How frequently Dirofilaria repens localizes in dog testes?

Dirofilaria repens (Spirurida: Onchocercidae) is the causative agent of canine subcutaneous dirofilariosis. Adults of D. repens localize in the subcutaneous tissues and fasciae and most of the infected animals are asymptomatic though dermatological disorders have been described sporadically. In this study, the gonads of 100 male dogs were inspected for D. repens presence from December 2020 to January 2022. All examined dogs were older than 48 months and underwent castration for several reasons. The testes and the superficial layers were examined with the aid of stereomicroscope; in addition, the blood of all included dogs was collected and analysed by Knott's test to assess the presence of microfilariae. Six out of 100 (6 %, CI95%, 2.2-12.6 %) examined dogs were positive for D. repens presence, and in all the cases the parasites were found beneath the tunica vaginalis layers. Microfilariae were found in 15 blood samples including 5 out of those 6 testes positive dogs thus resulting in a final D. repens prevalence of 16 % (CI95%: 9.4-24.7 %). No pathological changes and or lesions due to parasite presence were observed in the testes or in their layers. The present study represents the first survey focusing on the detection of D. repens in dog testes on a large sample size. Adult parasites were found in the testes of 6 out of 16 D. repens infected dogs accounting for 37.5 % of cases and suggesting as testicular localization is not uncommon. The absence of neoplastic or inflammatory lesions in D. repens infected testes suggests as these conditions do not act as attractive stimuli for the parasite localization. Finally, considering the zoonotic potential of D. repens and the large infection prevalence here reported, active surveillance in endemic areas is strongly advocated to limit the presence of reservoir and prevent further infections to animals and humans.