Abstract
Caseous lymphadenitis (CLA) or pseudotuberculosis is a chronic zoonotic bacterial disease caused by Corynebacterium pseudotuberculosis, which affects livestock and humans. This study aimed to describe the pathology, bacteriology and confirm the identity of the pathogen by 16S rRNA gene sequencing in Camelus dromedarius. A total of 12 camels with suspected CLA in three regions of Abu Dhabi Emirate (Abu Dhabi, Al Ain and Al Dhafra), United Arab Emirate (UAE) were subjected to clinical and postmortem examinations from January 2015 to December 2020. Clinically, camels were emaciated and showed the presence of external caseous abscesses suggestive of CLA. Postmortem examination showed multiple abscesses of variable sizes with caseous material encapsulated by fibrous tissue in the liver, lungs, muscle, and lymph nodes. Following clinical and postmortem examination, blood, pus and different tissue samples were collected for subsequent analysis. Histopathological examination of all organs stained with Hematoxylin and Eosin (H&E) indicated a central caseo-necrotic core that was admixed with bacterial colonies and infiltration of chronic inflammatory cells, surrounded by a pyogenic membrane, and an outer fibrous connective tissue capsule. Bacterial culture identified the isolates of Corynebacterium pseudotuberculosis biotype ovis strain, and these isolates were shown to be sensitive to all antibiotics tested (penicillin, ampicillin, Co-trimoxazole, enrofloxacin and tetracycline). Moreover, the identity of the isolates was confirmed by partial sequencing of the 16S rRNA gene which showed a 100% identity to Corynebacterium pseudotuberculosis. Phylogenetic analysis based on 16S rRNA gene sequence clearly differentiates Corynebacterium pseudotuberculosis from other species of Corynebacterium. Briefly, this study provided the basic information for infection of Corynebacterium pseudotuberculosis in Camels and will help in controlling of this pathogen in the region.
Highlights
Caseous lymphadenitis (CLA) is a chronic, contagious and non-fatal bacterial infection of livestock
The aim of this study is to report and describe pathological findings associated with CLA in dromedary camels in the United Arab Emirates (UAE) and further to confirm the identity of the pathogen by using bacteriological and molecular techniques
The present study describes the pathological, bacteriological and molecular analysis of a caseous lymphadenitis (CLA) in dromedary camels in three regions of Emirate of Abu Dhabi, UAE (Abu Dhabi (AD), Al Ain (AA) and Al Dhafra (Western Region, (WR))
Summary
Caseous lymphadenitis (CLA) is a chronic, contagious and non-fatal bacterial infection of livestock. It mostly affects sheep and goats, cattle, horses, buffalo, camelids, deer [1,2,3,4,5], and humans [6,7], it is considered a zoonotic disease. Camels are reported to be infected by both biovars especially in the co-herd breeding system [10,11,12]. In addition to Corynebacterium pseudotuberculosis, other pathogens such as, Corynebacterium ulcerans, Streptococcus spp., Staphylococcus spp. and Corynebacterium pyogenes were reported to be involved in the development of CLA of camels [2,3,10,13,14]
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