Mosquito-Borne Brain Infection More Severe Than Thought
Mar. 14, 2001 -- You may never have heard of La Crosse encephalitis, even though it's the most common mosquito-spread brain infection in the U.S. Now it looks like the disease -- and its long-term effects on children -- are more serious than once believed.
Connie Johnson of Charleston, W.Va., had never heard of it when her son Ronnie Mitchell, then 7 years old, came down with what her pediatrician said was a bad case of the flu. That was on a Thursday.
"Sunday morning, we were getting ready to go to church and I put him in the tub and he didn't seem to know what to do with the washcloth or anything," Johnson tells WebMD. "I called his name, and it was like he was trying to tell me something but his speech was garbled. We took him straight to the hospital and he had a seizure just as we went in. That Monday, he still was still not responding, and by that Wednesday it became so serious they called in a neurologist. They told me that it was a matter of life or death. One day he was OK, and two days later they are telling me he might die. Finally they realized it was La Crosse encephalitis. When you grow up you hear of snake bites, but never that a mosquito could bite you and you could die."
La Crosse encephalitis now is firmly established in 28 U.S. states, mainly those in the Midwest and central Atlantic. Spread by a type of mosquito called the treehole mosquito, it nearly always affects children -- and some of these children have long-lasting thinking and behavioral deficits.
James E. McJunkin, MD, and co-workers at the Health Sciences Center of West Virginia University in Charleston have treated 127 children hospitalized with La Crosse encephalitis from 1987 through 1996. Their report on these children appears in the current issue of TheNew England Journal of Medicine.
"Some children deteriorate after hospital admission," McJunkin tells WebMD. "Fifty percent [show up] with seizure and 10-15% deteriorate with recurrent seizure or [brain swelling], usually within the first 72 hours of admission."
The children ranged in age from 6 months to 15 years. None died, although several survived only because of aggressive intensive care.
Nearly as frightening is the finding from follow-up studies of 28 children who had the most severe symptoms. Many of these children had long-lasting changes in their behavior and ability to do their schoolwork. A normal IQ score is 100, but more than a third of these children had a full-scale IQ score of 79 or less.
"We found in following children over the long term that in about a third of children old enough to be tested, those children did seem to have suggestion of developmental problems, such as increase in hyperactivity measures in more than half of the kids," McJunkin says. "There was also a suggestion of a decrease in average IQ compared to the norm."