Scanning Electron Microscopic Findings on Respiratory Organs of Some Naturally Infected Dromedary Camels with the Lineage-B of the Middle East Respiratory Syndrome Coronavirus (MERS-CoV) in Saudi Arabia-2018.

Abdelmohsen Alnaeem,Maged Gomaa Hemida,Mohamed Refaat,Ibrahim Qasim,Abdulkareem Al-Shabebi,Samy Kasem,Ali Nasser Alhufufi,Ali Al-Doweriej,Abd-El Rahman Taha Hereba

doi:10.3390/pathogens10040420

Abstract

The currently known animal reservoir for MERS-CoV is the dromedary camel. The clinical pattern of the MERS-CoV field infection in dromedary camels is not yet fully studied well. Some pathological changes and the detection of the MERS-CoV antigens by immunohistochemistry have been recently reported. However, the nature of these changes by the scanning electron microscope (SEM) was not revealed. The objective of this study was to document some changes in the respiratory organs induced by the natural MERS-CoV infection using the SEM. We previously identified three positive animals naturally infected with MERS-CoV and two other negative animals. Previous pathological studies on the positive animals showed varying degrees of alterations. MERS-CoV-S and MERS-CoV-Nc proteins were detected in the organs of positive animals. In the current study, we used the same tissues and sections for the SEM examination. We established a histopathology lesion scoring system by the SEM for the nasal turbinate and trachea. Our results showed various degrees of involvement per animal. The main observed characteristic findings are massive ciliary loss, ciliary disorientation, and goblet cell hyperplasia, especially in the respiratory organs, particularly the nasal turbinate and trachea in some animals. The lungs of some affected animals showed signs of marked interstitial pneumonia with damage to the alveolar walls. The partial MERS-CoV-S gene sequencing from the nasal swabs of some dromedary camels admitted to this slaughterhouse confirms the circulating strains belong to clade-B of MERS-CoV. These results confirm the respiratory tropism of the virus and the detection of the virus in the nasal cavity. Further studies are needed to explore the pathological alterations induced by MERS-CoV infection in various body organs of the MERS-CoV naturally infected dromedary camels.

Highlights

The Middle East respiratory syndrome (MERS-CoV) was identified in 2012 in the Arabian Peninsula [1]
We selected two negative MERS-CoV dromedary camels to act as a negative control for the downstream testing of their respiratory organs with the scanning electron microscope (SEM)
The comparison of the genomic sequences of many MERS-CoV isolates from the Arabian Peninsula and Africa revealed some insights about the evolution of the virus and

Summary

Introduction

The Middle East respiratory syndrome (MERS-CoV) was identified in 2012 in the Arabian Peninsula [1]. Previous research studies confirmed the detection and characterization of MERS-CoV mainly from dromedary camels in the Arabian Peninsula [3,4,5,6,7]. One study detected antibodies in sera of some alpaca raised in MERS-CoV endemic areas. The MERS-CoV infection in camels was studied under the experimental infection approach [12]. The clinical course of MERS-CoV infection in alpaca under an experimental approach has been reported. These studies suggested both llama and alpaca might act as surrogate animals to study MERS-CoV infection, in countries, which do not have dromedary camels. Another study showed the high prevalence (61.5%) of the MERS-CoV -RNAs in lung tissues of dromedary camels submitted for slaughter in one slaughterhouse in the eastern regions of Saudi Arabia [6]

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