Questions & Answers about Mad Cow and vCJD
-- Frank Gillingham, MD
For an introduction to Mad Cow Disease and its human variant, vCJD, please see Mad Cow Disease: Advice for Expatriates and Travelers.
How did the epidemic start?
Scientists don't know for sure but it's believed that the use of cattle feeds containing meat and bone meal from animal carcasses, including sheep brain and spinal cord, resulted in the spread of a Prion disease to cattle. Sheep have long been affected by a Prion disease called scrapie. It's believed that humans become infected with vCJD by eating beef from cows infected with Mad Cow/BSE.
What are Prions?
These are unusual infectious agents that are felt to be the cause of Mad Cow and its human form, vCJD. They are mysterious because they appear to contain no genetic material (DNA or RNA). Rather, they are misshapen versions of normal proteins that cause disease apparently by inducing other proteins to become misshapen. Prions are difficult to detect and even harder to destroy.
In what countries has the disease been found in cattle?
There have been nearly 200,000 documented cases in Britain. On the continent there have been many fewer--between 1,000 and 2,000. Germany, Spain, France, Italy, Greece, Portugal, the Netherlands, and Belgium have all had documented cases. A handful of cases, or fewer, have also been found in Denmark, Liechtenstein, Luxembourg, the Falkland Islands, and Oman (most of these cases occurred at least several years ago and many were in cattle imported from the UK). The Czech Republic reported its first case in June, 2001. There was one documented case in 1993 in Canada, in an imported cow. There have been no documented cases in the United States.
The number of BSE cases in Britain continues to decline, with 1311 confirmed during 2000, 42 percent fewer than in 1999.
What's the name of the human form of Mad Cow?
vCJD, which stands for variant of Creudtzfeldt-Jakob disease. It is also sometimes known as nvCJD, or new variant of Creudtzfeldt-Jakob disease. Creudtzfeldt-Jakob (CJD) is a disease that has been known for many years which has similar symptoms and appears to have a similar cause, though it is spread in different ways. It occurs sporadically and rarely.
How many people have been diagnosed with vCJD (human Mad Cow)?
About 100 in Britain, five in France, and one in Ireland, as far as anyone knows. There is a single case under investigation in Hong Kong in an individual who resided for many years in the UK. Recently, scientists warned that the epidemic might end up being larger than originally believed, because some infected people might remain symptom-free for even longer than initially predicted. These infected people are believed to have acquired the disease before aggressive preventive measures were put in place.
Are some people more susceptible to vCJD than others?
Yes, it appears that some people are genetically more susceptible to vCJD--or at the least they become symptomatic faster after infection. The genetic marker that has been discovered is in the Prion protein gene (remember, Prion proteins are normal--it's only when they become misshapen that they cause disease).
What are the symptoms of vCJD?
Memory loss and progressive loss of the ability to think and reason. This is accompanied by hallucinations and uncontrolled body movements. Most victims die within a year after the symptoms begin.
How is the disease diagnosed?
Diagnosis is made by an experienced physician based on the patient's symptoms and a brain wave test, or EEG. Biopsy of the tonsils, along with MRI of the brain, has also been used successfully for the last year or two. However, these tests are not helpful to test the newly infected. On average, victims have been symptomatic about a half year before diagnosis. Definitive differentiation of vCJD (the human form of Mad Cow) and the older disease CJD occurs autopsy.
Is there a blood test for Mad Cow or vCJD?
Not yet. There are furious efforts underway to develop one and recent reports suggest that researchers are close. Other investigators are pursuing a urine test and at least one group has reported preliminary results.
Is there a particular part of the cow that is more likely to be infectious?
The brain and the spinal cord contain the greatest number of Prions and are therefore the most infectious. Some experts believe ground beef becomes contaminated during the slaughtering process and thus is riskier than steaks and other pure cuts of muscle (e.g. filet mignon), which are considered low risk. Certain other organ meats such as intestine are also considered highly infectious.
One particular delicacy -- the famous Italian fiorentina, or t-bone steak--has been hit hard by the outbreak. Butchers can sell these steaks only if they strip out the bone, which contains portions of the vertebral column considered to be potentially high risk. Meat lovers believe the bone is essential to the fiorentina's taste. An auction of the last authentic fiorentina's attracted some famous bidders--according to the Wall Street Journal, singer/songwriter Elton John paid $3,400 for a four pound piece of meat, a cut which might normally go for $50.
Have Europeans stopped eating beef?
Beef consumption fell about 30% initially but it is rising now. In fact, beef consumption in Britain last year exceeded that of 1995, the year before the disease appeared in humans. There has been much discussion about the outbreak and some dinner party menus have become subject to intense scrutiny!
What rules are in place to ensure the safety of beef purchased now?
Regulations vary across the EU, but in general all cattle more than 30 months of age must be tested before they are slaughtered for meat. (Mad Cow disease has never been found in any cattle less than 30 months of age, presumably because these younger animals have never been given infected feed). Animal parts containing brain and spinal cord, and other suspect organ meats, have been banned in all European countries where the disease has been found. Of course, the scrutiny of cattle feed remains intense. Slaughterhouses are held to much higher standards and high risk materials (brain, spinal cords, eyes, parts of the intestine, etc.) are carefully disposed of. While much research and discussion continues on the best way to slaughter and removed infected body parts from the food chain, many Europeans believe the beef supply is safer than ever.
Are milk and other dairy products safe?
The general belief is that they are, and there is some preliminary evidence confirming this. However, additional investigation is ongoing. A large study of dairy products sponsored by the British government began in the fall of 2000 and is expected to yield results in 2003. Almost all observers agree that if there is any risk in dairy products, it is extremely small.
Is Gelatin safe? What about beef fat (tallow)?
Unclear. Gelatin is derived from beef skin and bone material. It is used as a food stabilizer, emulsifier, thickener, gelling agent, and in a number of different ways. While production enhancements have been implemented and the risk is felt to be low, no governmental authorities have declared gelatin perfectly safe. The EU banned gelatin from the UK in 1997. The US continues to import products that contain gelatin that originated in the UK.
Beef tallow is also felt to be of very low risk, but the evidence is not definitive.
Can Mad Cow spread from a dam (a mother cow) to a calf?
Perhaps, but very rarely. (There have been a couple of cattle diagnosed that were born after feed restrictions were put in place. These cattle may have been infected by their mothers). It is not believed that one adult cow can infect another, except through contaminated feed. Similarly it's not believed that vCJD can be spread from one person to another.
What's the relationship between Mad Cow and Foot & Mouth Disease?
There is none, other than the unfortunate coincidence that they both were active problems in parts of Europe in the year 2000. Foot & Mouth Disease poses essentially no health risk to humans.
Why has the U.S. restricted blood donations from people who lived in the UK or Europe?
Though it's not known whether blood transfusions can spread vCJD, the American Red Cross and the Food & Drug Administration have taken the precaution of asking people who lived in affected areas during years that Mad Cow was prevalent not to donate blood.
US officials are also considering restrictions on cornea and other tissue donations from people who lived abroad during these times. It may be many years before it is known for sure whether blood transfusions spread the disease. Note that if you moved to Europe recently your ability to donate isn't restricted, because of the precautions in place to protect the beef supply.
Are there other diseases like Mad Cow & vCJD that are caused by Prions?
Yes, there are a few others. CJD itself has been recognized for years and continues to occur sporadically. It's unclear how the disease is spread in most cases, though documented spread has occurred after brain surgery. A disease called Kuru is also caused by a Prion--this disease was known only among the FORE tribe of New Guinea and was spread through ritualistic cannibalism of dead tribe members' brains and body parts.
There are several Prion diseases that occur in animals, the most common of which is scrapie in sheep. Chronic Wasting Disease or "Mad Deer" Disease--a Prion disease that occurs in the American West--is attracting a lot of attention as scientists try to decide whether humans are at risk of catching it through the consumption of venison, for example.
Last updated: July 12, 2001.
The author thanks Dr. Nancy Salzman, Paris, France, for assistance in preparing this article.