Overview and Prevalence of Genetic Defects
in the Rhodesian Ridgeback

By Cynthia Roethel, Senior Chair
RRCUS Health and Genetics Committee

 In 1996, the Rhodesian Ridgeback Club of the United States undertook the task of coordinating a nationwide health survey for the breed. The purpose of that survey was – and still is – to develop a better understanding of the health issues affecting Ridgebacks.

Since the survey’s inception a decade ago, there have been two tabulations of the data: the first after the initial data collection in 1996 and another in 2001. The information the health survey gives us is an invaluable tool: Besides identifying health issues, it allows us to monitor changes that might indicate an increase or decrease in the occurrence of a particular disease. 

At the 2002 Rhodesian Ridgeback Specialty in Lansing, Mich., the late canine geneticist and veterinarian Dr. George Padgett, DVM, presented a seminar on the “Control of Canine Genetic Disease.” Dr. Padgett was given our health survey to analyze, and he tailored his presentation to Rhodesian Ridgebacks. Going through our health survey, Dr. Padgett highlighted those diseases and conditions known to be heritable (genetic). His criteria for including a genetic disease were very straightforward: There had to have been an occurrence in at least one member of the breed that was confirmed by a qualified veterinary diagnostician.

Dr. Padgett acknowledged that there is a chance of error, but he asked us to consider that the best time to stop a genetic disease is when there is only one or perhaps a few cases of it in the breed. He reminded us that if 1 percent of the population is affected with a genetic disease whose mode of inheritance is recessive, it means that 18 percent of the population are carriers.

Dr. Padgett and I discussed where the Rhodesian Ridgeback stands in terms of genetic disease, and he commented that the breed is in the lower middle range in terms of number of genetic defects in purebred dogs.  Dr. Padgett also confirmed a hunch I have had for a long time: That clubs that actively pursue getting a handle on the health of their breed by doing comprehensive health surveys will always have a higher number of genetic defects identified, and that number will always be higher than what was previously assumed. (For more information about purebred dog breeds and genetic defects consult Dr. Padgett’s book, “Control of Canine Genetic Disease.”)

The Rhodesian Ridgeback health survey was designed to monitor trends over time. If all Ridgeback owners provide surveys on all Rhodesian Ridgebacks born after January 1, 1984 (healthy or not), and updated them when necessary, a diagnostic error would very quickly become obvious, as the disease frequency would decrease to nearly nothing. The need for health surveys on all Ridgebacks cannot be over-emphasized. This includes healthy, unaffected dogs, as well as dogs with health problems.

The health survey is a tool for us to critically evaluate the health of the Rhodesian Ridgeback breed as a whole. No survey is perfect – there can be numerous errors in the reporting of disease, starting at the veterinarian’s office and ending at the table when you fill out the survey. NONETHELESS, this is the best tool we have to assess the health of our breed.

In 2006, the RRCUS Health and Genetics Committee will debut a new electronic health survey that will be far easier to use than its paper-only predecessor, and which assures total confidentiality. Whether this survey is truly reflective of the health of our breed is solely dependent on YOU. See the Health Survey page for more information and instructions.

The diseases, modes of inheritance, frequency of each disease and Dr. Padgett’s guesstimation for gene frequency in the Rhodesian Ridgeback are listed below. These are in the order in which they appear in the health survey and are in no way prioritized. Also, the severity of the diseases varies widely. Some have little to no impact on the life of the dog with treatment, while others are severely debilitating.

Based on the data in the health survey, Dr. Padgett determined that each Rhodesian Ridgeback carries genes for approximately 6.6 of these genetic defects, which is about the same as we carry as humans. Dr. Padgett asserted that knowing which 6.6 genetic defects your Ridgeback carries, prioritizing them and then breeding away from them is the key to controlling canine disease.

GENETIC DISEASE, DISEASE FREQUENCY AND GENE FREQUENCY IN THE RHODESIAN RIDGEBACK

Age at diagnosis

Disease

Mode of inheritance

Disease frequency

Guesstimation of gene frequency (%carriers)

1

<8 years

Hypothyroidism

R

5.0/100

34.7%

2

<5 years

Addison's disease

UND

0.2/100

8.4%

3

<8 years

Hyperadrenocorticism

UND

0.1/100

6.0%

4

<3 years

Diabetes mellitus

UND

0.06/100

4.7%

5

<4 years

Hyperparathyroidism

UND

0.06/100

4.7%

6

<4 years

Autoimmune hemolytic anemia

UND

0.1/100

6.0%

7

<6 years

Immune mediated polyarthritis

UND

0.06/100

4.7%

8

<10 years

Immune mediated thrombocytopenia

UND

0.06/100

4.7%

9

<9 years

Systemic lupus erythematosus

UND

0.06/100

4.7%

10

<1 year

Von Willebrand's disease

R, Dinc

0.06/100

4.7%

11

birth

Hemophilia

X-R

0.06/100

4.7%

12

>4 years

Mast cell tumor

POLY

3.5/100

30.5%

13

>4 years

Hemangiosarcoma

POLY

0.6/100

14.2%

14

Birth

Ridgelessness

Complex

10.6/100

43.9%

15

<3 months

Dermoid sinus

R

4.7/100

33.9%

16

<1 year

Demodicosis

UND

1.5/100

21.4%

17

<1 year

Atopic dermatitis

UND

3.6/100

30.6%

18

<1 year

Food allergies

UND

1.2/100

19.4%

19

<5 years

Seasonal flank alopecia

UND

0.1/100

6.0%

20

<10 weeks

Ehlers Danlos syndrome

D

0.06/100

4.7%

21

<10 weeks

Umbilical hernia

R/Poly

0.5/100

13.1%

22

<6 months

Megaesophagus

R/UND

0.9/100

17.0%

23

<7 years

Pancreatic hypoplasia

R

0.06/100

4.7%

24

<1 year

Gastric Dilatation/Volvulus

UND

0.9/100

17.0%

25

<1 year

Subaortic stenosis

POLY

0.2/100

8.4%

26

< 2 years

Cardiomyopathy

POLY

0.1/100

6.0%

27

Birth

Persistent right aortic arch

POLY

0.06/100

4.7%

28

<1 year

Pulmonary stenosis

POLY

0.06/100

4.7%

29

<1 year

Laryngeal paralysis

D

0.06/100

4.7%

30

<1 year

Tracheal collapse

UND

0.1/100

6.0%

31

<3 months

Cryptorchidism

R/UND

1.0/100

18.0%

32

>1 year

Seizures (epilepsy)

R/UND

0.7/100

15.2%

33

>1 year

Degenerative myelopathy

UND

0.5/100

13.1%

34

<6 months

Deafness

UND

0.3/100

10.2%

35

</= 1 year

Wobbler syndrome

POLY

0.1/100

6.0%

36

<9 years

Cauda equina syndrome

UND

0.06/100

4.7%

37

<3 months

Hydrocephalus

POLY

0.06/100

4.7%

38

<1 year

Lumbar stenosis

UND

0.06/100

4.7%

39

<2 years

Hip dysplasia

POLY

2.20/100

25.2%

40

<1 year

Dental abnormalities

UND

1.40/100

20.8%

41

<1 year

OCD/FCP (elbow dysplasia)

POLY

0.7/100

15.2%

42

<1 year

Luxating patella

R

0.10/100

6.0%

43

<1 year

Osteochondritis dissecans

UND

0.4/100

11.7%

44

<1 year

Congenital vertebral abnormalities

UND

0.3/100

10.2%

45

<3 months

Open fontanelle

UND

0.2/100

8.4%

46

>1 year

Spondylosis deformans

POLY

0.2/100

8.4%

47

<4 months

Pectus excavatum

UND

0.1/100

6.0%

48

Birth

Cleft palate

POLY/UND

0.1/100

6.0%

49

<8 months

Hypertrophic osteodystrophy

UND

0.1/100

6.0%

50

varies

Cataracts

UND

1.0/100

18.0%

51

<6 months

Entropion

UND

0.6/100

14.2%

52

<3 months

Persistent pupillary membranes

UND

0.2/100

8.4%

53

<3 years

Glaucoma

UND

0.1/100

6.0%

54

<6 months

Ectropion

UND

0.6/100

4.7%

55

varies

Corneal dystrophy

UND

0.6/100

4.7%

56

Birth

Microphthalmia

UND

0.6/100

4.7%

57

<= 3 years

Excessive aggression

UND

1.8/100

23.2%

58

<1 year

Excessive Shyness

UND

0.8/100

16.2%

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