Published Date: 2013-11-19 17:24:58
Archive Number: 20131119.2064239
Date: Mon 18 Nov 2013
Source: CIDRAP [summarised, edited]
http://www.cidrap.umn.edu/news-perspective/2013/11/who-confirms-kuwaits-mers-cases-spain-cites-new-case
The
World Organisation for Animal Health (OIE) said on [15 Nov 2013] that
there was still no convincing evidence that camels are a source of
MERS-CoV infections in humans, despite recent findings pointing in that
direction. "Currently, there is no strong evidence to consider that
camels are a source of infection for human cases of MERS," the OIE said
in an update of its questions and answers about the virus.
In
serologic studies reported in recent months, camels in Egypt, Oman, and
the Canary Islands were found to have antibodies to MERS-CoV or a
closely related virus. Further, last week, Saudi health officials
reported finding the virus in a sick camel that belongs to a 43 year old
case-patient from Jeddah.
Saudi officials said the camel tested
positive for the virus by polymerase chain reaction. They said they were
sequencing the genomes of the camel and patient's isolates to see
whether they match; the results have not yet been reported.
The
OIE statement focused on the serologic findings and did not refer to the
report of the infected camel. "Currently, there is no strong evidence
to consider that camels are a source of infection for human cases of
MERS," the statement said. "Based on available epidemiological data, it
is difficult to explain the relationship between positive serological
results in camels and cases of human infections with MERS CoV.
"Indeed,
to date, there is no potential similarity between the strain of MERS
CoV isolated in humans and the suspicions shown in camels. It is
important to remain open minded about all potential sources of exposure
for human cases until more information is available."
The agency
went on to say that, thanks to cross-reactivity, serologic tests may not
distinguish between antibodies to different viruses that have genetic
or antigenic similarities. "Serology tests for MERS CoV have not yet
been validated in animals and may not be reliable," the OIE added. "If
these tests, which may not be sufficiently specific, are used in
animals, there is a risk that 'false positive' results will occur
because it may not be possible to differentiate antibodies to MERS CoV
from antibodies to other coronaviruses, commonly found in animals. This
is why tests in animal should focus on isolating and identifying the
virus itself," the agency said.
The OIE voiced a similar view
back in July [2013] in an earlier version of the question-and-answer
statement. At that point, there were no reports of serologic or
virologic findings pointing to camels as a source of the virus, but at
least one MERS patient had been reported to have had contact with a sick
camel before he got sick.
[byline: Robert Roos]
--
communicated by:
ProMED-mail
<promed@promedmail.org>
[OIE's "Questions and Answers MERS coronavirus (CoV)," updated on 15 Nov 2013, are available at http://www.oie.int/for-the-media/press-releases/detail/article/questions-and-answers-mers-coronavirus-cov/.
The following 2 passages may be of particular interest:
"1. What about serological tests in animals?
Serology
tests aim to detect antibodies produced by the animal against the virus
and not to search for the presence of the virus itself. Often, it is
difficult and sometimes impossible to distinguish antibodies to
different viruses having genetic or antigenic similarities, due to what
is known as serological 'cross reactivity'.
Serology tests for
MERS CoV have not yet been validated in animals and may not be reliable.
If these tests, which may not be sufficiently specific, are used in
animals, there is a risk that 'false positive' results will occur
because it may not be possible to differentiate antibodies to MERS CoV
from antibodies to other coronaviruses, commonly found in animals.
That is why tests in animals should focus on isolating and identifying the virus itself.
2. What would happen if MERS CoV is identified in animals?
If
information from public health investigations identifies a possible
animal source, OIE will support further joint investigations.
OIE
Member Countries would be obliged to report a confirmed case of MERS
CoV in animals to OIE, as an 'emerging disease' in accordance with
article 1.1.3 of the OIE Terrestrial Animal Health Code. If MERS CoV was
identified in an animal, this would not necessarily mean that the
animal is a source of human infection. Detailed investigations would
then be needed to understand the relationship between any animal cases
and human cases and whether a finding in animals would be significant
for human infection."
On 12 Nov 2013, Saudi Arabia's Ministry of
Health notified the 1st time that a camel related to a human case tested
positive for MERS-CoV by PCR (posting 20131112.2051424). Reportedly,
further testing was ongoing to sequence the patient and the camel virus
and compare genetic similarity levels to conclude causality. The results
of these tests are not yet available.
If the camel strain is
found homologous to the human strain, OIE's requirements, as spelled out
above, will have to be fulfilled, namely notification of the case as an
'emerging disease'. In the meantime, precautionary measures, including
the isolation of in-contact animals on the suspected farm, have been
undertaken by the Saudi authorities (posting 20131113.2053932).
For a recent response from neighbouring Dubai, see http://gulfnews.com/news/world/usa/mers-link-to-camels-opens-a-pandora-s-box-1.1255185. - Mod.AS
http://www.promedmail.org/direct.php?id=2064239
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