Equine Testicular Lesions Related to Invasion by Nematodes

Nematodes of the genuses Strongylus and Setaria are able to erratically migrate to the equine testis and provoke characteristic inflammatory changes. Moreover, the presence of living parasites in scrotal testes is a scarce finding in which only the tracts and related lesions may be observed. In a 20-year experience of equine testes observed in abattoirs, 13 cases of atypical inflammatory lesions in scrotal testes were collected. On opening of the vaginal cavity, hydrocele was consistantly observed, and the Morgagni's appendix was enlarged, prominent, and reddish. Large, elongated, or irregular prominent red to yellow areas were visible on the testicular or epididymal serosa. Edematous enlargement of the epididymal head or tail was occasionally observed. In two cases, the described lesions were detected together with nematodes of the species Setaria equina, free and viable or encapsulated in the visceral and parietal layers of the tunica vaginalis, confirming the hypothesized cause. Histologically, the serosal lesions were interpreted as parasitic tracts, characterized by hemorrhage and leukocyte infiltrates in recent lesions or by granulation tissue with numerous macrophages in elderly ones. In the latter, areas of squamous metaplasia could be observed in the appendix testis and in the epididymal duct. Associated microscopic lesions included diffuse periorchitis, lymphocytic interstitial orchitis with mild to severe degeneration of seminiferous tubules, and vasculitis, epididymitis, and sperm granuloma.