Parasites can damage heart tissue, nerve cells
By Sharon Kirkey, CanWest News Service
Published: Sunday, June 10, 2007

Tropical disease experts are warning of a new threat to Canada's blood supply, a "silent killer" that produces no symptoms for years while parasites slowly feed on a person's heart muscle and intestines.

Chagas disease is endemic in parts of Central and South America where it has already infected up to 20 million people and kills more than 50,000 every year.

Transmitted by blood-sucking "assassin" bugs, Chagas - named after the Brazilian doctor, Carlos Chagas, who discovered it in 1909 - can also be spread via infected blood transfusions.

Now, the parasitic infection is drifting northward because of immigration patterns and travel - including adventure and eco-tourists to such Chagas-hit areas as Colombia and parts of Brazil.

Chagas isn't a reportable illness in Canada; its prevalence is unknown. What's more, front-line doctors may know about West Nile virus or Lyme disease, but most would not know Chagas to see it, experts say. "I don't think the average primary care doc would know it [at] all," says Dr. Jay Keystone, professor of medicine at the University of Toronto.

It can take 20 years or longer for the parasite to cause sufficient damage to nerve cells and tissue in the heart to put people into heart failure. People can have strokes because of heart arrhythmias.

The disease can attack in other ways: Researchers recently reported the case of a 40-year-old man who was transferred to hospital from a Manitoba jail after a two-week history of headache, nausea, vomiting and drowsiness.

A CT scan showed what appeared to be a brain tumour; a biopsy revealed a huge abscess in his frontal lobes that, under the microscope, turned out to be related to the organism, Trypanosoma cruzi, or T. cruzi, which causes Chagas.

"Normally people get this in South and Central America, and to the knowledge of everybody who knew this fellow, he had never travelled to those areas," said Dr. Marc Del Bigio of the University of Manitoba's department of pathology.

The Canadian Blood Services told CanWest News Service it is preparing to screen the nation's blood supply for Chagas.

But just how extensively to test, what test to use and when testing should start have not been decided.

"We've been watching this Chagas for a long time," said Dana Devine, vice-president of medical, scientific and research affairs.

Two cases of blood-transmitted Chagas have been reported in Canada, in 1986 and 2000. Both donors were from the same Mennonite community in Winnipeg and had lived in South America.

The clinic where they gave blood has been closed. "We no longer collect blood in that area," Ms. Devine said.

She said the risk of blood-transmitted Chagas is believed to be "really very low" but "no one really understands what the scope of the problem may or may not be for blood systems in North America.

Dr. Keystone and other experts believe it is likely other transmissions via infected blood transfusions have occurred but gone unrecognized.

"It's a silent killer," said Dr. Keystone. "If somebody comes to you with heart failure, you would say, Oh, you probably have coronary artery disease.' He'd send you to a cardiologist." Chagas can be curable in the acute phase, if caught early. "But once you're in the latent phase and develop heart problems, it may not be curable," he said.