Introduction: Middle East respiratory syndrome coronavirus (MERS-CoV) is a novel coronavirus causing an ongoing outbreak in man, sometimes resulting in severe or even fatal pneumonia. Dromedary camels are suggested to be the reservoir host for MERS-CoV. Infected dromedaries shed the virus predominantly from the nose, but show no or only mild disease. To elucidate the pathogenesis of MERS-CoV infection, we inoculated dromedary camels with MERS-CoV.
Materials and Methods: Four 6- to 8-month-old dromedaries, serologically negative for MERS-CoV, were inoculated intranasally with MERS-CoV. Collection of swabs and evaluation of clinical signs were performed daily. The dromedaries were killed 4 or 14 days (n = 2 per day) after inoculation. Necropsy examinations were performed and samples of respiratory and extra-respiratory tissues were taken for pathology, immunohistochemistry (IHC), in-situ hybridization (ISH) and virology.
Results: The dromedaries demonstrated moderate rhinitis with nasal discharge, tracheitis and bronchitis associated with the presence of MERS-CoV by virus titration, intralesional virus antigen by IHC and viral RNA by ISH. High virus titres were excreted from the nose up to 6 days after inoculation. Virus antigen was present in a few cells of lymphoid organs such as pulmonary, tracheal and cervical lymph nodes and tonsils, but not in other respiratory or extra-respiratory tissues.
Conclusions: Experimental MERS-CoV infection in dromedaries predominantly causes upper respiratory tract disease with no/mild clinical respiratory signs, which corresponds with the role of dromedaries as a reservoir for MERS-CoV. Studies on the vaccination of dromedaries against MERS-CoV are still ongoing.