Wednesday, 30 April 2014

Von Willebrand Disease In Dogs Disease Treatment

The existence of Von Willebrand disease in Drahthaar has come to light, in my knowledge, many years ago, while researching the topic on the Dobermann.
Trying data on the Dobermann I came across those concerning the Kurzhaar; to which, given the close relationship between Kurzhaar and Drahthaar, I started to wonder if they were also affected mustachioed beautiful hounds.

I thought, as usual, to be a little 'paranoid health and instead ... although in United Kingdom there is total silence on this issue has not been hard to come across web sites and scientific articles that deal with the von Willebrand factor in Kurzhaar and Drahthaar: stands among all the club's website Verein Deutsch Drahthaar breed American (VDD / GNA) that talks about it extensively urging farmers to tests in their subjects.

But let's step back, wondering what is Von Willebrand disease: it is a disease of the blood present in people and animals who, in affected individuals, effects similar to those of hemophilia: blood does not clot or struggling do it and it is easy to attend to bleeding.
disease is named after its discoverer, Erik Adolf von Willebrand, a Swedish doctor who spotted her in 1926 as a common disease in the populations of some islands in Sweden and Finland.

Von Willebrand disease is caused by a deficiency of a clotting factor called von Willebrand factor or, in abbreviated form, vWF.
Von Willebrand factor is a large glycoprotein that works in harmony with another protein (FVIII: c): together they form the Factor VIII important for the process of blood clotting.
Regarding the dog, there are three types of Von Willebrand factor, so classified according to which the constituents of the molecule (multimers) fail fail in vWF:

The type 1 (lack of generalized multimers) - that is the most common type, the least severe and affects especially the Doberman Pinscher (but can also be found in other breeds such as the Weimaraner, the Bernese Mountain Dog, German Shepherd, Manchester Terrier, the Shetland Sheepdog and others). It is transmitted as an autosomal dominant trait with variable penetrance and expressivity.

The type 2 (lack of high molecular weight multimers) - rarer is more serious (it is found in Kurzhaar and Drahthaar). It is transmitted as an autosomal dominant trait with variable penetrance and expressivity.

The type 3 (absence of von Willebrand Factor) - extremely rare and severe because there is no production of von Willebrand factor. There are families of the Chesapeake Bay Retriever, Scottish Terrier Shetland and pastors affected by Von Willebrand disease type 3. It is transmitted as an autosomal recessive trait.

The majority of patients with von Willebrand disease type I can live a relatively "normal", this also applies to Drahthaar suffering from Type II: dogs can live as normal even if it is wise to pay close attention in the case of surgery, illness or accident. Recall that a trivial injury can cause death by exsanguination in the case of dogs with low production of vWF and are passed to chronicle the cases of specimens not identified as suffering from Von Willebrand disease, died of hemorrhage as a result of trivial surgeries.

In puppies excessive bleeding during caudectomia, removal of the spurs or the eruption of the teeth are a first sign and should alert owners and von Willebrand elevator.other lights are repeated and prolonged nosebleeds and excessive blood loss in case of scratches and minor injuries. In some specimens the von Willebrand factor is accompanied by hypothyroidism and it was noted that appropriate therapies for this hormone disorder leading to a "lift" of the vWF.

Similarly, also hormonal changes related to estrus and pregnancy, infection or depression of the immune system can lower the amount of vWF in the blood.
The Von Willebrand disease is undoubtedly an inherited disease, but the mode of transmission is not constant in all dog breeds.

That type 3, which is in Scottish, is called autosomal recessive.
What does this mean?

They are called autosomes all chromosomes except the X and Y chromosomes (those which determine the sex of the animal): the disease is not linked to the X or Y chromosomes and, therefore, its transmission is not sex-linked. Calling recessive mean that a dog, to be considered clinically affected, must bring in its genetic make-up of a pair of mutated genes must be homozygous for the gene that is mutated (ie have "mutated" is the gene received from his mother that one received from the father ): if the mutated gene was only one this dog would be called "bearer" (capable of transmitting the mutated gene to 50% of offspring), but not clinically affected by Von Willebrand disease.
In Drahthaar things get complicated, and Von Willebrand disease is inherited as an incomplete dominant trait.
for incomplete dominance means that the characters are not exactly a parent dominant over those of the other, but the characters have quantitative characteristics and the children have become an intermediate amount of the two characters.
easy to understand One example is the intersection of the Andalusian Chickens: chicken chicken blue + white = gray chicken.
Regarding the von Willebrand Drahthaar is also spoken in the character of penetrance and variable expressivity.

penetrance represents the frequency (number of patients) of the disease: not all individuals with the genotype of their patients manifest the disease phenotype. For example, if we say that a disease has a penetrance of 70% only 70 individuals out of 100 resulting suffering.
expressivity is instead the intensity with which nature manifests itself: we know that the amount of von Willebrand factor present in Drahthaar with the mutated gene ranges between 0% and 49%; the percentages of subjects to the limit or borderline range between 50% and 69% and between 70% and 180% in healthy subjects (guideline values) 1.

The distinction between healthy carriers and is actually much more nuanced because the penetrance and variable expressivity in addition to the examinations carried out incorrectly and / or to the fact that the amount of von Willebrand factor in the blood can change over time: hard therefore tell if a person is healthy or borderline carrier of the disease.
Similarly, subjects whose von Willebrand factor is below the norm may be suffering from the disease or simply be carriers, the carriers themselves (at the genetic level) can show or less a tendency to bleeding.
Overlapping percentages between carriers and is normal due to the expressivity and penetrance variables in addition to the examinations carried out incorrectly and / or to the fact that the quantity of von Willebrand factor present in the blood can change over time .

Measurement of vWF is carried out with a laboratory technique ELISA (Enzyme linked immunosorbent assay) that search for the factor vWF antigen.
IL vWF found is measured and compared to that of a healthy specimen.
Unfortunately, the amount of vWF in the blood is a simple and quantitative analysis can not tell us clearly whether a person is perfectly healthy (that has the pair of genes that encode the normal vWF) or carrier (has one of the two mutated genes), and then capable of transmitting the disease. The quantitative analysis while remaining a useful tool in the selection to which all, in the absence of alternatives, should resort, has its limits.
In 2002, however, a new study conducted by Cornell University 2 has identified the heritability of vWF concentration of 0.52% and, by analyzing a population of 331 Draahthaar model using a single locus with two different prediction models , was able to match the amount of vWF genotypes.
Consequently, according to the study, the subjects with AA have a quantity of vWF less than 1% while healthy carriers can be confused in the range of 68-72%.
Abstracts the study is available on Medline.
The American Kennel Club Verein Deutsch Drahthaar (VDD / GNA), the forefront with regard to the von Willebrand factor, leans against the laboratory of Hematology comparative Cornell University where he is currently also running a study on von Willebrand the Irish Setter .

The contact details are:

Marjory Brooks, DVM Dip. ACVIM
Comparative Hematology Section
Diagnostic Lab-Cornell U

In United Kingdom, the Foundation for Animal Health (FSA) is responsible for research and control of Von Willebrand disease.
Foundation for Animal Health was founded in 1992 by the SCIVAC (Society Companion Animal Veterinarian) and is based in Cremona, one of its goals there is the study and reduction of hereditary diseases in dogs and cats.
FSA is connected to similar institutions, research centers and breed clubs all over the world, to its interior there are scientific committees formed by experts, there is also a commission for the study of diseases of the blood.
For some breeds, identified the mutation, it has been developed a test that can identify the affected gene at the molecular level suffering from the DNA of the subject under consideration.

In 2004 a group of researchers has identified the mutated gene responsible for von Willebrand's disease type II in a family of Kurzhaar and Drahthaar.
research of the mutation by PCR (Polymerase Chain Reaction) has made ​​it possible to program pairs capable of producing puppies exempt.
It only remains to be hoped that this test will soon become a mass consumption and use, as well as abroad in United Kingdom.


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