Correlation of brachycephaly grade with level of exophthalmos, reduced airway passages and degree of dental malalignment' in Persian cats.

Jana Sieslack,Klaus Failing,Martin Kramer,Martin J Schmidt,Daniela Farke,Carlos E Ambrósio

doi:10.1371/journal.pone.0254420

Abstract

For many years, there has been a trend to breed cats with an increasing degree of brachycephalic head features, which are known to have a severe impact on the animals’ health and welfare. The direct relation between different grades of brachycephaly and their negative implications have not been researched in this species. The aim of this study was therefore to establish correlations between the different grades of brachycephaly and reduced upper respiratory airways, exophthalmos of the eye globes and malalignment of the teeth in Persian cats. Sixty-nine Persian cats of various skull dimensions and ten Domestic shorthair cats were recruited for the study. The cats’ skulls were examined using three-dimensional reconstructions created from Computed Tomography datasets. Brachycephaly was graded using established craniometric measurements (facial index, cranial index, skull index, craniofacial angle). The flow area of the nasal passageways at different locations, the amount of the eye globe not supported by the bony orbit and the axial deviation of the teeth were quantified and evaluated for a correlation with the grade of brachycephaly. The results of this study clearly show that increased grades of brachycephaly in Persian cats resulted in larger extra-orbital parts of the ocular bulbs. The brachycephalic skull dimension also resulted in a lower height of the naso-osseal aperture, while other areas of the nasal airways were not correlated with the severity of brachycephaly. Persian cats showed a significantly increased occurrence of premolar tooth displacement in the upper jaw with increasing brachycephaly grades. It was interesting to note that the measured values had a broad range and values of some individual Persian cats showed an overlap with those of Domestic shorthair cats.

Highlights

For many years, there has been a trend to breed companion animals with an increasing degree of brachycephalic head features [1, 2]
The original type was largely replaced by extremely brachycephalic cats that define the breed standard of the modern Persian cat today, even though it is known from dogs that high grades of brachycephaly can be associated with severe health problems [2, 5,6,7]
Twenty-one Persian cats had tear staining in both eyes, while 48 cats did not have staining underneath the eyes

Summary

Introduction

There has been a trend to breed companion animals with an increasing degree of brachycephalic head features [1, 2]. Since the middle of the last century, the morphology of the original Persian cat has gradually modified into an extremely flat-faced type with a large prominent forehead, severely reduced facial bones and large, round eyes [2,3,4]. The original type was largely replaced by extremely brachycephalic cats that define the breed standard of the modern Persian cat today, even though it is known from dogs that high grades of brachycephaly can be associated with severe health problems [2, 5,6,7]. It was recently shown that selection towards reduced facial bones leads to a fundamental change in morphology of the cranial cavity, causing intracranial overcrowding, herniation of the brain and internal hydrocephalus [10]

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Results

Discussion

Conclusion