Nutritional condition and survival of red foxes with sarcoptic mange

Abstract

We aimed to compare body condition, urine profiles, and survival times between red foxes (Vulpes vulpes) that were infected with sarcoptic mange and others that were uninfected. First we compared the relative body mass, chest girth, fat reserves, and urinary urea nitrogen:creatinine (UN:C) ratios of red foxes in three infection classes: uninfected, class I (no hyperkeratotic mange), and class II (hyperkeratotic mange present). Infected foxes had lower relative body mass and lower fat reserves than uninfected foxes. Both fat reserves and urinary UN:C data suggested that class II infection was more severe than class I infection. Urinary UN:C in class II foxes was significantly higher than in uninfected and class I foxes, indicating accelerated muscle catabolism in class II foxes. Elevated urinary UN:C has never been recorded in wild canids, indicating that these animals had been subjected to a period of prolonged starvation or chronic undernourishment. We also estimated the survival time of foxes once infected with mange from capture–mark–recapture data. Twenty-five foxes were caught at an early stage of infection and had a known date of death. Although some were treated once with ivermectin they did not recover, and their survival time was no longer than that of untreated infected foxes. Untreated infected adults survived for up to 271 days after capture, which is longer than previously suggested. Overall, the survival time of infected foxes was roughly one-fifth of that of uninfected foxes (matched by age and sex).