Canine Spirocerosis


Spirocerca lupi is a worm that affects dogs in RSA and some Mediterranean countries. The life-cycle involves a dung beetle and the immature worm is transmitted to the dog when it eats an infected dung beetle (or ingests anything that may have eaten a dung beetle e.g.: birds, lizards etc.) Your dog cannot get Spirocerca from eating dog faeces.

How does it affect my dog?

The worm is swallowed and once it reaches the stomach, it moves up through the walls of the stomach arteries into the main artery of the body, the aorta. It travels up through the wall of the aorta to where it lies adjacent to the oesophagus (Gullet) in the chest cavity and then burrows through the wall of the aorta into the wall of the oesophagus. The worm then forms a nodule around itself to protect it from the immune-system. It lies in this nodule until it matures into an adult worm and starts to lay eggs. These eggs pass from the oesophagus into the dog’s stomach and pass through the intestine into the faeces.

The eggs are then ingested by the dung beetle and hatch into immature worms inside it and the life cycle continues. Aberrant migration of immature worms can result in the worms forming nodules in the abdomen and spine but this is much rarer than the classic presentation. Parasitic nodules can undergo neoplastic (cancerous) changes over a long period of time.

What symptoms do I see?

The nodules in the oesophagus can remain dormant for weeks to months before they reach a size that will cause symptoms. The oesophagus will not be able push food down into the stomach therefore one of the main symptoms will be regurgitation. This differs from vomiting in that the motion is passive and there is usually no retching beforehand. The food is undigested and some dogs may eat the regurgitated food – this often delays the diagnosis as most owners are not aware that the dog is regurgitating its food until weight loss starts to occur. Some dogs will also show excessive retching and gagging without regurgitation.

Dogs that suddenly pause whilst eating, show exaggerated swallowing and then resume eating may have S.Lupi.
Other clinical signs of S.lupi include difficult/painful swallowing, weight loss, persistent fever, thickened painful lower legs due to bone inflammation (Maries Disease) and sudden death due to rupture of the aorta – the parasites can damage the aortic wall resulting in an aneurysm which may rupture at any time.

How can I tell my dog has S.lupi?

There is currently no blood test to diagnose Spirocerca lupi. Diagnosis is usually based on clinical signs and x-ray of the chest with or without barium as well as endoscopy of the oesophagus (a medical camera is passed through the mouth down the oesophagus to visualize the oesophageal wall.) This is done under anesthesia. Endoscopy is usually more sensitive than x-rays as smaller nodules can be visualized using this method and it can allow differentiation between Spirocerca nodules and oesophageal tumours.

What treatments are available?

Treatment of S.lupi involves the use of a dewormer that is registered for sheep and cattle and is not registered for use in dogs. It is, however, one of the most effective drugs we have against Spirocerca and is used routinely in veterinary practice. Affected dogs will need a blood test (Knotts test) to rule out a blood parasite prior to treatment as this treatment may result in a life-threatening allergic reaction if this blood parasite is present. Certain Collie Breeds and cross breeds may need further testing before any treatment is given. Adjunctive treatment may include anti-inflammatory drugs and anti-ulcer medication to soothe the painful oesophagus.

The drug will kill the Spirocerca parasites and the nodules will reduce in size and resolve over a period of a few weeks to months. It will not, however, treat the inflammation and damage to the aortic wall that has already occurred during the parasites’ migration. This means that aortic rupture and sudden death can occur even after treatment and resolution of your pet’s symptoms. Aortic aneurysms are “ticking time bombs” that cannot be treated with medication or surgery.

Can I prevent it from happening to my dog?

There is currently no preventative medication for S.lupi and routine canine dewormers are not effective against this parasite. Due to the increase in prevalence of this parasite in dogs in RSA, more research is being done on S.lupi and hopefully more economical diagnostic tests and treatment will become available. Additional measures include removing dog faeces and horse faeces from the property daily as dung beetles have been observed eating the faeces. Trying to prevent your dog “hunting” lizards, birds etc is another measure that can be taken, but this is not always feasible.

If one of my dogs has Spirocerca, what should I do about my other dogs?

If one of your dogs has been diagnosed with S.lupi then it is possible your other dogs have been exposed to the parasite. We would suggest screening your other dogs by doing chest x-rays and/or scoping and then doing a trial course of the treatment. Even if your other dogs are not showing clinical signs, adult parasites may be present in the oesophagus and shedding eggs which could re-infect other animals and continue the life-cycle.