http://www.nytimes.com/2003/05/23/health/23CND-SARS.html?ei=5070&en=1270bb5038a50c26&ex=1054872000&pagewanted=print&position=

May 23, 2003

Strain of SARS Is Found in 3 Animal Species in Asia

By KEITH BRADSHER with LAWRENCE K. ALTMAN
 

ONG KONG, May 23 — A virus virtually identical to the one thought to cause SARS in humans has been found in a tree-dwelling animal whose meat is a delicacy in southern China and in two other species, scientists here and at the World Health Organization said today.

The evidence reported today solves one scientific mystery because it is the first to show that the SARS virus exists outside humans, raising the possibility that it jumped from animals to humans.

The new findings could greatly increase the difficulty of containing SARS in humans because if certain species of wild animals harbor the virus it will be virtually impossible to eradicate the disease.

In linking the animals to SARS, scientists in W.H.O.'s laboratory network tested 25 specimens from eight species of exotic animals offered for sale in a market in Guangdong Province, where the first cases of the human disease are thought to have occurred.

The SARS virus was found in six masked palm civets — a cat-size animal that is served as food — and in the only raccoon dog tested. Evidence of the infection was also found in the blood of one badger.

The civet is the Himalayan, or masked, palm civet. It is related to the mongoose, resembles a large weasel and is a threatened species.

The Chinese government plans to start banning the sale of the animals, said Dick Thompson, a spokesman for W.H.O. But a Chinese scientist expressed doubt that the ban would succeed because the civet, in particular, has traditionally been considered a delicacy.

Liu Zhenhua, a prominent Guangdong chef, said in a telephone interview tonight that civets were eaten mainly in the autumn and winter because of the belief that they help people withstand cold weather.

Since the World Health Organization, a United Nations agency, first recognized the SARS epidemic in March, scientists have suspected that animals might be involved in the human epidemic. The reason is that a number of the earliest cases involved food handlers in markets in Guangdong Province who sold live exotic animals for human consumption.

Health officials have said that the first cases of the disease appeared to have occurred last November among people involved in the culinary preparation of rare animals in Foshan, 90 miles up the Pearl River from Hong Kong.

But whether the species were captured in the wild or raised on farms is not known, W.H.O. said. Nor, the agency said, is it known whether humans transmitted the virus to animals or vice versa.

"While it is more likely that these animals harbor the virus naturally, it is premature to say that the virus is found in nature" because the scientists have yet to determine the origin of the animals, said Dr. Klaus Stöhr, the head of the W.H.O. scientific team investigating SARS.

But if the virus is confined to species that are raised in farms, then bans on such farming might eliminate a source of the virus and could reduce the risk of spreading the virus from animals to humans in the future.

Dr. Stöhr said in an interview that the agency "believes that it is still possible to contain SARS if the person-to-person transmission of the virus is stopped" in affected areas. Dispersal of droplets of the SARS virus in coughs and sneezes is thought to be the primary means of spreading SARS, or severe acute respiratory syndrome.

Dr. Stöhr said that he received an unpublished report of the findings today from scientists at the University of Hong Kong and the Center for Disease Control and Prevention in Shenzhen, just across the Hong Kong border in mainland China. The findings open up many new avenues of research, he said.

One avenue is the need to determine the importance of seemingly minor differences in the genetic maps of the SARS viruses isolated from the animals in the market in Guangdong Province and those found in humans there and elsewhere.

The human SARS virus contains more than 29,000 nucleotides — units of the genetic map — 29 fewer than those found in the SARS viruses isolated from the animals. Though the number may seem trivial, even smaller differences in molecular maps can have major effects on viruses. One example is the influenza virus. The possibility exists that the SARS virus mutated if it jumped species, from animals to humans, Dr. Stöhr said. But, he also said, "what this means for SARS is unclear."

Other fundamental questions that scientists need to answer include:

¶Whether the findings were limited to one market or are representative of most other markets in the area.

¶How widespread the virus may be in wild or farmed animals.

¶How many species of animals are involved, and which ones.

¶Whether wild or farmed animals harbor the virus without becoming sick; the tested, infected civets appeared healthy.

¶Whether infected animals can produce enough virus to infect humans.

¶Whether the virus is in the feed supply and, if so, how it got there. One possibility is from human feces in fertilizer.

¶Whether the animals transmitted the SARS virus to each other in their cages, which are often stacked on top of one another in the filthy, crowded markets in Guangdong.

Another puzzle is why SARS seems to have started "more or less simultaneously in six cities" in Guangdong, Dr. Stöhr said. Infection through a wholesale distributor of animals or of their feed is a possibility.

Answers to some questions might come from taking the SARS virus isolated from the animals and giving it to primates in experiments like those conducted with the SARS virus isolated from humans.

The new findings emerged from a challenge the Chinese government made to scientists to find the source of the SARS virus. The scientists in Hong Kong and Shenzhen conducted a pilot study in which they bought live animals in different areas of a local market. The scientists were not able to determine the number of wholesalers that supplied the animals to the market. The scientists also could not determine the source of the feed for the animals.

After the scientists took the animals to their laboratories, they tested their sputum and feces. They found the SARS virus in the feces of all six civets and in the sputum, or mucus from the mouth, of four of the six, Dr. Stöhr said.

Masked palm civets have short fur that can be brown, orange, red or gray, with black bands on the head and feet. They eat mostly fruit, weigh up to 13 pounds and have bodies that grow up to two and a half feet long, with tails of nearly equal length.

Civets are grown on farms in Guangdong Province and are sometimes trapped in the wild for Chinese kitchens. The animals are becoming increasingly rare across their range, from Pakistan to Indonesia, because of deforestation, and their sale is banned in Hong Kong, where they are a protected species.

A ban on eating them is unlikely to succeed because the consumption of wild animals is so much a part of Chinese culture, said Professor Yuen Kwok-yung, a microbiologist at Hong Kong University.

"It is very difficult to stop a culture," Professor Yuen said. "It has been there for 5,000 years."

It is unlikely that diners can contract the disease from well-cooked animals of any type, Professor Yuen and W.H.O. officials said. The rearing, slaughter and preparation of infected animals are activities more likely to transmit viruses across species, he added.

The scientists also found the virus in the only raccoon dog, a dog resembling a raccoon, that was obtained. Antibodies in the blood from a Chinese ferret badger showed evidence that it had been infected with the SARS virus. But the tests were not intended to determine when the badger was infected.

The scientists also conducted laboratory experiments aimed at supporting the link between the animal and human SARS viruses. They did so by adding serum from the implicated animals that contained protective antibodies to test tubes containing the human SARS virus. The antibody-rich serum inhibited the growth of the human virus.

The scientists also performed the reverse experiment, adding antibodies from human sera that inhibited the growth of the animal SARS virus in test tubes. The findings strongly supported the link, Dr. Stöhr said.

The scientists found no evidence of the SARS virus in three hog badgers; three beavers; two Chinese muntjac; four domestic cats; and four Chinese hare, according to Dr. Stöhr.

Professor Yuen said that although no tests had been done, it was "theoretically possible" that household cats could become infected because they are similar biologically to civets. If so, it could make disease control more difficult.

Copyright 2003 The New York Times Company |