Experimental induction of epididymitis in sheep, by intra-urethral inoculation of Actinobacillus seminis: a bacteriological, serological, and histopathological study

Abstract

Actinobacillus seminis infection was experimentally induced in 18 6-month-old lambs. Four animals were kept as negative controls, three animals were inoculated with A. seminis by the intra-epididymal (IE) route, and 11 lambs were inoculated by the intra-urethral (IU) route, as follows: Five days prior to challenge, 4 lambs were given gonadotropin-releasing factor (GnRH), 4 lambs received ethylene glycol IE 24 h prior to challenge, and 3 lambs received no previous treatment. Two of the 4 negative controls received GnRH, and 2 received ethylene glycol. Serum samples were collected weekly for immunodiffusion. Similarly, semen samples were collected for bacteriological analysis. Animals were slaughtered 35 d postinoculation. Testis, epididymis, and accessory sex gland samples were collected for bacteriological and histopathological analyses. A. seminis was isolated from the semen of the GnRH-treated group, but not from the reproductive tract. Lesions had been previously observed in 3 of these 4 animals. A. seminis was isolated from both the ampulla ductus deferens and from the seminal vesicle of one ethylene glycol-treated animal. A. seminis was isolated from the semen of 2 of the 3 lambs that were challenged with no previous treatment. A. seminis was isolated from the inoculation site of one lamb and from the accessory sex glands of 2 of the 3 IE-inoculated lambs. Two of the 11 IU-inoculated lambs showed positive serological results. Two of the 3 IE-inoculated lambs had positive serological results. Histopathological lesions were consistent with epididymitis, including inflammatory infiltrates in the accessory glands. Results suggest that the accessory sex glands can be an A. seminis reservoir.