February 25, 2014
MERS Coronavirus Prevalent In Camels For At Least 20 Years
Lawrence LeBlond for redOrbit.com - Your Universe Online
Middle East Respiratory Syndrome-Coronavirus (MERS-CoV) has infected 182 people since it was first reported in September 2012. The disease, which has also resulted in 79 deaths over that time, has now been confirmed to be prevalent in dromedary camels throughout Saudi Arabia and has been for the past two decades, if not longer, according to an international study.
For the study, published in the American Society of Microbiology’s open-access journal mBio on February 25, researchers from the United States and Saudi Arabia conducted a widespread survey of dromedary camels, sheep and goats throughout Saudi Arabia, collecting blood samples and rectal and nasal swabs in November and December 2013. The team used mobile lab equipment to test the blood samples for antibodies reactive with MERS-CoV, and to test the swabs for active virus. The team also analyzed archived blood samples of dromedary camels taken from 1992 to 2010.
After the analysis was complete, the team found that 74 percent of the camels sampled had antibodies to MERS-CoV. Also, more than 80 percent of adult camels had antibodies to the virus. For camels two years and younger, the team found that 90 percent of samples from the east tested positive for the antibodies, while only five percent from the southwest were positive. And the antibodies were seen in camel samples dating all the way back to 1992, which offers strong evidence that either MERS-CoV or a closely related virus has been circulating in the animals for at least 20 years.
The research team also found that active virus was frequently detected in nasal swabs in 35 percent of young camels and 15 percent of adult camels across the country. The virus was less frequently detected in rectal swabs and not at all in the blood samples, indicating that the virus was most likely being spread via respiratory secretions.
"Our study shows the MERS coronavirus (MERS-CoV) is widespread," senior study author W. Ian Lipkin, of Columbia University, New York, said in a statement. "Adult camels were more likely to have antibodies to the virus while juveniles were more likely to have active virus. This indicates that infection in camels typically occurs in early life, and that if people get the virus from camels the most likely source is young camels."
While the evidence offers a pretty strong connection to the virus identified in humans, it remains unknown if camels or some other animal, such as bats, are the source of the human susceptibility. The spread of MERS-CoV in humans was of great concern through much of 2013, with some level of fear that an epidemic may have been in the making during the Hajj pilgrimage last fall. However, since the New Year arrived, there have only been six laboratory-confirmed cases of MERS-CoV in humans and has shown no sign of sustained human-to-human transmission.
While some intense efforts were made to identify bats as the source of infection in humans – a bat from Saudi Arabia was identified as having a 100-percent genetic match to the MERS-CoV found in humans – the first known case of MERS-CoV was in a Saudi Arabian man who had four pet camels.
Lipkin, who was also lead author of the team that found the genetic match in the bat study, said at the time: “There have been several reports of finding MERS-like viruses in animals. None were a genetic match. In this case we have a virus in an animal that is identical in sequence to the virus found in the first human case. Importantly, it’s coming from the vicinity of that first case.”
While the researchers speculate that camels are potential reservoirs for human transmission, this study does not prove that.
"Our findings suggest that continuous, longer-term surveillance will be necessary to determine the dynamics of virus circulation in dromedary camel populations," the authors wrote.