A camel that might have passed the Middle East respiratory syndrome coronavirus (MERS-CoV) to its Saudi Arabian owner had signs of illness, a Saudi health official said today in revealing a little more information about the situation.
Saudi officials reported yesterday that a camel had tested positive for MERS-CoV, a few days after its owner, a 43-year-old man from Jeddah, was confirmed to have the virus. The case marks the first time of the virus has been found in an animal.
In a ProMED-mail post today, Ziad A. Memish, MD, the Saudi deputy minister for public health, wrote, "Camels owned by the patient which were symptomatic with fever and rhinorrhea were tested for MERS-CoV and tested positive." ProMED-mail is the online reporting service of the International Society for Infectious Diseases.
Memish added, "This is the first time that a camel related to a case tests positive for MERS-CoV by PCR. Further testing is ongoing to sequence the patient [virus] and the camel virus and compare genetic similarity level to conclude causality."
He also said the 43-year-old patient, who has no underlying chronic diseases, is still in an intensive care unit.
His comments left it unclear whether more than one camel tested positive for the virus. Today the Saudi Ministry of Health (MOH) posted an English-language version of yesterday's Arabic statement about the findings, which said, "The initial laboratory test conducted on one of those animals was positive."
Recent studies revealed that camels in Oman, the Canary Islands, and Egypt carried antibodies suggesting past exposure to MERS-CoV or a closely related virus, but the Saudi report marks the first finding of the virus itself in an animal.
Search for animal source
Scientists have been searching for the animal reservoir and immediate source of MERS-CoV since the virus was discovered in September 2012. Bats and camels have been suspected to harbor the virus, and this week's report supports the view that camels may pass the virus to humans.
Contact with domestic animals has been cited in a few previous MERS-CoV cases. In commenting on Memish's ProMED post today, a ProMED moderator noted that a Qatari man who got sick with MERS-CoV in October 2012 owned a camel and goat farm and that some of the goats and a caretaker were sick at the time.
If camels can pass the virus to humans, exactly how they do it is unknown. Another ProMED moderator, Artak Stepanyan of Yerevan State Medical University in Yerevan, Armenia, commented today that camels are known to spit, which "may add effectiveness and range to their potential role as virus disseminators."
Serologic study finds no positives
In other developments, a serologic study published yesterday showed no evidence of MERS-CoV antibodies in two groups of Saudi Arabians who were tested in October 2012, shortly after the virus was discovered.
Saudi Arabian and German researchers tested 130 blood donors in Jeddah and 226 abbatoir workers in Mecca, using three different serologic tests, according to their report in the Journal of Infectious Diseases (JID). Eight samples were reactive in one test, but further testing indicated that the antibodies were specific for established human coronaviruses.
"There is no evidence MERS-CoV circulated widely in the study region in fall 2012, matching an apparent absence of exported disease during the 2012 Hajj," the authors wrote.
The findings fit with a few previous serologic studies that have found no MERS-CoV antibodies in residents in or visitors to Saudi Arabia.
In an accompanying commentary in JID, a pair of experts from the United Kingdom and Hong Kong, David F. Hui and Alamuddin Zumla, write, "these antibody studies do not provide proof of absence or presence of MERS-CoV because of limitations imposed by the restricted study design and small numbers studied."
They add that the MERS-CoV serologic tests that have been developed need to be independently evaluated and validated by using them on blinded samples from known positive and negative MERS cases.
Hui is with the Centre for Clinical Microbiology at University College London, while Zumla works in the Division of Respiratory Medicine and Stanley Ho Center for Emerging Infectious Diseases at the Chinese University of Hong Kong.
Macaques as MERS-CoV models
Another report published yesterday in JID adds to previous findings suggesting that rhesus macaques are good stand-ins for humans in studying MERS-CoV infections.
Researchers from Beijing and Hong Kong used intratracheal inoculation to infect macaques with MERS-CoV. The infected monkeys showed clinical signs of disease, virus replication, histologic lesions, and neutralizing antibody production, the authors said.
"The MERS-CoV rhesus macaque model will be instrumental in developing and testing vaccine and treatment options for an emerging viral pathogen with pandemic potential," Hui and Zumla wrote in their commentary.
Nov 12 ProMED post by Ziad Memish
Nov 11 Saudi MOH statement in English
Nov 11 JID serologic study
Nov 11 JID commentary by Hui and Zumla
Nov 11 JID study of MERS-CoV in macaques
Sep 23 CIDRAP News story about MERS-CoV in macaques