However, the finding should not be taken as evidence of infection of people from camels
Camels are catching a virus that has been sickening people in the Middle East, according to research just published. But the study has been unable to establish whether such animals could be a source of human infections.
The Middle East respiratory syndrome coronavirus (MERS-CoV) was first reported just over a year back. Since then, the World Health Organisation has been informed about 165 laboratory-confirmed cases of people infected by the virus, over 40 per cent of whom died. These cases have occurred overwhelmingly in the Middle East and the few that turned up in European countries were linked by travel to that region.
Genetic analyses of the MERS-CoV found in patients has shown that it had crossed over from some animal reservoir into humans several times. Although the virus is closely related to coronaviruses in bats, these flying mammals are considered to be an unlikely source of human infections. Determined efforts are therefore being made to identify animals that harbour the virus and might pass it on to people.
Several studies have already reported antibodies to the virus in camels in Oman, Canary Islands, Egypt, Jordan and Saudi Arabia, but not in farm animals such as goats, sheep, cows and chicken.
Researchers have now identified genetic sequences of the MER-CoV in nasal swabs taken from camels at a farm in Qatar where two men became infected in October this year.
“Our study provides virological confirmation of MERS-CoV in camels and suggests a recent outbreak affecting both human beings and camels,” observed the scientists from Netherlands, Britain and Qatar in a paper published in The Lancet Infectious Diseases.
But this should not be taken as evidence for infection of people from camels, they cautioned. “We cannot conclude whether the people on the farm were infected by the camels or vice versa, or if a third source was responsible.”
“This study conclusively shows that camels are readily infected with MERS-CoV,” commented J.S. Malik Peiris of the University of Hong Kong, whose laboratory was the first to isolate the SARS coronavirus that spread globally and created panic ten years back. More recently, he has participated in research that identified antibodies to the MERS virus in camels in Egypt and Saudi Arabia.
But with antibodies, “one could not be sure if the virus infecting those camels was identical to the MERS-CoV or a closely related novel virus,” he pointed out in an email. The new study “proves beyond doubt” that the MERS-CoV could indeed infect camels.
Moreover, it also showed that at the very least camels were likely to be an important link in the epidemiology of the MERS virus, he added.
“We cannot exclude the possibility that other common livestock species including cattle, sheep, and goats, or other animals including wild species were involved in the spread of MERS-CoV,” the researchers noted in The Lancet Infectious Diseases paper.
Although antibodies to MERS-CoV had not been found in animals other than camels, they should not be ruled out as potential hosts for the virus at this stage, according to Marion Koopmans of the National Institute of Public Health and Environment in Netherlands, one of the corresponding authors of the paper.
The receptor molecule that the virus used to infect cells was found in goats and sheep, among other animals, she noted in an email.
“An understanding of the role of animals in the transmission of MERS-CoV is urgently needed to inform control efforts,” remarked Neil M. Ferguson and Maria D. Van Kerkhove of Imperial College London in a commentary carried in the same journal. Substantially more genetic and epidemiological data from both animal and human cases was needed “to unravel the complex transmission dynamics of this virus.”