Researchers identify wild animal reservoirs for SARS

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The World Health Organization announced May 23 that researchers have identified two species—the masked palm civet and the raccoon dog—that harbor a coronavirus nearly identical to the severe acute respiratory syndrome virus.

Research teams in Hong Kong and Shenzhen, China, took samples of wild animals being sold for human consumption at markets in southern China, where many species of wild animals—including masked palm civets and raccoon dogs—are considered delicacies.

The researchers identified a virus identical to SARS, except for one additional small genetic sequence, in masked palm civets and raccoon dogs. All six civets that were tested seroconverted in the presence of the SARS coronavirus isolated from humans, and their sera inhibited the growth of the SARS virus. Reciprocally, human serum from SARS patients inhibited the growth of the coronavirus isolated from these animals.

One other species, the Chinese ferret badger, also had antibodies to the SARS virus.

Officials from the World Health Organization were cautious about interpreting the results of the study.

"At present, no evidence exists to suggest that these wild animal species play a significant role in the epidemiology of SARS outbreaks," according to a statement from the WHO. "However, it cannot be ruled out that these animals might have been a source of human infection."

The study provides the first evidence of a nonhuman host of the disease.

Many fundamental questions remain about the role of animals in the SARS epidemic, according to the WHO. Studies must be conducted to determine how widespread the SARS virus might be in animals in southern China, whether these animals can excrete virus in an amount sufficient to infect humans, and whether the virus can be transmitted from animal to animal.

The SARS virus—a coronavirus unlike any known coronaviruses found in human and domestic animals—emerged in China in November 2002 and by February 2003 had developed into a global epidemic.

At press time in late May, there were more than 8,221 reported cases—65 in the United States—of SARS in humans, with 735 deaths—none in the United States, according to the WHO.

(See JAVMA, June 1, 2003, page 1481, for more information on SARS.)