Ovine genital actinobacillosis: a review.

Actinobacillus seminis infection in rams constitutes a spectrum of pathological changes in various genital organs, with a predilection for the cauda epididymis. There is a need to understand the disease, as it represents a significant factor contributing to infertility and sterility. Here, we aim to provide a comprehensive overview of the biological characteristics of A. seminis, modes of transmission, epidemiology and pathogenesis, clinical signs and pathological changes of the disease, the laboratory techniques that have been used in diagnosis, differential diagnosis, treatment and prevention, and the considerations that need to be taken into account for future research.

Early sequential findings in the genitalia of rams experimentally infected with Actinobacillus seminis.

AIM: To investigate and assess the sequential pathological changes in the epididymis and testis of young rams injected intra-epididymally with Actinobacillus seminis. METHODS: Twenty yearling Suffolk and Suffolk-cross rams were randomly divided into two groups comprising 16 test and four control animals. Each test ram received 2.3 x 109 cfu/ml of A. seminis injected intra-epididymally. Every 24 h post-inoculation (p.i.), two test rams were randomly selected, euthanised, and necropsied, until the end of the experiment at 192 h p.i. One control animal was euthanised at 24 h, 48 h, 96 h and 144 h p.i., respectively. The reproductive tract of each ram was carefully examined, lesions photographed, and tissues cultured. Thin sections of tissue samples were fixed and examined by light microscopy; additionally, epididymal tissues were examined by scanning electron microscopy (ScEM). RESULTS: Gross lesions were observed in the cauda epididymis of all test rams, and ranged from swelling at 24 h p.i. through enlargement and granuloma formation from 72 h p.i., to gradual enlargement and increasing firmness by 192 h p.i. Gross testicular atrophy was observed in three rams. Histologically, spermatic granulomas were evident in the epididymis and the tunica vaginalis of 10 and four rams, respectively. Cauda epididymitis was present in all rams, and caput and corpus epididymitis in eight and four rams, respectively. Interstitial orchitis was observed in seven, testicular degeneration in 14, and localised and diffuse tunica vaginalitis in 12 rams. Epididymal vasculitis and infiltration of eosinophils were observed as early as 24 h p.i. Moderate disruption of the epididymal duct from 72 h p.i., with subsequent release of spermatozoa into the interstitium, was revealed by ScEM. Actinobacillus seminis was cultured from the granuloma of six test rams from 72 h p.i. CONCLUSIONS: Actinobacillus seminis has the ability to persist in the genitalia of young rams following experimental infection. Suppurative epididymitis is observed as early as 24 h p.i., and spermatic granuloma within 72 h p.i. Infiltration of eosinophils appears to be an early host response to the bacterium, and may play a role in the pathogenesis of the epididymitis.

Epididymal and testicular lesions in rams following experimental infection with Actinobacillus seminis.

AIM: To investigate and assess the epididymal and testicular lesions in rams up to 44 days after inoculation with Actinobacillus seminis via various routes. METHODS: Forty-four young (18-24 months old) rams were randomly divided into nine test and two control groups (n=4 per group). The test rams were infected by installation, drenching or injection of A. seminis organisms cultured for 24 h in a brain-heart infusion (BHI) broth containing 2.3 x 10(9) cells/ml, via the following nine routes: intra-epididymal (1 ml), intravenous (3 ml), intra-urethral (3 ml), intra-preputial (3 ml), vas deferens (1 ml), intramuscular (3 ml), oral (10 ml), intranasal (3 ml), and intra-conjunctival (3 drops). All test rams were necropsied 9-44 days post-inoculation (p.i.). Control rams were subdivided into in-contact and non-contact groups and necropsied at 45 and 46 days p.i., respectively. Thin tissue sections were examined for histopathology. RESULTS: Gross lesions were evident only in rams inoculated intra-epididymally. Epididymides on the inoculated side were two to three times larger than those on the un-inoculated side, and the testes attached to the inoculated epididymides were also enlarged. Fibrinopurulent periorchitis and tunica vaginalitis were seen in three rams and atrophy in one. Microscopically, epididymitis was present in 17 (47%) rams, the highest incidence being in the cauda, followed by the caput and the corpus epididymis. Seminiferous tubular degeneration with areas of lymphocytic infiltration were seen in four rams: three inoculated via the cauda epididymis and one via the urethra. No epididymal and/or testicular lesions were seen in rams inoculated via the nasal and conjunctival routes. CONCLUSIONS: Injection of A. seminis in young rams by all routes except intra-conjunctival and intranasal resulted in epididymitis, predominantly in the cauda epididymis. Development of lesions in the reproductive tract following non-genital routes of inoculation supports earlier suggestions that non-venereal transmission of genital actinobacillosis occurs. This study confirmed the predilection of A. seminis for the epididymis, especially the cauda.

Experimental transmission of Actinobacillus seminis infection to rams.

Nine groups of four 18- to 24-month-old rams were inoculated with Actinobacillus seminis by the following routes: intraconjunctival, intranasal, oral, intravenous, intramuscular, intraepididymal, vas deferens, intraurethral or intrapreputial. Eight similar rams were left uninoculated as controls. Systemic clinical signs were minimal and were confined primarily to the inoculation sites and the scrotal contents. Mild to severe epididymitis resulted from all the routes of inoculation except intraconjunctival and intranasal. Direct inoculation into the genital tract, especially into the cauda epididymis, was more effective. Intrapreputial and intraurethral inoculation led to ascending urethral infection, and inoculation into the vas deferens resulted primarily in descending infection of the accessory sex glands. A seminis was isolated from 11 of the 36 test rams (30.6 per cent); 26 of the 36 rams, some from each of the test groups except those inoculated intravenously, reacted serologically.