Middle East respiratory syndrome coronavirus infection in dromedary camels in Saudi Arabia

Abstract

The Middle East respiratory syndrome (MERS) is proposed to be a zoonotic disease; however, the reservoir and mechanism for transmission of the causative agent, the MERS coronavirus, are unknown. Dromedary camels have been implicated through reports that some victims have been exposed to camels, camels in areas where the disease has emerged have antibodies to the virus, and viral sequences have been recovered from camels in association with outbreaks of the disease among humans. Nonetheless, whether camels mediate transmission to humans is unresolved. Here we provide evidence from a geographic and temporal survey of camels in the Kingdom of Saudi Arabia that MERS coronaviruses have been circulating in camels since at least 1992, are distributed countrywide, and can be phylogenetically classified into clades that correlate with outbreaks of the disease among humans. We found no evidence of infection in domestic sheep or domestic goats. IMPORTANCE This study was undertaken to determine the historical and current prevalence of Middle East respiratory syndrome (MERS) coronavirus infection in dromedary camels and other livestock in the Kingdom of Saudi Arabia, where the index case and the majority of cases of MERS have been reported.

FIG 1

Prevalence of MERS-CoV antibody reactivity in serum (A) and nucleic acid detection in nasal swabs (B) by geographic region in KSA DC. Images were created with software from ESRI maps.

FIG 2

MERS-CoV proteins detected by Western blotting in sera from KSA DC. S, spike glycoprotein; N, nucleocapsid protein.

FIG 3

Relationship of partial spike (A, 1,044 nt) and ORF1ab (B, 2,009 nt) sequences derived from DC with selected human-derived MERS-CoV sequences. Maximum-likelihood trees were inferred on the basis of p distance. The scale bars indicate the base difference per site. GenBank reference sequence accession numbers are shown.