Update 2022 - 2023: 'Preventing hereditary oesophageal dysmotility'

Thanks to the support of Friends of Veterinary Medicine donors and partners, the research team has succeeded in screening animals and collecting DNA, bringing us one step closer to the goal of getting a decrease in this nasty disease. In this annual update, we take you through the developments made possible by everyone who supports this project.


Three White Swiss  Shepherd pups are frolicking about in a treatment room at the Expertise Centre Genetics of the Faculty of Veterinary Medicine. The pups are here to investigate the function of their oesophagus.  Unfortunately White  Swiss Shepherds, are  prone to Congenital Idiopathic Megaoesophagus (CIM), also known as oesophageal paralysis. The Latin name literally means congenital (innate) idiopathic (no known cause) mega (big) and oesophagus. The name also characterises the condition accurately: paralysis causes the oesophagus to be open and lose its function.  

Congenital Idiopathic Megaoesophagus (CIM)

Affected pups start having trouble eating in the first weeks of life, during the transition from milk to solid food. They are at risk of serious and possibly fatal complications and have to eat upright to prevent food accidently going into the trachea, causing severe aspiration pneumonia.  CIM is seen sporadically in various breeds, but has an above-average occurrence among certain breeds such as the White Swiss  Shepherd,  German Shepherd, and the Irish Setter.

“For this project, we were contacted by breeders of  White Swiss Shepherd dogs, who indicated that theirpups were prone to congenital megaoesophagus,” says Dr. Hille Fieten, Coordinator of the Expertise Centre Genetics. “These pups regurgitate food. The first question we then ask ourselves is: is it a hereditary condition? If it occurs more often than we see in the general dog population, we know there is a hereditary cause. . We then started making swallowing studies of the parent animals and the littermates of pups with congenital megaoesophagus. This is how we found out that the parent animals also showed a disturbed oesophagus motility  in some cases. The dogs didn't have full paralysis of the oesophagus, but we did see that the function of the oesophagus was highly disrupted and that food accumulated  in the oesophagus. It was an unexpected discovery that there are a fair number of dogs with mild to seriously aberrant oesophagus motility. This is why we started to further investigate the DNA of the affected animals and the parent animals.”

Gaining more knowledge about CIM 

The project has multiple goals. The first is to gain more insight into the variations of the symptoms and the development of the condition, such as whether or not the oesophagus motility can still improve in the dogs' first year of life. A second goal is to make a detailed chart of how often the condition occurs, how it is passed on and how breeders can reduce the occurrence of the condition by means of screening potential parent animals and select parents accordingly. “Thirdly, we want to identify genetic markers associated with the condition by means of a Genome Wide Association Study, GWAS for short,” Hille Fieten explains. “Our fourth goal is to identify and validate the causal mutations, and we eventually want to develop a DNA test breeders can use to prevent the birth of pups with congenital megaoesophagus. In 2022, we added another goal: we want to investigate whether or not the mutation in MCHR2, which has been found in German Shepherds previously, has a predicting value for having congenital megaoesophagus or oesophageal dysmotility in our study population. If this is the case, this mutation can possibly be used as a DNA test by the breeder to reduce the likelihood of pups with congenital megaoesophagus. Finally, we want to use the gained knowledge to support breeders in preventing more pups with this condition from being born.”

Swallow studies

By late 2021, swallow studies had been made of 53 dogs. Between January 2022 and February 2022, 66 dogs were provided for swallow studies or, if they had oesophagus paralysis, for X-Ray photos. Scoring of  swallow studies was further standardised in 2022. Fieten says: “Every dog receives a score on a scale from 0 to 20. A dog who scores a 0 has a normal oesophagus motility, a dog who scores 20 has no oesophagus motility and has megaoesophagus. Besides this, blood samples are taken and an extensive medical history of each dogs is requested in order to eliminate any other causes of the found deviations. Currently, we perform follow up swallow studies in dogs that were sceened as a puppy at 6 and 12 months of age.  In these screenings, we saw comparable results at both ages. The number of animals we followed up on is currently too small to be able to definitively say whether or not the oesophagus motility changes during the first year of life.” 

Fieten explains that in the past years, > 100 dogs were screened and DNA samples were taken from all of them. “We generate attention for the research project, such as by giving lectures to breeding organisations and veterinarians. In 2023, the owners of dogs who participated in the research at a young age will be contacted for follow up studies We also want to better inform vets, because this will lead to more adequate diagnoses for dogs with milder complaints and owners being well informed. Knowledge among breeders will also ensure that breeding animals will be better screened and dogs with oesophageal dysmotility will be used less often for breeding. Eventually, our goal in this is to achieve a reduction of animals with this severe disease.” 

The research team would like to sincerely thank the partners and donors of the Dwarfkezen project for their support. Together, we are making a difference! Do you also want to contribute to a future without 'Esophageal Paralysis'? Support this project!