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All reported cases of Middle East respiratory syndrome coronavirus (MERS-CoV) infection have had links to the Middle East. Although the primary reservoir may be bats (the virus replicates in bat cell lines and is closely related to viruses in Pipistrellus bats in Europe and Asia), none of the patients involved has reported direct contact with these animals, and some have reported contact with goats or camels. The epidemiology suggests multiple independent introductions into the human population. As part of the search for virus sources, investigators (including some with a patent pending for a MERS-CoV receptor) tested animal sera from several countries for specific serum IgG antibodies to MERS-CoV, severe acute respiratory syndrome coronavirus, and human coronavirus OC43 (as a proxy for a bovine coronavirus).
All 50 specimens from dromedary camels in Oman and 14% (15/105) of those from such animals in Spain (Canary Islands) had MERS-CoV neutralizing antibodies. Titers ranged from 1/320 to 1/2560 in Omani camels and from 1/20 to 1/320 in Spanish ones. No such antibodies were found in sera from other camelids, including llamas and alpacas — or from sheep, goats, or cattle — in Europe. The only animal sera tested from the Middle East were from camels.
Reusken CBEM et al. Middle East respiratory syndrome coronavirus neutralising serum antibodies in dromedary camels: A comparative serological study. Lancet Infect Dis 2013 Aug 9; [e-pub ahead of print]. (http://dx.doi.org/10.1016/S1473-3099(13)70164-6)
de Wit E and Munster VJ. MERS-CoV: The intermediate host identified? Lancet Infect Dis 2013 Aug 9; [e-pub ahead of print]. (http://dx.doi.org/10.1016/S1473-3099(13)70193-2)
Comment
Camels are among the main sources of meat and milk in the Middle East. Camels in multiple areas of Oman and in the Canary Islands have been infected with the Middle East respiratory syndrome coronavirus or a closely related pathogen, suggesting that they may be reservoir hosts, although the authors note that limited attempts to identify viral sequences in Spanish camel sera and fecal specimens have so far been unsuccessful. Editorialists emphasize the urgent need for extensive serosurveys of people, livestock, and wild animals in the Arabian peninsula to identify potential reservoir hosts for the virus. The authors note the usefulness of comparative seroprevalence testing of historical and more-recent samples from camels with available epidemiologic background information and virologic assessment of seroconverting animals. The reservoirs — which could be multiple — must be determined before interventions to halt zoonotic transmission can be developed.