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Keywords:

  • inheritance;
  • nictitans;
  • prolapsed nictitating membrane gland;
  • third eyelid

Abstract

Objective

To investigate the inheritance of prolapsed nictitating membrane glands (PNMG) in a large pedigree of purpose-bred mongrel dogs.

Animals studied

Two lines of purpose-bred mongrel dogs kept at a research facility with controlled environment were analyzed for frequent occurrences of PNMG. The first line (GS line) consisted of 201 dogs, derived from one German shorthaired pointer and seven mongrel dogs. The second line (M line) was established from one mongrel dog and three miniature longhaired dachshund (MLHD) dogs followed by closed breeding practice (n = 50). The two canine lines were connected by a female dog, which contributed genetically to both lines.

Procedures

Medical records of all dogs were reviewed retrospectively for signalment, parental data, and the presence of PNMG. Pedigrees were constructed to facilitate assessment of inheritance.

Results

The overall prevalence of PNMG in the GS line was 4.0% (8/201) over a 12-year period. The prevalence in the M line was 10.0% (5/50) over 6 years, which increased to 23.1% (3/13) when only dogs aged 2 years or older were considered. Analysis of the pedigrees ruled out simple modes of Mendelian inheritance in both canine lines.

Conclusion

The high prevalence of PNMG in two canine lines bred and maintained under a strictly controlled environment supported the involvement of genetic risk factors. The mode of inheritance remains to be determined, but it appears to be complex and potentially multigenic.