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CANINE PITUITARY DWARFISM
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Pituitary Dwarfism in the German Shepherd
Dog - Fred Lanting
Pituitary Dwarfism in the German Shepherd
Dog (part 2) - Fred Lanting
A Small Problem-Dwarfism in Dogs - Fred
Lanting
Pituitary Dwarfism: A Spectre of the Nineties?
Pituitary Dwarfism in the German Shepherd
Dog
Part of a Set of Articles
on Dwarfism
Fred
Lanting
(original
version appeared in Dog World US, Dec. 1984)
Dwarfism is a condition of abnormally small stature,
and usually is characterized by altered body proportions. Dachshunds,
Basset Hounds, and Corgis are examples of achondroplastic dwarfs;
they have more or less normal sized torsos and heads but shortened
limbs, and are accepted as typical of their breed. Alaskan Malamutes,
on the other hand, are not considered acceptable if they have their particular
blood cell related disease. In that breed, both achondroplastic dwarfism
and hemolytic anaemia are inherited as pleiotropic conditions, meaning
a single gene giving multiple phenotype effects. Additionally, there are
dwarfism abnormalities in other breeds such as pseudochondroplastic dysphasia
in Miniature Poodles.
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Three littermates, two with
the pituitary dwarfism defect. It is probable that the intermediate-size
pup on the left was able to utilize more growth hormone and delay the closure
of physes (ossification of cartilage).
Photo courtesy Prof. E. Andresen, Copenhagen.
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In the German Shepherd Dog, however, there is a little known
dwarfism that yields a nearly perfectly proportioned but considerably
down sized version. An acceptable term to use would be proportional
or pituitary dwarfs, even though all types of dwarfism have their origins
in that gland. The fact is (or was until this article appeared), many
do not know about the existence of this type of dog, even though it is
not all that rare. Possibly because of the large scale line breeding by
a West Coast kennel that produced winning dogs, the incidence rose for
a number of years in the U.S. Due to line breeding on certain British
and German dogs, there was a noticeable number appearing both in England
and Australia, countries which rely heavily on German lines. One genetic
analysis of Australian data indicated that two dwarfs might be expected
out of 1000 pups when “any dog” is bred to “any bitch”. The recurrent risk
for any dog or bitch bred to a parent of a dwarf is seven per 1000; a parent
of a dwarf to a half sibling of a dwarf is 272 per 1000; and parent of
dwarf X parent of dwarf is 235 per 1000. The roughly 25% risk in the latter
two matings is typical of what one would expect when two normal carriers
of a simple Mendelian trait are bred to each other.
Of course, that 25% is an average. I recently (1984) examined
pups from a litter of six in which three were pituitary dwarfs, but
both parents were of normal size. Now remember, these were not abnormal
in proportions, only in size and unseen body chemistry. The little Shepherds
I examined that year had beautiful temperaments, and were active and
apparently healthy at the time I first saw them at almost four months
of age. They weighed about five pounds, while a normal litter mate was
about 32 pounds. There was something that had not appeared in the scientific
literature but which I noticed in this litter, as well as in photographs
of other litters: pituitary dwarfs seem to squint in bright sunlight more
than do their normal siblings. Another facial characteristic of miniature
Shepherds is a fox like appearance, coming from wide set ears. I believe
this to be a result of disrupted proportions of skull vs. base of the
pinna (ear shell), which to some extent is seen in Welsh Corgis also.
A somewhat snipey (pointed) muzzle is due partly to a shortening of the
skull and, in some individuals, a slight overbite.
The Arkansas litter I visited was no combination of junkyard
genes, but sired by an AKC Champion and with two Champion grand sires.
The whole pedigree was full of recognized and respected kennel names
and individuals. Indeed, the trait has been known for many years to
be carried by “champion quality” dogs. The gene seems to have first
arisen, possibly as a mutation, around 1940 or shortly before. It’s
almost 100% sure that one of the most valuable German Shepherd Dogs
of all time, Vello zu den Sieben Faulen, is a major source in bloodlines
since the late 1950s. But we cannot lay all the blame at his feet, nor avoid
all his descendants. Nor would we want to, for many of the breed’s best
lines are based on Vello. Only a percentage of his (or any dog’s) progeny
would carry the defective gene, and presumably many of the earlier dogs
who exhibited it in their progeny were removed from the gene pool. The
SV doesn’t favour continued breeding of dogs that produce defects, and
they have the power in Germany to prevent such dogs from further use by
denying registration. However, when a dog is valuable in other respects,
such as the Sieger Uran WildsteigerLand?, a blind eye is used to look
in that direction.
Some non show lines occasionally come up with pituitary dwarfs,
such as the white German Shepherd bitch I found, who at two years of
age weighed only 15 pounds (some get as heavy as 30 pounds or so, but
most are smaller). Her skin was milk chocolate in colour, thin, wrinkled,
dry, and lacking in elasticity or tone. She had almost no hair on the trunk,
neck, and wear areas such as buttocks, etc. Primary or guard hairs were present
on a few areas of the head and feet, and the rest of the body was either
bald or lightly covered with secondary hairs (puppy fuzz or undercoat), which
were easily pulled out with the fingers. All these signs are very common
in these animals as adults, with the skin ranging from brown to grey in
colour. Dogs which would otherwise be plush or long coats usually look like
Chinese Crested Dogs — if they live to maturity — with feathery fringes around
the ears and feet, and bald elsewhere unless treated with growth and/or
thyroid hormones.
External or obvious characteristics aren't the only things
different about pituitary dwarfs. Blood chemistry tests show that
hormones that are supposed to be circulating may be absent or at very
low levels. The methods are too involved to go into here, but briefly
stated, there are ways to assay the activity of endocrine glands and
amounts of their secretions. The hypophysis (commonly known as pituitary
gland) is the “master” gland of the body, situated in the centre of
the head at the base of the brain. It produces a number of hormones,
including GH (growth hormone). IFG (insulin like growth factor) circulating
in the blood is interdependent with GH. The pituitary gland is affected
by others, but it is more the director of the body’s other endocrine glands,
such as the thyroids and gonads. The thyroids have a say in the maturing
process, metabolism, development of form and behaviour, and physical and
mental activity. Muscular weakness and the skin/hair problems described
above are due to inadequate or absent thyroid activity, which in turn is
due to lack of proper direction from the pituitary. Your veterinarian can
explain T3 and T4 to you if you wish to study thyroid function more fully.
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Priscilla, a four-year-old
pituitary dwarf. Her coat was maintained by regulating her thyroid hormone
levels.
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The effects of
this type of dwarfism can be mitigated or delayed by administration
of thyroxine and GH, but this is a very expensive proposition at present.
It is thought that if recombinant genetics (gene splicing) and RNA production
of human growth hormone becomes feasible, the price may go down. Dogs
apparently respond to human GH, but not the other way around. Eventually,
at the age of normal skeletal maturity or a bit later, the growth plates
in the dwarfs bones close and no further growth is possible, regardless
of GH injections. Another problem in treating the condition is that most
owners don’t present the pups to a veterinarian until their litter mates
are twice their size. The affected pup grows normally until three to
eight weeks, when the brakes are applied and the normal siblings leave
him behind in growth.
Although it is possible that pituitary dwarfism in the GSD
is a polygenic disorder of a threshold nature, most investigators
so far believe it a result of a simple autosomal (not sex linked) recessive
trait. In most characteristics inherited in this simple method, the recessive
gene can be hidden for many generations before it is paired with another
identical recessive gene. Genes operate in pairs, and only when both
of the pair are the recessive alleles, does the trait manifest itself.
When only one recessive gene exists, its dominant partner dictates the normal
or dominant phenotype characteristic. Its like a Labrador Retriever that
inherits one gene for black coat colour and gets the recessive gene for
yellow from his other parent. He himself is black, because that first gene
is dominant over yellow and does not allow the yellow to predominate or
show in the phenotype (appearance).
However, some recessive traits are only partially covered
up by the dominant member of such a heterogenous gene pair. Often, one
can see the faint hint of a saddle in a sable German Shepherd Dog which
is heterogenous (has one sable gene and one black and tan gene). Similarly,
it may be possible to “see” other recessives through the use of blood
tests, examination of the eyes retina, etc. Achondroplastic dwarfism in
the Malamute, for example, is connected with a blood cell disorder, both
being pleiotropic results of the same defective gene. Because of the effect
the pituitary has on thyroid function and on other glands, it may become
possible to detect the “carriers” in a GSD litter among whose members
some dwarfs have appeared. In a statistically typical litter of 12 produced
by two normal appearing carriers of the recessive gene, suppose three
homozygous dwarfs and three pups without the gene. The other six are
heterozygous carriers and appear normal (like their parents) but will
contribute one recessive gene to each pup they produce in the future.
It is unfortunate that such abnormalities are often hidden
from the public by breeders and owners who are fearful, mercenary,
proud, or ignorant. Most pups are sold about the time the growth rate
difference begins, so many cases reported to veterinarians have been
“single incidences” as far as the buyers and their vets could tell. Others
may be put down by embarrassed breeders who don’t want it known they
have produced such anomalies. Since the health of pituitary dwarfs is
more precarious than that of normal pups, it can be assumed that many
that die at birth, are resorbed during gestation, or die before the trait
begins to appear, may be dwarfs. The Arkansas breeder who called me
to ask what she had, and invited me to see them, upon discovering half
her litter were dwarfs, decided not to put them down and cover up, but
rather care for them and share their stories with responsible breeders
and veterinary researchers. She even intended to train and show at least
one in obedience and was, at this first writing, hoping to persuade the
AKC that there are no rules against it. From such an open minded approach,
we may be able to make an educated guess as to pedigree origin of the defect,
plus discover some means of identifying normal appearing carriers.
She even briefly entertained hopes to try breeding these
dwarfs with each other or with siblings or parents, trying to duplicate
the occurrence. I guessed (correctly) that she might find it difficult.
Development of the gonads varies from atrophied testicles and absence
of oestrus to normal testicles and seasons. If she had been successful
in reproducing the condition, we may have seen the AKC faced with difficult
decisions: they cannot justify withholding registration privileges or
show/trial eligibility because of the pure pedigree, so do they create
a separate variety within the breed, as exists in Dachshunds, or a separate
breed as they did with Norwich and Norfolk Terriers? Doubtful. The only
alternative is to keep them in the regular classification and hope judges
will not place them for reasons of not being of sufficient breed type. The
German club has disqualifications for those outside size limits; the AKC
does not. By the way, for several years, a pituitary dwarf attended the
German Sieger Show (as a spectator) and was seen by thousands.
One problem I can foresee in attempts at breeding these,
besides lowered fertility, is whelping. Pituitary dwarfs start life
off at normal size, which for a Shepherd is in the neighborhood of one
pound, give or take about four or five ounces depending on the number
of whelps. If a dwarf bitch were impregnated (artificially, of course)
by a normal sized carrier male, some of the whelps could be normal sized
and the bitch would not be able to pass them or possibly even carry them
without damage to them and/or herself. If a normal sized carrier bitch were
bred to a dwarf male, it shouldn't be any more of a problem than when
two normal sized dogs with the recessives are mated together. So far, nobody
has engineered such a mating, to my knowledge.
Size of the dwarfs varies a great deal. As of this (1984)
writing, the ones I have examined were 5.5 months old and weighed seven
pounds. Others at skeletal maturity (when growth plates close and bones
don’t grow any longer) have been reported to weigh from under 15 pounds
to slightly over 30 pounds. Normal weights for GSD bitches are 55-75 pounds,
and for males 70-90 pounds. It’s not unusual for a bitch to give birth
to ten pounds of puppies, plus carry the extra weight of fluid and placental
tissue. For a dwarf bitch, that percentage would be impossible, I would
think.
The variable size of the pituitary dwarf Shepherds reported
so far is an indication of the possibilities that the trait itself could
be a threshold polygenic trait (unlikely), but the variation could
also result from modifier genes governing varying time of growth cessation.
There are some differences in absence, presence, or level of growth
hormone in untreated dwarfs, and those that grow to be larger than others
before the growth plates close may simply have more GH. Since the “problem”
has been swept under the rug so often, and is rare enough to begin with,
professors at veterinary colleges are in disagreement over the meagre
information that is available. Thanks to the breeder in Arkansas, several
universities and the Morris Animal Foundation were currently studying
the data and the dogs.
This type of pituitary dwarfism involves the German Shepherd
Dog, but a breed from the Russia-Finland? border, called the Karelian
Bear Dog, is also affected. The reason is that the Karelian (Finnish
spelling is Carelian) has the GSD as part of its ancestry, and the affected
individuals had some GSD carriers in their pedigrees. The scientific
literature has reported one Yorkshire Terrier, one “Toy Pinscher”, and
two “Spitzes” as well, but it is highly doubtful that those are the same
genetic defect. If I find several examples, as there are in the GSD, I’ll
withdraw my doubts.
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The author with two littermates
of Priscilla at about 4 months of age.
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Osteochondrodysplasias, Leg Deformities, and
Dwarfism in the Canine
(Part
2 of a series on dwarfism)
©
2004, Fred Lanting
There has been renewed interest in the subject of “abnormal”
bone lengths, joints, angles between limbs, and related phenotypic
variations from what I have called “the ancestral type”. We need to
establish some definitions of terms before entering into a discussion
of the subject. The “ancestral” phenotype in my arbitrary definition
(which, however, is in line with the views of many or most professionals
in animal science) is one that comes to mind when one thinks of the
Jackal, Northern Wolf, and descendants of the extinct Pale footed Wolf
(such as sight hounds). The head is neither brachycephalic (pushed-in/shortened)
nor exaggeratedly long and narrow (the dolichocephalic Borzoi, etc.),
the leg length is such that the total height at withers is roughly twice
the distance from elbow or chest to the ground, and limbs give an impression
of being straight. Typical examples of ancestral types are the German Shepherd
Dog, Saluki, various Spitz breeds, and many pariah breeds such as found
in every corner of the world.
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Figure 1.
Normal proportions and leg length in a Havanese, with about as much chest
depth as the distance from elbow to floor.
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Figure 2.
Chondrodysplastic dwarf “Hav” with bottom of chest well below
the elbow, & with shortened limbs.
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“Abnormal” phenotypes
(and this will rouse the ire of many people who love their dogs and
think of them as being “normal”) include breeds specifically bred to
produce the characteristics that would be agreed on as being “faults”
in the ancestral types. Think of the (“English”) Bulldog, Pekingese, Corgis,
Dachshunds/Teckels, and others. I have long maintained that there is a
genetic defect affecting primarily the hypothesis or pituitary gland, the
“master gland” that so greatly influences the functions of the others as
well as developmental processes.
Some variation within normal parameters results from the
tremendous plasticity of the canine genotype, but here we are more
interested in the departure from those limits of normality. Whatever
the combinations of defective DNA nucleotide pairs (adenine-thymine,
cytosine-guanine, etc.), and which glands or organs they initiate the
changes in, many of the irregularities we are discussing here manifest
themselves in the cartilage that is on the ends of bones and “bone centres”.
Bone centres are those hard, mineralized portions of a growing bone
that become enlarged (almost entirely on their long axis surfaces) and
fused together to form the eventual limb, and the cartilage between most
bone centres is called a “growth plate” or physis. It gradually “calcifies”
into bone tissue, thus uniting epiphysis (called a cap or head, usually)
and metaphysis (shaft); it disappears during maturation. But if there is
an abnormal coding of the nucleotide pairs, there is an abnormal calcification
process, a “growth plate disturbance”.
If one bone in a two-bone limb segment (such as the tibia/fibula
or ulna/radius combinations) has more of a disturbance than the other,
or if one end of the growing bone’s cartilage is disrupted during remodeling
into bone tissue, there are unequal rates of growth and consequent bowing
of that limb, with one part wanting to be longer than the other part
does. In some dogs, disruption of normal cartilage bone turnover at
the ends can keep a single bone from growing in length, or if the disruption
is laterally asymmetrical, the femur or humorous may also become slightly
bowed. The pull of muscles and ligaments on different parts of such bones
also has some effect on shape.
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Figure 5. “Dusty”, side view,
9 months old
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The general definition of “dysplasia” is poor or abnormal
(dys-) shape or form (-plasia). Here, we are talking mostly about bone
(osteo-) and cartilage (chondro-), and mostly about those tissues in
joints. But just as the poet says, “no man is an island”, and genes that
cause one thing can sometimes also cause something else. Some times it
is a very obvious double influence, such as the gene that causes both deafness
and white coat phenotypes in some breeds, or dwarfism and blood disorder
in the Malamute. Most of the time, the influence of one gene or set of nucleotides
is less obvious.
A couple more definitions would be helpful at this point,
although you should realize that there are sometimes loose adherence
to strict interpretation of such definitions:
• chondrodysplasia: any growth plate (cartilage) disturbance
resulting in canine dwarfism; in human pathology, it has a different
meaning: enchondromatosis, a rare disorder marked by enlarged cartilage
and tumours in joints.
• chondrodystrophic: semantically similar to the above,
but while –plasia refers to changeable shape, –trophic refers to growth.
Thus, an abnormal cartilage growth pattern.
• achondroplasia: that type which results in an individual
with extremities shorter than the trunk. Examples in dogs include Basset
Hound, Shih-Tsu?, and others mentioned elsewhere
In humans, it usually is marked by stubby hands, large head
with sunken nasal bridge and, frequently, spinal column deformities.
CHONDRODYSTROPHY
Several breeds are of a body type we call chondrodystrophic,
such as the Dachshund and Corgi. They have shorter legs (often bowed)
and other dwarf characteristics in parts of the body. Frequently, these
breeds also have a shorter vertebral arch that tends to produce a smaller
vertebral canal. The vertebral body centres of ossification unite with
the arch prematurely, with the same type of dystrophic bone growth
pattern that causes shorter “long bones” in those breeds. See Chapter
16 in my 2004 orthopaedics book for more illustrations and discussion
on dwarfism. In some chondrodystrophoid breeds such as the Basset, a
premature closure of the distal metaphyseal plate of the ulna (near the
wrist) was thought by Herron, Grüll, Henschel, and von Hitz to
cause fracture of an already closed anconeal process at the other end
of that limb. Kasström and colleagues (and later, Wind) thought that
this condition in certain dwarfed breeds “was the result of an abnormal
pressure on the anconeal process... by the shortened ulna.” This anomaly
in the anconeal process is not the same as the failure to unite, and obviously
has a different genetic origin. Dr. Wind, the eminent expert on elbows,
has observed that many cases of elbow dysplasias include subluxations associated
with dwarfism.
There are
many types of dwarfing related to slow endochondral bone formation
(at the ends). Dwarfism can be proportionate or disproportionate, depending
on the specific gene defects. Examples of the former include the pathological
pituitary dwarfism of the German Shepherd Dog and the related Karelian
Bear Dog. You can see GSD pituitary dwarfism in “The Total German Shepherd
Dog” (www.Hoflin.com). The non pathologic selective miniaturization seen
in Shar-Pei?, Bull Terriers, Australian Shepherds, Poodles, and numerous
other miniature and toy breeds and varieties probably should not be
included in a discussion of dwarfism. Disproportionate dwarfs include
Bulldogs, Basset Hounds, Pekingese, Dachshunds, Corgis, and many more
that we see only in this form. While some would object to inclusion of
their favourite breed here, it is still true that these are results of
genetic defects. There are also “unnatural” occurrences of disproportionate
dwarfism in breeds where you might not expect it: Malamutes, GSDs, and
a few other “accidentals”. Of course, if one were to deliberately line breed
on these defects, a sub-population of short legged representatives would
be more common. That is what happened with a branch of the Parson Jack Russell
Terrier, now known by several similar names in various show registries.
Some of these defects involve irregularities in the construction
of the hypothesis (pituitary gland), as I have said; others may involve
primary proteoglycans degradation that results in mucopolysaccharidoses,
or other metabolic abnormalities. The various types of mucopolysaccharidoses
involve enzyme deficiencies, incomplete fusion of the sacrum, incompletely
developed vertebral end plates, short limbs, abnormal joint mobility,
and other signs and deformities. Some osteochondrodysplasias (you now
know how to break that word into segments, and what they mean) can be recognized
at birth, others not until skeletal maturity approaches. The most common
seen at birth is the achondroplasias of rabbits, mice, and humans, although
some (erroneously?) apply that term to conditions in dogs, too. Some
achondroplasia is from sporadic mutation, and most seem to be transmitted
by a dominant gene. A few authorities have claimed that achondroplasia
is not seen in the canine, but Aegerter and Kirkpatrick describe it as
a genetic chondroblast (cartilage cell) disturbance in the epiphysis.
Betts calls it “a symptom rather than a disease” and does not hesitate
to apply the word to the “normal” condition seen in the Dachshund, Beagle,
Basset Hound, French Bulldog, Pekingese, and similar breeds. He properly
excludes pituitary dwarfs, miniaturized but proportionate breeds, Malamute
dwarfism, and the dwarfism of Labs with retinal dysplasia. Various forms
of chondrodysplasia affect Cocker Spaniels and German Short haired Pointers.
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Litter mates Angel
(chondrodysplastic Dwarf) and Othello (normal leg lengths)
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Miniature Poodles are occasionally found with a form of osteochondrodysplasia
that has sometimes but properly erroneously referred to as “achondrodysplasia”.
An increased collagen concentration and RNA content is often found
in affected cartilage of such dwarfs, though DNA content is normal. There
are differences in appearance between individuals because of modifier
genes as well as environmental forces. Miniature Poodles with inherited
epiphyseal chondrodysplasia are rhizomelic (it seems the shortness of their
limbs comes primarily from the retardation of growth nearest the hips
and shoulders) and often have ventrodorsal compression of the chest and
enlarged joints. Occasionally a spontaneous mutation will produce symptoms
similar to congenital spondyloepiphyseal dysplasia and “achondrodysplasia”,
and variations on these are seen in many breeds, including multiple epiphyseal
dysplasia in Miniature Poodles and Beagles.
Asynchronous (unequal) growth of the radius and ulna, that
is, when these two bones’ growth rates are not coordinated, is found
in non dwarfs in a wide continuous “spectrum” of severity, often unnoticed
by the average dog observer (and many a licensed dog show judge!). Dwarfism
is often an accompaniment to that asynchronous growth of the “double
bones” in either front or rear limbs. Such dogs also have nearby limb
segments shortened, such as the humours or femur. The more extreme
end of that range is considered by some to be “normal” in some breeds
(to name some more: Corgis, Basset, Lhasa Apso, and Pekingese). However,
elbow subluxation accompanied by pain has been reported in these dwarf
breeds, and probably has a causal connection. While carpal valgus (turning
out at the pasterns) and external rotation of the foot are “acceptable”
within the descriptions of “breed type”, the occasional or perhaps frequent
abnormalities of the ligaments and joints in the elbow that accompany
this should be avoided or treated.
OTHER SIGNS
Chondrodysplasia in the most general sense is sometimes called
a syndrome, other times part of a syndrome, the definition of that
word being a collection of interconnected symptoms. Some dogs may have
many, some a few, and others no readily observable symptoms. The clinical
signs may be very mild, from almost undetectable bowing or shortening
of the legs, to obvious skeletal deformity and the presence of several
health problems. Chondrodysplasia Punctata is one name applied to a syndrome
of multi-systemic disorders, and is so-called because of the “dots” of
calcium phosphate deposits in the softer cartilage. It reminds me of the
school of art made popular by Georges Seurat called “Pointillism”. This genetic-metabolic
problem has various skeletal expressions. Depending on the particular
variety, the mode of inheritance could be autosomal recessive or dominant,
or X-chromosome-linked recessive or dominant, some with full penetrance,
and some not.
Besides skeletal indications, there are eye disorders such
as microphthalmia (smaller eyes than they should be), lens detachments,
cataracts, glaucoma, retinal defects, and nystagmus (jerking or twitching
of the eyeballs). Other occasionally reported symptoms are problems
with internal organs, head and neck bone defects, partial deafness, alopecia,
and luxated patellas (for more on this stifle problem, see my upcoming
orthopaedics book or some of the websites that carry my articles).
PREMATURE PHYSIS CLOSURE
Premature closure of growth plates happens because, in some
etiology (manner), the ossification process of endochondral cartilage
is disturbed. Overfeeding and mineral supplementation are definitely
contributors, but genetic susceptibility has to be taken into account,
as well — probably much more. Ettinger mentions that “the most common
cause of premature growth interference has been direct trauma to the growth
plate area”, though HOD and achondroplasia have also been reported in
association with it. But he and his sources may have been giving too much
credit/blame to physical or mechanical damage. The distal (furthest part)
radius and ulna seem to be the most frequently involved sites for these
disturbances.
Growth disturbances in the radius and ulna can be related
to an outward twisting of the top of the ulna away from a good fit with
the humeral condyles, enough so that subluxation or even luxation takes
place. This lateral rotation may also exist independently, with no observed
growth plate disruptions in those bones. The radius head can also dislocate,
and both may occur at the same time, so there is quite a variety of
changes possible, although the disorder is rare.
If the dislocations are not accompanied by (or secondary
to) such asynchronous growth manifestations as seen in the ulna and/or
radius, they are called congenital elbow dislocations. The premature
closure of physes in ulna or radius, retained cartilage, chondrodysplasia
or achondrodysplasia, and synostosis are separate problems. A condition
of missing digits called ectrodactyly and another abnormality called
cleft hand deformity have been seen in conjunction with congenital luxations
and subluxations (also called arthrodysplasia) in the elbow.
ROOTS OF MANY OF THESE DEFECTS
Cholesterol has had a bad name among fad diet promoters and
people too lazy or busy to physically work off their calories. It is
a product of the liver, necessary for the synthesis of Vitamin D as
well as the assimilation of it, essential fatty acids, and Vitamins A,
E, and K, but in sedentary people and those with genetic inability to metabolize
it correctly, it can build up in the blood vessels and contribute to heart
disease and stroke risk. At least some chondrodysplasias involve an error
in the coding for biosynthesis of cholesterol. Since in the Havanese, a
miniature Cuban breed, those who evidenced this dwarfism tested as having
abnormal levels of several cholesterol related sterols, a program of blood
serum testing was undertaken. It was found that Havanese with normal straight
legs had no such metabolic abnormality. in the body. These vitamins are
needed for calcium utilization, bone development, and healthy eyes. The
appearance of congenital defects, including osteochondrodysplasias, can
often be blamed on inability to use these chemicals. Tracing a structural
defect to its headwaters of a genetic defect expressed in a metabolic disorder
along the route, is akin to finding the source of the Nile or Amazon.
PLEIOTROPIC DEFECTS
Pleiotropy is the phenomenon of having more than one phenotypic
expression (often in grossly different manifestations) caused by the
same gene — the same genetic defect. Alaskan Malamutes’ dwarfism is a
pleiotropic genetic defect that shows up as both dwarfism of their particular
type and a blood disorder. It has been fairly extensively studied, and
while one dog may vary in appearance considerably from the other, the
disorder is a simple autosomal (not sex linked) recessive trait with
complete penetrance. Asynchronous growth of the radius and ulna (one
at a different rate or completion than the other, remember) is part of
the deformity in this breed. The chondrodysplasia in this breed has at
times been mistaken for the Vitamin D deficiency called rickets, but
only the tubular bones are affected, other than retarded ossification
of the lateral tarsal (cuboid) bone. The head, spine, and other bones are
not stunted or changed, and body length is normal. The gene that causes
this chondrodysplasia also creates a macrocytic hypochromic anaemia; the
discovery of this being indicative of the way carriers may be found. A
third effect of this one gene, by the way, is a different ability to bind
certain trace minerals in the liver.
While on a judging assignment in Alaska in the early 1980s,
I was presented with a Malamute from show lines, which had from an
early age walked flat on its wrists. Because the forearm did not appear
bowed I initially thought it might have been a case of carpal luxation
syndrome that I had been seeing with increasing frequency in American
German Shepherd Dogs. I lost track of the owner and did not see any radiographs
or blood analysis. Later, after seeing more Malamute Chondrodysplasia,
I reconsidered my tentative “diagnosis”. I think now that it could possibly
have been both disorders occurring concurrently in the same dog, but
more likely the carpal luxation was a result of the chondrodysplasia gene.
Unfortunately my photographs of that dog were lost, but I later obtained
pictures of other Malamutes, though without the extreme flat carpus.
A few other problems are similar, in that one gene (or gene
pair, really) can cause ocular-skeletal dysplasia in Labrador Retrievers
and possibly Samoyeds, for example. In this disorder, several defects
in the eyeball, iris, and arteries serving the eyes are found in the same
dogs that have short, thick leg bones (micromelia), prominent carpi (wrists)
and elbows, and east west stance in front. Hind legs usually are hyper
extended (straight in stifle) yet still very short.
Great Pyrenees have their own style of micromelic dwarfism,
too, as do a few other breeds. It is a simple recessive genetic trait,
showing some similarities to Malamute dwarfism, and is marked by short
curved ribs, underdeveloped rear limbs, all legs shortened, and abnormalities
in the cartilage and bone of the vertebrae. Endochondral ossification
disturbance can usually be seen on radiographs by 8 weeks. Often, ossification
of the vertebral bodies, especially in the neck, is delayed right from
the beginning, and visible on radiographs taken at 8 weeks of age. The metaphyses
of the radius, ulna, and tibia are usually flared like the bell-bottom trousers
of the hippies in the early 1970s or the sailors of a generation earlier.
The condition does not automatically result in DJD (degenerative joint
disease).
Norwegian Elkhound chondrodysplasia is similar to the other
canine dwarfisms as well as to human spondylometaphyseal dysplasia;
it is widespread in the breed, and may be associated with glycosuria
(sugar in the blood), although in one study this was not found. Some
curvature of the front legs may be noticed as early as 5 weeks of age,
and all limbs are short in proportion to the body. It is also a simple
recessive trait.
A disorder almost identical to the chondrodysplasia in two
of the above-named breeds has recently been found in Akitas. Knowing
how such reports usually lead to the identification of the same disease
in other breeds (as has happened in panosteitis, GSD myelopathy, etc.),
it is not very risky to predict that more will be added to this list
in the future, though not at a high rate, given the very obvious nature
of dwarfism and most breeders’ desires to sweep it under the rug or eliminate
it.
On an excellent website called http://www.rhosyngsd.com/ , there was
a good description and illustrations of dwarfism in the Havanese breed,
and an ancillary discussion of dwarfism in the GSD, even though the site
owner did not want to use that word for the condition. Havanese with
dwarfism display ocular abnormalities as do a few other breeds. the front
legs to grow crooked or bowed, and all four legs are shortened, giving
the height-to-length ratio an undesirably short aspect. Havanese breeders
have reported that all cases of early onset cataracts leading to premature
blindness, and nearly all “other serious health problems reported in Havanese
within the past few years, have been in dogs that also exhibit the symptoms
of chondrodysplasia”. In Havanese, it also has been noted that some dogs
have such subtle signs that they appear to have a straight leg on one
side but not the other — asymmetric. Furthermore, that such asymmetrical
dogs, if they are also diagnosed as having cataracts, will have the cataract
in the eye that is on the same side as the crooked leg! The rhosyn website
mentioned above says, “To date, no Havanese with straight legs have been
diagnosed with early onset cataracts!”
Many other dysplasias considered as a sub category under
osteochondrodysplasias result from disturbed ossification along the
periphery (outer edge) of the growth plates in various bones such as
the ribs, vertebral processes, skull, and elsewhere. Certain dwarfism
characteristics have been made part of the breeds’ show standards and
are not much covered here, but even some breeds that are not normal
skeletally, anyway, such as Dachshunds and French Bulldogs, sometimes
are even more afflicted with chondrodysplasia than their artificially-considered
“normal” compatriots. In many cases, dwarfisms with partial penetrance
or expression may go unrecognized, with the breeder considering the mildly
affected pup to be simply a “runt”.
Recently, some cases of chondrodysplasia/chondrodystrophy
of the sort found in the Corgi have been reported in German Shepherd
Dogs in Australia. The German Shepherd Dog Council of Australia website, http://www.gsdcouncilaustralia.org.au
, has some more details on the investigation there. Some of the
bitches whelping such dwarfs are daughters of popular showdogs such as
Hammer v Waterkant, Lindendale Strike Force, Leitungen Prince Rowdy, and
the highly respected German export Iwan v Lechtal. Cases have been reported
all across the country: in Canberra, South Australia, New South Wales
and Western Australia. One cryptic comment from Downunder was, “The common
denominator in all cases has been the Stud Dog.” I found this dog is Aimsway
Abacus, a son of German import Balou v Eppelin and a local bred bitch, Rakishka
Ali; Abacus line breeding is: Eiko-Vasall? Kirschental (5-5). Most people
are reluctant to `fess up to genetic problems for fear of losing face —
or stud fees. Fortunately, there is a move for openness in Australia concerning
this appearance of achondroplastic dwarf GSDs, even though at this time
it appears the incidence is considerably less than the incidence of
pituitary (proportionate) dwarfism in the GSD that I reported on several
years ago. Some examples of the latter are shown in my GSD book.
Credits: photographs kindly supplied by
Rhosyn kennels in Australia.
photos copyrighted © 2000 – 2003 by Rhosyn:
http://www.rhosyngsd.com/
*************************************
A Small Problem: Dwarfism in Dogs
Confusion
Continues
Fred Lanting
This is a follow up article to the one I wrote entitled “Osteochondrodysplasias”
in February of 2004. While that was a rather long piece, it still
did not address all that people want to know about the subject. Nor
will this, but at least we can look at some other aspects, including
a little deeper delving into the questions about the genetics of dwarfism.
There are miniature and toy versions of “standard” size breeds,
but this is not the same as dwarfism, the latter being the result of
an abnormality rather than a variation within normal limits in genes.
People are always developing miniaturized strains by selectively breeding
small examples to each other, and continuing to select until “regular”
size individuals no longer appear. Some years ago, the heiress to a margarine
fortune started to develop miniature Borzois. While some detractors accused
her of using Whippets to jump start the reduction in size, it really doesn’t
matter much. Livestock breeders know that you can introduce a gene for
some dominant characteristic such as colour, but then keep breeding the
other structural phenotypes back into in the original breed in such a way
that the “new breed” (really a minor variation on the one they started with)
will look and perform no differently, except for that colour. Or whatever
trait they want to introduce.
There is also no reason to believe she did not simply choose
the smallest Borzoi from her extensive kennel and, in successive
generations, bring down the size until the partners would “breed true”,
in regard to that characteristic while not losing proportions or other
qualities. Several years earlier, another woman developed a strain of
Boxers that matured at 12 pounds body weight by selective, not cross-,
breeding. While these examples never caught on, numerous such projects
have, to some extent: the Shar-Pei?, Australian Shepherd, Teacup Poodle,
Bull Terrier, and numerous others. Miniatures do not have enough genetic
change to classify their genes or body phenotypes as “abnormal” and,
with the minor exception of a little difference in the head, miniatures
have the same proportions.
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Karelian Bear Dog.
Some cases of GSD pituitary dwarfism have been found in this breed, but
that is because there is some German Shepherd ancestry in the lines. This
is a normal dog.
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There is a type
of dwarfism that also produces proportional but suddenly smaller dogs.
I say “suddenly” because unlike the “breeding down” through many generations,
proportional dwarfs appear without successively smaller individuals
in the line of descent. So far, I have found the particular type that
I am thinking of, in only the German Shepherd Dog and in a breed with
the GSD in its ancestry, the Karelian Bear Dog. Affected dogs are called
Pituitary Dwarfs because the immediate cause, or at least the noticeable
defect, appears in the hypophysis on the bottom of the brain. The anterior
lobe of this endocrine organ is rightly called the “master gland” because
of its governing or influential effect on other organs, specifically the
glands. Minor abnormalities in this gland are what create the body types
of Bulldogs, the acromegalic Saint Bernard, Dachshunds, and endless other
examples of a departure from the more “normal” or “ancestral” types such
as the GSD, sighthound, Pointer, etc. Anatomic and functional abnormalities
in different parts of the hypothesis make for the difference between the
Boston Terrier and other breeds intentionally selected for their abnormalities,
for example.
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Many Cocker Spaniels have
short legs, but this one has true dwarf characteristics. Exact type of
dwarfism is unknown.
|
Proportional dwarfism
in the GSD is called “pituitary dwarfism” because an old name for the
hypothesis, or part of it, is “pituitary gland”. Since this master
gland controls much of the activity of other glands, it is not surprising
to see abnormalities in thyroid function, and thus the inability to
grow a normal coat. Most pituitary dwarfs look like Chinese Crested or
other “hairless” breeds although by carefully dosing with thyroid hormones
(and possibly the more expensive growth hormones), a normal coat can be
maintained. See my article in the December 1984 issue of Dog World, which
I may re-issue if there is enough interest. We can deduce that it is
caused by a defect in a different part of the pars distalis of the hypothesis
than different types of defects or in different gland parts in other breeds.
We can make such deductions because such breed differences have been traced
to such anatomic irregularities by Stockard and others at least as far
back as the 1940s.
The non proportional canine dwarfs, like their human counterparts,
result from genetic defects that take root in other parts of this
master gland, and therefore other endocrine glands and organs. But
there is much confusion, disagreement, and lack of knowledge leading
to frequently inadequate definitions. In my other article, which you
might call Part One of a trilogy, I mentioned that various terms are
used; I would like to here suggest that we settle on one umbrella word
to cover all or most others: either chondrodysplasia or chondrodystrophy.
The first simply means an abnormal development or shape (-plasia) of
cartilage (chondr-). The latter is “translated” as poor (dys-) growth
(troph-) of cartilage. Either would be a less cumbersome term than I
used as the title of Part Two, osteochondrodysplasias, which includes
the “osteo-” simply to emphasize that the bones are also abnormal. I
think we do not need such a mouthful, and that readers will assume the
inclusion of shortened bones in the term “chondrodystrophy”. A possible
drawback to using chondrodysplasia is that it might someday be confused
with enchondromatosis, a rare disease often involving tumours; these
words are used interchangeably in human medicine. On the other hand,
chondrodystrophy is sometimes used as part of a longer term for different
disorders, also. Most of the time, though, it refers to a congenital
defect in the formation of bone from cartilage.
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Achondroplastic dwarfism
is a different type. It is quite rare in the GSD. These are littermates.
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Achondroplasia
is one of those words that uses the prefix “a-” to denote or connote
an absence or deficiency of something. In this case, it means a lack
of (good) shape, growth, or form of the cartilage. Aplasia, for example,
means “lack of development”, as illustrated in my 2004 book by the radiographic
picture of an Airedale whose acetabulum and top portion of the femur
did not develop at all from cartilage. The achondroplastic limbs of the
Dachshund means that these extremities failed to elongate like the
development in normal dogs. Achondroplasia of the skull is obvious in
the Bulldog. In either example, the word refers to a disordered chondrification
(and of course, later ossification) of the ends of bones. In most breeds,
this is most obvious in the long bones (limbs). It is simply arbitrary
preference that I use the words chondrodystrophy and chondrodysplasia more
often.
But what about the genetics? To even attempt to delve into
the mysteries of inheritance of various forms of dwarfism, one must
be prepared to consider different genetic causes and expressions in
what, on first glance, is easy to assume are the same conditions. Only
by crossbreeding can we make better guesses. A couple of the most active
researchers into inheritance of traits and practitioners of crossing
breeds to get answers were Stockard in the 1920s to `40s, and Whitney
in the `30s to `50s.
Basset breeders know that achondroplasia is dominant
in their breed, and some think that this means the F1 progeny will
always have the same leg length as the Basset. But in crosses between
Bassets and GSDs, typically about half the legs (dogs) are intermediate
in length, the other half being normal (long, GSD type) in length. The
same when a Bassett Bloodhound? with intermediate length legs is crossed
to a long legged dog such as the GSD or any other breed.
Cocker Spaniels often have shorter legged individuals, but
the mutation to achondroplasia is not frequent, and is definitely
recessive. Other races breed true every time, such as Corgis. It appears
that “reverse mutation”, that is, a normal leg length offspring being
produced by two typical Corgis, just does not happen. Yet we know that
we can suddenly find Corgi style legs in pure bred pups of Cocker, German
Shepherd, and other breeds. Corgis (and dogs with this mutation suddenly
appearing) may have a slightly different genetic code and type of dwarfism
than do Bassets and Dachshunds. English Bulldogs seem to have a type
of dwarfism more like the Basset than the Corgi. The short legs of the
Clumber Spaniel or the Beagle are almost certainly not examples of true
dwarfism, as the shapes of the joints and bones are more like those of
the normal length breeds. Sometimes non dwarf short legs are selected
for by misguided breeders (and the judges who reward their dogs!), as
in the cases of modern Golden Retrievers, and GSDs from American or “Alsatian-British”
lines. There is still a great deal to be sorted out, when it comes to
defining the genetic differences in the dwarf dogs. Only when breeders
are open and honest, and share their experience and dogs with researchers,
will we make progress in unraveling the rest of this riddle.
Permission
to reprint this article may only be given by the author Fred
Lanting
Fred Lanting is a German Shepherd Dog breeder,
judge, and breed authority, and is the author of books on Canine Hip
Dysplasia and Other Orthopaedic Disorders. Reprinted with kind permission
of Fred Lanting Author of The Total German Shepherd
Dog. This is the expanded and enlarged
second edition, a "must" for every true GSD lover. It is an excellent
alternative to the "genetic history" by Willis, but less technical and
therefore suitable for the novice, yet very detailed to be indispensable
for the reputable GSD breeder. Chapters include: History and Origins,
Modern Bloodlines, The Standard, Anatomy, The German Shepherd in Motion,
Shows, Showing, and Training, The Winners, Nutrition and Feeding, General
Care and Information, Health and First Aid, Parasites and Immunity, Diseases
and Disorders, The Geriatric German Shepherd, Breeding, Basics of Genetics,
Reproduction, Whelping, The First Three Weeks, Four to Twelve Weeks, Trouble-shooting
Guide
|
© All use of the above
must be by prior permission, and carry this copyright notice. Fred Lanting,
Canine Consulting. Seminars: Canine HD & Other Orthopaedic
Disorders; Gait & Structure (Analytical Approach); more.
Fred is an international all breed judge, and senior lecturer
in anatomy and can be contacted at: mrgsd@hiwaay.net and www.MrGSD.com
Articles can be found on many additional websites.
|
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***********************
Pituitary Dwarfism: The Spectre of the Nineties?
by John
R Walker (1992)
http://www.accdata.co.uk
An Introduction and Summary.
This is one of the more complex bio-medical areas of research,
in any species, and not one which is easy to write about so that the
information can be understood by readers with no relevant training.
I am writing this because I have recently suffered the misfortune
to produce one dwarf bitch puppy ~ full details will appear later unless
I am prevented from doing so. My research into why I produced this defect
from 55/60 German and 59/60 Stud book breeding has frankly horrified
me, but it has not really surprised me, to the extent that I am considering
whether or not to quit the breed.
Pituitary dwarfism was probably first reported by Moch and
Haase (1953) and since then, the defect, or deficiency, has largely
been ignored. At the risk of stating the obvious, for 40 years.
Continuing to call the problem 'pituitary dwarfism' is, in
my opinion, a mistake because it tends to trivialize what I perceive
to be a serious breed problem. It also moves the focus of attention to
the short term; the problem is usually seen and depicted as being no more
than the creation of a few defective puppies that have to be euthanised
and the loss borne.
The true perspective shown by the genetic studies and by
the physiological and biochemical studies is that of a serious long
term problem which I would suggest is probably even serious enough to
endanger the viability or even the survival, of what we regard as the
quality, or top end, of the breed. The problem must show increasing
frequency as time goes on. I believe that the long term viability of the
breed and its current fitness for work have already suffered.
We long since stopped calling this condition 'dwarfism' in
man. It is time we did the same for GSD and started to give the condition
the same serious consideration that we give to it in our own species.
More correctly the problem is not one of 'dwarfism' but apparently one of
pituitary insufficiency or hypopituitarism. The pituitary gland is arguably
the most important gland in the body, sometimes called the master gland.
This controls the function of most other glands in the body and their associated
metabolism, therefore a body existing in a hypopituitary state is, in
effect, fundamentally unhealthy and weak. Remember hypo is low, hyper
is high, relative to the norm.
Amongst other relatives of GSD dwarfs intermediate, that
is predominantly lower, levels of a relative hormone have been shown
in a Danish study (Willeberg, Kastrup and Andresen- 1975 compared with
unrelated 'control' animals. This study concentrated on somatomedins
which mediate the effect of growth hormone in man and dog. A number of
other parallel conditions are known from human studies.
The pituitary gland produces 6 main hormones, with most of
the releasing or effector hormones required being produced in the
hypothalamus, a large gland at the base of the brain - very close
by. In the foetus part of the pituitary is formed from 'brain tissue'
and part from the tissue which forms the roof of the mouth.
There has been extensive study of the hypopituitary state
in man and the physiological abnormalities show a fairly consistent
pattern occurring in a series of overlapping 'stages' each linked to
a particular hormone or group of hormones produced by the pituitary glands.
One of these conditions is the human dwarf condition. Most
physiological and biomedical and hereditary mechanisms are remarkably
similar between man and dog in most respects - this is how we seek
to justify allowing Beagles to smoke cigarettes and so on. It is therefore
entirely reasonable to expect to see predominantly the same pattern
of 'stages' appearing in GSD's. The physiological, biomedical and hereditary
evidence appears to support this hypothesis from the literature and
from my own limited observations.
What we see in the 'dwarf' puppy is effectively a serious
(usually terminal) case of hypothyroidism where the sufferer has also
failed to grow - growth hormone and thyroid activity are largely controlled
by the pituitary gland. In physiological/pituitary biochemical terms,
the growth hormone insufficiency can be regarded as 'stage 2'. The hypothyroid
condition can be regarded as 'stage 3'.
'Stage 1' is death; the Danish, Australian and my
own observations all note still-born and short lived (fading) puppies
associated with the production of 'dwarfs' and, again, there is an obvious
link to the pituitary hormone (endocrine) system.
The main genetic studies (Andresen and Willeberg 1976), (Andresen
1978) and (Nicholas 1978) show adequately that the genetic mode of inheritance
is simple autosomal recessive, though the Danish population was highly
inbred and polygenic, threshold inheritance cannot be ruled out entirely.
Assuming that the autosomal recessive theory with a possible
gene-dosage effect is correct, then this mean that the normal state
is dominant and that two affected animals must be mated in order to
produce a dwarf puppy. It also means that heterozygotes (carriers of
the affected gene) appear to be perfectly normal, fully grown animals.
Herein lies part of the problem. It is therefore possible to mate a carrier
dog or bitch to a normal partner ad infinitum without producing a dwarf
puppy or seeing any other problem which one might immediately associate
with 'dwarfism'. Many breeders will be doing this unwittingly as I have
done. This in turn produces a further 50% of carriers and only 50% normal
animals. In this way a pool of defective genotypes with apparently normal
phenotypes is being created unseen.
When two carriers are mated the situation gets worse. In
theory (remember these figures only apply to large populations and
not necessarily to individual litters of puppies) then the ratio of
carriers remains the same at 50% but the ratio of normal animals produced
falls to 25% with the other 25% being 'scrap' as dwarfs or dead puppies.
This is the normal Mendelian 1:2:1 ratio and the Danish, Australian and
my own ratios agree fairly well with the prediction. In this case two
thirds (67%) of the survivors are defective genotypes; but they all look
normal.
The other side of the problem lies in the evidence that apparently
normal looking carriers do, in fact, have abnormal hormone balances.
They are probably not normal fully functioning animals but are animals
which function under pysiological/biomedical stress. In consequence
these animals will be less viable than truly normal animals and will
show tendencies arising from physiological stress; typically a predisposition
for infection, deficiency diseases and reduced fertility, libido as
well as possible character and temperament problems, which we can all
do without. In other words, they may well be costing more than the average
in veterinary services.
I have identified a number of possible deficiencies from
the human condition and I have been able to correlate these (in theory
at least) with some of the known health and management problems which
have come to prominence in the breed over the last 10 to 20 years- problems
which have not been explained to my satisfaction by other hypotheses.
It is my belief that efforts should be made to identify those
animals within the breeding population which carry the defective genetic
material and that these animals should be graded out of the breeding
population - voluntarily by preference and by compulsion if necessary.
In severity I have come to regard the problem as being slightly
less serious than haemophilia and slightly more serious than Hip Dysplasia.
I fully support the Kennel Club in their stand against haemophilia
by requiring known affected bloodlines to be tested clear prior to
registration. I do not support the call for limitation on hip scores
prior to registration or breed surveying. This reflects the reliability
of the tests currently available upon which to make the value judgment.
I am particularly keen to prevent the importation of more
defective genotypes. The problem with hypopituitarism is that there
is no accurate canine test available at the moment.
However, a major immuno-dignostic biochemical manufacturer
with many years of experience in the human condition is currently developing
a canine version of one of the standard human tests at their veterinary
research and development centre in Germany. This test, or developments
from it, may well be able to identify the carriers from the normal animals
in the breeding population. If a reliable cost effective test can be
produced then I certainly recommend that it should be used on animals
from relevant bloodlines and that stud dogs and brood bitches should
be advertised as being 'clear' of this problem.
The other method of identifying bloodlines at risk is by
pedigree comparisons. I have already started a database of affected
bloodlines on a pedigree recording program which should assist in the
identification of the heterozygotes (carriers) in the population.
I would be pleased to hear from any breeder who has produced
a 'dwarf' puppy of known descent - confidences will be honoured if
requested. Obviously, a combination of testing and pedigree recording
would be better still.
The Danish work shows that the problem is one which must
affect virtually every important German bloodline since the War. I
am not interested in pre war genealogy. I do not know whether the defect
arose as a mutation around that time or if it carried through. I am only
interested in the effect this defect through modern bloodlines is having
on the breed now and for the future.
Many of the known carriers are VA (Excellent Select) animals
which derive from the German inbreeding
program to rebuild the breed after the war time depletions. The flow
chart fig.1, shows part of the production arising from two matings between
Lex Preußenblut and Maja vom Osnabrücker Land. Lex Preußenblut
died young in suspicious circumstances but it has not been possible to
determine whether either, or possibly both, were heterozygotes (carriers)
or not.
Rolf (SZ640721) and Rosel vom Osnabrücker Land(SZ640725)
are effectively implicated as carriers (Andresen 1976 & 78) though
Ina (SZ693527) may have escaped. Hein vom Richterbach (SZ700070) and
Vello zu den Sieben-Faulen (SZ 935874) are effectively implicated as
carriers though Cäsar von der Malmannsheide (SZ862862) may
have escaped. In fig.1 an unshaded symbol means either a normal animal
or status unknown.
The Australian work (Nicholas 1978) implicates Vello as the
ancestor of 7 out of 8 dwarfs in his study. In modern pedigrees I would
also pick out Lasso di Val Sole (SZ1378829) twice Italian Sieger (1978&79)
and Uran vom Wildsteiger Land (SZ1526684) twice German Sieger (1984&85).
Both these important sires are included in the pedigree of my own recent
'dwarf' litter within 4 generations.
Although the physiological evidence has been around since
the 1950's, the genetic and some biochemical evidence has been around
since the 1970's the probable implications appear to have been overlooked,
misunderstood, or deliberately covered up. Is this the breed's best
kept secret? Or is this the breed's second best kept secret after haemophilia?
References:
Andresen, E. (1978) Herkunft und Verbreitung von hypophysaren
Zwergwuchs bein Hund und Grundlage zur Ermittlung von Anlagetragern
verschiedener genetisch bedingter Krankheiten unter Andwendung biochemischer
Methoden - Kleintier Praxis 23:66-74. Andresen, E. & Willeberg, P.
(1976) Pituitary Dwarfism in GSD: additional evidence of simple autosomal
recessive inheritance- Nord Vet. Med. 28:481-6 Moch, R. & Haase,
G. (1953) Hypofunktion der andenohypophyse eines hundes- Tierarztl Umsch
8:242-4 Nicholas, F.W. (1978) Pituitary dwarfism in GSD's: a genetic
analysis of some Australian data- J. Sm. Anim. Pract.19:167-74 Willberg,
P., Kastrup, K.W. & Andresen, E. (1975) Pituitary dwarfism in
GSD's- studies on somatomedin activity- Nord. Vet Med. 27:448-54.Willis,
M.B. (1991) The GSD- A Genetic History. HF&G Witherby p.82&p.84.
This article can only be reprinted with permission from
author
The above information is simply informational.
It's intent is not to replace the advice of a veterinarian nor to assist
you in making a diagnosis of your pet. Please consult with your own veterinarian
for confirmation of any diagnosis. Your pets life may depend on it.