Breed Survey 2006
Analysis of National Rhodesian Ridgeback Club Breed Genetics Survey Data
Many thanks to the 25 breeders who submitted information to the Breed Genetics Survey. Information was received on 1397 pups born in 166 litters (average litter size 8.4 pups) from across the country. The breakdown of the 166 litters geographically was as follows: 52 from Victoria, 39 from NSW, 29 from Queensland, 20 from South Australia, 1 from West Australia and 25 not stated.
When considering the information provided, it must be accepted that conditions not seen prior to the pup leaving the breeder are likely to be under reported in this survey. These include heart murmurs, entropion, torsion/bloat, neurological problems, hip dysplasia, hypothyroidism, skin problems/allergies, cancers (including mast cell), elbow disease, and other skeletal issues. However, most of the data gathered can be provided by breeders prior to the pup leaving. Some key findings from the survey are:
The rate of dermoid sinus is now 4.7% (4.5% if pre 1996 litters are excluded) as compared to 6.7% in the 1996 survey. While it is uncertain if this is due to selective breeding practices or the use of folic acid, it is tempting to speculate the latter has had some impact on the incidence of this condition in our breed.
The rate of ridgeless is largely unchanged (6.8% now as compared to 6.3% in 1996)
The difficulties of breeding ridgebacks for the show ring is borne out by three additional figures. 20.8% of pups born have ridge faults, a further 2.8% have incorrect colour and 3% have mouth faults. This suggests nearly 26% of pups are removed from the gene pool due to these factors.
A total of 35% of pups are unsuitable for breeding due to all the factors mentioned above.
Given the small sample sizes I have put NA (not applicable) in some of the analysis columns to indicate a sample of 1 or 2 dogs which will not provide data of any value.
Other issues may be under reported as the question was not specifically asked eg the rear dew claw figure is reported at 1.4%. However, where it was reported nearly 50% of the litter had rear dew claws.
Some interesting comments/issues from the survey:
o One breeder put “not yet” next to a number of issues. As most long term breeders get to see most issues, this seemed a very pragmatic approach!
o One breeder reported a familial link for torsion/bloat
o The majority of the heart murmur cases were reported as Subaortic Stenosis (numbers up from 0.4% in 1996 to 1.1% in 2006,spread over most states)
o Some breeders provided numbers of liver/brown nosed pups. This data was not collated as it was not specifically requested (not seen as a genetic “issue”) - but may be of interest next time around!
o Very few breeders reported hip dysplasia- either this is not a problem in the breed or a clearer definition may have helped (eg AVA/BVA score greater than 15).
NRRC SURVEY RESULTS 2006
Some comparative data from the 2001 Rhodesian Ridgeback Club of USA (RRCUS) Health Survey is of interest. This is based on a sample of 1763 dogs and as such is more likely to provide accurate data as it seems to be based on dogs bred and kept by US breeders. For example the underlying dataset started with 278 breeders returning information on 1263 dogs. As this is an average of 4.5 dogs per breeder it is more likely to represent longer term information on dogs kept in addition to issues seen in litters. From the 2001 data the 10 diseases/disorders that affected the greatest number of Ridgebacks, based upon number of Ridgebacks affected per susceptible survey population were as noted in Table I below.
TABLE 1 Incidence of Diseases/Disorders
A summary of the information gained by the RRCUS was as follows:
“Hypothyroidism continues to be our number one endocrine disease, and a statistically significant number (83%) of these dogs are spayed or neutered. Unfortunately, we cannot be certain from this data what occurred first (spaying/neutering vs. the diagnosis of hypothyroidism) but, in most cases, it appears that spaying/neutering occurred first. This supports observations in the veterinary literature of an increased frequency of hypothyroidism in neutered dogs.
Ridgelessness and dermoid sinuses continue to be our major dermatologic concerns, but we are not euthanizing these dogs quite as frequently. In the 1996 survey, 73% of ridgeless dogs were euthanized vs. 68% in the 2000 update; in 1996, 61% of Ridgebacks with dermoid sinuses were euthanized vs. 52% in the 2000 update. Allergic dermatitis is also of concern for Ridgeback breeders, including atopic dermatitis, food allergies, and occasionally flea allergy dermatitis.
Urinary incontinence remains a problem limited primarily to spayed females (74% of the affected dogs were spayed females, the remainder were males) supporting a diagnosis of “spay” or “estrogen-responsive” incontinence.
The incidence of hip dysplasia has basically remained constant (2.7% in 1996 vs.2.5% in 2000) but the incidence of elbow dysplasia in the susceptible survey population has almost doubled (.5% in 1996 vs. .9% in 2000). Keep in mind that these are very small numbers of affected dogs, but perhaps this is a trend we need to monitor.
Excessive aggression is still our primary behavioral concern. Although environment and socialization opportunities can significantly impact a Ridgeback’s level of aggression, genetic influence on behavior cannot be ignored when making breeding decisions.
Mast cell cancer is without question the most frequent type of cancer seen in the Rhodesian Ridgeback. The RRCUS Health and Genetics Committee has prioritized mast cell cancer as an area of research. We have recently “combined forces” with the Chinese Shar-Pei Club of America, the Staffordshire Bull Terrier Club of America, and the Boston Terrier Club of America in sponsoring AKC/CHF research on the biology and genetics of canine mast cell tumors.
Lastly, it is sad to see that the number one cause of death in Ridgebacks over 6 months of age is a very preventable problem- hit by car. It cannot be overemphasized to Ridgeback owners, and especially puppy buyers new to the breed, that the sighthound nature of these dogs can easily get them into trouble when allowed off lead in unsecured areas.
The comparison of the key US issues and the Australian data shows some areas of commonality and some where the Australian data differs e.g. the dermoid sinus- rates are very similar, as are issues such as death from chasing cars-although we did not collect this data. However, there are some areas of difference:
The Australian rate of ridgelessness is less, although it has risen slightly between surveys (now 6.8% compared to the US rate of 10.6%)
Hypothyroidism rate in the US is 5.8%compared to 0.3% in Australia. It is tempting to speculate the Australian rate would increase if we were to introduce the screening levels seen in the US, but there is a big gap between the current Australian rate of 0.3% and the US rate of 5.8%
Allergic dermatitis- this is probably also under reported in the Australian survey (0.6%)
Mast cell tumours are infrequently reported in the Australian data (0.2%) compared to 4.1% in the US. It is tempting to speculate this is due to the different gene pools, in addition to under reporting in Australia.
With an increasing globalization of our gene pool it is worth noting the issues seen in other countries- and the US data is the best source of this at present. In addition to the other conditions reported in their data (and probably under reported in ours) the comments on the genetic underlay to aggressive behaviour from the US data are worth noting and taking into account in breeding programmes.
Thanks again for your input. I hope this information can be used to structure improved breeding programmes and to raise awareness of issues we may see in the future- as well as those we are seeing now.
For the NRRC December 2006