Spirocerca lupi is a deadly parasitic worm, different to the regular worms found in animals. Dung beetles ingest spirocerca eggs present in bird faeces (especially Hadida bird droppings) and the immature larvae hatch inside. Dogs are infected when they eat the infected dung beetles. The dung beetles usually associated with spirocerca infections are only approximately 6mm in length and are not the usual large dung beetles you may be thinking of.
Once the beetle has been ingested by a dog, the larvae emerge in the stomach of the dog. The larvae burrow through the stomach wall and enter blood vessels around the stomach. The larvae migrate within the walls of the blood vessels until they reach the large artery which leaves the heart, known as the aorta. The larvae live within the wall of the aorta for a period of a few months, maturing into young adults and causing a weakening of the aortic wall, otherwise known as an aneurysm.
The young adult worms then migrate directly to the oesophagus (the food pipe). The worms have also been known to migrate to other locations in the body, including the spinal cord. Once inside the oesophagus, the worms form nodules in the oesophageal wall, mating, laying eggs, and starting the life cycle over again. The worms can survive in these nodules for up to two years, laying eggs through a small opening in the nodule which are swallowed and passed out in the faeces.
Symptoms include retching, vomiting (especially directly after eating—regurgitation), weight loss, difficulty in swallowing, excessive salivation, thickening of the forelimb (in the late, cancerous stages of the disease). Sudden death may occur due to rupture of the aortic aneurysms. Spirocerca lupi is often called “the silent killer” as sudden deaths may occur with no outward signs of ill health.
Treatment is often difficult as signs are only noticeable once the disease is already progressed too far. Early stages are not easily picked up. Unfortunately, there is no treatment for aortic aneurysms or cancerous nodules, which usually spread very quickly to the lungs. Early infections can be treated by killing the larvae.
Therefore, prevention is the better way to go. If you have a lot of Hadidas or your dog is prone to eating bugs in the garden, it is advisable to treat monthly to prevent the devastating effects of chronic infestation. This can be done by monthly deworming with a specific brand of dewormer called Milbemax (available over the counter) or a spot on such as Advocate.
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