neglected tropical disease — or one that causes chronic, debilitating, communicable diseases for people living in poverty in developing countries.

In people, the worldwide burden of such diseases is measured in disability-adjusted life years, or DALYs. The assessment is a measure of the gap between current and ideal health status, calculated by adding years of life lost and years lost due to disability. One DALY can be considered equivalent to one lost year of healthy life.

Frankly, it’s staggering to note that the disease burden for people suffering from Chagas disease is 662,000 DALYs, Healio reports.7 One reason such diseases proliferate is because they cause disability rather than death. While this is one of many infections that could be easily and inexpensively treated and even prevented, infected people often can’t afford it.

Further, the disease is considered to transmit more easily through prolonged exposure. Dr. Monica E. Parise and Dr. Laurence Slutsker from the CDC’s Division of Parasitic Diseases and Malaria and Center for Global Health, and Dr. Peter J. Hotez from the National School of Tropical Medicine at Baylor University, wrote:

“The perception that parasitic diseases are no longer relevant or important is a major impediment to implementing currently available control and prevention strategies. The neglected parasitic infections in the United States are part of the global burden of parasitic diseases, and strategies that reduce or eliminate them in the United States can someday be applied globally.”8

More on Kissing Bugs

As a nocturnal insect that feeds on blood, kissing bugs are marquis- or football-shaped insects that as adults are comparable in size to a penny. They usually have a subtle band around the edge of the outside “shield” that appears to be stitched with red-orange thread. In the U.S. the highest density is in Arizona, New Mexico and Texas, but 28 states have reported having them.

While some of the insects in the Reduviidae family, called reduviids (to which kissing bugs belong), eat plants and other insects, kissing bugs can inflict a bite to remember. They can feed on both wild animals and pets, and all may be susceptible to Chagas disease. However, dogs can also be infected by eating infected bugs.

Kissing bugs, their secluded habitat and the animals (and humans) they feed on can act as a “reservoir” for the parasite. But studies have been few and far between, so how to remedy the problem was tackled by a group of scientists led by Christine Weirauch, Ph.D., a professor of entomology at the University of California, Riverside’s College of Natural and Agricultural Sciences.

Between 2005 and 2015, the researchers conducted polymerase chain reaction (PCR) testing on the gastrointestinal contents of 64 specimens of kissing bugs gathered from rural areas of the U.S., South and Central America. DNA blood analysis showed that 24 of the samples revealed host associations, and 20 specimens — 31.3 percent — of kissing bugs were infected, which led to the announcement regarding the four new animal hosts, Healio9 reports.

Potential Victims of Kissing Bugs and Chagas Disease

As mentioned, domestic animals are also victims of this disease and may carry the parasite. Dogs, nonhuman primates, woodrats, coyotes, armadillos, mice, raccoons, skunks and foxes are also susceptible. However, “Studies have not been conducted to determine if all these species actually suffer from disease when infected, or if they can be silent, unaffected carriers of the parasite,”10 according to the Texas Chagas Task Force (in conjunction with the CDC).

Dogs with Chagas disease may develop severe heart disease, but may show no symptoms. However, it can cause heart rhythm abnormalities and sudden death, bloat and an inability for fluids to be pumped through their bodies. The most common test for canine infection with the Chagas parasite is a blood test called the indirect fluorescent antibody (IFA) test.

The IFA doesn’t test for infection with the parasite, but rather tests for antibodies to it. A positive result indicates that a dog has been exposed at some time in past. Canine testing for the Chagas parasite is available through the Texas Veterinary Medical Diagnostic Laboratory,11 but unfortunately, treatments are scarce.

That said, scientists documented Chagas disease in domestic dogs throughout many counties in Texas, particularly South Texas, documenting 537 cases of canine Chagas disease in 48 counties from 1993 through 2007.12 They noted a number of factors that influence the manifestation of the disease, including:

  • The age of the dog
  • The activity level of the dog
  • The genetic strain of the parasite

There are measures people in areas where kissing bugs may be prevalent can take, particularly in kennels, since they would be a perfect environment for the disease’s transmission cycles, TAMU asserts:

“Kissing bug control can be difficult in kennels, particularly in areas where human development is relatively recent and kennels are surrounded by natural habitats where wildlife occur. Adult kissing bugs engage in nocturnal flights to search for mates and mammals for blood-feeding.

Because adult bugs fly towards lights, we recommend that lights be turned off at night around kennels. Some insecticides are effective against kissing bugs when sprayed around the kennel area. However, because kissing bugs can fly in from many yards away or from nearby wildlife habitats, new colonization of treated areas can easily occur.”13

Ways to Handle Chagas Disease

Investigating areas where kissing bugs may reside (as well as those of the newest carriers added to the list) could reduce the incidence of Chagas disease, CDC authorities reason. One of the agency’s main aims has become educating the public regarding the previously unforeseen implications of the problem.

To control the disease in these wild animals, Eric R. Gordon, Ph.D., from the department of entomology at UCR suggests monitoring the bioaccumulation of the parasite where the disease apparently stems. Gordon explains:

“If kissing bugs also feed on these carnivores, as has occurred for the tayra in our study, they are likely to be one of the important links in the transmission chain of the disease in the wild. If a vaccine becomes available one day in the future, they are good candidates to target for immunization to halt the natural spread of the parasite and potentially help to eradicate the pathogen.”

According to the Texas A&M task force, while most states aren’t required to keep track of the number of people infected with Chagas disease, the symptoms, including loss of appetite, body aches, fever, fatigue, headache, rash, diarrhea and vomiting, often look like any number of other diseases. Healio also notes:

“The acute phase of Chagas disease consists of mild, nonspecific infectious symptoms lasting [four] to [eight] weeks and is often undiagnosed. The chronic phase results in a lifelong infection if not treated. Many patients may remain asymptomatic, but Chagas cardiomyopathy results in 20 to 30 percent of patients.

This is mediated by an inflammatory immune response and progresses to dilated cardiomyopathy and congestive heart failure. Another less common manifestation of chronic Chagas disease affects the esophagus or colon and can lead to esophageal reflux, weight loss, aspiration and sometimes megacolon.”14

While the U.S. Food and Drug Administration (FDA) hasn’t approved any drugs for Chagas disease, two medications, nifurtimox and benznidazole, have been deemed effective, but must be obtained from the CDC. Because there are not readily available, highly effective treatments for Chagas disease, avoiding contact with lissing bugs is the most commonsense approach. Here’s an extreme close up of a kissing bug:

triatomine assassin beetle

Using safe insect repellents and keeping pets inside at night are common sense tactics that can reduce exposure in endemic areas.

Studies on Other Animals With Chagas Disease Symptoms

Interestingly, pigs, which have been referred to as “opportunistic omnivores,” were found in one study to be subject to T. cruzi transmission. However, when tested, only 6 percent were infected, and no blood samples tested positive.15

However, another study shows hunters, including those in the U.S., may be impacted by T. cruzi due to exposure to animals infected with the parasite. It documents several species of wildlife commonly hunted in Texas and other states, and suggests the use of personal protective equipment for hunters when handing animals to reduce their risk.16

Finally, the Texas A&M University Veterinary Teaching Hospital was presented with a conundrum involving a 10-year-old Quarter Horse from South Texas that exhibited lameness and ataxia, or loss of control of their muscles and movement. The horse had been treated for protozoal myeloencephalitis, another type of parasite, but its symptoms worsened.

Subsequent tests confirmed T. cruzi, spurring scientists to recommend that although further study should take place, testing for Chagas disease would be wise should clinical neurological signs occur in other cases, especially in areas of the south. The study was reported in Veterinary Parasitology in 2016.17

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