Med. Weter. 2021, 77 (11), 535-537

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Pathological findings in common foxes suffering from cardiorespiratory syndrome
Introduction: Cardiorespiratory syndrome of common foxes has been reported since the 1980s. Although the condition is observed at a number of farms in Europe and America, its etiology still remains elusive. Materials and methods: The study was conducted at a common fox (Vulpes vulpes) farm located in Central Poland, having a total of 500 females and 150 males and an average yearly production of 1,900 cubs. Deaths due to cardiorespiratory syndrome were recorded at the farm in 2012 and 2013, corresponding to 5.32% and 2.14% new young mortality rates, respectively. Postmortem examination included 38 foxes that died in 2013, as well as 12 hearts collected from foxes that died in 2012. Results: Gross pathological findings documented in the examined material were generally typical for the cardiorespiratory syndrome of foxes. However, detailed pathological examination of the hearts revealed a dilatation of the right atrioventricular opening and abnormal structure of the tricuspid valve in all cases. The septal cusp was shortened, thickened, and immobilized due to fusion with the interventricular septum. Conclusions: The fact that tricuspid valve dysplasia was observed on postmortem examination of all animals that died with the symptoms of cardiorespiratory syndrome confirms a potential involvement of congenital heart defects in the etiology of this condition.
Keywords: atrioventricular valve dysplasia, cardiorespiratory syndrome, common fox, lung-heart syndrome, tricuspid valve, mitral valve, heart defect, pathology