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Spirocerca : A new concern for dog owners

There is a parasite called Spirocercalupi whichhas been an ever-increasing problem in dogs in certain parts of Johannesburg in recent years.

Spirocerca is a type of worm, which has a life cycle in which it is carried by dung beetles. There are several hundred species of dung beetle, certain of which are found here in Johannesburg. The ones associated with Spirocerca infections are only about 6mm in length. When a dog ingests the dung beetle carrying the worm larvae, the worm begins its life cycle in the dog. The larvae burrow into the stomach wall of the host dog, migrate along the arteries, and spend some time in the wall of the aorta. Thereafter, they mature into adult worms, and migrate to the wall of the oesophagus (swallowing tube), where they live, reproduce and lay eggs.

As they complete this life cycle, they cause various degrees of damage to the aorta and oesophagus, resulting in disease varying from rupture of the aorta and sudden death, to large nodules in the oesophagus, which may become cancerous at a later stage.

The symptoms seen in the dog are variable, and usually include gagging, repeated swallowing and retching; and later,coughing or difficulty in breathing, regurgitation and/or vomiting.

Diagnosis is best made via oesophageal endoscopy (putting a scope into the oesophagus) under general anaesthetic. Chest x-rays and stool samples may also be useful.

Although we have not yet seen cases arising from our local parks (George Lea Park and Field and Study), this parasite does seem to be becoming more and more common. We are now recommending that all dogs that spend a lot of time in public parks or who interact with lots of other dogs, as well as those dogs which have a propensity to eat stools of dogs or other animals, should be treated monthly as a prophylactic (preventative) measure.

This prophylaxis may take the form of monthly Advocate from Bayer, a spot on treatment that also controls fleas (but not ticks), or, alternatively, a monthly oral dose of Dectomax, which is a parasiticide registered for sheep, goats, cattle and pigs. Dectomax is not a registered medicine for dogs, because in certain individual dogs, it can cause serious side effects. The dog breeds which are a concern are Collies and Collie crosses, as well as some German Shepherds. The reason for this is that these dogs have a mutation of a gene called MDR1, which makes it impossible for them to metabolise the drug in Dectomax. Because these are serious side effects, if your dog belongs to any of these breeds, there is a blood test available to detect the MDR1 gene. If this proves positive, we know that those dogs should not be given this, or any similar drug.

Please feel free to discuss this issue with our vets.

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