October 16, 2013
Twice As Many Humans Carry Mad Cow Protein As Thought
Brett Smith for redOrbit.com - Your Universe Online
The disease, also known as variant Creutzfeldt-Jakob disease (vCJD), emerged after widespread exposure to contaminated beef in the food chain. It is a debilitating brain disease that is incurable and deadly.
Although there have been just under 180 UK cases of vCJD to date, British officials have said most of their citizens have probably been exposed to the proteins responsible for the condition. The relatively low number of cases indicates that infection with the disease-causing protein hardly ever causes vCJD in humans.
Despite this, UK health officials have taken steps to secure the blood supply and keep surgical instruments sanitary – mitigating two other potential sources of transmission.
In the BMJ study, researchers looked at more than 32,000 tissue samples taken from human appendixes removed between 2000 and 2012. Sixteen of these samples tested positive for the vCLD protein, pointing to an overall frequency of 1 per 2,000 people – much higher than previous research that estimated a 1 in 4,000 frequency.
"It is a concern that a proportion of those who are carriers might ultimately develop the disease," Sebastian Brandner, professor of neuropathology at University College London, told The Guardian's Ian Sample. "But the other real public health issue is that these people might transmit it through blood transfusions."
"Although the results of this latest study indicate a higher prevalence than the first survey, they are consistent with the previous findings and the range of the prevalence estimates largely overlap," said Noel Gill, lead investigator on the report at Public Health England. "We have looked at a larger number and a wider age group of patients and this new estimate is more precise.
"We are definitely concerned, but we are also reassured by the absence of a large number of blood transmission cases to date," Gill added.
The study researchers said there is a chance the proteins discovered in the appendix samples are unrelated to the infected meat that flooded the UK food chain in the 1980s and 1990s. To see if this is the case, researchers are currently testing appendix material collected in the 1970s and earlier.
According to the Centers for Disease Control and Prevention (CDC), the first probable infections of the disease in cows happened during the 1970s with two cases of the disease being identified in 1986. Previous theories have said mad cow disease came about as a result of feeding cattle food derived from infected sheep parts. Strong evidence indicates its spread throughout the United Kingdom was fostered by feeding rendered, infected bovine meal to young calves.
US officials have only seen anecdotal evidence of mad cow disease in American cattle. Officials have speculated that the prevalent use of soybean feed in North America has prevented an outbreak of the disease on the other side of the Atlantic.