BASE - A new strain of BSE?

[Tofu looks better every day. -x]

February 17, 2004
Research in Italy Turns Up a New Form of Mad Cow Disease
By DONALD G. McNEIL Jr.
 
 new form of mad cow disease has been found in Italy, according to a study 
released yesterday, and scientists believe that it may be the cause of some 
cases of human brain-wasting disease.

While the strain has been found in only two Italian cows, both apparently 
healthy, scientists in Europe and the United States said it should provide new 
impetus in Washington for the Department of Agriculture to adopt the more 
sensitive rapid tests used in Europe because it may not show up in those used 
in the United States.

Along with the Italian study, there have been recent reports of unusual types 
of mad cow disease in France and Japan, and scientists say the discovery of 
new forms suggests that many cases of "sporadic" human disease — by far the 
most common kind, responsible for about 300 deaths a year in the United 
States — are not spontaneous at all, but come from eating animals.

The brain-destroying diseases involve prions — misfolded proteins that are 
believed somehow to induce other proteins to fold incorrectly, leaving patches 
of useless debris and holes that turn brains to sponge.

The study, by a team from universities in Turin, Verona, Brescia and Milan, 
was edited by Dr. Stanley B. Prusiner, who won a 1997 Nobel Prize for his 
prion work. It appears this week in The Proceedings of the National Academy of 
Sciences.

Two American experts not involved in the study said the findings were 
sobering. Dr. Pierluigi Gambetti, director of the National Prion Disease 
Pathology Surveillance Center at Case Western Reserve University, called the 
report "very convincing." Dr. Paul Brown, a prion expert at the National 
Institutes of Health, said it "opens the possibility of a second strain of the 
agent in circulation — and that's probably not good news."

Current American testing focuses only on finding the prion that causes bovine 
spongiform encephalopathy in cows and "variant" Creutzfeldt-Jakob disease in 
humans.

But the disease found in two aged dairy cows in Italy is so different that its 
discoverers gave it a new name, bovine amyloidotic spongiform encephalopathy, 
or BASE, because it forms amyloid plaques in the brain — round, dark clumps of 
sticky protein junk.

"We don't know if this disease is passed to humans," said Dr. Salvatore 
Monaco, a neurologist at the G. B. Rossi Polyclinic in Verona and an author of 
the study. "But it is very similar to a subtype that causes sporadic C.J.D. in 
humans."

In the past, some people with cases diagnosed as sporadic have said they ate 
squirrel brains, pig brains or raw meat, but no link to a different prion was 
established, said Dr. Michael C. Hansen, who studies prion diseases for 
Consumers Union. Recently, he said, a new prion strain closely related to a 
French strain of scrapie, a sheep disease, was found in a French cow.

Both the Italian cows, one 15 years old and one 11, appeared healthy. Their 
unusual strain was discovered only because Italy tests all cattle over 30 
months old slaughtered for human food. By last August, it had tested 1.6 
million and found 103 that tested positive for prions.

Finding a new strain in apparently healthy cattle "suggests that all 
surveillance should be like we do in Italy," Dr. Monaco said.

Many American prion experts concur. The United States now plans to test only 
40,000 cows this year, focusing on those too sick to walk, and using an 
immunohistochemistry test that takes about eight days and is "much less 
sensitive," Dr. Gambetti said, than tests used in Europe that take only hours.

Besides forming plaques, the strain differs in that it appears in much older 
cattle. Most cows with the well-known strain die before they are 10. Also, the 
new prions collect in different parts of the brain — the olfactory bulb and 
thalamus, rather than the brain stem. The two cows also had relatively 
fewer "holes."

Those characteristics resemble the ones found in about 30 percent of humans 
who have the sporadic form of Creutzfeldt-Jakob disease.

In the United States, about one person per million develops and dies of the 
sporadic form each year, meaning that there are usually about 300 cases in the 
country. (For unknown reasons, Italy has nearly two cases per million; 
Switzerland has about three.)

Only one person in the United States has had variant Creutzfeldt-Jakob, the 
human form of mad cow disease, which was first described in the 1990's and has 
killed about 150 Europeans; she grew up in Britain and was probably infected 
there.

Most sporadic cases are among the elderly, while in Britain the variant form 
struck many people under 30. Victims of both rapidly develop staggering, 
memory loss and dementia, fall into comas and die.

Dr. Brown said the discovery did not suggest that many humans were suffering 
from undiagnosed illness. If that was the case, he said, the number of 
sporadic cases found in Britain since 1994 should have shot up; they have not.

The sporadic form has been assumed to arise spontaneously because there has 
been no other obvious cause, said Dr. Laura Manuelidis, a Yale 
neuropathologist who studies the disease.

But human cases from several countries produce different symptoms when 
injected into susceptible mice, showing that there are several human strains. 

Dr. Manuelidis is skeptical of the conventional wisdom that prions, which 
contain no DNA or RNA, can transmit infections. She believes that a slow-
acting virus, not yet discovered, may be the cause. 

To make her point that such infections may have been crossing species well 
before mad cows created a scandal in Britain a decade ago, she read from an 
old report she has posted on her office door.

It is from an 1883 issue of the Medical Veterinary Review: A veterinarian 
named Serraet from southwest France describes a cow he saw die of the symptoms 
of scrapie, which had then been known in sheep for 100 years: itching, 
nervousness, partial paralysis and, ultimately, coma.

Dr. Serraet ends with a suggestion: "I would advise the managers of cattle 
abattoirs to sell the meat only to lower-class butcher shops." 


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