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2012-06-14

Kissing disease (Chagas) continues to threaten humans, pets

By Carolyn B. Edwards BCC Staff Writer

CNN recently referred to the spread of Chagas disease from Central and South America into the United State as "the new HIV/AIDS." Their scary headline resulted from a story in a recent issue of PLoS Neglected Tropical Diseases in which infectious disease specialists and other scientists argued that Chagas (pronounced Sha-gus) "has become so widespread and serious... that it deserves to be considered a public health emergency." Readers of the Courier were informed about the threat last summer when a story ran in our June 23, 2011, issue.

A large number of an insect called the "kissing bug" or "bloodsucker" were sighted in the county. One resident was bitten and had a serious reaction to the bite. He was tested for Chagas and the test, fortunately, was negative. It may only be a matter of time, however, before a human, or an animal, tests positive for the disease here.

With the onset of summer temperatures, residents are warned to be on the look-out for the 1-inch long black and orange insect.

Currently, Chagas disease is not a reportable condition in Texas, so it is difficult to get reliable statistics about how many people or animals have been diagnosed with the disease.

A growing threat

Long common in Central and South America, Chagas' disease is being diagnosed more and more often in South Texas.

It is estimated that 10 million people are living with Chagas infection, about 1 million in the United States. About 3 million of those infected are at risk of Chagas' worst complications, enlarged heart and heart failure. "And wherever blood donations are not tested for the protozoan, the blood supply - as well as organ transplants - are at risk," said Maryn McKenna in a May 30 on-line article.

The deadly parasite, Trypanosoma cruzi, which infests the insect, can be transmitted via blood transfusion and organ donation. An FDA-approved test for Chagas in donated blood has been in effect for two years and positive donations clearly demonstrate the spread of the disease in the US.

However, the test is not mandatory in Texas, nor is the disease reportable at this time.

The reduvid bug, attracted to exhaled carbon dioxide, frequently bites its victims near the lips, hence the nickname, "kissing bug." The genus usually found in Texas and across the southwest US, however, is Triatoma, which has a more tapered, slender and straighter proboscis (beak) than the South American Reduvius. A study in Arizona concluded that while more than 40 percent of the triatomine bugs found tested positive for Chagas' disease, the disease remains rare in the US.

"People have been bitten here for a long time, for decades," said research biologist Carolina Reisenman, "so my suspicion is we should see cases already if the transmission is efficient." It may be, the study concluded, that the triatomine insects don't act the same way as their cousins to the south, or that the disease they carry is a different strain.

Another study found the bugs are present in 97 of Texas' 254 counties and over half of the bugs collected tested positive for the disease pathogen.

Since 1955, however, only six cases in humans have been confirmed in the state.

Dogs also at risk

Dogs seem to be especially at risk for the disease, possibly because they may eat the bugs. Over 530 cases of Chagas have been confirmed in dogs in Texas over the past 15 years.

The bug infests kennels and other facilities used to house dogs. The disease is transmitted to the animal either through bites, by the dog eating the bug or its feces and through feces accidently rubbed into an open cut, the eyes or mouth.

TDH leading study

The Texas Department of Health, the Centers for Disease Control and Preventon, the University of Texas and the University of North Texas are working on a study of triatomine bugs to determine their rate of infection with the potentially deadly parasite, Trypanosoma cruzi.

"During studies conducted in South Texas in 1999, 7.5 percent of 375 tested stray dogs were positive for Chagas' antibodies. Additionally, 18 percent of 132 tested coyotes were seropositive, and 40 percent of tested vector insects were positive for the disease-causing trypanosome," a TDH report states. The TDH encourages veterinarians to notify the department's Zoonosis Control Division about any confirmed positive diagnoses.

Not a spider bite

Bites of the bloodsucking conenosed bug are often misdiagnosed as spider bites.

While most bites are never felt by the hosts, they can be extremely painful for some people, causing burning, itching, swelling, red blotches, welts and rashes. Other symptoms may include enlarged lymph nodes, liver, spleen or heart; meningoenchphalitis, fainting spells, nausea, diarrhea and anaphylactic reactions.

The bloodsucker inserts a piercing stylet into the host of their blood meal. It numbs the skin, so bites often are not felt until later. After feeding, the bug, which uses only the red blood cells of the host, defecates the excess water and salt, spreading the parasite that causes Chagas through the wound or any opening in the skin. The insect completes its feeding in as little as 10 minutes.

According to Rick Vetter in the Dermatology Online Journal, the engorged culprit is often found when looked for. The insect seeks shelter in and around bedding or under cushions after feeding. A thorough search for the bug can assist in a correct diagnosis.

Symptoms

Immediate symptoms can be limited, after which the disease usually goes dormant. It re-emerges years or even decades later, causing severe heart or gastrointestinal problems. There are treatments for acute infections, but once the disease causes major organ damage, it cannot be reversed.

In the first phase of the disease, symptoms may include fever, general ill feeling, swelling of one eye or swollen red area at the site of the insect bite.

The acute phase can include constipation, digestive problems, pain in the abdomen and swallowing difficulties. Complications can include cardiomyopathy, enlargement of the colon, enlargement of the esophagus with swallowing difficulty, heart disease, heart failure or malnutrition.

The disease can be transmitted by blood transfusions, organ transplants and in childbirth, as well as by ingestion of raw or undercooked meat from infected animals and ingestion of infected bugs.



Pictured: Map showing inroads made by Chagas disease in Texas. Courtesy of Sarkar.

Photo Courtesy Region 8 TDSHS;
from stonewaresnake Triatoma sanquisuga


How to Submit bugs for testing...

The state department of health provides free testing of Triatomine bugs for the parasite Trypanosoma cruzi. Go online to download the "Texas Triatomine Bug Submission Form." Place the bug, dead or alive into a pill vial or suitable container. Each bug should be labeled separately. Place the vial(s) and the form(s) in a padded envelope or mailing tube.

Contact the Region 8 Zoonosis Control office at 830-591-4385, fax 830-278-7170, email Edward.wozniak@dshs.state.tx.us for information about where to mail your specimen.