HAMILTON, Mont., March 25 (UPI) -- Researchers at the National Institute of Allergy and Infectious Diseases reported Monday they have decoded the DNA of bacteria that rheumatic fever, which is the leading cause of preventable childhood heart disease worldwide.
Dr. James M. Musser of the Laboratory of Human Bacterial Pathogenesis in Hamilton said his team has "solved the DNA sequence of the group A strep strain that is the main cause of rheumatic fever."
"We anticipate that this will accelerate the development of new vaccines to prevent rheumatic fever," he told United Press International. Musser and colleagues report their findings in the current issue of Proceedings of the National Academy of Sciences.
Untreated strep infections can progress to rheumatic fever, which often causes a rash as well as painful swelling of joints, but in its most severe form attacks the heart, damaging heart valves and causing rheumatic heart disease.
Once a common childhood illness in the United States, rheumatic fever was virtually eliminated by the introduction of antibiotics. In the late 1980s, however, rheumatic fever outbreaks occurred in Salt Lake City and in several other cities in the United States.
Musser told UPI his team analyzed DNA obtained from bacterial cultures taken from patients infected in Salt Lake City. The strep strain responsible for that outbreak is called M18, which appears to have undergone some genetic alterations that affect symptoms. Typically, a strep infection causes severe sore throat that will send the patient to the doctor, where a strep test can confirm the presence of infection and antibiotic treatment started.
Musser said it appears infection with M18 is not accompanied by a sore throat, so the infection remained untreated and progressed to rheumatic fever.
Dr. Blaise Congeni, head of the division of infectious diseases at Akron Children's Hospital in Akron, Ohio, said the same strain of strep caused rheumatic fever outbreaks in Akron, Toledo and Pittsburgh at the same time as the Salt Lake City cluster of cases. Congeni, who was not associated with the study, said the work by Musser's team suggests that "something about the rheumatic fever bug has changed."
Congeni said infectious disease specialists already know rheumatic fever is attacking a different population in the United States.
"Historically, it was associated with poor people who had limited access to health care services," Congeni said. Recent outbreaks, however, have occurred among more affluent populations with good access to care.
"That suggests something different about the disease," Congeni added. The lack of early symptoms is one explanation.
Congeni said from the time of infection "we have about nine days to treat before the infection progresses to rheumatic fever." Fortunately, he added M18 responds well to antibiotics so every M18 infection does "not lead to rheumatic fever."
Rheumatic fever is most common "among children aged 5 to 15. It is extremely rare to have a case in a 3- or 4-year-old. Also, if a child has symptoms of a viral infection -- runny nose, sneezing, wheezing -- it unlikely is strep or rheumatic fever, Congeni said.
The World Health Organization estimates 1 percent of all school age children in Africa, Asia, Latin America and Mediterranean countries show symptoms of rheumatic fever. In the United States, 2 million Americans have a history of rheumatic fever and each year 5,000 American deaths are associated with it.
(Written by Peggy Peck in Cleveland, Ohio)
