Abstract
Replicative
capacity of Middle East respiratory syndrome coronavirus (MERS-CoV) was
assessed in cell lines derived from livestock and peridomestic small
mammals on the Arabian Peninsula. Only cell lines originating from goats
and camels showed efficient replication of MERS-CoV. These results
provide direction in the search for the intermediate host of MERS-CoV.
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Conclusions
Transmission of MERS-CoV between humans is still limited, and the
identification of an intermediate animal host could enable the
development of public health measures to prevent future spread of the
virus among humans. Although MERS-CoV neutralizing antibodies have been
detected in camels from Oman, Spain, and Egypt, the virus has not
previously been detected in camels (
8,9).
An informed focusing of investigations on a select group of species,
such as camels, could benefit epidemiologic investigations. To identify
potential intermediate host species of MERS-CoV, we used in vitro
testing to determine virus permissiveness in select cell culture models.
In general, cell lines cannot depict the full pathogenicity of in vivo
infection because infection is influenced by epithelium-specific
differentiation of target cells and the presence of immune cells.
However, for viruses such as CoVs, whose tropism is believed to be
determined mainly by the availability of an appropriate entry receptor (
10),
epithelial cell cultures could indeed constitute valid surrogates of
virus permissiveness in vivo. With these limitations in mind, our
results are in concordance with the findings of MERS-CoV neutralizing
antibodies in camels and with information regarding patient contact with
animals in reports of 2 human cases of MERS-CoV infection (
11,
15).
One of the patients owned a farm on which camels and goats were kept.
Before onset of his own illness, the patient reported illness in several
goats on his farm. The patient did not have direct contact with
animals, but he reported having eaten goat meat and having had contact
with one of the animal caretakers, who suffered from respiratory disease
(
15). The second patient reported direct contact with a diseased camel shortly before onset of his symptoms (
11).
In our study, production of infectious virus particles was seen in
goat lung and kidney cells and in camelid kidney cells. Excretion
patterns indicative of kidney infection should be investigated once
further clues to the identity of the MERS-CoV animal reservoir become
available. Our preliminary findings suggest that ungulates, such as
goats and camels, are a possible intermediate host of MERS-CoV; thus,
exposure to urine and feces from these animals might constitute a source
of human infection. Moreover, food products derived from these animals
(e.g., meat and milk) should be tested for their potential to transmit
MERS-CoV. The results of our study suggest that investigations into the
MERS-CoV animal reservoir and intermediate host should focus on caprid
(e.g., goats) and camelid hosts, and we identified several new cell
lines for use in virus isolation studies.
Dr Eckerle is a virologist at the Institute of Virology in Bonn,
Germany. Her primary research interest is characterization of novel and
emerging zoonotic viruses.
http://wwwnc.cdc.gov/eid/article/20/2/13-1182_article.htm
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