Doctors suspect bacteria in paralyzing illness

June 26, 1993|By Douglas Birch | Douglas Birch,Staff Writer

A team of medical sleuths led by a Johns Hopkins neurologist has cornered a prime suspect in its hunt for the cause of an illness that paralyzes thousands of Chinese children each summer.

Dr. Guy M. McKhann, director of Hopkins' Zanvyl Krieger Mind-Brain Institute, and colleagues from the United States and China, first recognized in 1990 that the life-threatening paralysis was caused by a previously unidentified disease.

Now the scientists -- who include researchers from Hopkins, Harvard, the University of Pennsylvania, Vanderbilt University and two Chinese hospitals -- are trying to confirm their hunch that the illness is linked to a common bacteria, Campylobacter jejuni.

"There is increasing evidence that this disease process is associated with this organism -- the question is how," said Dr. McKhann, who first learned of the annual epidemic during a visit to the Beijing Children's Hospital in 1986.

The illness, which investigators first named Chinese Paralytic Syndrome but now call Acute Motor Axonal Neuropathy, strikes perhaps 5,000 children in rural villages across China in the steamy summer months.

Doctors suspect the same disease has stricken children in Brazil, Japan, Spain and other countries as well.

Dr. McKhann was the lead author of an article in the April 1993 issue of the Annals of Neurology, a scientific journal, which reported that victims usually show signs of having been exposed to the Campylobacter j. bacteria, a common cause of diarrhea.

A few weeks ago, Dr. McKhann, Dr. Tony W. Ho of Harvard and Dr. Irving Nachamkin of the University of Pennsylvania traveled to major hospitals in Beijing and Shijiazhuang, in anticipation of the annual summer onslaught of young patients.

They helped Chinese physicians set up studies aimed at determining if patients have all been exposed to a single, so far unidentified strain of Campylobacter j.

If a single organism is found, scientists think they can explain many puzzling features of Acute Motor Axonal Neuropathy, or AMAN, which behaves much differently than other paralytic illnesses.

Polio, for example, usually occurs in clusters of unvaccinated children living in urban areas. Guillain-Barre syndrome usually affects adults several weeks after a respiratory infection and has no particular geographic or seasonal distribution.

AMAN strikes rural children, ages 5 to 8, during the summer -- typically after a period of heavy rain. While the disease occurs only in the countryside, there are no clustered outbreaks. It seldom paralyzes two children from the same family or even the same village.

It strikes very quickly, usually without any prior signs of illness.

"You often have people say they started falling down in the morning," said Dr. Ho. "By the afternoon, they are lying flat on their backs. The next day, they can't breathe."

Paralysis peaks within seven days, killing about one in 20 patients who make it to the hospital. In survivors, recovery usually begins after about 20 days. By the end of six months, patients can generally begin to stand and walk again. Most eventually recover fully.

After studying the outbreaks for three years, the team thinks the illness may work this way:

A particular strain of Campylobacter may be carried in the feces of certain animals or insects, perhaps chickens or flies. Heavy summer rains wash contaminated soil into water supplies in rural areas, where sanitation is poor.

When this bacteria infects certain children, it causes their bodies to produce antibodies that attack both the bacteria and the victim's nervous system. This assault by the body's defenses on the body itself is called an autoimmune disorder.

Not all children are susceptible, because their immune systems respond differently.

Identifying a single strain of bacteria common to AMAN victims could be tricky. More than 100 strains of Campylobacter jejuni have been identified.

But physicians seem confident. "If there is one strain responsible, we should get it this year," Dr. Ho said. "We've been casting a pretty wide net."

The researchers will use the techniques of modern molecular chemistry to find the cell type of AMAN patients. This procedure, which is routinely done for patients waiting for organ transplants, could identify individuals most at risk.

Identification of the bacteria that causes the disease could lead to public health measures to curb its outbreak. And it could lead to new treatments for AMAN patients.

Now, the annual epidemic creates a significant public health problem, physicians said. Pouring into the pediatric wards of large regional hospitals each summer, paralyzed children quickly fill all the available beds and the limited number of mechanical respirators.

In many cases, family members must sit by a child's bedside 24 hours a day for several weeks, manually pumping air into the lungs with a bag-shaped manual respirator.

Dr. Ho pointed out that strict population controls in China mean that a single fatal illness can leave a family childless.

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