TORONTO - Tuberculosis infection rates among international adoptees to the United States has risen dramatically over the past 20 years, according to new findings which add weight to a call for Canada to screen all incoming adoptees for the disease.
The American study followed up on 869 foreign-born children adopted into U.S. families from 1986 through 2001. Twelve per cent of the children were infected with tuberculosis and the rate of TB infections among the adoptees rose seven per cent with each passing year through the period studied.
"These kids are getting infected very, very early in life," said lead author Dr. Anna Mandalakas, who runs the adoption health service at Rainbow Babies and Children's Hospital in Cleveland, Ohio.
"So during this first two years of life if they're in an orphanage, a huge number of these children are getting infected."
The authors of the study, which was published Tuesday in the journal Pediatrics, say the findings support the current call from the American Academy of Pediatrics that all international adoptees undergo a skin test for tuberculosis immediately after adoption.
Two Canadian tuberculosis experts recently urged that TB screening policy for international adoptees be instituted in Canada, suggesting in a commentary in the Canadian Medical Association Journal that provinces and territories should follow up with adoptive parents to ensure these children get timely and thorough testing.
TB rates among the children in the American study ranged from nearly 15 per cent in adoptees from Eastern Europe, 14 per cent from Russia and 13 per cent from Korea to between 12.5 per cent and 11 per cent in India, China and South America, 8.3 per cent in Central America and the Caribbean and 2.8 per cent in Southeast Asia.
Canadians routinely adopt children from these same regions or countries, some of which have among the highest rates of tuberculosis globally. According to Citizenship and Immigration Canada, an average of 2,000 children a year are adopted into Canadian families from abroad.
The medical examination required of immigrants to Canada isn't geared towards detecting latent tuberculosis infection or TB disease in children under 11 years of age, Dr. Richard Long and co-author Jody Boffa of the tuberculosis program evaluation and research unit at the University of Alberta wrote in the Canadian Medical Association Journal earlier this summer.
But given the risk faced by international adoptees, this special group ought to be screened, Long and Boffa suggested. Their commentary noted that four in 10 foreign-born children under the age of five found to be infected with tuberculosis in Alberta between 2004 and 2006 were international adoptees.
Long said children infected with latent or even active TB don't pose a risk to others, because children under nine or 10 years of age rarely transmit disease. But the infection is a real threat to their own health, he said in an interview.
Infection with Mycobacterium tuberculosis, the bug that causes TB, doesn't always lead to active disease. In many people the bacteria remains latent. Infected adults have about a five to 10 per cent chance of developing active tuberculosis sometime in their lifetime.
With young children, however, the risk that infection will lead to disease is much higher. Infants under a year have a roughly 50 per cent chance of developing disease and children aged one to two have a 20 per cent chance. And if active TB develops, it can progress beyond the lungs, the typical site of disease.
"Little children not only have a higher risk of getting disease from infection itself, they're at higher risk of getting severe forms of disease - and by severe forms I mean central nervous system or disseminated TB," said Long, who also serves as Alberta's medical officer of health for tuberculosis.
A TB expert at Toronto's University Health Network agreed.
"They're a relatively small population, but they're a really high risk population," said Dr. Michael Gardam, who is head of infection control for that network of three central Toronto hospitals. Gardam was not involved in either the study or the commentary.
"Because these kids are not coming from healthy, happy homes. They're coming from environments where they're very likely to have been exposed to tuberculosis. And I think it makes perfect sense to be screening them."
Both Mandalakas' study and Long's commentary recommend the screening begin swiftly after an international adoptee arrives in his or her new home.
And both recommended that the initial skin test be followed up three to six months later with another. That's because a test performed immediately after arrival might not detect an infection that occurred shortly before a child left an overseas orphanage.
Children who test positive should be put on a nine month course of antibiotics, Mandalakas said. She also suggested orphanages involved in international adoptions should test for tuberculosis among employees.
