Extended Viral Shedding of MERS-CoV Clade B Virus in Llamas Compared with African Clade C Strain

Abstract

Middle East respiratory syndrome coronavirus (MERS-CoV) clade B viruses are found in camelids and humans in the Middle East, but clade C viruses are not. We provide experimental evidence for extended shedding of MERS-CoV clade B viruses in llamas, which might explain why they outcompete clade C strains in the Arabian Peninsula.

Keywords: MERS-CoV; MERS-CoV clade C; Middle East respiratory syndrome coronavirus; Spain; camelid; llama; virus transmission; viruses.

Figure 1

MERS-CoV RNA and infectious virus shedding in llamas experimentally infected with MERS-CoV Egypt/2013 (red) or Qatar15/2015 (blue) strains. A–C) Viral RNA and infectious MERS-CoV shedding of inoculated animals. Genomic (A) and subgenomic (B) viral RNA were quantified in nasal swab samples collected at different times after MERS-CoV inoculation. Infectious MERS-CoV titers (C) were demonstrated in nasal swab specimens collected on different days after MERS-CoV inoculation. Solid lines indicate mean values determined for different MERS-CoV–inoculated groups; shadings represents SD intervals. D–F) Infection profile of naive in-contact llamas). Genomic (D) and subgenomic (E) viral RNA quantified in nasal swab samples collected at different times after MERS-CoV inoculation. Infectious MERS-CoV titers (F) were demonstrated in nasal swab samples collected on different days after MERS-CoV inoculation. Solid lines indicate mean values of the groups of animals infected by contact; shaded areas represent SD intervals. Colored dashed lines indicate mean values calculated for MERS-CoV–inoculated animals. Horizontal dashed lines depict detection limits of assays. Cq, quantification cycle; MERS-CoV, Middle East respiratory syndrome coronavirus; TCID₅₀, 50% tissue culture infective dose.

Figure 2

Mixed model analyzing the transmission competence of each MERS-CoV strain over time in investigation of llamas experimentally infected with MERS-CoV. Boxplots show daily virus shedding of sentinel llamas infected with MERS-CoV Egypt/2013 (red) or Qatar15/2015 strains (blue) after direct exposure to inoculated llamas. A, B) Genomic (A) and subgenomic (B) viral RNA quantification in nasal swabs collected throughout the study. C) Infectious MERS-CoV titers. Only the time points considered in the mixed models are represented. Horizontal lines within boxes indicate medians; box tops and bottoms indicate interquartile ranges; error bars indicate 95% CIs; black dots indicate outliers. p values are indicated above the boxes; p values indicate statistical differences between areas under the curve of the experimental groups, as calculated by Wilcoxon test. Cq, quantification cycle; MERS-CoV, Middle East respiratory syndrome coronavirus; TCID₅₀, 50% tissue culture infective dose.