For years, scientists have known that the sweetly named kissing bug found throughout South and Central Texas carries the parasite that causes Chagas disease, a major killer in parts of Latin America.

What wasn't known is if those Texas bugs infect people, although they clearly infect animals — including bomb-sniffing dogs at Joint Base San Antonio-Lackland and nonhuman primates at the Texas Biomedical Research Institute.

That question is slowly being answered, and the news isn't good. At an infectious disease conference here Wednesday, state and local health officials said the bug not only invades homes in the region, but likely has infected at least a handful of people inside them.

Roger Sanchez, an epidemiologist with the Metropolitan Health District, said at least two San Antonio women with lab-confirmed Chagas disease — one 17 years old, the other 46 — have no history of travel outside Texas.

“So is there (human) transmission? I think so,” Sanchez told a group of researchers and public health professionals at the annual James Steele Conference on Diseases in Nature Transmissible to Man. “We don't know the extent of the transmission locally.”

Although hundreds of thousands of immigrants from Latin America living in the United States are thought to be infected with Chagas, health officials have had little way of knowing who was infected and where they were exposed. In recent years, some — but not all — blood banks, including the South Texas Blood and Tissue Center, have been using a fairly new test to screen donors.

Those results have started to give them recently infected patients to interview.

Chagas has been likened to AIDS in that people often have few symptoms after infection, followed by a latent period that can last years. Serious disease doesn't always follow, but when it does it can cause massive enlargement of the heart, esophagus or colon.

An experimental treatment, available only from the Centers for Disease Control and Prevention, works best if given early in the disease process, experts say.

Five species of triatoma bugs found around San Antonio carry the infection, the most common of them Triatoma gerstaeckeri — a flat, dark brown teardrop-shaped bug with lighter stripes mostly obscured by its wings. Adults are often more than an inch in length.

“Triatoma bugs are very secretive creatures of the night,” said Dr. Edward Wozniak, a Uvalde-based veterinarian with the Texas Department of State Health Services, who studies the bugs. “There are a lot of them around, yet you don't see them.”

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Some experts had speculated that modern housing might keep the bugs out, but Wozniak has found them within the exterior walls of homes west of San Antonio. He said more research is needed to find the best way of keeping them out.

The state health department is in the process of adding Chagas to the list of diseases that must be reported by law, because of the growing evidence of local infection. That change could be in effect by early next year, officials said.

“People like to think of this as a tropical disease, and that somehow the Rio Grande river stops them from coming across,” Wozniak said. “I don't think the Border Patrol has gotten that efficient.”

dfinley@express-news.net