Milbemax tablets and Advocate Spot on are now registered to control Spirocerca with monthly treatment.
We are starting to see an increase and the prevalence of a silent killer worm in dogs. It is often only found after it is too late to treat the disease and we want to try reduce the incidence by trying to prevent it.
Spirocerca is a nematode that forms a nodule if the pets oesophagus. This often becomes cancerous and causes problems swallowing.
A dung beetle would ingest worm eggs while working with and rolling these infected faeces. The eggs hatch, releasing larvae, which mature to the infective stage within the beetle.
1 A dog may then eat the intermediate hosts, such as a bird or beetle, thereby ingesting the larvae.
Migration of the worm 1-5 in text
Once the dog has eaten a beetle or other intermediary carrying larvae of Spirocerca lupi, the larvae are released within the dog's stomach during the digestive process.
3 The larvae reach the aorta (the main artery in body) via small arteries that drain the stomach. In the main artery they mature, a process which takes about three months, after which they pass through the wall of the artery into the wall of the oesophagus.
4 In the oesophagus wall they form a swelling, known as a granuloma, in which the worms live.
5 The worms produce eggs through a small hole in the granuloma that are then passed in the faeces.
As the worms grow bigger the granuloma grows bigger. One obvious problem is in swallowing. Now sometimes, dogs will vomit, retch or regurgitate. Other times, it may be more subtle. Dogs may just be off there food; lick their lips; cry when swallowing; 'cough' or 'retch'. Some dogs just lose weight but continue eating.
Some Consequences Of Spirocercosis
Apart from the manifestations and consequences mentioned,
the worm can also:
Kill patients by damaging the aorta
Obstruct the oesophagus
Trigger the immune system
Migrate to places other than those expected
Granulomata can transform into cancers. Usually malignant osteosarcomas, which can spread to other organs, especially the lungs.
How Is It Diagnosed?
Firstly, the vet must suspect it. Given its propensity for bizarre manifestations, this can sometimes be hard. Nonetheless, it can be diagnosed in most cases by a combination of careful questioning, chest X-rays, fibre-scope (endoscopic) evaluation of the oesophagus and stomach and special faecal flotation techniques. Sometimes, the diagnosis is just a surprise.
Keeping the garden clear of dog faeces will help in reducing the number of dung beetles.
We now have a registered medication to prevent Spirocerca. Monthly treatment with Milbemax tablets or Advocate spot on works effectively if given every month.
We recommend all dogs to be put on a monthly treatment from a young age.
How Is It Treated?
Advocate is also registered to treat Spirocerca. Unfortunately this will work to kill the worms but the tumours and other complications will often not respond to treatment as the disease is usually only noticed once there are tumours formed, for this reason we recommend using advocate monthly to prevent the disease.