vCJD: a short history
A short history of vCJD, or “mad cow” disease: what causes it, how does it affect people and why is it so hard to detect?
“It is something no-one understands or has ever seen-it may even be some bizarre “twilight zone” lifeform…. It triggers diseases that can’t be detected until you are dead. It can’t be cured and it’s always fatal”.
These words were penned by journalists Jennifer Cooke and Bob Beale in 1994, as the world faced a slow-growing outbreak of an unknown disease.
For years, this disease has meant people who lived in the UK during the outbreak weren’t able to donate blood in Australia, nor in many other countries.
But now, with the approval of the TGA and state, territory and federal governments, Lifeblood can welcome these people to donate blood. What was the disease behind the restriction?
For information about why the restriction was in place, and why it’s safe to lift it now, see our companion article: “vCJD: how data drives our donation decisions”
When did vCJD start?
The story begins when a new disease began to spread in British cattle. The first known case was in a cow recorded in 1984, who lost weight, developed tremors, lost co-ordination and died. This disease in cattle is now known informally as “Mad Cow Disease”, and is technically called “Bovine Spongiform Encephalopathy” (which translates literally as “Cow spongey brain disease”, because the brain of infected animals develops a sponge-like appearance). In the mid to late 1980’s, mass slaughter of cattle in the UK was used to control the spread. The disease in cattle peaked in the UK between 1992 and 1993. At the time, authorities believed the disease wouldn’t be able to spread from cattle to humans.
But in 1995, Stephen Churchill, a 19-year-old in the UK, died after an unexpected illness. Over six months, Stephen developed depression, lost his co-ordination and memory, and died in a care home. The symptoms looked like Creutzfeld-Jakob disease, which normally affects much older people. More unusual and similar deaths in young people followed, and pathologists identified a new disease, which they called vCJD (variant Creutzfeld-Jakob disease). The cause was tracked down to eating infected beef.
By October 2000, 80 people in the UK had died of vCJD. Globally, 81 percent of the people who have died from vCJD had lived in the UK for more than six months between 1980 and 1996. There is no treatment or cure for vCJD and, the time from infection until death is thought to be from five years to several decades. Cases peaked in the UK in 2000, and the last known case in the UK was detected after the patient had died in 2016.
What causes vCJD and can we test for it?
vCJD is hard to detect because it’s carried by an unusual infectious agent, known as a prion. A prion is a misfolded version of one of the body’s own common proteins, and it can trigger a “chain reaction” that leads to tangled protein deposits that damage the brain. Compared to bacteria and viruses, prions are a relatively new discovery, having first been described 1982. They’re technically not even alive.
Unlike viruses, bacteria or parasites, and other life forms, prions don’t carry any genetic instructions in the form of DNA or RNA. Instead, prions are variations on common proteins made by mammalian cells.
Because they don’t contain DNA or RNA, prions are invisible to diagnostic tests like PCR, which have been used so effectively to detect SARS-CoV-2, the virus causing COVID-19. And because they’re made of a protein that naturally exists in the body, they can “hide out” amidst their normal counterparts, which means that developing a specific test is incredibly challenging.
Despite these challenges, several tests have been developed, although those that are reliable enough to be useful can’t process the high volume of samples that’s needed for blood donor screening. Because vCJD is now so rare, it’s getting more and more difficult to gather the many samples needed to prove a test is reliable.
Aside from the technical challenge, such tests for an incurable disease would come with significant ethical, legal, social and economic costs and therefore would not likely be suited to use in asymptomatic heathy people.