Bona, S. (1995). A population genetic study of the breeding situation and inherited diseases particularly eye and joint in the Golden Retriever and Labrador (Eine populationsgenetische Untersuchung zur Zuchtsituation und zu erblich determinierten Erkrankungen – insbesondere Augen- und Gelenkserkrankungen- beim Golden und Labrador Retriever).
Abstract: The first half of this thesis describes the origins of the 2 breeds,the breeding of retrievers in Germany, standards and regulations forthe breeds, and inherited defects and diseases in retriever breeds. The second half reports the authors investigations. Litter size averaged 7.86 and 7.42 in the Golden Retriever and Labrador respectively. The trait appeared to be unaffected by inbreeding. Heritabilities in the 2 breeds were 0.128 plus or minus 0.0475 and 0.158 plus or minus 0.0949 respectively for hip dysplasia, 0.292 plus or minus 0.126 and 0.117plus or minus 0.138 for elbow dysplasia, and 0.068 plus or minus 0.07 (Golden Retriever only) for cryptorchidism. The incidence of progressive retinal atrophy in the dogs studied was 3.9%, and that ofheterozygotes for the defect approximately 32%.
Cox, V. S., Wallace, L. J., & Jessen, C. R. (1978). An anatomic and genetic study of canine cryptorchidism. Teratology, 18, 233-240.
Abstract: Cryptorchidism was found in 12 dogs of a colony of over 100 purebred and crossbred Miniature Schnauzers. At least nine affected dogs were derived from the same sire directly or indirectly. Of the 12 cases, five were unilateral and seven were bilateral. Eight affected dogs were studied anatomically. All unilateral retained testes were on the right side, and right sided bilateral retained testes were always smaller than their left sided counterparts. With one exception, ectopic testes were in the abdominal position. Developmentally the morphological appearance of the epididymis of abdominal testes was very primitive in bilateral cases but nearly normal in the unilateral cases. The degree of inbreeding was greater for bilateral cases than unilateral cases. The high incidence of cryptorchidism in this colony indicates the hereditary nature of the condition in the Miniature Schnauzer; morphological observations suggested a multiple gene defect.
Pendergrass, T. W. & Hayes Jr, H. M. (1975). Cryptorchism and related defects in dogs: epidemiological comparison with man. Teratology, 12, 51-55.
Abstract: A study of 1266 dogs with cryptorchidism from a series of large clinics and hospitals showed eight breeds (Chihuahua, Miniature Schnautzer, Pomeranian, miniature Poodle, standard Poodle, Shetland Sheepdog, Siberian Husky, Yorkshire Terrier) had an excess risk of the defect. Mixed breeds, Beagles and Labrador Retrievers had a significantly low risk. Review of the medical histories revealed that hip dysplasia, patellar dislocation, defects of the penis and prepuce, and umbilical hernia were excessively associated with cryptorchidism. Testicular neoplasms were diagnosed 10.9 times more commonly among cryptorchid dogs.
Romagnoli, S. E. (1991). Canine cryptorchidism. Vet Clin.North Am Small Anim Pract, 21, 533-544.
Abstract: Canine cryptorchidism is a congenital defect that results from sex- limited autosomal recessive gene(s). Incidence is higher in some breeds, especially in smaller and inbred ones. Parents of affected puppies are carriers. Unilateral cryptorchid dogs can be fertile, and affected individuals and their siblings should be eliminated from a breeding program to decrease incidence of the defect. Androgen and gonadotropin treatments have been tried with little or no success. Bilateral orchidectomy is the treatment of choice because of the common sequelae of testicular neoplasia and torsion.
Sittmann, K. (1980). Cryptorchidism in dogs: genetic assessment of published data. In (pp. 247).
Abstract: The analyses involved official records compiled for dissertations on German Boxers (GB) by 3 authors (1938, 1939 and 1968) and on German Shepherd Dogs (GS) by 3 authors (1932, 1957 and 1964). Extensive under-reporting is illustrated by incidences of 3.9 plus or minus 0.2% and 6.1 plus or minus 0.3%, the 1st for males registered in the studbook (1964), and the 2nd for a sample, included in the 1st, from the more reliable “family performance file” (1957). Biases were studied via litter size distributions, sex ratios and affected- male full-sib and half-sib families. Heritability estimates were 0.50-0.80. However, segregation ratio estimates for GB sibships with at least 1, 2 and 3 cryptorchids of 16.0 plus or minus 5.1, 29.6 plus or minus 5.1 and 49.5 plus or minus 13.6% resp., and similar estimates for subsamples of GBs, favour very few recessive genes over polygenic inheritance with 1 or 2 thresholds.
V. N. Meyers-Wallen. Inherited disorders in sexual development. J Hered 90 (1):93-95, 1999.
There is no abstract, but cryptorchidism is listed under “Miscellaneous Male pseudohermaphroditism:
“Cryptorchidism is included here because the mechanism of abnormal testis descent is incompletely understood. While cryptorchidism can be associated with other defects in sexual development, it also occurs as an isolated defect. As an isolated defect, cryptorchidism is the most common disorder of sexual development in dogs, occurring in as many as 13% of dogs presented to small animal clinics (Dunn et al, 1968). it is likely that some forms of canine cryptorchidism are inherited, since there is a high frequency in some breeds and within some families of breeds, and the frequency increases with inbreeding. In Angora goats, it has been proposed that cryptorchidism is inherited as a single locus, sex-limited, autosomal recessive trait. In swine, it has been reported as a sex-limited autosomal trait involving at least two gene loci.”