Back to the title page | E-thesis main page

4. REVIEW OF THE LITERATURE

4.1. THE FINNISH KENNEL CLUB CONTROL PROGRAMME (PEVISA) FOR CANINE GENETIC DISEASES

4.1.1. Background

Increased knowledge of canine inherited diseases, their pathogenesis and genetics promoted the need for control measures. Hip dysplasia (HD) was the first disease that was commonly considered a genetic defect which needed strict control programmes. After Schnelle (1954) proposed the first classifying system in 1954, control programmes were started in many countries in the late 1950s and other countries followed in the 1960s (Paatsama,1962; Paatsama, 1978; Paatsama, 1979; Freudiger at al., 1973; Bargai et al., 1988; Hedhammar, 1991; Hedhammar et al.,1996; Willis, 1997; Paatsama, 1998).

Since then control programmes for other inherited diseases, e.g., elbow dysplasia (ED) and inherited ocular diseases, have also been established in many countries (Jolly et al., 1981; Bedford, 1989; Walde and Neumann, 1991; Anon., 1993; Paatsama, 1978; Hedhammar et al., 1996). The first PEVISA programme was started in Finland in 1984, when hip radiographs of parent animals were required for retriever breeds as a prerequisite for litter registration. In 1988, the first Finnish eye screening programme was established for collies and Dobermans. The present directives for the Finnish Kennel Club Control Programme for Canine Genetic Diseases ( PEVISA ) were accepted by the Council of the Finnish Kennel Club on 20 November, 1993 (Anon., 1998).

4.1.2. Present situation

Ninety-two breeds have an official PEVISA programme. Breeds, diseases included in the programme and restrictive methods for each breed are accepted by the Board of the FKC after an application from the official breed club. The application of a breed club must be accepted in two general meetings of a breed club, and it must be based on previous screenings or other results that confirm the disease frequency or its clinical importance to the breed.

The programme is based on obligatory screening of all breeding animals. All screened animals must be identified either by tattoo or a microchip. All screening results are registered by the FKC and are public to breed clubs as well as breeders. In some breeds only screening is compulsory, but for some breeds and diseases, screening results may forbid a dog from being used in breeding.

4.1.3. Genetic diseases in the Finnish Kennel Club Control Programme (PEVISA)

4.1.3.1. Orthopedic diseases

Hip dysplasia

Canine hip dysplasia is commonly considered to be a quantitatively inherited trait. Heritability estimates between breeds in different studies vary from 0.17 to 0.6 (Fisher, 1979; Lingaas and Klemetsdaal, 1990; Swenson et al., 1997A; Tomlinson and Mclaughlin, 1996). Environmental factors -- such as feeding and exercise -- and their role in development and severity of hip dysplasia have also been widely studied and discussed (Aichinger, 1997; Brass,1989; Schwalder et al., 1996; Swenson et al., 1997A; Tomlinson and Mclaughlin, 1996).

The PEVISA hip dysplasia control programme is based on subjective evaluation and scoring of standardized radiographs. The scoring is done according to the FCI-scoring system (Brass and Paatsama, 1983) by veterinarians authorized by the FKC. For 73 breeds, hip scoring is demanded before breeding. Thirty-two of these breeds have threshold scores for hip dysplasia that exclude a dog from breeding. These threshold values vary between breeds: in some breeds only dogs with no signs of hip dysplasia (grades A and B) can be used for breeding, and some breeds discard only the most severe form of hip dysplasia (grade E).

There are different opinions as to the clinical importance of hip dysplasia and of the possibilities to predict the development of clinical signs from radiographs. Joint laxity has been shown to be important in predicting hip dysplasia and degenerative joint disease. Susceptibility for degenerative changes has also shown to have significant between-breed variation, e.g., German Shepherds seem to be more prone to develop degenerative joint disease than Rottweilers (Lust, 1997; Popovitch et al., 1995; Smith, 1997). Also the reliability of subjective scoring systems has been questioned (Stur et al., 1996; Flückiger, 1997; Smith et al., 1997), but no objective system has yet been presented.

Elbow dysplasia (ED)

Elbow dysplasia (ED) is a developmental disorder of the elbow joint. ED was reported in the veterinary literature for the first time in 1974 (Olsson, 1974) and ever since, its importance as a cause of forelimb lameness has been widely recognized. The term ED includes several different pathological changes in the elbow joint such as fragmented coronoid process (FCP), osteochondritis dissecans (OD) and ununited anconeal process (UAP) (Gröndalen, 1979; Hayes at al., 1979; Studdert et al., 1991). Elbow dysplasia is shown to be a quantitatively inherited trait with moderate heritability (Guthrie and Pidduck, 1990; Gröndalen and Lingaas, 1991; Swenson et al., 1997B).

The screening protocol for elbow dysplasia was developed by the International Elbow Working Group (Paatsama, 1992; Audell, 1993). In Finland, screening for elbow dysplasia was started in guide dogs in 1978 and more widespread voluntary screening for risk breeds in the 1980s (Paatsama, 1984; Mäki, 1998). Bernese Mountain Dog was the first breed to be officially screened for ED in 1994. At present 14 breeds have obligatory elbow screening in health programme. Standardized radiographs are evaluated by the same veterinarians who score hip radiographs for the FKC. Elbows are scored from non-affected (grade 0) to affected from grade I (mildly affected) to grade III (seriously affected).

Patella luxation

Either medial or lateral patella luxation has been diagnosed in numerous breeds, but typically it is seen in small toy or terrier breeds. The severity and clinical symptoms of the luxation vary. Congenital anatomical deformities of the hind leg cause recurrent luxation with no trauma association (Piermattei and Flo, 1997).The inheritance of patella luxation is not clear, but breeding with affected animals is not advisable (Putnam, 1968; Priester, 1972). Patellar examination was added to the control programme of the Finnish Spitz in 1994, and currently palpatory examination for patella luxation is required for six breeds. The palpation is done according to a certain protocol, and there are approximately one hundred veterinarians with special training who are entitled to issue official patella certificates. Especially toy breed clubs promote voluntary examination before accepting dogs in breeding. These unofficial certificates are not registered with the FKC.

4.1.3.2. Ocular diseases

The FKC gave authorization to few veterinary ophthalmologists to give official FKC eye certificates in 1985. Before that time unofficial certificates were given by some veterinarians who had specialized in ocular diseases. The first official control programme for inherited eye diseases was started 1988 when an eye examination certificate based on an ophthalmological examination was required for Dobermanns and collies that were supposed to be used for breeding. At present there are 19 approved eye panelists who examine about 8000 dogs annually (Liman, personal comm.). Forty-five breeds have obligatory eye screening and in 20 breeds the diagnosis of inherited ocular diseases will exclude a dog from breeding.

Collie eye anomaly (CEA)

CEA is a congenital disease of the posterior parts of the eye. It is caused by a defect in embryonic differentation. It has been diagnosed in collie breeds and is thought to be an autosomal recessive trait (Yakely et al., 1968; Rubin, 1989). Ophthalmoscopically, CEA is usually divided in three form. Chorioretinal dysplasia (CRD) is the mildest form and may have very little effect on sight. These minor changes are found best in puppies under three months of age. Later these changes can be hidden by retinal pigmentation, and dogs can be classified normal in ophthalmoscopic examination. Coloboma of the optic disc can vary in size and effects. Small colobomas have little or no effect on vision, but large colobomas may cause marked reduction of vision. The most serious form of CEA is retinal detachment, often accompanied by intraocular bleeding. Detachment can be congenital or usually occurs early in life -- before seven weeks -- but it can also appear later, then usually between one to two years of age. Retinal detachment causes severe loss of vision and in serious cases total blindness (Bjerk s, 1991; Narfström et al., 1997; Rubin, 1989).

Glaucoma

Glaucoma is perhaps the most painful eye disease in dogs. It can be secondary due to some other ocular disease or primary that is due to an inherited defect in the aqueous drainage pathway (Bedford, 1997). Primary glaucoma can be subdivided into narrow-angle and open-angle type. Cottrell and Barnett (1987) have showed the angle closure form to be dominantly inherited in Welsh Springer Spaniels, and open-angle glaucoma in Beagles is caused by an autosomal recessive gene (Gelatt and Gum, 1981). In other affected breeds the mode of inheritance of narrow-angle glaucoma has not been established yet. Typical breeds for the disease are spaniel and spitz breeds. Narrow-angle glaucoma is usually diagnosed in middle-aged or older dogs. Toy and Miniature Poodles can be affected by both open-angle and narrow-angle glaucoma. There is a need for further studies to establish the mode of inheritance of glaucoma in most breeds affected. (Barnett, 1988; Smith, 1989; Gelatt, 1991).

Hereditary cataract (HC)

Inherited cataract can sometimes appear congenital and is often associated with other ocular malformations, such as microphthalmia. In most affected breeds the mode of inheritance has not been established. The more common form of inherited cataract is developmental. Then the symptoms can be seen later in life. Cataract has been proven or is suspected to be hereditary in many breeds and the list of affected breeds is continuously growing. There is a great variety among different breeds concerning the age of onset and the speed of progression. The shape and location of cataract opacities also have some breed specificity. In some breeds there even seem to be two different forms of inherited cataracts: an early-onset, rapidly progressing form and a late-onset, slowly progressing form, both of which are supposed to be caused by different genes (Narfström et al., 1997; Barnett, 1988; Smith, 1989; Dodds et al., 1981).

Lens luxation

Lens luxation affects mostly terrier type dogs, usually at three to four years of age. It is a displacement of the lens due to the degeneration of its suspensory apparatus. In most patients lens luxation can lead to secondary glaucoma. Recessive inheritance has been shown in several terrier breeds and Border Collie (Barnett, 1988; Rubin, 1989; Bedford, 1997).

Persistent hyperplastic tunica vasculosa lentis / persistent primary vitreous (PHTVL/PHPV)

Persistent hyperplastic tunica vasculosa lentis / persistent primary vitreous is a congenital eye anomaly that has been described in detail by Stades (1980) in Dobermanns in the Netherlands. Further studies in Dobermanns and also in Staffordshire Bull Terriers could prove the disease to be inherited, the mode of inheritance in Dobermanns is probably incomplete dominant (Stades, 1983). For Staffordshire Bull Terriers, also autosomal, recessive inheritance has been suggested (Leon et al., 1988). It has also been suggested that heterozygous dogs might be phenotypically free or show grade I signs (Stades, 1983; Leon et al., 1988). There are also clinical findings of PHTVL in other breeds, but their number is so small that no conclusion about inheritance can be made. Clinically PHTVL can be divided in subgroups according to the severity of the symptoms. PHTVL can be diagnosed already in puppies, although mild, grade I cases can sometimes be misdiagnosed as free, when not examined biomicroscopically. More severe forms can also be difficult to distinguish from primary cataract or retinal detachment (Stades et al., 1991; Boeve et al., 1992; Bjerk s ,1990; Narfström et al., 1997.)

Progressive retinal atrophy (PRA)

The name PRA covers several types of retinal dysplasias or degenerations. All forms of PRA are progressive and inherited, although there is great variety in expression and etiology in different breeds (Clements et al., 1996; Petersen-Jones, 1998). Ophthalmoscopically PRA is divided into generalized and central PRA. Central PRA is also called "retinal pigment epithelial dystrophy" (RPED). Generalized PRA has proven to be inherited recessively; the only exception is the Siberian Husky, which has sex-linked inheritance of PRA (Acland et al., 1994), the inheritance of RPED remains unclear (Bedford, 1997). There are proofs for both recessive and dominant inheritance, and environmental factors may also have a role in expression (Bedford, 1989; Bjerk s,1991A; Narfström et al., 1997).

Retinal dysplasia (RD)

Primary retinal dysplasia is believed to be inherited as an autosomal recessive trait. It has been described in a number of breeds with a large variety from spots around retinal vessels to complete detachment of the neuroretina. Retinal detachment causes total blindness, but dogs with retinal folds have practically no impairment of vision. Retinal dysplasia can also be secondary due to intrauterine trauma, maternal infections or various other causes (Barnett, 1988; Bedford, 1997; Narfström et al., 1997).

Superficial punctate keratitis

Superficial punctate keratitis is seen occasionally in all breeds, but most commonly in the Longhaired Dachshund thus causing suspicions of genetic background. The disease has been suggested to have recessive inheritance (Brandsch and Nicodem, 1982). It is supposed to be immune-mediated, but the pathogenesis is not totally understood (Rubin, 1989; Narfström et al., 1997).

4.1.3.3. Other diseases

Dobermann hepatitis

Dobermanns have high incidence of chronic liver disease that is reported to have genetic background (Speeti, 1998). Dogs in a subclinical stage of the disease have continuously elevated liver enzymes (Speeti et al., 1996). Since 1995, all breeding Dobermanns must have two liver enzymes -- alanine amino transpherase and alkaline phosphase -- examined less than 10 months before the dogs are accepted for breeding.

Copper toxicosis

Inherited copper toxicosis is an autosomal recessive disease of Bedlington Terriers Clinically the disease manifests itself as acute or chronic liver failure, but many dogs can remain asymptomatic for long periods in spite of copper accumulation in the liver (Johnson et al., 1980; Eriksson, 1983; Herrtage et al., 1987). The disease can be diagnosed from liver biopsies, but recently also a DNA marker test was developed (Binns, 1997). In Finland, since 1 January, 1998 all breeding Bedlington Terriers have to be tested either with liver biopsy or DNA test.

Familial nephropathy

In the English Cocker Spaniel an autosomal, recessive form of familial nephropathy is known (Steward and Macdougall, 1984; Nash, 1989). According to the PEVISA scheme no offspring of an identified carrier is registered, but no diagnostic or other control measures are required.

Mitral valve insufficiency

The Cavalier King Charles Spaniel is shown to have higher prevalence of mitral valve insufficiency at a younger age than other breeds on average (Häggström et al., 1992). Another study indicated that the development of mitral insufficiency in this breed is due to a polygenic threshold trait (Swenson et al., 1996). Since 1997 a certificate of heart auscultation has been required for Cavalier King Charles Spaniels before breeding.

4.2. HEALTH PROMOTION AND HEALTH PROGRAMMES

4.2.1. Implementing a health programme

4.2.1.1. Programme planning

Traditionally health programmes have focused on primary prevention or health protection, that is on disease avoidance or control of disease incidence (Stachtchenko and Jenicek, 1990; Beitz, 1998). For a successful prevention programme the disease in question must meet certain criteria:

  1. The disease frequency must be sufficiently high to make the disease economically or socially important to control in target population (Jolly et al., 1981).

  2. The incidence of the disease within a breed must be verified with appropriate surveys and screening (Jolly et al., 1981; Rubin 1989; Slater, 1996).

  3. The disease must be well-defined and described in order to enable the diagnosis.

  4. Diagnostic methods and tests should be simple enough and economically feasible (Jolly et al., 1981; Rubin 1989).

  5. In the case of controlling inherited diseases the mode of transmission of the disease in question must be known (Rubin, 1989).

  6. The goal of the control programme, which may be either complete elimination or reduction of the incidence, must be established by the key groups, e.g. a breed club, breeders and dog-owners. Clearly defined objectives and consensus about the goals of a programme among various groups is essential for the success of a programme.

  7. Because primary prevention demands active involvement of key groups, test methods and control measures should be acceptable to them. This requires educational measures, so that key groups learn to understand the rationale and importance of the programme and also modify the actions accordingly (Jolly et al., 1981; Rubin, 1989; Beitz, 1998). Key groups' own success in establishing programme goals and measures used ensures that key groups find the programme useful and beneficial to them and thus motivates target groups for better commitment, which is vital for maintaining a functional programme. Without realistic goals and objectives commitment is difficult to achieve.

4.2.1.2. Programme evaluation

A successful health programme needs careful evaluation. Evaluation can be aimed at the process, impact or outcome of the programme (Downie et al., 1992). Evaluation is needed to assess the methods and the use of resources, as well as the short-term and long- term effects of the programme and ethical considerations (Downie et al., 1992; Beitz, 1998). Without clear objectives evaluation is very difficult. Thus objectives should be specific, measurable, achievable, results-oriented and timely (SMART). Unrealistic expectations of the programme's impacts can lead to disappointments; thus early evaluation should have emphasis on the process itself and not yet on the outcome (Downie et al., 1992). Evaluation of economic benefits can be difficult and misleading: economic measurements that are able to take all of the actual costs and benefits into account are in most cases very difficult to construct. Also in many cases measurements of short-term economic results is done, but evaluations of future benefits are forgotten or in practice impossible to perform (Richardson, 1998). In many cases the outcomes and benefits of a health programme are not economic, but focus instead more on disease prevention, individual or social well-being. Depending on the disease in question and the anticipated outcome, measurements of benefits can be made with appropriate clinical trials or health surveys (Stachtchenko and Jenicek, 1990; Richardson, 1998).

4.2.2. Values, attitudes and health behaviour

4.2.2.1. People and pets

Animals can have different roles in people's lives: they can be objects or status symbols for their owner's ego or they can be used, for work for example in hunting (Beck and Katcher, 1983; Savishinsky, 1986). In modern society companion animals are more and more seen and treated as human beings that serve their owners as friends, partners, children or child substitutes. A pet may even act as an extension of its owner, when the owner projects his or her own personality onto the animal and absorbs the animal's nature (Beck and Katcher, 1983; Savishinsky, 1986; Serpell,1986; Hirschman, 1994 ). On the other hand for some people a dog can be an aid for example hunting or other work or a producer of merchandise (puppies) to sell. Thus the treatment a dog gets and decisions an owner makes for a dog can be dependent of its role and very variable according to the owner's attitudes to and expectations of a dog.

4.2.2.2. Attitudes, information-search and decision strategies

Knowledge and information is necessary but not sufficient to appropriate health behaviour (Rudd and Glanz, 1990). This is valid in a person's own behaviour and decision making , but also in decisions and actions a dog-owner or a breeder takes for his or her animal. Information must be relevant and understandable to a target group to ensure effective communication, well-informed decision making, satisfaction and co-operation between customers and providers (Joos and Hickam, 1990). A person's health behaviour and attitudes can be affected by his or her personal feelings of self-management or social reactions to his or her attitudes. Also, initiation and maintenance of health-related behaviour need different conditions (Siegrist, 1988). Attitudes are acquired through personal experiences and are relatively stable. However they can change or be changed. This change most often takes place through new information which is inconsistent with a person's previous attitudes and beliefs. The change is affected by the type of information, the communicator's prestige and assumed intentions as well as by the target groups' previous commitments, likes and dislikes or how appealing they find the new information (Downie et al., 1992).

Information search and methods of handling the information in decision-making processes can greatly vary according to a person's level of expertise. In their decision-making processes experts and consumers focus on different types of information and handle the information differently. In addition to cognitive activity in decision making and behaviour, consumer choices are based on emotions. Consumers judge the information more based on subjective feelings and make holistic classification and choices (Alba and Hutchinson, 1987; Elliot, 1998). Social environment has more effect on consumers than on experts: consumers are more likely to make decisions which they find socially acceptable. Also, they tend to avoid unpleasant knowledge, and they interpret information so that it is emotionally more pleasing to them (Elliot, 1998).


Back to the title page | E-thesis main page