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 Researchers from the Netherlands and Qatar used gene-sequencing
techniques to show that three dromedary, or one-humped camels, on a
farm in Qatar where two people had contracted the MERS coronavirus
(CoV) were also infected.
The study, published in the Lancet Infectious Diseases journal on
Tuesday, confirms preliminary findings released by Qatari health
officials last month. Camels are used in the region for meat, milk,
transport and racing.
But the researchers cautioned it is too early to say whether the
camels were definitely the source of the two human cases — in a
61-year-old man and then in a 23-year-old male employee of the farm — and more research is needed.
"This is definitive proof that camels can be infected with MERS-CoV,
but based on the current data we cannot conclude whether the humans
on the farm were infected by the camels or vice versa," said Bart
Haagmans of Rotterdam's Erasmus Medical Centre, who led the study
with other Dutch and Qatari scientists.
He said a further possibility is that humans and camels could have
been infected "from a third as yet unknown source".
"The big unknown is the exact timing of infections, both in the
persons and in the camels," he added. Both the men infected in Qatar
recovered.
Scientists around the world have been searching for the animal
source, or reservoir, of MERS virus infections ever since the first
human cases were confirmed in September 2012.
Globally to date, the World Health Organisation (WHO) says there
have been 163 laboratory-confirmed human cases of MERS, including 71
deaths. The WHO is also aware of around a dozen other probable but
unconfirmed MERS cases in people. CASES AROUND THE WORLD
In humans, MERS cause coughing, fever and pneumonia, which can be
fatal. Cases have so far been reported in Saudi Arabia, Qatar,
Kuwait, Jordan, United Arab Emirates, Oman, Tunisia, France,
Germany, Spain, Italy and Britain. British researchers who conducted some of the first genetic analyses
on MERS last September said the virus, which is from the same family
as Severe Acute Respiratory Syndrome, or SARS, is also related to a
virus found in bats.
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In the Qatar study, researchers collected clinical samples — including nasal swabs, blood and rectal swabs, as well as stool
samples — from 14 dromedary camels living in a barn in Qatar where
in the previous week, the 61-year-old owner of the barn had been
diagnosed with MERS infection.
The samples were sent to laboratories in the Netherlands for genetic
analysis and antibody testing, which confirmed the presence of MERS
in three of the animals.
Researchers said the virus gene sequences were very similar — although not identical — to those identified in the two people from
the same site.
They also noted that all 14 of the camels tested had antibodies to
MERS, suggesting the virus might have been circulating among the
animals for some time, allowing most of them to build up immune
protection against infection.
Since they were not able to say definitely whether the virus had
passed from the camels to humans, or the other way, the researchers
stressed they also could not rule out that other common livestock
species, like cattle, sheep and goats, or other animals, may be
involved in the spread of MERS.
To help find more answers, they said, researchers should aim to plot
detailed case histories of all human cases of MERS, including any
exposure to animals or animal products as well as links with other
infected people.
(Editing by Alister Doyle)
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