The Kooiker dog, officially called ‘het Nederlands Kooikerhondje’ and hereafter called Kooiker dog, is a small Spaniel-type breed historically used to catch ducks in a decoy [1, 2]. Although the breed dates most likely back to the 16th century  it faced extinction in the 20th century as it had lost its purpose. However, shortly after World War II the breed was re-established by Baroness van Hardenbroek van Ammerstol by carefully selecting a small number of Kooiker dogs. Although she was able to retrieve 30 Kooiker dogs only 10 dogs were used to re-establish the breed [1, 4, 5]. The breed gained popularity and currently it can be found throughout Europe, the USA and Japan. The total number of Kooiker dogs born between 1942 and 2022 is approximately 35000.
When using such a small number of dogs to re-establish a breed there is an increased risk of genetic disorders. The Dutch breeders association (Vereniging Het Nederlandse Kooikerhondje - VNHK), aware of these risks, promoted the use of all dogs for breeding to limit inbreeding and health records were kept in a club register that contains info of all Kooiker dogs born across the globe . Despite this, the first hereditary disease identified in the breed was hereditary necrotizing myelopathy described in 1993 by Mandigers et al.,  and von Willebrand Factor Deficiency in 1994. Our group, the Expertise Centre of Genetics, found both the causative mutation for von Willebrand Factor Deficiency as well as the causative mutation of hereditary necrotizing myelopathy [6-8]. Hence neither of these two diseases still exist within this breed.
Currently we are working on a disease first noted in 1970: Kooiker dogs having neuromuscular problems . The Kooikerdogs are presented with clinical signs of exercise intolerance, a stiff gait, cervical ventroflexion, sialorrhea and difficulty eating. We have described in detail the clinical and pathological presentation of this disease, polymyositis, in the international journal 'Animals' .
We already have found the causative mutation (publication expected early 2024) but we are now working on:
Kooikerdogs with polymyositis are still welcome for clinical workup as well as treatment. If you want to support our research this can be done using the following link. The link will transfer you to our foundation collecting financial support to enable this research.
Dr. Paul Mandigers