Blood Test Mad Cow

When chowing down on a hamburger fresh off the grill, chances are you’re not thinking about the risk of bovine spongiform encephalopathy (BSE). Variant Creutzfeldt–Jakob disease (vCJD), better known as the human form of “mad cow disease,” is a degenerative brain disorder caused by eating meat from an animal infected with BSE. Earlier this month, a patient in Texas died from vCJD. 

The fatality in Texas was only the fourth ever reported case of vCJD in the U.S., though it seems likely that the infection occurred outside the country, according to the Centers for Disease Control and Prevention (CDC). It's difficult for doctors to pinpoint vCJD cases because, until now, there were no diagnostic tests for the condition.

Today in the journal PLOS PathogensFrench researchers report that they have created a blood test that can detect vCJD in humans and animals during the early stages of infection. Because vCJD can incubate without causing any symptoms, a test to detect infection in both humans and animals could help prevent further outbreaks.

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“Until now, there is no invasive test allowing us to detect or confirm infection by vCJD in humans,” says study co-author Olivier Andréoletti of the Ecole Nationale Vétérinaire de Toulouse in France. While further study is needed, a blood test to detect vCJD prions (misfolded proteins) in animals and humans before symptoms develop could help to keep the number of cases in the U.S. at just four.

Worldwide, more than 220 vCJD cases have been reported. Most occurred in the United Kingdom and France, according to the CDC. There is another classic form of CJD that is not caused by BSE and it results in one or two U.S. cases per year.

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BSE is part of a family of transmissible spongiform encephalopathies (TSEs), diseases characterized by the spongy degeneration of the brain. As you can imagine, once the brain goes spongy, neurological and muscular function begin to deteriorate as well. BSE can affect many different species, from cows to humans to cats and others, according to the World Health Organization. BSE has a long incubation period of four to five years, but once symptoms appear, it can be fatal within weeks for cattle.

vCJD likely spreads when people eat beef exposed to BSE, but recently, secondary cases have been identified in patients who received blood transfusions from apparently healthy donors, the study authors wrote.

“vCJD is probably transmissible through transfusion and injection of plasma derived product,” Andréoletti says. “There are many potential blood donors in the UK and other countries that are currently incubating asymptomatically... Each of them could be a source of contamination.” 

Andréoletti's blood test was able to identify three out of four vCJD patient samples the team studied, and no false positives were reported in 114 healthy controls.

“[Because of] the high analytic sensitivity of the assay, 5nL of blood are sufficient to detect vCJD, and its capacity demonstrated in a vCJD primate model to detect infected individuals in the early stage of the incubation period [was surprising],” Andréoletti says.

Before the test is ready for market, further study is needed. The sample pool needs to be expanded and the team must find the right company to develop a marketable product, Andréoletti says. 

But this study could not be more timely. Likely due to the Texas vCJD case, Andréoletti says that there have been a number of requests from U.S. researchers about the study.

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