Inheritance of cataract in the Bichon Frise
M. R. Wallace,* E. O. MacKay,† K. N. Gelatt† and Stacy E. Andrew†
*Departments of Molecular Genetics and Microbiology,
and Pediatric Genetics, College of Medicine,
†Small Animal Clinical Sciences, University of Florida, Gainesville,
FL 32610, USA
© 2005 American College of Veterinary Ophthalmologists
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Abstract
Objective To determine the mode of inheritance of cataract
formation in the Bichon Frise.
Materials Thirty-six closely related Bichon Frise dogs in a
pedigree of 61 dogs were examined using slit-lamp biomicroscopy and
indirect ophthalmoscopy over a period of 10 years.
Results Of the 61 related dogs, 36 were examined repeatedly.
Twelve cataractous dogs were diagnosed (three males and nine
females). Cataractous dogs resulted from matings between unaffected
parents, and when one parent was cataractous and the other parent
was unaffected. Age at onset of cataract formation ranged from 18 to
160 months. Available information suggests that the cataracts are
inherited as an autosomal recessive trait.
Conclusion Cataracts appear inherited in the Bichon Frise as
an autosomal recessive trait. Additional cataract × cataract matings
are necessary to confirm the autosomal recessive heredity.
Key Words:
autosomal recessive, Bichon Frise, cataracts, dog, heredity |
INTRODUCTION
Most clinical studies of inherited primary cataracts in dogs have
reported limited numbers of dogs.
1The mode of inheritance in these studies was often
proposed but not validated because of insufficient numbers of dogs
and specific types of matings. In addition, most inherited canine
cataracts of dogs affect the adult animal, and development of the
cataracts often spans several years requiring multiple eye
examinations. Hence these studies often must span a decade or more.
We reported possible inherited cataracts in the Bichon Frise in 1996
and in 2003.2,3 The 1996 report involved 1202 dogs
in the Canine Eye Registry Foundation database (CERF: 1991–96), 27
Bichon Frise in the University of Florida Veterinary Medical
Teaching Hospital (UF-VMTH) medical records, and 230 dogs examined
at special Bichon Frise eye clinics (KNG and SEA) and patient
information provided by cooperating American College of Veterinary
Ophthalmologists Diplomates. The 2003 report included CERF data with
406 dogs with cataracts in a population of 8222; 406 dogs with
cataracts in a population of 1407 patients presented to veterinary
medical teaching hospitals (Veterinary Medical Data Base; VMDB); 57
cataractous Bichon Frise in the UF-VMTH, and 391 dogs examined at
special clinics (223 dogs with cataracts).
Cataract formation in this breed is also associated with pre- and
postoperative retinal detachments, and presents a special risk
factor in cataract surgery in the breed.3,4 In the
2003 report, retinal detachments were diagnosed in 33% of the UF-VMTH patients, and 13% of the VMDB patients. The high risks of
retinal detachments, cataract formation and lens-induced uveitis
have resulted in the recommendation to veterinary ophthalmologists
that Bichon Frise dogs presented for cataract surgery undergo
retinopexy before or at the time of cataract surgery. Cataractous
Bichon Frise presented to one practice specializing in retinal
detachment surgeries had a prevalence of 50% retinal
detachments; after retinopexy prevalence of retinal detachments was
reduced to 10%.4 Hence, elimination of the cataractous
trait in this breed may be the best solution because cataract
surgery is not always successful nor possible.
In 2003 report, in the cataractous groups involving 1191 affected
dogs, gender seemed unimportant.3 Dogs most often became
affected between the ages of 2 and 8 years, and initial cataract
involvement affected the anterior and posterior cortices equally.
This delayed onset of cataract development has presented difficulty
in obtaining meaningful pedigrees. Nevertheless, based on available
dogs, the mode of inheritance for cataract formation in the Bichon
Frise was proposed to be autosomal recessive.3
In this report, a family of cataractous and normal Bichon Frise dogs
is presented with clinical examinations over 10 years to document
the mode of inheritance.
RESULTS
There are 61 dogs in the pedigree, and the eyes of 36 dogs were
examined repeatedly (Fig. 1). There were 12 cataractous dogs, and
all resulted from mating of one cataractous parent and one clear
lens parent or two unaffected parents. Of the 12 cataractous
animals, 9 were females and 3 were males. The age at onset of
cataracts for these 12 animals ranged from 18 to 160 months.
Unaffected animals in the most recent generation of dogs are too
young to absolutely rule out this cataractous trait. The
pedigree strongly supports our hypothesis that cataracts are
inherited in the Bichon Frise as an autosomal recessive trait. This
is by far the best fit for mode of inheritance given that both
genders are affected, some offspring from unaffected parents have
developed cataracts, and other affected dogs arise from a
cataractous × unaffected mating. Furthermore, the consanguinity
present also fits the hypothesis of unaffected parents being
carriers of the same mutation. This is also highly consistent with
the small numbers of dogs used to establish the breed in the USA (n=
9) 5 and the increasing frequency of this trait over time. However,
the lack of cataractous × cataractous matings and limited number of
dogs can not completely validate this hypothesis at this time.
DISCUSSION
Primary breed-related cataracts are common in purebred dogs, and ≈60
breeds of dogs are reported with primary cataracts above the
baseline of 1.6% prevalence of the mixedbreed/hybrid canine
population.6 In the veterinary medical teaching hospitals
in North America primary cataracts have occurred in nearly 40 000
dogs and have increased in frequency from 0.95% (1963–1774) to 2.42%
(1994–2003). Nearly 160 breeds of dogs have been diagnosed with
primary cataracts in this recent report.6 Clinical
studies involving inherited cataracts in dogs have many challenges,
including random matings, long periods and repeated eye
examinations, limited funding, continued breeder cooperation and
interest, and uncontrolled geographic distribution of animals.
Affected × affected matings are unusual and unintentional, and
usually result before cataract formation is detected in both dogs.
The current literature on inherited cataracts in dogs consists of
almost all clinical studies, and indicates that most pedigrees were
incomplete and limited numbers of dogs were available. As a result,
the mode of inheritance was usually proposed but could not be
validated statistically except in the Miniature Schnauzer with
inherited autosomal recessive congenital cataracts. In the clinical
report by Rubin et al. there were 12 litters from cataractous ×
unaffected matings, and two litters of two puppies each from
cataractous × cataractous patients.7 The subsequent
laboratory investigation of the Miniature Schnauzer involved
cataractous × cataractous matings (18 matings; 87 cataractous pups),
cataractous × normal (2 matings; 11 normal dogs); and cataractous ×
carrier matings (18 matings; 39 cataractous pups and 42 normal lens
pups).7 Our careful long-term analysis in this report
strongly supports the presence of an autosomal recessive form of
cataract in the Bichon Frise.
ACKNOWLEDGMENTS
Support was provided, in part, by the Bichon Frise Club of America,
the American Kennel Club-Canine Health Foundation, the Hayward
Foundation, and the Gwathmey-Adams Laboratory for Vision Research,
University of Florida.
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Davidson MG, Nelms SR. Diseases of the lens and cataract
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- Gelatt KN, MacKay EO, Dao V et al.
Inherited cataracts in the Bichon Frise: a preliminary report. 27th
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- Schmidt GM, Vainisi SJ.
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- Stubbs BB. The Complete Bichon
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- Gelatt KN, MacKay EO. Prevalence
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- Rubin LF, Koch SA, Huber RJ.
Hereditary cataracts in Miniature Schnauzers. Journal of the
American Veterinary Medical Association 1969; 154: 1456–1458.
- Gelatt KN, Samuelson DA, Bauer
JE et al. Inheritance of congenital cataracts and microphthalmia in
the Miniature Schnauzer. American Journal of Veterinary Research
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