Research in Italy Turns Up a New Form of Mad Cow Disease

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http://www.nytimes.com/2004/02/17/health/17COW.html?th

 

February 17, 2004Research in Italy Turns Up a New Form of Mad Cow DiseaseBy

DONALD G. McNEIL Jr.

 

Anew 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. "

 

Copyright 2004 The New York Times Company

 

 

 

 

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