ABOUT HV (HEMIVERTEBRAE)

Hemivertebrae are bones of the spine that are abnormally shaped. Because of their abnormal shape these bones tend not to align correctly with their adjacent bones in the spine. This can lead to instability and deformity of the spinal column, which in turn can lead to the spinal cord or the nerves arising from it becoming compressed and damaged. This causes pain – which can be severe – wobbliness (ataxia) on the hind legs and can also cause loss of hind leg function and incontinence (inability to control passing urine or faeces).

Pain from spinal cord compression can be severe. Affected dogs can also lose function in their hind legs and sometimes lose bladder and bowel control. Not all animals with hemivertebrae develop symptoms, some just have mild signs of ataxia and some have no signs at all.

Dogs with severe clinical symptoms may need major surgical interventions by specialists, which have their own welfare impacts, and, despite this, some may not recover and need to be
euthanised on humane grounds.

Young dogs are most commonly affected when problems associated with skeletal deformities develop as their skeleton grows. The clinical signs associated with the condition can develop rapidly over days, or gradually over weeks and months. Severely affected individuals would, without surgery, have permanent major disability. Even where surgery is possible, some animals may have unacceptable levels of disability necessitating euthanasia.

Therefore this condition can severely limit both the quality and length of life.

The Pug breed have a scheme in place that is recognised by the Kennel Club and generously supported by Dick White Referrals near Newmarket who will examine and give their expert opinion on every X ray sent to them at no cost to the Pug owner. This scheme is gathering information that will be used for research in the future as well as determining the scale of the problem and enabling breeders to make more informed decisions.

For full instructions on how to participate in this screening process, please see below.

HEMIBERTEBRA SCREENING PROCEDURE

These notes describe the Hemivertebrae Screening Procedure and provide helpful instruction to those participating in Screening. They have been effective from 1 January 2013 and are subject to change.

Introduction

Hemivertebrae (HV) is a thought to be an inherited condition, but environmental factors may influence the development of the condition. Screening results do not therefore absolutely reflect the transmission of HV of an individual animal but should be regarded only as an indicator of risk of the condition.

1. Why Screen?

The main purposes of screening is the examination of radiographs of the spine for hemivertebrae and the issue of a report in respect of that examination. The examination is conducted by the evaluation of a radiograph for any anatomical and pathological changes indicative of HV and a report is created. Many clinically sound dogs may show signs of HV in their radiographs and should not therefore be used for breeding. The scheme does not cover any other hereditary or clinical defects which may need to be considered when choosing suitable breeding stock.

2. How to Submit a Radiograph to the Scheme

The owner should approach their veterinary surgeon and request that the dog be radiographed for this screening scheme. For this scheme, the dog should be at least 12 months old – there is no maximum age. The dog should also be permanently identified by ideally microchip, or tattoo. When arrangements with the veterinary surgeon for the dog’s spine to be radiographed have been made, the owner should take the Kennel Club (KC) registration number or certificate, if available. In addition, the owner must complete and sign the first section, Section A, of the Submission form (the Owner’s declaration) to confirm the details relating to the dog being screened.

The following procedure should be observed: –

The minimum age of a dog for submission under the Scheme is 1 year. There is no upper age limit – The dog must be permanently identified by either microchip or tattoo – The Kennel Club (KC) Registration Certificate of the dog if it is registered with the KC. The Downloaded Submission Form must be presented at the time of screening.

3. Process for Radiography of the Spine

A lateral and Ventrodorsal/dorsolateral radiograph of the thoracolumbar spine segments is required for scoring. The veterinary surgeon should radiograph the dog’s spine as indicated below.

a. Safety. The Guidance Notes for the Safe Use of Ionising Radiations in Veterinary Practice (1999) should be followed. Since the radiography of dogs for the purposes of this Scheme would not constitute exceptional circumstances: – It is necessary to employ general anaesthesia, narcosis or deep sedation to enable only mechanical (i.e. non-manual) restraint for the positioning of the animal. – Collimation of the primary beam should be clearly visible on the radiograph.

b. Positioning. A standard position for radiography must be employed. Accordingly: – The dog should be placed in latero-lateral and ventro-dorsal view of the spine form T1 to L7 centred on T8-L1 – In order to have a diagnostic radiographic study the dogs should be anesthetised or sedated.

c. Confirming Identification. To confirm the identity of the dog, both the Kennel Club registration number (if applicable), and the microchip or tattoo number should be radiographed onto the film or digital image. For dogs not Kennel Club registered, the breed club or veterinary practice identification should be used. In addition, the date of radiography and the marker(s) should be included

d. Images. To assist in the best possible assessment of the radiograph, please ensure that the exposure and processing is checked before submission to the scheme. It may be useful to check the radiograph immediately after processing, in the event of incorrect positioning or problems with film quality. Digital images may be submitted, but should as DICOM files, one dog per disc. This must include the KC registration number, microchip/tattoo number and date of radiography as part of the original image.

4. How Results are Reported

The results of the screening scheme will be provided to the owner of the dog. The veterinary surgeon who has undertaken the radiograph should have confirmed the identification of the dog (including KC number, microchip/tattoo) and confirm this by signing the middle part (Section B) of the certificate. The veterinary surgeon assesses the radiograph, to determine presence/absence and if present, a description of the severity of the condition. A report will describe the presence, severity, and treatment recommendations, if applicable.

5. How Results Are Used

The results of the radiograph will be reported to the submitting veterinary surgeon within 1 month of the correct submission. The owner will receive a photocopy of the certificate, from the submitting surgeon, with the completed original retained by the veterinary surgeon. Relevant details of the report may be sent to a geneticist for statistical analysis as arranged by PDWRA. Should copies of the certificate be required, they will only be supplies to the owner originally identified on the HV certificate. This may incur an additional fee.

The X ray can be submitted either electronically or on a disc by post accompanied by the completed submission form to –

Giunio Bruto Cherubini DVM, Diplomate ECVN, MRCVS European Veterinary
Specialist in Neurology, RCVS Recognised Specialist in Veterinary Neurology,
Hon. Assoc. Professor in Veterinary Neurology – University of Nottingham

Dick White Referrals, Six Mile Bottom, Cambridgeshire, CB8 0UH, United Kingdom

Tel: 44.01638.572012 | Mob: 44.07817761970 | Fax: 44.01638.572013

E: gbc@dickwhitereferrals.com | Visit Website | Download Screening Form

QUESTIONS AND ANSWERS ABOUT HEMIVERTEBRAE (HV)

Hemivertebrae (HV) – and butterfly vertebrae – are congenital vertebral malformations that result when the vertebrae are not developed properly. HV is seen commonly in small brachycephalic breeds of dogs (screw-tail breeds). In fact the kinked tail can be secondary to HV in the tail vertebrae. Thus, the occurrence of this problem in certain families of dogs suggests the possibility of a hereditary problem. The wedge-shaped vertebrae deformity can lead to secondary progressive spinal cord compression. This may become sufficiently severe to cause marked progressive neurological deficits affecting the pelvic legs. In this case, neurosurgery is the only treatment, but this option is available in only a few specialist neurosurgery centres such as Dick White Referrals.

It is important to remember that Pugs can suffer from many other neurological spinal problems such as slipped disc, spinal cord malformation, spinal cyst, degenerative spinal cord diseases etc. Thus, any Pug with neurological problems, should be assessed by a specialist veterinary neurologist.

This is a very important point and only the results of ongoing research will be able to tell us if this is an hereditary condition. Thus, dogs with any congenital anomaly should not be used for reproduction, even though this carries a risk of losing other good breed qualities. Until further scientific information becomes available, it is advisable to use common sense and caution in the presence of hemivertebrae in Pugs. The HV problem can be in fact be prevented by intelligent breeding practices.

It is necessary ONLY if you wish to breed from your dog.

There is a general feeling that this is a quite wide spread problem in Pugs and many are euthanised due to this, although many breeders report never having seen dogs with it. Only by screening will we be able to assess the prevalence of the condition. Although the condition can be treated surgically, there are very few neurosurgery centres in the UK able to perform the necessary neurosurgery. Dick White Referrals is one of the few.

At the moment there is no DNA test. This congenital malformation is also most likely to be caused by the combination of complex hereditary disorders rather than a simple single DNA abnormality.

To obtain radiographs of diagnostic value, the Pug needs to be positioned perfectly on the radiographic table and this is difficult to obtain in most dogs with sedation alone. Poor quality radiographs can cause difficulty in making a proper diagnosis of presence or absence of HV.

Specialist anaesthetists feel more secure having small brachycephalic dogs  (with possible upper airway problems) anaesthetised, rather than just sedated. Thus most of them are VERY reluctant to sedate any Pug. So whilst anaesthesia is preferred radiographs will be accepted for dogs that have been sedated.

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