Tropical diseases surfacing more in Texas

Houston scientists have launched an attack against little-known tropical diseases, scourges of the developing world, increasingly showing up in poor areas of Texas.

The diseases, spread by all manner of blood-sucking insects, cyst-forming tapeworms and tissue-invading bacteria and viruses, typically don't kill, but they cause chronic disabilities that trap sufferers in lasting poverty.

"They may have been here all along, but now that we're looking we're seeing these diseases more and more," says Dr. Peter Hotez, a Baylor College of Medicine infectious disease professor leading the effort. "They have a huge impact - heart disease, epilepsy, mental retardation – even though they fly beneath most everyone's radar."

Hotez calls it "a national disgrace that these diseases are not higher on the public health agenda." He says the reason is that they afflict "forgotten people, not wealthy people living in the suburbs."

The discovery of more cases in the United States, however, is starting to get attention. In Texas, those include an outbreak of dengue fever in Brownsville; common occurrences in Houston of a tapeworm that invades the brain; and a parasitic disease, transmitted by "the kissing bug" and affecting the heart and digestive system, that scientists now estimate afflicts more than a quarter of a million people living in Texas.

Hundreds of thousands

Hotez reported in a scientific journal last month that hundreds of thousands of people in Texas are afflicted with "neglected tropical diseases." This term was coined to distinguish overlooked diseases prevalent in low-income regions in Africa, Asia and the Americas from HIV-AIDS, malaria and TB, tropical diseases known to all and benefitting from celebrity spokespeople. By contrast, neglected tropical diseases come with multisyllabic names like neurocysticercosis and leishmaniasis.

Neglected tropical diseases affect some 1.4 billion people worldwide and Hotez compares their burden to that of AIDS. Dating to biblical times and before, they were little studied until around the turn of the 20th century, when British scientists began investigating diseases in their tropical colonies.

The academic institutions that employed those scientists - the London School of Hygiene & Tropical Medicine and the Liverpool School of Tropical Medicine - are models for what Hotez is building at Baylor. The leading tropical medicine expert in the United States, Hotez was recruited from Washington, D.C., last summer and immediately announced plans for Baylor to house the nation's first tropical medicine school, a vaccine development arm and a clinic at Ben Taub General Hospital.

On Friday, the clinic had a visit from a Hispanic man with what turned out to be neurocysticercosis, the disease in which tapeworms invade the brain. The symptoms weren't severe - mostly mild to moderate headaches he'd had for the last four months - but an abnormal CT scan that led him to the clinic caused alarm.

"It made me think of a news report I'd seen on Univision where doctors found worms in someone's brain," Silvestre Roman, 42, a Houston restaurant dishwasher, said through a translator. "That worried me."

20-year tapeworm

Dr. Laila Woc-Colburn, the clinic director, found Roman's tapeworm, likely there for 20 years, had calcified and thus doesn't put him at risk for the seizures and epilepsy it could have caused if it were still alive. But that also meant she couldn't give him anything for the tapeworm, which comes from pork and is typically transmitted in contaminated food or water.

Baylor researchers last year reported in a scientific journal about more than 100 neurocysticercosis cases they've treated at Ben Taub since the 1990s.

Dengue fever, the best known of the neglected tropical diseases, made national headlines in 2005 after Brownsville was found to be ground zero for a U.S. outbreak and health investigators determined 38 percent of the town was at risk for the most dangerous form of the illness.

The mosquito-transmitted disease still is thought to have a foothold in Texas. Less than two years ago, public health officials warned the disease could become a major threat in Houston, Corpus Christi and other Gulf Coast cities from Texas to Florida.

Among the hardest of the diseases to detect is Chagas, which is caused by the Triatomine insect, or kissing bug. Symptoms initially may resemble the flu but the parasite often survives for decades, contributing to heart failure or digestive diseases later in life.

Baylor blood tests have found its incidence in dogs under a year of age in South Texas and Houston has essentially quadrupled in recent years, a hike the researcher says means people are at increased risk.

"These diseases are on the increase in poor parts of Texas and the United States, but we really don't know how much because no one's looked before and few doctors recognized the disease," says Hotez. "That's what needs to change."

todd.ackerman@chron.com