Background.Arcobacter is an emerging zoonotic enteropathogen associated with spontaneous abortion, diarrhea and mastitis in domestic animals.Materials and methods. Thirty male pathogen-free albino rats were infected with a single challenge of Arcobacter butzleri (10 8 cfu/ml) isolated from the stool of healthy pigs with the aim of investigating the effects of A. butzleri on rat testicular histology and spermatogenesis.Results. In previously healthy male albino rats, A. butzleri caused testicular degeneration associated with reduced sperm count and motility.Conclusions. The result of this study suggests that A. butzleri produces testicular degeneration and the associated disruption of spermatogenesis in albino rats; hence, its infertility potential in livestock industry and its economic importance should be further investigated. Key words:Arcobacter butzleri, testicular degeneration, infertility,pathogenicity, sperm count, albino rats INTRODUCTIONArcobacter is an emerging enteropathogen with an increasing evidence of the zoonotic potential associated with prolonged diarrhoea and occasional systemic infections such as bactereamia and peritonitis in humans (1). An evidencebased semi-quantitative method for prioritization of foodborne zoonoses ranked A. butzleri as a microbe of "significant importance" (2). Arcobacter was first isolated from aborted bovine and porcine fetuses (3), especially A. butzleri and A. skirrowii which were isolated from aborted fetuses and placenta of bovine, porcine and ovine origin (4). Although no remarkable pathological changes were identified, the clinical signs associated with Arcobacter infection include infertility, chronic discharge during oestrus, stillbirth and late-term abortions (5).The pathogenicity and virulence mechanisms of Arcobacter species are still poorly understood, despite its increasing incidence and isolation from clinical and food products (6). The virulence of A. cryaerophilus was also first described when it was observed that the strains tested induced the accumulation of fluid and electrolytes in the rat ileal loop assay and showed an in vitro invasion of Hep-2 128Yemisi Olukemi Adesiji, Benjamin Obukowho Emikpe, Ahmed Bayo Opalekunde cells (7). Several studies were reported on their adhesion capacity (8-10), invasiveness (9, 11), and cytotoxicity (12)(13)(14) in several cell lines. Collectively, in these studies, the strains tested showed adhesion, invasion, and cytotoxicity, toxicity and adherence being the most commonly observed effects. The differences observed among different studies may be due to the origin of the strains (environmental versus clinical) as well as to different cell lines used in the studies, A. butzleri being the most invasive species in experimental animal infections (15). Other animal models and in vivo experiments have been reviewed in another recent publication (16). The presence of adhesion molecules in A. butzleri have been proven by the capacity of the strains tested to agglutinate human, rabbit, and sheep erythrocytes, and hemagglut...