info for hc

HC

HC was first described in Staffords over 30yrs ago although anecdotal evidence suggests that cases had been occurring for many years previously. The main ophthalmologist involved was Dr Keith Barnett, who published much of the early work, and it was clear that it was hereditary in its transmission and that a defective recessive gene was involved. A list of affected dogs and carriers was published at the time. This resulted in considerable acrimony, which may have led to matters being hushed up, and we ought to be aware that some of the dogs on the list might have been misdiagnosed as ophthalmic tests were not as good as those of today. Since then cases have occurred spasmodically but it gained greatest prominence a few years ago when a top quality red dog turned out to be a carrier along with other dogs and bitches which were closely related. Prior to that there was the well publicised case of two rather unrelated brindles being bred together producing three litters containing a number of affected offspring.

Clinically, cataracts develop in a puppy's eyes and, in time, progress so the sight is totally lost. It is important to note that both eyes are affected and that the condition is progressive. Initially it was thought that HC developed from about six to eighteen months of age with later onset being highly unlikely. This belief came about as it was between those ages that owners might become aware that their dogs' eyes were ‘not quite right' or that they were becoming increasingly opaque as the cataracts developed. Consequently it has sometimes been claimed that if it started under six months old it could not be HC – this is not true! . Using state of the art testing, the early changes may be detected very early, possibly around 9-10wks, maybe even at 8wks, old.

As stated above, it was soon clear that it was inherited via a recessive gene. This means that both the sire and dam of any affected puppies must be carriers of HC even although both do not suffer from it. Let us call the normal gene ‘X' and the bad recessive ‘x'. As a dog has two copies of the gene, one being inherited from each parent, it may therefore be: ‘XX' – normal sight and a non-carrier; ‘Xx' – normal sight but a carrier capable of passing the defective gene to offspring; ‘xx'- clinically affected and which will pass the gene on were it ever to be bred from. When two carriers are mated the offspring will, on average, be 25% affected, 50% normal but carriers, 25% normal and non-carrier. Looking at it another way, this means that any unaffected sibling of an affected dog has a two-thirds chance of being a carrier. It should also be noted that roughly a quarter of puppies from the brindle mating referred to above were affected, as could be expected. Some have forgotten about this brindle pairing and allowed discussion to concentrate on the problems encountered in reds. This is most unfortunate and it must be stressed that HC is not related to colour in any way whatsoever; it is just coincidence that the main problems recently have been in reds. In fact if you trace back the pedigrees of those red dogs for over seven generations you will encounter brindle carriers identified 30yrs ago.

(It is also of interest that Boston Terriers may also suffer from HC, which is virtually identical clinically to that in Staffords. If this is proven to be to the same genetically then it may be postulated that the defective gene was present, or originated, in the bull and terriers crosses of around 200yrs ago, from which both breeds were developed.)

The only treatment available for HC is surgical removal of the cataracts which is very expensive.



PHPV

This was first described in Staffords in the 1980's although there are earlier reports of it in Dobermanns in Holland . PHPV is the failure of the blood vessels supplying the developing eye of the puppy in the womb to wither and disappear completely by the time it is born. The amount of material remaining is variable. In mild cases there may just be some spots, or possibly a small encapsulated cataract, behind the lens while more severe cases will have greater quantities of residue from the foetal blood vessels.

In Staffords, mildly affected dogs are unlikely to have any further problems and will go through life as if nothing was amiss. However more severe cases have a high risk of problems, such as the development of secondary cataracts, which may lead to loss of vision. Both eyes are usually affected, as with HC, but unilateral cases with only one eye involved are not uncommon with PHPV, especially if mild.

There is little doubt that PHPV in an inherited condition. There have been several suggestions for its mode of transmission but none have been substantiated so for the moment we have to accept ‘We simply do not know'.



EYE TESTING



Responsible breeders have for many years have been getting their dogs eyes tested by the ophthalmologists to ensure they are clear clinically of HC and PHPV. The earliest and one of the best times to test is when puppies are 6-7wks old and many breeders test whole litters at this age – the importance of this cannot be over-stressed! A definitive affected/unaffected diagnosis of PHPV can be made at this stage; consequently puppies may then be sold as being free of the condition or sold, if not seriously affected, as pets with endorsed papers to prevent their being bred from. However no decision can be made on HC at this early age so testing when older needs to be undertaken. Normally it is recommended that dogs are tested when 18mths old and certainly before being bred from. It should be realised that failure to test breeding stock might leave the breeder open to litigation should any of the conditions appear in the offspring.

The need for subsequent testing is debatable. If a dog passes its eye test for HC and PHPV at 18mths or older then it may be considered clear for life. However some breeders re-check at intervals when older or maybe before further litters. This may be regarded as unnecessary but they must be complimented for being so conscientious. Some vets too may suggest that all dogs, including Staffords, are re-tested yearly. This would seem to be to ensure that no other conditions, such as those that occur commonly in other breeds, have developed. Some may consider this wise but others might think it a ploy to fill the coffers. It is up to individuals to decide, especially as nothing more is likely to be found.

The testing of eyes is done mostly under the KC/BVA scheme with all reports being submitted and published in the Breed Record Supplement. Some testing may also be done under the European scheme but results of this are not made public. The KC/BVA scheme operates through a network of vets, with the necessary training in ophthalmology, covering the country. These vets will do the bulk of the testing and owners usually go to their local one for initial tests. If necessary the vet may suggest, and the owner may request, a second opinion arranged through the scheme co-ordinator or by reference to the Ophthalmology Dept. of one of the University Veterinary Schools. In fact it is recommended that the owner of any dog failing its eye test through HC or PHPV should seek a second opinion to confirm the diagnosis.

To the layman a diagnosis of affected or unaffected for HC and PHPV seems to be as clear as night and day. However this may not always be quite as simple as one might think as a case that occurred not so long ago exemplifies. A bitch was failed by one vet, so we were told, but then passed by one of possible greater experience. This led to some heated and forthright comments on the internet which could have produced a disastrous loss of confidence in the system, despite none knowing precisely what the initial vet had said to the owners. As people only take in part of what they are told and relaying the tale further leads to increasing distortion of the truth, it is easy to understand how matters can spiral out of control. The fact is that the vets can, and do, have problems. Eyes that are crystal-clear are no bother but often material, such as vitreous strands and debris, may be found within the eye. The question is one of deciding if this is significant of a pathological condition and, if so, is it inherited. It may be that no decision can be made in some instances, especially with young dogs, and re-testing a few months later may be necessary to see if there have been any changes or further developments. Any vet with a problem will frequently discuss the findings with the ‘top men' to ensure the diagnosis is as accurate as possible. Of course the odd vet may not be as good or as conscientious as we would like – it is to be hoped the system weeds them out but bear in mind the option of a second opinion.

i've read this on another site, very informative, are your staffs tested ?

yes they are