As with all breeds, there are certain conditions and health issues that pug breeders need to be aware of. Many can be minimised or avoided by breeding with knowledge and conscience. It is possible to test potential breeding stock for some issues, and many responsible breeders now do so. The following health tests are available.
Inbreeding coefficient (COI) The Inbreeding Coefficient is a measure of how closely related two pugs are, and therefore how ‘inbred’ the puppies of a potential mating between the two will be. By their nature, all pure breeds have a reduced level of genetic diversity. Indeed, breeders will often ‘line breed’ (a form of inbreeding) to cement ‘good’ traits within their line. There is, of course, a danger of it also cementing bad traits. In particular, inbreeding can cause the rapid build-up of disease genes in a population.
The website of the English Kennel Club (www.thekennelclub.org.uk) has a free and easy service called Mate Select where the Inbreeding Coefficient can be instantly calculated by inputting the sire and dam registered names. All pug breeders should avail of this service when planning a litter.
The Inbreeding Coefficient is expressed as a percentage. A score of 100% would mean that the two animals are genetically identical clones. A low score means that the sire and dam are not closely related, and the resulting puppies are genetically diverse. Breeders should aim to produce puppies with a very low COI. The average COI within the breed is currently 5.7%. Breeders are recommended to aim for litters that score lower than this.
Patellar Luxation Many small breeds, including pugs, can suffer from this orthopaedic condition where the rear knee joint is mis-formed and the knee cap slides out of its groove as the dog moves. It is more common in females than in males. It may affect one or both knees. A vet can diagnose luxating patella by feeling the joint. On every routine visit to the vet before a pug is two years of age, breeders should ask the vet to check the patellas. The condition is at least partly genetic. Affected dogs should not be bred from.
Hip Dysplasia This is another orthopaedic condition that can affect pugs. The hip socket is poorly formed causing lameness and arthritis. Unlike patellar luxation, hip dysplasia requires a general anaesthetic for diagnosis. For this reason, general screening is not recommended. (This situation may change in the future. One company in Ireland has started scanning puppies for hip dysplasia without sedation being required.) Should a pug be diagnosed with hip dysplasia, it should not be bred from. The condition is at least partly genetic.
Pug Dog Encephalitis (PDE) PDE is an inflammatory disease of the central nervous system causing seizures, depression, wobbliness, and blindness. It is progressive and fatal. It is likely that many pugs in the past have been incorrectly diagnosed with epilepsy, when the illness was in fact PDE. PDE is a hereditary disease. There are a couple of laboratories that test for PDE. The test involves a simple swab from the pug’s mouth. Tested pugs may be N/N (clear of PDE), N/S (carriers, at low risk of developing PDE), or S/S (susceptible to PDE). Pugs that are S/S should not be bred from. Carriers (N/S) may be bred from. Comprehensive breeding information for tested pugs comes with the results and on the laboratory websites.
This is a simple test, and isrecommended for all breeding pugs. PDE Testing kit can be ordered from the following websites:
Hemivertebrae Hemivertebrae is a malformation of the spine causing pain, loss of use of the hind legs, and incontinence. The symptoms vary across a range. Mildly affected dogs may live relatively normal lives. Badly affected dogs may require extreme surgery or euthanasia. The disease is believed to be genetic, possibly linked to the genes for a curly tail. As yet, the genes responsible have not been identified and there is no genetic test to identify carriers or affected dogs.
Diagnosis of hemivertebrae required a radiograph under general anaesthetic. The UK’s Pug Dog Club currently runs a screening programme and are encouraging pug breeders to have their pugs radiographed. (http://pugwelfare-rescue.org.uk/hemivertebrae-screening-scheme/) At present, most breeders feel that the general anaesthetic involved is too risky.
Breeders should not breed from affected pugs, and should be very careful if breeding from a line in which hemivertebrae has been recorded.
Eyes Pugs are prone to Brachycephalic Ocular Syndrome. Their flat faces, over-nose wrinkle and large eyes, can result in eye problems. Large eyes are easily damaged and ulcerated. If the over-nose wrinkle is too large, or the eyelashes and whiskers are incorrectly formed, secondary entropion, trichiasis, and pigmentary keratitis may result. Specialist eye vets can examine the eyes to identify potential problems. One possible schedule is to have a pug’s eyes tested at 6 months, 1.5 years, and then every 3 years thereafter. Potential problems that can be identified include:
Lagophthalmos - the inability to completely close the eyelids
Dry Eye (Keratojunctitvitis Sicca) - a disorder caused by lack of tears or excessive evaporation
Entropion – the eyelids are rolled in causing the lashes to rub off the eye.
Trichiasis – an ingrowing eyelash
Pigmentary Keratitis - a dark film that grows over the eye causing blindness. Many older pugs become blind due to this condition.
Pug breeders should always aim, through careful choice of sire and dam, to avoid breeding puppies with over-large eyes, over-large nose wrinkle, or misformed lashes and whiskers.
Brachycephalic Obstructive Airways Syndrome (BOAS) All brachycephalic (short-faced) breeds, including pugs will have less free breathing than long faced breeds. Problems arise in dogs that are badly affected. They may find breathing difficult, especially during exercise or hot weather. The Dept. of Veterinary Medicine at Cambridge University (UK) is currently undergoing research, and has an excellent website (http://www.vet.cam.ac.uk/boas/about-boas). All breeders should make themselves familiar with the symptoms of BOAS, and should aim to breed any breathing problems out of their line through careful choice of sires and dams.