Evaluations of the pathophysiology and reproductive pathology of bucks inoculated with Corynebacterium pseudotuberculosis and its immunogen mycolic acid extract

Corynebacterium pseudotuberculosis is the causative agent of caseous lymphadenitis, a chronic disease of sheep and goats, characterized by the formation of suppurative abscesses in superficial and visceral lymph nodes and internal organs of small ruminants. Little is known about the male goat`s reproductive pathophysiology inoculated with Corynebacterium pseudotuberculois and its immunogen mycolic acid extract. Hence, this study was designed to determine the concentration of testosterone hormone and proinflammatory cytokines of the experimental animals and to determine the histopathological effectof male reproductive organs and the associated lymph nodes. A total of 12 bucks, divided into 3 treatment groups of equal numbers (4 goats per group) were selected in this study. Group 1 (Negative control group)was inoculated intradermally with 2ml of sterile phosphate buffered saline (PBS) pH7. Group 2 (Positive control group)was inoculated intradermally with 2ml of 1×10⁹ colony forming unit (cfu) of C. pseudotuberculosis. Group 3 (Mycolic acid group) was inoculated intradermally with 2ml of mycolic acid extract. During the post inoculation period of 60 days, the goats were observed for clinical signs. Body temperature was taken daily. Heart rate, respiratory rate and body score were measured on weekly basis. Lymph nodes were checked daily and findings were recorded. All experimental animals in Group 1 survived throughout the course of study period with no evidence of clinical manifestation. There was an increment in body temperature observed from week 0 to week 3 for group 2 (PC) compared to group 1 (NC). In Group 3 (MA), there was an increased in body temperature observed during week 0- 3 but not as severe as group 2. However, the heart rate and respiratory rate of both groups 2 and 3 were normal. The concentration of testosterone hormone in group 2 increased significantly (p < 0.05) in week 4, 5 and 8 but decreased in weeks 1 and 6 post inoculation. In group 3, the mean concentration of this hormone was increased significantly (p < 0.05) in weeks4,5, 6 and 8 post inoculation but decreased in week 1. The concentration of interleukin 6 (IL 6) in group 2 showedno significant difference (p>0.05) but increased significantly (p<0.05) in group 3 at week 1 post inoculation compared to group 1. For concentration of interleukin 1β (IL1β), both groups 2 and 3 showed significant difference (p < 0.05) in weeks1 and 2 post inoculation. For tumor necrosis factor-alpha (TNF-α) concentration, both groups 2 and 3 did not show any significant difference (p > 0.05) compared to group 1. The concentration of Interferon-γ (IFNγ) of group 2 was significantly increased (p < 0.05) in weeks 1, 2, 3and 4 where else for group 3 was not significantly different (p > 0.05) compared to group 1. Both groups 2 and group 3 showed a reduction in semen qualities as compared to group 1 but the severity were more intense in group 2 if compared to group 3. The cellular changes were observed in both group 2 and group 3 as compared to group 1. The cellular changes of the epididymis in both groups 2 and 3 represented by degeneration and necrosis, haemorrhage and congestion, and also the presence of abnormal sperms in the epididymal tubules. The cellular changes of the testes in groups 2 and 3 represented by an irregular shape and shrinkage of the semineferous tubules, less spermatid cells in the semineferous tubules, degeneration and necrosis, and also haemorrhage and congestion. However, the severity was more intense in group 2 if compared to group 3. Histopathologically, both group 2 and group 3 showed the cellular changes of the lymph nodes represented by infiltration of the inflammatory cells, oedema and haemorrhage and congestions but in lesser extent of severity ingroup 3 if compared to group 2. Conclusively, this study demonstrated some clinical manifestations, changes in concentration of testosterone hormone, changes in the cytokinesconcentrations, with histopathology cellular changes and deterioration of semen quality in both groups 2 and 3. However, for group 3, the changes were less severe comparedto group 2. Hence, concluded that Mycolic acid is not a good immunogen.

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