Human 'Mad Cow' Could Cause Eventual Epidemic

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Human 'Mad Cow' Could Cause Eventual Epidemic

06.22.06, 12:00 AM ET

 

THURSDAY, June 22 (HealthDay News) -- Variant Creutzfeldt-Jakob

disease, or vCJD, the human form of " mad cow disease, " has a long

incubation period and could cause an eventual epidemic, researchers

report.

 

Reporting in the June 24 issue of the Lancet, they looked at a similar

disease -- linked to cannibalism -- to better understand the impact

such an epidemic might have.

 

Mad cow disease, or bovine spongiform encephalopathy (BSE), is caused

by misfolded brain proteins called prions, which cows contract through

contaminated feed. Humans can catch the human form the disease, vCJD,

by eating contaminated beef. So far, the fatal degenerative illness

has infected about 160 people in the United Kingdom. More cases have

been confirmed in six other countries, including the United States.

 

Now, researchers at University College London have determined, through

the study of a similar disease, that BSE has an incubation period of

more than 50 years before it actively becomes vCJD.

 

Patients in Papua New Guinea with a disease called kuru -- the only

currently epidemic human prion disease -- were studied to determine

how long the disease was dormant before symptoms appeared.

 

Kuru occurs in Papua New Guinea society because the disease was

transmitted through cannibalism -- a common cultural practice up until

1960. By comparing the birth year in relation to the cessation of

cannibalism in the community, the researchers were able to assess

incubation periods of the disease.

 

Eleven participants in the kuru study had minimum incubation periods

of between 34 and 41 years, the researchers calculated. They could

more accurately calculate the date of infection for men, and estimated

an incubation period of between 39 and 56 years, with the potential

for even seven years longer.

 

The researchers also noted a genetic variation in some kuru patients

that has been known to promote long incubation periods.

 

John Collinge, one of the researchers, wrote in a prepared statement

that the current small cohort of vCJD patients " could represent a

distinct genetic subpopulation with unusually short incubation periods

for BSE, " suggesting that many more vCJD patients who caught the

disease via contaminated beef could emerge in the coming decades.

 

" A human BSE epidemic may be multiphasic, and recent estimates of the

size of the vCJD epidemic based on uniform genetic susceptibility

could be substantial underestimations, " Collinge said.

 

More information

 

The U.S. Centers for Disease Control and Prevention has more

information on variant Creutzfeldt-Jakob disease.