Genetic testing of Belgian Shepherd Dogs – what have we learned so far?

The Belgian Shepherd Dog is an alert and energetic medium size dog breed that originated in Belgium where it was used to herd sheep. Nowadays the Belgian Shepherd is a versatile sport and working dog, as well as show dog and family pet. The four breeds/ breed varieties are Tervueren, Malinois, Groenendael (Belgian Sheepdog in US) and Laekenois. The breed varieties vary in coat texture, length and color.

During recent years, a number of Belgian Shepherd owners and breeders have opted to test their dog with the Optimal Selection™ (US) / MyDogDNA® (Europe) DNA testing service. This DNA test provides the owner with results for more than 180 inherited disorders, 20 traits including coat color and coat type variants, and genetic diversity information for the individual dog and the overall breed population. We are now in a good position to look back and summarize what we have learned about the Belgian Shepherd Dog through genetic testing to date.

Genetic diversity in Malinois and Tervueren is higher than average for purebred breeds

We measure a dog’s genome-wide diversity by screening thousands of sites in its DNA and calculating the number of measured genetic sites at which the dog is heterozygous, i.e. has inherited a different allele (genetic variant) from its dam and sire. When looking at all dogs we have analyzed so far taken together, we find that the genetic diversity in the Belgian Shepherd Dog Malinois and Tervueren populations is higher than in purebreds in general. The median heterozygosity level in Malinois is 38.9% and in Tervueren is 35.4%, compared to the overall purebred median of 33.8%. The heterozygosity level of Groenendaels (33.6%) is slightly lower than the purebred median. (Figure 1.) Only a few Laekenois dogs have been tested, but the results indicate high genetic diversity (41.4%). Another reference point to illustrate the scale on which the provided heterozygosity values should be interpreted is provided by mixed breed dogs, with a median of 43.3%.

High genetic diversity in Malinois most likely has a historical background since the World Wars did not have such devastating effect on the Malinois as they did on the Tervueren and Groenendael. Populations of Tervueren and Groenendael were diminished drastically during the World Wars and the breed had to be restarted almost from the beginning, creating a massive population bottleneck effect. Whereas, the Malinois population survived better through the wars and reached its original population size and quality in a shorter time than other Belgian Shepherd breed varieties.

Figure 1: Genetic diversity in Belgian Shepherd Dogs Malinois, Tervueren and Groenendael

The Optimal Selection™ / MyDogDNA® test measures a dog’s genetic diversity by screening thousands of sites in its DNA. Frequency graphs depicting the diversity distribution and median within the breed are drawn, enabling comparison to the broader purebred population, or mixed breed dog frequency distribution curves. These graphs are available online in each dog’s report, and are updated with each tested dog.

Belgian Shepherd Dogs have medium to high level genetic diversity compared to other popular breeds tested. The Parson Russell Terrier and Danish-Swedish Farmdog are examples of extensively tested breeds that show high levels of genetic diversity. On the other hand, the Kromfohrländer and Cavalier King Charles Spaniel are examples of abundantly tested breeds that have very low genetic diversity. (Table 1.)

Maintaining and even improving genetic diversity is important for every breed. It is particularly important for breeds in which the genetic diversity level is already low. Low genetic diversity predisposes the dog to recessively inherited hereditary disorders by increasing the risk for inheriting the same recessive disease mutation from both of its parents. Low genetic diversity may also increase the risk for autoimmune disorders and predispose to inbreeding depression.

Table 1: Heterozygosity Level in MyDogDNA/Optimal Selection tested breeds

Breed Tested Dogs Median heterozygosity level Heterozygosity range
Mixed Breed >100,000 43.4% 16.5 - 50.7%
Belgian Shepherd Dog - Laekenois 4 41.4% 34.7 - 41.7%
Danish-Swedish Farmdog 300 - 500 41.4 % 32.6 - 46.3 %
Parson Russell Terrier 300 - 500 41.4 % 29.0 - 46.3 %
Barbet 100 - 300 40.9 % 31.8 - 46.5 %
Jack Russell Terrier 100 - 300 40.8 % 28.0 - 47.0 %
Chihuahua 100 - 300 39.8 % 22.2 - 45.7 %
Coton de Tulear 300 - 500 39.4 % 29.9 - 44.9 %
Finnish Lapphund 100 - 300 39.1 % 29.3 - 45.4 %
Havanese 100 - 300 39.0 % 26.1 - 44.4 %
Belgian Shepherd Dog - Malinois 66 38.9 % 25.1 - 43.2 %
Boerboel 300 - 500 38.9 % 26.1 - 43.5 %
American Hairless Terrier 100 - 300 38.6 % 26.1 - 43.5 %
Dutch Shepherd Dog - Shorthaired 100 - 300 38.4 % 27.2 - 43.9 %
Australian Shepherd 300 - 500 38.3 % 26.5 - 46.2 %
American Staffordshire Terrier 100 - 300 37.7 % 21.4 - 43.9 %
Papillon 100 - 300 37.0 % 24.3 - 41.6 %
Yorkshire Terrier 100 - 300 36.4 % 19.7 - 43.4 %
Border Collie 100 - 300 36.3 % 24.3 - 45.8 %
Rhodesian Ridgeback > 500 35.7 % 24.1 - 41.3 %
Labrador Retriever > 500 35.6 % 22.6 - 46.0 %
Lagotto Romagnolo > 1 000 35.4 % 20.5 - 42.5 %
Belgian Shepherd Dog - Tervueren 54 35.4 % 29.3 - 41.1 %
Beagle 100 - 300 34.5 % 22.9 - 43.4 %
Finnish Hound 300 - 500 34.3 % 28.1 - 38.9 %
French Bulldog 300 - 500 34.3 % 24.0 - 41.3 %
Old English Sheepdog 100 - 300 33.7 % 22.3 - 39.4 %
Belgian Shepherd Dog - Groenendael 78 33.6 % 18.9 - 42.2 %
English Springer Spaniel 100 - 300 33.1 % 13.1 - 42.2 %
Curly Coated Retriever 100 - 300 32.3 % 20.4 - 41.4 %
Golden Retriever 300 - 500 32.0 % 19.6 - 41.6 %
Briard 100 - 300 31.6 % 24.3 - 38.2 %
German Shepherd Dog 300 - 500 31.5 % 22.8 - 46.5 %
Whippet 100 - 300 31.3 % 18.0 - 41.1 %
Finnish Spitz 100 - 300 31.2 % 21.4 - 39.2 %
White Swiss Shepherd Dog 100 - 300 31.2 % 22.6 - 37.4 %
Norwegian Elkhound, Grey > 500 31.0 % 23.5 - 39.7 %
English Cocker Spaniel 100 - 300 30.3 % 21.2 - 42.7 %
Swedish Vallhund 300 - 500 30.2 % 17.6 - 35.6 %
Shetland Sheepdog 100 - 300 29.8 % 21.6 - 38.0 %
Bernese Mountain Dog 100 - 300 29.6 % 18.0 - 46.4 %
Flat Coated Retriever 100 - 300 29.5 % 21.4 - 36.2 %
Rottweiler 100 - 300 29.4 % 24.2 - 35.1 %
Bulldog 100 - 300 28.0 % 19.8 - 36.4 %
Chinook 100 - 300 28.0 % 20.0 - 46.6 %
Dutch Shepherd Dog - Rough-haired < 100 26.7 % 23.7 - 44.1 %
West Highland White Terrier 100 - 300 26.7 % 17.3 - 34.6 %
Dobermann 100 - 300 26.4 % 19.5 - 34.9 %
Dandie Dinmont Terrier 100 - 300 26.3 % 21.1 - 30.4 %
Kromfohrländer 100 - 300 26.0 % 20.4 - 45.2 %
Cavalier King Charles Spaniel 100 - 300 25.4 % 14.7 - 30.6 %
Dutch Shepherd Dog - Longhaired < 100 25.4 % 19.4 - 43.8 %

 

Populations do not differ significantly between countries

Genetic diversity in Belgian Shepherd dogs does not differ significantly between countries. The majority of the tested dogs are from the United States and European countries such as Finland, United Kingdom, Netherlands, Austria and Czech Republic. Genetic diversity in the Belgian Shepherd Malinois and Tervueren seems to be slightly higher in the United States than in Europe, and European Groenendael dogs have slightly higher genetic diversity than the US population. All tested Laekenois dogs are from Europe. (Table 2.)

Table 2: Genetic diversity of Belgian Shepherd Dogs in US and European populations

  US US Europe Europe
  Tested Dogs Heterozygosity Level Tested Dogs Heterozygosity Level
Malinois 47 39.02 % 11 38.26 %
Tervueren 37 35.21 % 17 34.92 %
Groenendael 56 33.23 % 20 34.43 %
Laekenois 0   4 41.40 %

Belgian shepherd dog varieties do not seem to have evident genetic differences between US and European countries. Tested dogs from different countries all cluster together in multiple dimension scaling plot analyses without showing distinct subgroup separation between countries (Figure 2, and see interactive graphs online: https://www.mydogdna.com/crm/index.html#en/breeds). The Finnish population of Tervueren and Groenendael dogs are genetically more similar than the US population. However, there are fewer dogs tested in Europe than there are in the United States. Most of the tested Belgian Shepherd dogs in Europe are from Finland.

Figure 2: Genetic relationships in Belgian Shepherd breed varieties Malinois, Tervueren and Groenendael

Each tested dog is represented by a dot in the graph. The graph reflects how similar or different the genomes of dogs are within breed/breed variety. Dogs with similar genomes cluster together, distanced from dogs that differ genetically from them.

Breed varieties differ genetically

In contrast to the lack of clear genetic differences within breed varieties, evident differences are seen when comparing breed varieties to one another.

Common historical background of Tervueren and Groenendael can be seen as genetic similarity of these two breed varieties. Tervueren and Groenendael dogs are known to descend at least partly from the same founding dogs. In addition, Tervueren-Groenendael crosses were accepted until 1963 without permit of exemption from the breed’s country of origin.

Malinois and Laekenois dogs group together as very closely related varieties. Malinois and Laekenois descend at least partly from the same breed founders, and Malinois has been used in Laekenois breeding over the years to bring in new genetic material/variation to this small numbered breed variety, which could explain that they seem to be genetically very similar. (Figure 3.)

Many countries allow crosses between certain Belgian Shepherd varieties and occasionally puppies of different varieties can be born within the same “purebred” litter of one variety. This is reflected in the graph as some dogs that differ genetically from the main populations of the breed varieties.

Figure 3: Genetic relationships and average genetic differences in Belgian Shepherd breed varieties

The graph shows how closely related the different breed varieties are. The table shows an average genetic difference percent between and within groups. Every group in the plot has a row and a column in this table. Each number in the table shows the average difference between individuals in the column group and the row group. The difference is shown as a percentage of the measured positions in the genome. The smaller the difference, the darker the number's background. The exact percentage is not shown when there are too few individuals tested in the group (e.g. within the Laekenois group).

On average, Groenendael individuals (25.5%) are more genetically similar to other Groenendaels than Tervuerens to other Tervuerens (26.9%) and Malinois to other Malinois (29.0%).

Groenendael dogs are, on average, 28.7% different from Tervuerens, but 34.8% different from Laekenois and 33.8% different from Malinois. The genetic difference between Malinois and Laekenois is 31.1%, and 32.7% between Malinois and Tervueren. These values also indicate the closer genetic relationship between the Groenendael and Tervueren dogs and between the Malinois and Laekenois dogs.

Genetic disorders in Belgian Shepherd dogs

Belgian Shepherd dogs are not particularly prone to any major health concerns and there are currently not many breed-specific DNA tests available for the breed.

However, Belgian Shepherds, especially the Malinois type, can suffer from an autosomal recessive syndrome called Spongy Degeneration with Cerebellar Ataxia (either SDCA1 or SDCA2) that can be tested for with a DNA test. SCDA1 and SCDA2 are caused by two separate mutations in the genes KCNJ10 and ATP1B2 that can both cause the aforementioned neurological disorder. The age of onset is usually 6-8 weeks in SCDA1 and 4 weeks in SCDA2. The first observable sign is poor coordination of movements (ataxia). Affected dogs may also suffer from episodic myokymia (involuntary localised muscle contractions) and/or seizures. The condition can lead to neuromyotonia (generalized muscle stiffness). Affected dogs remain aware of their surroundings during neuromytonia attacks and are at risk of overheating. Long-term prognosis of this disorder is poor. Testing for SDCA1 is a very recent addition to the Optimal Selection™ (US) / MyDogDNA® screening panel, and conclusions regarding the mutation carrier frequency cannot be made yet. A test for SDCA2 is in the development pipeline.

Degenerative myelopathy (DM) is neurodegenerative disease of the spinal cord that is inherited in an autosomal recessive fashion. DM is primarily seen in adult German Shepherd dogs but many other breeds have been reported to also be affected. Affected dogs first begin by exhibiting muscle wasting, proprioceptive deficits, and knuckling of the hind feet. As the condition progresses, it moves up the spinal cord and the dog’s neurologic deficits mirror the progress, losing fecal and urinary continence and eventually involving the front legs and the brainstem. Genetic testing for DM is available for Belgian Shepherds and we have observed a low mutation carrier frequency of 5% in Malinois, but not detected the mutation in other breed varieties to date. We want to emphasize that it is not yet clear if all dogs carrying two copies of the very common DM-associated mutation will develop clinical signs, especially considering the variable presentation noted amongst the more than 100 other breeds found to carry it. Clinical signs of DM typically develop at an old age and some genetically affected dogs may never develop signs during their natural lifespan. It is currently unclear, whether the disease process is ongoing in these dogs or if the mutation does not cause disease in all breeds. More research is therefore needed before an assessment can be made regarding the relevance of genetic testing for DM in Belgian Shepherds, and before conclusive breeding advice can be given.

Idiopathic epilepsy is a common disease in domestic dogs but relatively few risk genes have been identified to date. Professor Hannes Lohi’s research group at the University of Helsinki has done research on epilepsy in Belgian Shepherd dogs over recent years. The research group has identified and published (Seppälä et al., PLOS ONE 2012) a risk locus for canine idiopathic epilepsy in Belgian Shepherd dogs in the ADAM23 gene on chromosome 37. The research on ADAM23 as an epilepsy candidate gene has continued, although the causative genetic variant remains yet to be identified.

Coat colors are highly fixed

The genetics of canine coat coat color is a fascinating but often complex area of speciality, so don’t be discouraged if you find that understanding this section requires some background reading!

Testing for genetic variants influencing coat color in Belgian Shepherds has provided us some interesting observations. The coat color commonly seen in the Malinois, Tervueren and Laekenois is sable with a melanistic mask. Indeed, all Malinois and Tervueren dogs seem to be homozygous for the coat color determining E-locus Em (dark facial mask) allele, which means that this allele is fixed in the population and explains the masked appearance of all dogs. 

Also, the majority of the Malinois and Tervueren dogs are homozygous for the coat color A-locus ay allele responsible for the sable coat color (Malinois 81.8%, Tervueren 92.5%). (Figure 4.) However, there are also dogs that are heterozygous for (carry only one copy of) the ay allele (Malinois 18.2%, Tervueren 7.6%) meaning that there are dogs in the population carrying alleles for other A locus determined color patterns (wolf gray, black-and-tan, and recessive black) - even though these phenotypes are rarely seen in Belgian Shepherd dogs.

Figure 4: Color combination commonly seen in Malinois, Tervueren and Laekenois

Malinois, Tervueren and Laekenois dogs have the solid sable coat color with dark mask on the muzzle. The underlying genetic determinants are revealed through DNA testing.

Belgian Shepherd Groenendael dogs have the dominant black coat color. The majority of Groenendael dogs are homozygous for the K-locus KB allele responsible for the dominant black color (71.8%). Part of the Groenendael population is heterozygous for the KB allele (KB/ky) (28.2%) which explains why breeding of two Groenendael dogs can occasionally lead to sable offspring when a ky/ky genotype in a puppy allows the A locus determined color to be expressed. Groenendael dogs can be homozygous or heterozygous for melanistic mask and sable coat color but these genotypes are usually not observed in the phenotype because of the dominant black color. (Figure 5.)

Figure 5: Color commonly seen in Groenendael

Groenendael dogs have the solid dominant black coat color that hides the expression of the melanistic mask and the A locus colors, such as sable.

Allele frequency is a relative measure of how often an allele at a specific genetic locus is observed in the population. Fixed alleles such as the melanistic mask in Malinois and Tervueren and the ky allele (non-black) in Malinois, Tervueren and Laekenois can be seen in the color frequency table with a frequency of 100%. Many Groenendael dogs carry A locus colors for sable, black and tan and recessive black even though these phenotypes are not observed in this breed variety because of the dominant black color. Few individuals carry rare color alleles that are not usually expressed in Belgian shepherds such as dilution in Malinois. (Table 3.)

Table 3: Color allele frequencies in Belgian Shepherd breed varieties

BASIC COLORS - E locus and K locus        
  Melanistic Mask (Em) Melanistic Mask (Em) Dominant Black (K) Dominant Black (K)
  Em allele E allele K allele ky allele
Malinois 100.00 % 0.00 % 0.00 % 100.00 %
Tervueren 100.00 % 0.00 % 0.00 % 100.00 %
Groenendael 72.44 % 27.56 % 85.90 % 14.10 %
Laekenois 87.50 % 12.50 % 0.00 % 100.00 %

 

 

BASIC COLORS A locus            
  Sable (ay) Sable (ay) Black and Tan (at) Black and Tan (at) Recessive Black (a) Recessive Black (a)
  ay allele no ay allele at no at allele a allele no a allele
Malinois 90.91 % 9.09 % 3.85 % 96.15 % 0.76 % 99.24 %
Tervueren 96.23 % 3.77 % 3.77 % 96.23 % 2.88 % 97.12 %
Groenendael 58.97 % 41.03 % 41.03 % 58.97 % 38.89 % 61.11 %
Laekenois 75.00 % 25.00 % 12.50 % 87.50 % 0.00 % 100.00 %

 

Modifying colors        
  White Spotting (sp) White Spotting (sp) Dilution (d) Dilution (d)
  Solid White Spotting Non dilute Dilute
Malinois 100.00 % 0.00 % 92.00 % 8.00 %
Tervueren 99.04 % 0.96 % 100.00 % 0.00 %
Groenendalen 87.67 % 12.33 % 99.32 % 0.68 %
Laekenois 100.00 % 0.00 % 100.00 % 0.00 %

 

Summary

The Belgian Shepherd Dog is an alert and active dog breed that has medium to high genetic diversity compared to purebred dogs in general. The median heterozygosity level of the Belgian Shepherd Dog Malinois (38.9%) and Tervueren (35.4%) is higher than in purebreds overall (33.8%). On the other hand, the heterozygosity level of Groenendaels (33.6%) is comparable to the purebred median. Only a few Laekenois dogs have been tested, but the results suggest high genetic diversity (41.4%). The observed genetic diversity in Belgian Shepherd dogs does not differ significantly between US and European countries. Informed actions for future maintenance of the breed’s gene pool become a possibility now that the current basal level of breed genetic diversity has been explored. Such actions include future genetic monitoring of changes in the breed’s overall diversity level over time, and incorporating a direct DNA testing based measure of inbreeding as one supportive tool into mate selection strategies.

Belgian Shepherd dogs do not seem to have evident genetic differentiation or line separation within breed varieties. Tested dogs of the same breed variety do not show distinct subgroup separation between US and European countries. However, evident genetic differences are seen when comparing breed varieties to one another. Tervueren and Groenendael dogs have a common historical background and they are more closely related to one another than to other Belgian Shepherd breed varieties as would be expected. Common historical background can also be seen in the closely related Malinois and Laekenois varieties. In addition to common ancestors, Tervueren-Groenendael and Malinois-Laekenois crosses in the course of history can explain the closer genetic relationships of these breed varieties.

There are currently not many breed-specific DNA tests available for disorders seen in Belgian Shepherd Dogs. However, Belgian Shepherds, especially the Malinois type, can suffer from an autosomal recessive syndrome called Spongy Degeneration with Cerebellar Ataxia (SDCA1 and SDCA2) for which genetic testing is available. The widespread degenerative myelopathy (DM) mutation was also observed in Belgian Shepherd dogs. More research is warranted before conclusions on the relevance of DM genetic testing in Belgian Shepherds are made.

Belgian Shepherd dogs Malinois, Tervueren and Laekenois usually have a sable coat color with a melanistic mask. The Em allele responsible for the melanistic mask is fixed in the Malinois and Tervueren populations, meaning that all dogs of these breed varieties will display the dark mask on the muzzle. The characteristic color of Belgian Shepherd Groenendaels is dominant black, which hides the expression of other color alleles carried by the breed, such as melanistic mask and sable.

The genetic diversity plots provided by the Optimal Selection™ (US) / MyDogDNA® (Europe) DNA testing service offers current information about the genetic diversity of the Belgian Shepherd breed varieties as the graphs are updated with every tested dog. Plots illustrating the genetic relationships within and between Belgian Shepherd breed varieties are also updated to enable monitoring of the population. For instance, potential subgroups between countries or between working lines and show lines could be discernible in the future as the number of tested dogs increases. Up to date information and plots on Belgian Shepherds is accessible online through the breed search portal at https://www.mydogdna.com/crm/index.html#en/breeds.

The Optimal Selection™ (US) / MyDogDNA® (Europe) DNA testing service is committed to providing genetic information useful for breeders by offering insight into inherited disorders and traits carried by potential breeding dogs, as well as the genetic diversity and relationships of individuals and populations. The service also features a Breeder Tool assisting in evaluation of potential matings that maintain or increase genetic diversity. Learn more at: https://www.optimal-selection.com/optimal_selection_dogs/ (US) or www.mydogdna.com (Europe).