Recent research has shown that MERS-CoV can replicate in cell lines taken from bats and is closely related to a bat coronavirus currently circulating. However, it seems unlikely that the virus is transmitted directly from bats to humans, considering their generally shy nature and nocturnal habits. Human-to-human transmissibilty of the virus seems to be rare, many researchers suspect another animal reservoir for the virus exists.

An international team of researchers, led by Dr. Chantal Reusken of the National Institute for Public Health and Environment in Bilthoven, Netherlands, collected 349 blood serum samples from a variety of livestock animals, including dromedary camels, cows, sheep and goats. Samples from animals closely related to dromedaries were also taken. The animals came from a variety of countries, including Oman, Netherlands, Spain and Chile. This is the first reported animal serological study for MERS-CoV.

Researchers analyzed the samples for the presence of MERS-CoV specific antibodies, SARS coronavirus reactive antibodies and another strain known as HCoV-OC43 that is closely related to the bovine form of the virus and can infect humans. The researchers found no evidence of cross reactivity between antibodies of any of the three.

No MERS-CoV antibodies were found in the blood serum taken from 160 cattle, sheep and goats from the Netherlands and Spain. However, MERS-CoV specific antibodies were found in all 50 samples taken from dromedary camels in Oman. Since these samples were taken from camels in different locations, the data suggests MERS-CoV, or a similar virus, is circulating in the dromedary camel region.

Low levels of the same antibody were also found in 17 percent of the serum samples taken from camels in the Canary Islands, a location not previously known for circulation of the virus. No virus specific antibodies were found in tests on 34 animals that are closely related to the dromedary, such as Bactrian camel, alpaca, and llama sampled in the Netherlands and Chile.

According to the authors, “The dromedary camels that we tested from the Middle East (Oman) were more often positive and had much higher levels of antibodies to MERS-CoV than the dromedary camels from Spain. The best way to explain this is that there is a MERS-CoV-like virus circulating in dromedary camels, but that the behavior of this virus in the Middle East is somehow different to that in Spain.”

“As new human cases of MERS-CoV continue to emerge, without any clues about the sources of infection except for people who caught it from other patients, these new results suggest that dromedary camels may be one reservoir of the virus that is causing MERS-CoV in humans. Dromedary camels are a popular animal species in the Middle East, where they are used for racing, and also for meat and milk, so there are different types of contact of humans with these animals that could lead to transmission of a virus.”