RHODESIAN RIDGEBACK CLUB OF THE UNITED STATES, INC.
1996 NATIONAL HEALTH SURVEY

Download forms (PDF file) to report data for this ongoing Rhodesian Ridgeback health survey, or to update a dog previously reported to the survey.

In 1995, the Health and Genetics Committee of the Rhodesian Ridgeback Club of the United States (RRCUS) recommended to the Board of Directors that RRCUS undertake a survey of the incidence of the health problems, diseases, and disorders that affect Rhodesian Ridgebacks in the U.S. Through the use of a large-scale health survey, RRCUS would be better able to critically evaluate the state of the health of the breed, identify the significant health problems, and thus be in a better position to evaluate and support research efforts geared towards understanding and addressing these problems. A breed health survey would provide data to assist in grant allocation and in the designation of funding for projects that involve health issues, so that resources and energy could be used to make such decisions as appropriately as possible. The 1996 RRCUS Health Survey can be refined and modified, if necessary, and used as an assessment tool in the future to monitor any changes in the status of the health of the breed now that the methods have been developed and the 1996 data has been generated and analyzed.

The American Kennel Club established the Canine Health Foundation in 1994 to facilitate canine genetic research and to provide parent clubs with support in their efforts to improve the health of their dogs and to help in prioritizing breed-specific research projects. The AKC Canine Health Foundation has encouraged the parent clubs to begin by identifying the major health issues that affect their breeds. In April of 1997, the AKC sent to all parent clubs a "Model Health Questionnaire for Parent Clubs" which was designed to be used as a template for any parent club interested in conducting a health survey for their breed. However, this questionnaire seemed to be designed primarily to assess disorders which were suspected of having a significant genetic component. It did not include any classifications for Infectious Diseases, Toxicological Disorders, or Trauma, which the RRCUS Health and Genetics Committee felt were important categories for the purposes of collecting as much information as possible about the factors that affect the morbidity and mortality of Rhodesian Ridgebacks. The RRCUS 1996 Health Survey covered a broader scope of health problems and causes of morbidity and mortality in the breed and, at the same time, allowed for more detailed information within categories. For example, the AKC Model Health Questionnaire categorized Behavior Problems under "Temperment" (sic), and had only three codes, "Other", "Agression" (sic), and "Shyness". The 1996 RRCUS Health Survey included these three behavior problem categories and also requested input on excessive barking, separation anxiety, stereotypes, and noise/thunderstorm phobia. In addition, data on whether dogs are spayed or neutered and at what age was not gathered by the AKC Model Health Questionnaire. If, in the future, it is thought that any comparisons of the incidence of health problems between breeds would be meaningful (and caution must be used in any such attempt, particularly because of sampling differences), it might be possible to convert the RRCUS results to the AKC diagnostic codes for at least some portion of the data. One element that was elicited by the AKC Model Health Questionnaire that was not specified by the 1996 RRCUS Health Survey was the age of onset of the disease/disorder. In retrospect, this might have been useful, particularly in determining whether dogs were spayed or neutered prior to developing diseases/disorders or subsequently.

Procedure

A mail-in health survey was designed for the RRCUS by the members of club's Health and Genetics Committee, under the advisement of a veterinary epidemiologist (Correa, 1995). The survey form was designed to elicit signalmen information (sex, date of birth, date of death, color, whether spayed or neutered and if so, at what age) and whether each dog had experienced any major health problems. A "major" disease or health disorder was defined as one that

1) was potentially life-threatening;
2) significantly affected the quality of the dog's life; or
3) significantly affected the dog's potential as a breeding animal.

Results

Two hundred seventy-eight completed surveys were returned (a 48% response rate) representing 1,263 Rhodesian Ridgebacks. The number of dogs included per completed survey ranged from 1 to 60, with a mean of 4.5 dogs per respondent. Of the 1,263 Ridgebacks, 550 (44%) were male (368 or 67% intact, 182 or 33% neutered). Six hundred sixty-eight (53%) were female (409 or 61% intact, 259 or 39% spayed) and 45 (3%) did not indicate the sex of the dog (many of these were neonatal puppies that were euthanized). Black-nosed Ridgebacks accounted for 90% of the total (1136) and approximately 10% (127) were liver-nosed. Nine hundred thirty-four of the dogs were still alive at the end of the survey period, while 329 had died or been euthanized.

Four hundred ninety-eight (53%) of the 934 Rhodesian Ridgebacks alive at the survey's completion reported no major health problems. Of these 498 live and healthy dogs, 292 (59%) were female (211 or 72% intact, 81 or 28% spayed) and 206 (41%) were male (166 or 81% intact, 40 or 19% neutered) and 452 (91%) were black-nosed and 46 (9%) were liver-nosed. No statistical relationship was found between number of dogs per disease/disorder category and color or between number of dogs per disease/disorder category and sex.

A complete listing of the survey results based upon the fifteen disease disorder categories can be found in Tables 4-19.

The ten diseases/disorders that had the greatest number of dogs affected, based upon total number of Ridgebacks affected per susceptible survey population are noted in Table 1.

Table 1: Incidence of Diseases/Disorders

The causes of death/euthanasia listed for the 329 dogs that had died or were euthanized by the end of the survey period are as noted below in Table 2. Causes of death/euthanasia are not listed or are listed as "unknown" for 28 of the deceased dogs in the survey, or 8.5%.

Table 2: Causes of Death/Euthanasia (All Ridgebacks)

It must be noted that Table 2 reflects all of the causes of death for all Ridgebacks reported in the survey. Many of these causes of death/euthanasia applied primarily to neonatal puppies. If the causes of death for only the Ridgebacks who survived to the age of six months are considered (this was done, for example, in the Irish Wolfhound Study of causes of morbidity and mortality in 1988 by Bernardi), the data would be as shown in Table 3. There were 154 pediatric deaths and 174 adult deaths in the RRCUS data.

Table 3: Causes of Death/Euthanasia for Ridgebacks Over the Age of Six Months

These causes of death/euthanasia do not account for all of the deceased Ridgebacks in the study, because the remainder of the causes of death were either unknown, not listed, or were widely dispersed among the categories with no other single cause of death accounting for more than three dogs.

Table 4. Toxicological Disorders

Table 5. Infectious Diseases

Table 6. Endocrine Diseases

Table 7. Immunologic/Hemotologic Diseases

Table 8. Oncological Diseases/Cancer

Table 9. Dermatological Disorders

Discussion

     Several of the disease/disorder categories warrant additional comment. In the Endocrine Disease category, there was a statistically significant (p <.001, chi square test) correlation between hypothyroidism and having been spayed or neutered (48 of the 56 Ridgebacks that were hypothyroid were spayed or neutered, or 85% of the hypothyroid dogs). This information must be interpreted carefully. In order to appreciate the clinical significance of this finding, additional information would be needed, particularly the age at which hypothyroidism was diagnosed and the age at which the dog was spayed or neutered. (This survey collected the latter information but not the former). It may be, for example, that dogs who were diagnosed with this disorder were then spayed or neutered so a casual relationship cannot be assumed on the basis of this data. However, this finding warrants further investigation as to the question of whether spayed or neutered dogs are more likely to develop hypothyroidism than intact dogs.

     In the Dermatologic Disorders category, it was interesting that the survey respondents reported owning/ producing more ridgeless Rhodesian Ridgebacks than they did liver-nosed Ridgebacks. Ridgeless Ridgeback puppies were more likely to be euthanized than puppies with a dermoid sinus. (The RRCUS Code of Ethics describes both ridgelessness and dermoid sinus as "serious defects or faults") Although only 54 Ridgebacks were reported to have clinically significant allergic dermatitis, the actual number is probably somewhat higher. Some of the dogs reported to have chronic otitis (ear infections) and chronic staph pyoderma (skin infections) may have an underlying allergic etiology.

     Incontinent Ridgebacks accounted for 61% (20 of the 33) of the dogs in the Urinary Disorders category. Of these 20 dogs, 13 (65%) were spayed females, 5 (25%) were neutered males, and 2 (10%) were intact females. This correlation may reflect the possibility that major cause of urinary incontinence may be estrogen-responsive or so-called "spay incontinence", though again the age of onset of the disorder would be necessary in order to support that hypothesis.

     Hip dysplasia was the number one disorder reported in the Musculoskeletal Disorders category, with an overall incidence of 2.7%. This rate is probably significantly lower than exists in the general Rhodesian Ridgeback population, since the majority of the survey respondents were RRCUS members who are presumably well-informed about PennHip/OFA screening for hip dysplasia and thus may have been successful in reducing the incidence to below that for the entire Ridgeback population. With heightened breeder awareness of elbow dysplasia in large breed dogs (i.e., fragmented coronoid process, ununited anconeal process), and increased interest in OFA screening for these disorders, perhaps elbow problems can be kept to a minimum in this breed, as reflected by the low incidence (11 dogs) reported in this survey.

     Excessive aggression was ranked as the most commonly occurring Behavioral Disorder and was also in the list of the ten most frequently reported health diseases/disorders overall. Whether the excessive aggression was directed towards dogs, people, or other animals was not specified in all cases, nor was the particular pattern of aggression noted for all cases (whether fear induced, dominance, territorial, predatory, etc.). Although environmental conditions and socialization opportunities can significantly affect a Ridgeback,s level of aggression, genetic influence on behavior cannot be ignored when making breeding decisions.

     Under the Oncological Disease category (cancer), mast cell tumors comprised 36% of the total reported neoplasias (tumors). Rhodesian Ridgebacks may be overrepresented in this disorder, since mast cell tumors have been reported in the veterinary literature to account for only 7-20% of skin/subcutaneous tumors (Page, 1993). The vast majority of mast cell tumors in dogs are skin tumors. Although many researchers have expressed a clinical impression that there may be a correlation between cutaneous (skin) mast cell tumors and allergic skin disease (Hamilton, 1998), the results of the 1996 Health Survey did not support this hypothesis. In fact, only one Ridgeback that had mast cell tumors also reported allergic dermatitis.

     Of the 12 Ridgeback bitches reported to have had mammary cancer, six were intact. Of the spayed bitches, one was spayed at less than one year of age, one was spayed between the ages of one and two years, and the other four were six years of age or older when they were spayed. Although this is a small number of animals, it supports the belief held by many veterinarians that intact bitches and those spayed later in life are at a greater risk of developing mammary cancer than those spayed at a young age, although again this results cannot be overinterpreted as the age at which the bitches developed mammary cancer was not known.

     Finally, 25 Ridgebacks in the survey population were hit by cars and 68% of those died or were euthanized as a result of their injuries. Obviously, this is a management issue rather than a genetic one. It would be interesting to note how many of these dogs were injured while in pursuit of prey, thus acting upon their predatory tendencies and pointing out once again the importance of properly confining Ridgebacks, as being hit by a car was a more significant risk to Ridgeback life than any other disease or disorder except ridgelessness or dermoid sinus. This fact should be borne in mind by Ridgeback owners or potential puppy buyers, and breeders may need to emphasize this danger to prospective owners.

Conclusion

     With the information gained from this survey, RRCUS members can now begin to objectively evaluate Ridgeback health issues. At the 1997 AJC-Canine Health Foundation Health Conference, Dr. Jerold Bell of Tufts University emphasized that ranking breed-related genetic disorders by frequency of occurrence does not automatically prioritize them as health issues. Many factors can affect the priority of a disorder, such as the clinical impact of the disease, its mode of inheritance, and the demographics of the defective gene(s) as it relates to the breeding population. We will need the thoughtful input of our membership to evaluate these factors.

     Once we have prioritized our health issues, we can initiate efforts to support research that specifically applies to our breed. It is our responsibility as guardians of the breed to protect more than just our breed standard; we are ultimately responsible for the future of the health and well-being of Rhodesian Ridgebacks.

     *Special thanks to all who took the time to complete the survey, to Peggy Schmidt for her tireless efforts in computer formatting the health survey; and especially to Pete, Fanny, Ed, Angel, Lisa, Spencer, and Art for being faithful companions, dedicated guardians and constant reminders of what,s really important in life.

     *Note: The RRCUS Health Survey is never done! It is meant to serve as a perpetual data base to monitor the health of the breed. Any RRCUS members interested in completing the survey may still do so. This applies to new members as well as those who did not fill out the survey the first time. Those of you who have completed the survey are encouraged to update the information about your Ridgebacks, health periodically as their health status changes. Copies of the 1996 RRC?US Health Survey and information about updating can be obtained by contacting Dr. Betsy Pethick at:

Parkway Animal Hospital
1610 Old Apex Road
Cary, NC 27513
(919) 460-0741

References:

1. Bernardi, Gretchen. Longevity and morbidity in the Irish Wolfhound in the United States, 1966 to 1986. Harp and Hound, 1988 Vol 1.

2. Correa, Maria DVM, personal communication, 1995

3. Hamilton, Terrance A., DVM, personal communication, 1998, OVMA Conference, Columbus, Ohio

4. Page, Rodney, DVM, Behavior and Management of Common Tumors in Companion Animals, 1993. Notes from North Carolina Small Animal Academy, Sanford, NC, March 1993 Meeting.