Article – Spirocercosis (Parasite – Spirocerca lupi)
The silent killer
Spirocerca lupi is a deadly worm that lives in a dog’s oesophagus after a long journey through the body. On its journey to the target organs (oesophagus and aorta) S. lupi causes serious damage that leads to disease of the intestinal, respiratory and circulatory system.
This parasite primarily infects dogs and is commonly found in warm African countries. There has been an increase in canine S. Lupi cases in the green belt areas due to development of favourable conditions for the carrier of this worm. The carriers are mostly dung beetles but certain animal species that prey on dung beetles (so-called transport hosts e.g. mice, lizards, birds and rabbits) can also be a source of infection for dogs.
The life cycle begins with the adult worm living within lumps (nodules) in the wall of the oesophagus. The female worm drills a hole through the nodule and lays her eggs into the lumen of the oesophagus, which is then excreted in the dog’s vomit or faeces.
The egg-infected excretions serve as a meal for dung beetles. The eggs are ingested by the dog either through ingesting the dung beetles or the transport host. The eggs hatch in the stomach and the larvae that emerge then bore through the stomach wall and move along the wall of small blood vessels towards the aorta. The larvae will reach the aorta and migrate through the aortic wall into the oesophagus within 3 weeks. Maturation of the worms occur within 3-6 months and laying of eggs commence soon thereafter, which makes the dog infective for other dogs.
How do I know if my dog has spirocercosis?
Early diagnosis is challenging due to non-specific clinical signs. In most cases it will only be diagnosed in the advanced stages when oesophageal nodule formation has occurred causing symptoms like vomiting, regurgitation, weight loss, increased salivation, dysphagia (inability to swallow ) and odynophagia (painful swallowing). Chest radiographs are helpful to detect signs of possible S.lupi infection, but final diagnosis requires endoscopy of the oesophagus to visualize the nodules.
The adult worm can live up to 2 years in the oesophagus before turning the benign nodules into deadly cancerous growths. Thickening of the lower limbs, known as Marie’s disease, may occur during the cancerous stage of the disease. Damage to the wall of the aorta is responsible for the formation of aneurysms (weakened artery wall) that can rupture and cause fatal haemorrhage. S. Lupi is often called the “silent killer” due its ability to cause sudden deaths with no outward signs of illness.
Treatment involves a series of doramectin injections for at least 12 weeks, then repeat endoscopy to determine whether the nodules have decreased in size or disappeared. Unfortunately there is no curative treatment for cancerous nodules or aortic aneurysms. Surgical removal of cancerous nodules can be attempted after having a CT scan done for lung metastases, but also involves placement of a PEG-tube in the stomach (to feed the dog post-operatively) and adjuvant chemotherapy.
Prevention is better than cure. This doesn’t mean you have to get rid of your beautiful garden but it is necessary to keep your garden free of dog faeces. Dung should be removed from the garden on a daily basis to prevent it from being a source of infection for other dogs, as well as dung beetles & transport hosts. It should be placed in municipal waste to ensure removal from the property. There are currently two products on the market that have been shown to assist in the prevention of spirocercosis in non-infected dogs. A topical product called Advocate or an oral dewormer called Milbemax can be used on a monthly basis to help protect your dog from this silent killer.