Dubduba syndrome: an emerging neurological disease of camels with a possible viral etiologic agent.

摘要

Following reports on the emergence of a new neurological disease in camels at the north-eastern region of Saudi Arabia, a study was carried out to investigate the magnitude of the problem and to identify its aetiologic agent. Based on results of a questionnaire study, the disease appeared for the first time during the rainy season in the year 2004. It affected >3 years old female camels and was limited to those herds that were grazing in the Dubduba area of northeastern Saudi Arabia. For this reason, The disease was named Dubduba syndrome due to this reason. The disease was sporadic, affecting 1 or 2 camels in the herd at a time, but the mortality rate in those affected animals was very high (>90%). The clinical signs were fever, Parkinsons-like tremors of the head, paralysis of the lower lip, motor paralysis, recumbency and animals usually die within 3-5 days of the appearance of symptoms. Postmortem examination of three camels was performed. Congestion and haemorrhages were evident in the brain and meninges. Congestion, haemorrhages and necrosis were observed in the liver, kidneys, heart and stomach. Histopathological examination of the brain and spinal cord showed non-purulent meningoencephalomyelitis, nerve cell necrosis, gliosis and presence of intracytoplasmic inclusion bodies in the nerve cells. The liver was massively fatty degenerated and necrotic. Coagulation necrosis was noted in the renal tubular epithelium which also contained intracytoplasmic inclusion bodies. Since the histopathological findings of Dubduba disease supported a virus infection, virus isolation was attempted on SPF embryonated eggs and laboratory rats but the results were negative. Immunohistochemical studies on paraffin tissue sections of the brain were negative. The following viruses were likely the cause the above lesions: Rabies, Crimean-Congo fever, Equine herpes, West Nile fever (WNF), Panflavivirus, paramyxovirus and Rift Valley Fever viruses. Listeriosis was also negative. A novel viral encephalitis disease was most likely to be the cause of Dubduba syndrome of camels.