Investigation of Skin-Gut Axis Interaction in Demodex canis-Infected Dogs via Serum Zonulin Concentrations

Abstract

Demodicosis is a common dermatological condition in dogs, resulting from the uncontrolled proliferation of Demodex canis mites. Disruption of the intestinal barrier integrity can trigger not only infectious and inflammatory diseases but also extraintestinal disorders, including dermatological conditions. In this context, zonulin, the only known physiological regulator of tight junctions within the intestinal epithelium, holds particular significance. The aim of this study was to investigate the effect of Demodex canisinfection on serum zonulin levels in dogs and to contribute to the understanding of the complex and bidirectional relationship between dermatological diseases and intestinal barrier integrity. The study included a total of 25 adult dogs of various ages and sexes: 15 dogs diagnosed as Demodex canis-positive by microscopic examination and 10 healthy control dogs with similar age and sex distribution. Dogs in the affected group were evaluated at two time points—before and after treatment—to assess therapeutic efficacy. Serum zonulin levels in all groups were measured using the ELISA method. The results revealed that pre-treatment serum zonulin levels in dogs with Demodex canis infection (mean 12.8 ± 3.735 ng/mL) were significantly higher than both post-treatment values (mean 4.096 ± 2.693 ng/mL) and those of the healthy control group (mean 2.177 ± 1.953 ng/mL). Statistical analysis demonstrated a highly significant mean difference of 8.704 ng/mL between pre- and post-treatment groups (p < 0.0001), and a mean difference of 10.623 ng/mL between the pre-treatment and control groups (p < 0.0001). Conversely, the difference in serum zonulin levels between the post-treatment and control groups (mean 1.919 ng/mL) was not statistically significant (p = 0.2706). These findings indicate that zonulin levels are significantly elevated in dogs with demodicosis, suggesting a disruption of intestinal barrier function during Demodex canis infection. The observed increase in zonulin may also reflect an associated systemic inflammatory response. The normalization of serum zonulin levels following treatment implies a restoration of intestinal barrier integrity. Overall, the results highlight the potential involvement of the gut-skin axis in the pathophysiology of Demodex canis infections.