July 15, 2015 — In a paper published today in the journal Infection Ecology & Epidemiology, researchers are reporting having recorded the highest ever rate of MERS-CoV shedding camels at a single location. Fifty-nine percent of the dromedaries sampled at a slaughterhouse in Doha, Qatar, showed evidence of the virus.
“This is a remarkably high number,” said co-author Chantal Reusken, of the Viroscience department at Erasmus MC, Rotterdam, in the Netherlands. Reusken along with fellow researchers in Qatar, have been studying MERS-CoV shedding patterns to better understand exposure risks in humans.
Previous studies have implicated zoonotic transmission in a large proportion of MERS cases – and mounting evidence points to dromedary camels as key reservoir hosts. At the Doha market, only five people perform camel slaughters. All five were tested and four of them were found to have MERS- CoV antibodies, though none reported to have had severe health complaints.
Aside from the unprecedented number of MERS-CoV shedding camels, Reusken along with her colleagues made a second striking observation as well during the study: the study suggests that camels can be re-infected by the virus. “What we found was that even camels with high levels of neutralizing antibodies to the virus were still shedding,” she said. “This could have huge implications to virus control measures.”
“While natural immunity differs from vaccine-induced immunity, the former which can be much stronger, this could mean that vaccine strategies for camels won’t work. We need to be aware that immunity cannot be complete.”
Other studies of camel populations in the Middle East have not reported the high degree of shedding the team found at the Doha market, which is an intake point for camels imported from Australia, the Middle East region and East Africa.
Reusken emphasizes that camels of different global origin have varying levels of immunity, citing Australian camels as an example of a population naïve to the virus. “We believe this particular market environment is fertile soil for circulating the virus within the camel population,” said Reusken.
This particular environment, though, is not limited to the Doha market. Reusken points to international camel races as a comparable setting where a pool of camels from diverse origins are suddenly mingling, creating opportunity for the virus to spread.
In controlling the virus, Reusken said that behaviors, such as those related to how camels and camel products are handled, need to be considered in devising a strategy.
“We need to look at the broader picture of the role the dromedary plays in society, looking at how we use them and treat them – and how this has changed over the past two decades during which we’ve seen the rise in MERS.”
The paper, titled High proportion of MERS-CoV shedding dromedaries at slaughterhouse with a potential epidemiological link to human cases, Qatar 2014, is freely available online at the peer reviewed journal Infection Ecology & Epidemiology.
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Infection Ecology & Epidemiology – the One Health Journal – publishes original and cross-disciplinary research from across medical and ecological disciplines engaged in describing the complexity of zoonotic infections and the interface between wild and domestic animals, and humans.Tags: Chantal Reusken, IEE, MERS, MERS-CoV