Absence of MERS-CoV antibodies in feral camels in Australia: Implications for the pathogen's origin and spread

Crameri, Gary; Durr, Peter A.; Barr, Jennifer; Yu, Meng; Graham, Kerryne; Williams, Owen J.; Kayali, Ghazi; Smith, David; Peiris, Malik; Mackenzie, John S.; Wang, Lin-Fa

In contrast to the severe acute respiratory syndrome coronavirus (SARS-CoV), which was introduced into the human population through a single or a limited number of spill-over event(s) [4, 5] , current epidemiological studies suggest that there have been multiple introductions of different MERS-CoV strains into human population from animal reservoir(s) [6] . For SARS-CoV, there is now increasing evidence indicating that it is a bat-borne virus transmitted to humans via intermediate hosts such as palm civets and raccoon dogs [7] [8] [9] [10] [11] . For MERS-CoV, the natural reservoir host(s) has not yet been determined, nor how different strains of the virus have been transmitted to human populations on multiple occasions since its first discovery in 2012 [6] . Although there are reports of MERS-like CoVs in different bats around the world, discovery of closely related viruses and virus-neutralising antibodies in dromedary camels has led to the hypothesis that they are likely to be the major reservoir of MERS-CoV and camel-to-human transmission is the main route of spill-over events [6] . However, it is presently not clear whether MERS-CoV was introduced into the camel populations recently or whether it has adapted to camels as a natural reservoir from ancient times. A retrospective search for MERS-CoV antibodies indicated that the virus was circulating among the camel populations in the Middle East and Africa as early as 1992 and 1983, respectively [12] [13] [14] [15] . In a recent study, the detection of a MERS-CoV conspecific virus from an African bat suggests that the MERS-CoV may have originated from an African bat, followed by bat-to-camel transmission in Africa, then the introduction of MERS-CoV to the Middle East through camel exportation/importation [6, 16] .