Park Worm – Spirocerca lupi
Park worm is a parasitic roundworm (nematode) that infects dogs. The name "park worm" was given to it because the first cases in Israel, diagnosed in the 80's, were in dogs which common denominator was the National Park in Ramat Gan. This name is misleading and causes many dog owners to disregard this dangerous disease, mainly by saying they do not walk their dogs in parks. In fact, park worm can be found all over the country.
An infected dog's stool contains the eggs of the worm. These are taken up by small dung beetles (some are smaller than 1cm) which are the worm's intermediate host. A single dung beetle can contain up to 150 worms. When a dog, which is the worm's final host, eats feaces or any other rotting organic material and swallows an infected beetle or eats an animal that has eaten a beetle, the beetle breaks up in its stomach, the worms are released and make their way through the stomach's wall and along the walls of the arteries towards the aorta. From the aorta, as they mature, they continue migrating in the dog's body towards the oesophagus, where they burrow, reach adulthood and start laying their eggs, which pass through the dog's intestinal tract and are released in its feaces.
The body's reaction to the worms' presence in the oesophagus manifests as granulomas, a sort of "bumps" in the oesophagus's inner wall. When these granulomas are large they cause coughing, difficulty swallowing, regurgitation, vomiting, etc. which are the disease's characteristic clinical signs. However, the disease can also manifest in neurological disorders, due to worms migrating to the spine, drastic weight loss and even sudden death, due to rupture of an aortic aneurism leading to internal bleeding.
When dogs are brought to the clinic because of coughing, difficulty swallowing, vomiting, etc. they are x-rayed. If opacity is seen at the caudal end of the oesophagus, the dog will undergo endoscopy. The endoscopy procedure is done under general anaesthesia and during it an optic fiber is inserted into the oesophagus in order to look for granulomas containing the adult worms.
A "good" outcome of the endoscopy would be the discovery of such granulomas, then the dog will start a weekly treatment by injections for several months and at its end will undergo another endoscopy in order to make sure the oesophagus is clear of granulomas.
In worse cases, the outcome of the endoscopy would be to find that the granulomas have undergone cancerous transformation. In some cases, cancerous transformation can be suspected already by the x-ray, due to calcification at the caudal end of the oesophagus and presence of metastasis in the lungs.
Unfortunately, there is no vaccine against park worm; therefore the only way to prevent a dog from getting sick is by preventive (prophylactic) treatment by injections every two months. Our recommendation to treat against park worm every two months is based on the recommendation of the Veterinary Hospital in Beit Dagan. Also, it is very important to clean after your dog and collect his stool, not to allow dogs to run alone and even use a muzzle with dogs that eat everything they find, in order to prevent the spreading of the disease.
Dogs of certain breeds, such as Australian Shepherd, Border Collie, Collie, etc. are known to carry a mutation in the MDR-1 gene. This mutation makes the drug that is used to treat park worm toxic to these dogs. It is, therefore, very important to take blood from dogs of these breeds, and those that are crossed with them, for a genetic test. Dogs that are negative for the mutation can be treated like any other dog.