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  Hydrocephalus

 

FOOD FOR THOUGHT

 

FOR CASUAL CONSUMPTION ONLY: NOT TO BE INGESTED WITHOUT THE PROVERBIAL GRAIN…

 

Lisa Warren

   

HYDROCEPHALUS - A BREEDER'S EXPERIENCE 

 

Let me establish at the outset that I do not profess to have any background in science, or in genetics beyond what I learned about Mendel's peas in Biology 101 plus whatever I have added to that over the years through the study of dogs.  What I do have, unfortunately, is quite a bit of first-hand experience with hydrocephalus.  For those readers who are completely unfamiliar with this affliction, it is defined by Webster's as "an accumulation of serous fluid within the cranium, especially in infancy, due to obstruction of the movement of cerebrospinal fluid, often causing great enlargement of the head; water on the brain."      

Our first encounter with hydrocephalus was in a litter of two.  One of the pups was considerably smaller than a normal mini, and had a skull shaped more like that of a Chihuahua than a dachshund: domed, with an abrupt stop and a soft spot.  She also had a much shorter body than one expects, and was extremely animated, probably hyperactive.  Andrew and I were living in Australia at the time, and our veterinarian assured me that, while we were dealing with an abnormality of some sort, he felt sure that there was not a genetic factor at play.  That puppy had an abnormal heart, and lived to be about four months old.

     A second such puppy appeared about two years later, and lived to about four months.  Three years later we got another similar puppy who died at about three months of age.  We were living in a different part of Melbourne by then, and another vet echoed the opinion of the first one.  However, I was not convinced at this point, having noted that all three of these puppies had been in line-bred litters.  Questioning other breeders brought forth no one who had any similar experience, or at least no one who was willing to discuss it.  I was perplexed.

       The next incidence was a puppy that did not have the same appearance as the first three.  She was small, but not so small as to set off any alarms.  Her head was certainly not ideal, but no less so than many pet dachshunds.  Her only symptom was a constant runny nose that did not respond to antibiotics as it should have if it had been of bacterial origin, and did not clear up on its own, as it would have if it were due to a virus.  Most days she was bright and lively and altogether like a normal puppy, but there were days when it was clear that she was sick, very much like a child with a cold.  It  was a source of considerable consternation to me that there seemed to be no veterinary expertise available to help her, and that her affliction could not be identified.  When she was about nine months old, we returned to America.  We left her behind with a very kind friend since we were convinced that an arduous trip would possibly be too much for her.  At this point we had made no connection in our minds between her and the first three abnormal puppies, as she did not seem to share any of their symptoms.  We later learned that she died at about eighteen months of age, suddenly, and probably due to heart failure.

     When we had been back in the U.S. for about a year, we did a mating between a bitch and her grandson.  Both of these animals were themselves the result of out-crosses, and neither of them had been a parent of any of the puppies discussed so far.  In this litter was a puppy with all of the symptoms we had encountered: extremely small size, odd head shape with a pronounced soft spot, hyper-animation, and the constant runny nose.  With that one puppy, all of my doubts and questions came to resolution, because it linked the other pup with the runny nose to those that had preceded her, and all of them to this most recent one.  Our vet here identified the affliction, and the pedigrees gave me all I needed to track exactly where the origin was in our bloodline.

     Now, it is entirely possible that I am mistaken about what I have surmised to be the mode of inheritance of hydrocephalus, but it seems to act exactly like a simple recessive trait, and what little veterinary information I have been able to find supports that.  For those even less schooled in genetics than I am, think of the afflicted puppy from two normal parents as being like a black and tan from two red parents:  each parent must be a carrier of the recessive gene, and neither parent can single-handedly produce the trait in his or her offspring, as the gene in question must be married to the same gene from the other parent to produce an afflicted puppy.  This means, of course, that a given dog or bitch may be a carrier and never throw an afflicted puppy, but each of that carrier's offspring has a fifty/fifty chance of being a carrier.  (It should also be noted that hydrocephalus can occur as a congenital problem rather than as a genetic one, having nothing to do with anything other than that particular puppy's pre-natal development).

     The range of symptoms is broad.  Any, all, or none of the following may appear in a given puppy: a soft spot on the top of the head, evident in some toy breeds but not commonly found in dachshunds; extremely small size; failure to thrive; inability to nurse; appearance of hyperactivity; oddly shaped head and low, wide eye placement, the combined effect of which brings to the observer's mind a human child with Down's syndrome; heart problems; an unrelenting runny nose.  I must add that our few fading puppies over the years have been from parents that could have been carriers, causing us to wonder if that too was a result of hydrocephalus, but undetected because the pups did not survive long enough for any obvious symptoms to appear.  

     I would like to point out that not one of these hydrocephalic puppies has seemed mentally retarded in any way.  As a matter of fact, most of them have been the most outgoing in the litter and the first to do everything, thereby appearing to be the most intelligent.  Each of them has been affectionate, good-natured, and altogether charming, compounding the heartbreak when they die.

     It seems possible that a given dog might carry two recessive genes for this affliction and show no outward signs, and a knowledgeable and very helpful Canadian breeder has told me a story of just such a dachshund.  She had been shown and was pointed, and then had a litter which produced a hydrocephalic puppy.  She was later placed in a pet home with a well-to-do couple who doted on her.  Her owner accidentally slammed a car door on her head one day, and while she seemed to suffer no long-term damage, they chose to have an M.R.I. done to be certain.  To the great surprise of the veterinarian and probably everyone involved, she was found to have a brain which occupied only a small part of her skull, the rest being filled with fluid!  She was diagnosed at that point with hydrocephalus.  One of our own dogs, now just over a year old, has a runny nose, but no other discernible evidence of the disease. We have x-rayed both his chest and his head, and all seems normal.  Our vet was difficult to convince, and she may only be humoring me now in agreeing that this pup is hydrocephalic.  He even looks perfectly normal; I believe, in fact, that he could be finished if we showed him.  So, since not all afflicted ones have the runny nose, it is not impossible to believe that there are some dogs with two recessive genes for this syndrome who display no symptoms at all. 

     We have had to wonder if our problems did not start with such a dog.  Our first Australian stud dog, the sire of our first hydrocephalic puppy from a bitch who was related to him, was the sire of two outcrossed litters for us from another bitch. (Incidentally, there were six champions from these litters, two of them all-breed best-in-show winners and another a multiple group winner,  demonstrating that this gene, like most others, does not affect the appearance of carriers.)  We went on over the next few years to breed from those six champion offspring.  We have subsequently traced the gene for hydrocephalus back to five of them with certainty, and cannot totally rule out the sixth.  Could it have been pure bad luck that every one of his pups that we chose to go on with turned out to be a carrier, or was it inevitable because he could only pass along the recessive (bad) gene to all of his offspring, having two of them himself?  We will never know, but I will probably always wonder.

    Several American breeders have told me that they have had a puppy with symptoms described here, or know of another breeder who did.  Most, like us, did not know what they were seeing, and the breeders I have talked to did not have a recurrence, a fact directly attributable to the breedings not having been repeated.

    Our latest encounter with this problem is very recent.  We imported a dog from Australia from a bloodline different from the one that we developed there.  This new import had been used extensively at stud in Australia, and, to his breeder/owner's knowledge, had never produced a hydrocephalic puppy.  This was, as one might assume, very important to us, as his ability to help us dig out of this particular hole was an important factor in our decision to purchase him, along with other of his attributes which we hoped to add to our bloodline.  Much to our dismay and shock, this dog produced an afflicted puppy in his first litter from one of our own bitches.  But this is worse: an outside bitch, from a bloodline not known to be carrying this gene, also produced an afflicted puppy when she was bred to this dog, her litter being born a few weeks prior to our own.  Now, we needed to make absolutely certain that one of our other dead-keen and oh-so-clever males, known to be a carrier, had not gotten to this visiting bitch. This is something that has never happened here, and it was surely impossible, as bitches in season are housed in the equivalent of a concrete bunker.  But the "impossible" does happen from time to time and, truth be told, we would have been relieved to learn that it had happened, feeling that temporary embarrassment and an unsolved mystery as to how it had occurred were preferable to learning that our new import was a carrier.  We therefore did a DNA test to determine paternity, and the imported dog did prove to be the sire.  (At least we now have scientific proof of our bad luck!)  As upset as we are about our dashed hopes for the new dog, I feel worse for the other breeder: Andrew and I are dealing with a devil we know all too well; she is now dealing with the new knowledge that she has one of the breed's usually-lethal genes to consider as she goes forward, whether she chooses to use offspring from this litter or not.  She kindly tells me that she would rather know than be in the dark, and has been completely cooperative about this whole development.

     As nasty recessive genes go, I suppose there is at least one aspect of this one that makes it preferable to some others, those that evidence themselves later in the afflicted dog's life, such as progressive retinal atrophy (P.R.A.), disc disease, or epilepsy.  I do realize that this is something like comparing a rotten pear to a rotten apple, but there are a formidable number of health-related genetic problems out there, and a breeder takes a chance with every breeding, whether out-crossed or within the line, and whether or not the stud's owner has been honest and forthcoming.  With hydrocephalus, most afflicted animals are identifiable at about three or four weeks of age, and therefore are not incorporated into a breeding program.  With other problems, a dog may have sired numerous litters, spawning a large number of carriers into the gene pool, before it is known that he has the disease. 

     Permit me a brief digression.  There is a chronic disease in quarter horses known as "tying up" which nearly devastated the breed.  Horses with this syndrome will just fall over one day, not dead, but unable to move for a period of time.  It all goes back to one magnificent horse who was used extensively at stud.  For quite some time everyone who bred to him and got the problem kept quiet about it, each thinking that it was unique to his own particular horse and being reluctant to deal with the gossip and innuendo that would result about his own bloodline if he were to go public with the problem.  Similarly, P.R.A. became a huge problem in English mini-longs at least partly due to the breeders who were quite aware that they had the problem in their lines but were unwilling to be honest about it.  Finally, the lid was blown off the whole thing by a very successful breeder who clearly cared more about the future of the breed than the reputation of his own bloodline. At that point, one of those breeders who had kept the problem under wraps for so long is reported to have said that, while she knew her extensively-used stud dog was a carrier, she had kept it a secret because she could not afford to lose the stud fees that he was bringing in.  Such stories cause me to fervently hope that my trust in cosmic justice is not misplaced.

     So, with hydrocephalus we are dealing with a self-limiting disease which seems not to be widely known or even recognized, with a diverse set of symptoms ranging from usually fatal to occasionally (and rarely, I hope,) totally absent.  The question: how should breeders, aspiring to do more good than harm as a result of their efforts, proceed when such a gene is discovered in the line?  Should the whole bloodline be scrapped?  That was my initial reaction when we first sorted out what the problem was.  Andrew was convinced otherwise.  He felt that we were not likely to be the only ones with this problem and therefore were not necessarily going to make a significant impact on it by turning away from the line that we had developed, one which has produced many animals very pleasing to us in many ways.  He also maintained that if we were to start over, we could quite easily get involved with something worse in our view, a problem that does not evidence itself so early in the puppy's life.  It has taken me a long time to come around to his viewpoint, but these most recent events, along with stories of other breeders' discoveries of other diseases, have convinced me that there are merits to his arguments.  This is not to say that we feel we can go forward willy-nilly, pretending that the problem does not exist.  But I do believe, after long and sometimes heart-wrenching consideration, that the answer is a controlled program which attempts to contain and eventually eliminate the problem without sacrificing the desirable elements of the bloodline.  And a necessary part of this effort is limiting outsider access to the bloodline to a very few people whom we know we can trust to be as conscientious about this as we intend to be.

     I wonder how much of this disease exists in our American gene pool.  I know of a pup acquired from a pet shop who died of it, and have heard of several other smooth and longhaired pups from show lines, both standard and miniature, who had it.  It is probably not rampant, being so often fatal and therefore self-limiting.  But perhaps reading this will help a few other breeders to identify the problem and thereby limit its spread.

     I would welcome any information that readers might have about this subject, and will gladly discuss it with anyone who has questions, although most of what I have learned is detailed here.  Our e-mail address is ElysiumDox@doglover.com

 (Author's postscript)  Since this article was originally published in the spring '96 issue of "The Dachshund Review", we have taken two young afflicted dogs to the University of Pennsylvania's Genetic Diseases specialists.  They have confirmed that we are dealing with a simple recessive gene.  They have also informed us that the runny noses are probably a result of failure of the cilia, the tiny hairlike structures that move the body's normal fluids, to function adequately.  The fluids therefore build up to levels that cause discomfort to the dog, and that must be moved by coughing or sneezing.

This is a syndrome that has been observed in dogs of other breeds who were known to be hydrocephalic.

 

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