Camels are an essential source of labor, transportation and food for millions of people in the Middle East, Africa and Asia. But at least in Saudi Arabia they also may harbor a dangerous coronavirus, according to a study in mBio this week.
The study, a comprehensive survey of dromedary camels throughout Saudi Arabia, found the virus causing Middle East Respiratory Syndrome (MERS), called MERS-CoV, in camels throughout the country. Adult camels were more likely to have antibodies to the virus while juveniles were more likely to have active virus, hinting that infection in camels occurs early in their lives, and if people get the virus from camels it is most likely from contact with young camels, said the researchers, directed by Ian W. Lipkin of Columbia University, New York. In addition, antibodies to the virus were observed in archived camel blood serum dating back to 1992.
MERS is a serious viral respiratory illness that has been identified in 182 people since 2012, 79 of whom have died from the condition. While most infections have occurred in Saudi Arabia, the origin of disease, in most cases, has remained unknown.
As often happens in science, finding the link to camels was somewhat incidental. In 2012 Saudi Arabia’s Deputy Minister of Health, Ziad Memish, asked Lipkin’s team to help identify an animal source of MERS after the infection was identified in the first victim, an elderly man who had died. Suspecting bats, the team made news headlines last year after reporting they had found a virus in an Egyptian Tomb Bat genetically identical to the one found in the man; the bat was just a few miles from the man’s home. During their sleuthing, the team noted that the man had four pet camels, and “we were struck by that,” Lipkin says. So they collected a dozen or so blood samples from camels, and from some cows and sheep, too.
But bringing the samples back to the United States for analysis proved challenging, Lipkin says, because of concerns about spreading foot-and-mouth disease. Arriving home at New York’s John F. Kennedy Airport, Lipkin’s team found their samples held up by customs, while a series of government agencies including the Department of Homeland Security and the Department of Agriculture became involved. Eventually, says Lipkin, the samples were transported by special hazard truck to the National Biodefense Analysis and Countermeasures Center in Frederick, Md., where they were tested for foot-and-mouth disease. After the samples were cleared, the special hazard truck returned them to New York.
To avoid such snafus during the current study, Lipkin’s colleague Thomas Briese and associates brought a mobile laboratory to Saudi Arabia, where they worked side by side with Abdulaziz Alagaili, Osama Mohammed, and Iyad Zalmout of King Saud University and the Saudi Wildlife Authority in Riyadh testing camel blood samples and swabs from camels’ noses and rectums, and analyzing archived camel serum samples from as early as 1992.
They found that 74 percent of camels sampled countrywide had antibodies to MERS-CoV. More than 80% of adult camels throughout the country had antibodies to the virus, while in camels age two or younger the prevalence ranged from 90% in the eastern part of the country to 5% in the southwest.
Active virus was most frequently detected in nasal swabs, in 35% of young camels and 15% of adult camels countrywide, but less frequently in rectal swabs and not in blood, indicating that the virus most likely is spread by respiratory secretions.