Juvenile Renal Disease

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In January of 1990, I had my twenty-one-month-old Standard Poodle puppy put down. She was one of three puppies in a litter of eleven to die of Juvenile Renal Disease. All three of the puppies with the disease appeared healthy and grew normally until clinical signs appeared at ten months in one, and twenty months in the other two.

She died two weeks after being diagnosed. The disease is devastating. The prognosis is dismal. Nobody expects to lose a puppy of that age. I have been collecting information since her death on the disease that killed her.

Despite the fact that several articles on Juvenile Renal Disease and Familial Renal Disease were published in veterinary journals in the 1970s, and many others have been published since that time on JRD in Dobermans Pinchers, Alaskan Malamutes, Norwegian Elkhounds, and Samoyeds as well as in Standard Poodles, most individual cases of JRD are treated by owners and veterinarians as isolated occurrences rather than as the manifestation of a genetic disease.

The disease is also well known in Rottweilers, Shi Tzus, and Lhasa Apsos, and is seen in Soft Coated Wheaten Terriers, Portuguese Water Dogs, Shar Peis, Miniature Schnauzers, and Cocker Spaniels, among others. It is now being seen in Golden Retrievers, a breed in which it had not before been recognized.

Symptoms

Early symptoms of Juvenile Renal Disease include drinking copious amounts of water, something that might not be readily apparent in a house with more than one dog, frequent urination, and dilute urine which has little color or odor. Some affected puppies will leak urine, others won’t.

As the disease progresses, vomiting, weight loss, anorexia, lethargy, and muscle weakness are seen. There is often a chemical odor to the breath, and teeth are sometimes discolored. Some puppies grow normally until they are diagnosed, and some appear as failures to thrive.

Treatment for JRD consists of a low protein prescription diet, Hill’s K/D, and, in addition, IV fluids can be given to act as a kind of dialysis. Epogen, an expensive drug which needs to be carefully monitored, can be also be given to treat the hypoproliferative anemia of chronic renal failure. Some Veterinary schools are experimenting with kidney transplants, but transplanted kidneys in dogs are commonly rejected.

These treatments are palliative at best, and the prognosis for JRD is grim. Puppies usually die within several months of being diagnosed, almost always before age two.

I do know of several dogs who have JRD with less severe kidney involvement, and who are being well maintained on low protein diets. These dogs are both more than three years old, and were diagnosed before they were symptomatic. One because his litter was decimated by the disease, and one because his vet was giving free BUN tests to his/her clients.

Recognizing the Problem

If a breeder is informed about a medical problem in a puppy she has sold, and often she is not, or, if just the owner of the dam is informed, and it is only one puppy in a litter about whom she is informed, it is usually treated as an isolated incident.

Unless there are multiples in a litter, and the breeder is informed about each, the fact that the illness from which a puppy is suffering is a genetic disease is not recognized, and no recognition is made nor thought given to those littermates who are carriers. Without an understanding of the genetics involved, and most veterinarians treat isolated incidences as being from an unknown cause rather than as Juvenile Renal Disease, veterinarians are unable to offer counseling to breeders, and more and more carriers are unknowingly bred.

In the breeds in which JRD is known to occur many of the puppies who fall into the “fading puppy syndrome” and die at a young age may well have died of JRD. Many stillborn puppies are victims of this disease. Often, however, an affected puppy will grow normally until it is between ten and twenty-four months of age before it is symptomatic, diagnosed and dies.

Heritability

George Padgett, D.V.M., a geneticist and professor of pathology at Michigan State University, told me that JRD affects about 20 breeds. In most of the breeds in which it has been studied it is a simple (one gene), autosomal (not sex-linked), recessive (both parents have to carry the gene) disease. Both parents of an affected puppy are therefore defined carriers.

The presence of just one affected puppy determines that both parents are carriers. Littermates of an affected puppy have a 66% chance of being carriers. Aunts and uncles of an affected puppy have a 50% chance of being carriers, as do grandparents. According to Dr. Padgett, if a sire has produced an affected puppy, and is, therefore, a defined carrier, he has also proven bitches who are probably clear: those who when bred to him have produced sizeable litters in which there were no affected puppies.

“Proven” is used rather loosely here, since statistically a dog mated to a carrier and producing six normal offspring would still have a 17.8% chance of being a carrier. Twelve normal offspring would reduce that chance to 3.17%. The preceding figures which refer to simple autosomal recessive anomalies are from Malcolm B. Willis’ book Genetics of The Dog. If the disease is caused by a simple autosomal recessive gene, both parents must be carriers of the gene to produce an affected puppy.

However, even if only the sire or only the dam is a carrier, the other parent being clear, 50% of all the puppies born are carriers themselves. If the cause of JRD is polygenic, several genes would be necessary collectively in order for the disease to occur. In Samoyeds the mode of inheritance is now known to be x-linked recessive. In that breed, only males are affected with the disease, but females pass it on through the x chromosome.

Eliminating JRD

Among the pedigrees I have collected are those of twenty-five litters of an American Champion sire. There are a large number of American Champions among his offspring. In two of these litters there was one puppy with JRD. The sire is, therefore, a carrier, and half of the puppies in every one of his litters are carriers.

This is just one sire: the arithmetic is stunning. The possibility that this will not eventually touch every breeder in the breeds in which it is known is unlikely, and, by the time it does, it will be difficult if not impossible to eliminate.

In order for Juvenile Renal Disease, sometimes called Familial Renal Disease, Renal Dysplasia, or Congenital Hypoplasia to be studied in any breed, several things have to occur. Breeders of breeds affected by this disease should have any stillborn pups and all pups who die before being sold, autopsied if only to look for this one disease.

If the puppy is seen to have JRD, (the kidney cells actually have to be studied under a microscope, since occasionally the kidneys appear normal to the naked eye), the rest of the litter can be tested. Bloodwork should be done to look for an elevated BUN, and urine tested to establish a urine protein creatinine ratio.

Unaffected litter mates should all be considered carriers since there is no way to distinguish a carrier from a noncarrier puppy. The only positive outcome of having an affected litter that I can think of is that it enables the breeder to identify carriers and potential carriers.

Every affected litter has the potential to stop carriers from producing more carriers. If an autopsy shows that a puppy did not die of JRD, that is also useful information. I realize those post mortem examinations are expensive, though a restricted exam to look for one specific finding would be much less expensive.

I can assure anyone that is infinitely more expensive on an emotional as well as a financial basis not to have an autopsy done to look for this disease. Once carriers and dogs who are clear have been identified, concerned and careful breeders can work to systematically breed the disease out.

George Lees, DVM of Texas A & M University is currently doing research on Juvenile Renal Disease in Cocker Spaniels. The Soft Coated Wheaten Terrier Club of America is sponsoring research by Dr. Shelley Vaden at the North Carolina State University College of Veterinary Medicine. Dr Vaden is collecting health records on SCWT, and she has established a breeding colony.

The Department of Human Genetics at Michigan State University has a large grant to be used in gene marker research. The initial effort will be to develop 400 DNA probes in order to saturate the dogs’ chromosomes with the probes. After the probes have been established, screening can begin for linkage of any dog disease gene of interest.

Eventually, the benefits will be that dogs will be able to be screened for the carrier state of the gene. This research will not be completed for many years. In the meantime, since the funding is sufficient only to develop the probe system and not to study any particular disease, funding will have to be a provider by breeders themselves or by other outside sources for the study of specific disease gene projects.

For the first few individual studies, the estimate is that the cost will run from $25,000 to $50,000 to screen through the 400 probes to establish a close linkage. In order to carry out screening for linkage for this or any other genetic disease, pedigrees of 15-20 litters in which there are at least two affected and two unaffected puppies must be identified. Blood samples from at least two affected puppies and two unaffected puppies in each litter, as well as from both parents have to be available for study.

Puppies from a repeat breeding are considered littermates for this purpose. The blood samples can, of course, be stored for future use. Several other universities, such as Texas A & M and the University of California at Berkeley are involved in DNA research also.

Waiting for DNA testing to become readily available is not a feasible solution to the problems of genetic diseases. Selectively breeding away from carriers now is the only responsible action. In some instances, careful breeders have succeeded in largely eradicating some genetic disorders from their breeds. Success depends on a number of factors. Every puppy buyer must be encouraged to report any major illness back to the breeder.

Breeders must have a clear understanding of the modes of transmission of genetic disorders that affect their breeds. Known carriers, as well as possible carriers, (littermates and offspring of those discovered to be carriers), must be conscientiously kept out of the gene pool. A method of communication among breeders must be established. Clearly, an open registry such as the open registry begun in July, l992 for Sebaceous Adenitis in Standard Poodles (this disease also occurs in other breeds) is an important step forward and an invaluable resource.

Registries in many canine diseases are being established at the GDC (Genetic Disease Control) in Davis, California. In Europe, open registries have made it possible for careful breeders to greatly reduce the number of cases of some genetic disorders.

An open registry would include the names of carriers of the disease as well as the names of dogs who are clear, those who when bred to a carrier did not produce any cases of the disease in a litter of significant size. Obviously, the early onset of Juvenile Renal Disease allows carriers to be identified much sooner than does a disease which manifests itself later in life.

Malcolm B. Willis wrote in his introduction to Genetics of The Dog, “We are the custodians of our chosen breeds during the relatively short period of our dog breeding lives. It behooves us to hand over the material we breed within a better state than when we received it or we have achieved nothing and the breeds we profess to love will be the sufferers.”

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