May 14, 2010 -- Researchers and legislators are trying to determine just how far some obscure but deadly third world diseases have penetrated into the United States.
Studies in recent years have shown that diseases typically confined to less-developed countries have entered the United States, coming over the border or arising in places where conditions abruptly changed, like post-Katrina Louisiana. But poverty and a lack of access to healthcare have made it hard to determine how severe the problem might be.
"The poverty in the U.S. tends to concentrate in certain pockets," said Dr. Peter Hotez, chair of the department of microbiology, immunology and tropical medicine at George Washington University Medical Center. He cited the Mississippi delta, post-Katrina Louisiana, the border region with Mexico and U.S. inner cities: "Those particular areas, for all practical purposes, resemble a developing country."
Some of the diseases that are part of this surveillance effort include Chagas disease, caused by ticks that can cause heart enlargement and ultimately death; trichomoniasis, a sexually transmitted disease that can cause inflammation and difficulty urinating; and toxocariasis, which is spread via infected dog feces in soil and can cause vision and breathing problems and developmental delays.
Some of these diseases, which Hotez calls the neglected infections of poverty, can spread among people through sexual transmission or via blood. However, they stay mostly under the radar because, at least for now, more affluent Americans are unlikely to contract these diseases.
"These diseases are not occurring among people in the suburbs," said Hotez.
Substandard housing and dirty soil, like that found in sandboxes in urban playgrounds, are the preferred residences of the critters that can cause these infections.
Many of the diseases may go misdiagnosed when infected people do make it to a doctor.
A recent effort to make a survey of the prevalence of these diseases was sponsored in the House version of the health care reform bill by Reps. Gene Green (D-Texas) and Hank Johnson (D-Georgia). The amendment was dropped during reconciliation to pass the Senate version of the bill.
Scott Goldstein, legislative director for Johnson's office, said that efforts would continue to get a survey of the infectious diseases covered in the original amendment as a stand-alone bill.
"Once we [complete the survey] we can have a better idea whether new guidelines need to be issued," he said. "The researchers we've talked to have said it's quite possible these things have been out there in the United States."
Johnson's district includes parts of Atlanta, where many may be infected.
"We have some significant areas where people are very poor in our district, but that's not unique to our district," Goldstein said.
"Once people learn about it, I don't think it will be tough to get people to sign on," he said.
Although the Congressional Budget Office did not score the amendment as part of the original bill, the study would likely cost a few million dollars.
A Possible Asthma Link?
Because of the lack of studies of the neglected infections of poverty, it is unclear what the next steps would include.
After rising concerns about Chagas disease, the American Red Cross began screening blood donations for it in 2006.
But it is less clear what might be done about perhaps the most widespread of these infections, toxocariasis.
Caused by a roundworm spread by dog feces that typically infects children playing on the ground, 14 percent of the U.S. population was found to have been exposed to it in a CDC study, using data collected between 1988 and 1994.
There may be a link between toxocariasis and asthma, though past studies have been inconclusive. There is a relationship, say doctors, but it may simply be that both happen in poor living conditions.
Hotez believes that better surveillance of toxocariasis might lead to a drop in asthma cases, as drugs are available to treat the roundworm, distinct from the medications to treat asthma. Doctors may currently be treating asthma symptoms rather than the cause, he said.
"It can cause symptoms as the larva are migrating and enter the lungs," said Susan Montgomery, a researcher with the CDC's section on parasitic diseases. But, she said, "[The] specific syndrome of asthma has not been causally linked to toxocariasis."
But others are less sure.
"Toxocariasis doesn't cause a lot of clinical disease," said Dr. Robert Tolan, Jr., chief of the division of allergy, immunology and infectious diseases at the Children's Hospital at Saint Peter's University Hospital and a clinical associate professor of pediatrics at the Drexel University College of Medicine in Philadelphia.
Despite a high infection rate, Tolan said the worst cases, such as where a child develops a vision problem because of a worm infection, might only happen once every 10 years or so.
He said that he feels other infections, such as Chagas, may be more pressing to study because of the severe illnesses they can cause.
Montgomery expressed some optimism that toxocariasis infection may have dropped since the last survey, mostly through greater efforts at getting animals de-wormed.
"It's possible all of that good veterinary care is reducing the human risk of toxocariasis," she said.
But she said the survey itself would still be important.
"We suspect a portion of them did and may have pretty severe illness," she said of the millions that had been infected. "It is a health disparity and one that we feel is important to address."