Spirocerca lupi

24th Apr, 2023

Written by Dr Mirjam van der Wel, Veterinarian, Port Elizabeth

Introducing Spirocerca lupi, a rather unpleasant worm that can cause severe disease and even death in your dog.

People mostly associate worms with gastro-intestinal problems (vomiting, diarroea), but this little monster gives a number of different symptoms.

Your dog picks up this worm by eating dung-beetles. Not the big dung beetles, but little ones.

This is what happens: Your dog (definitive host) eats the beetle (intermediate host) containing the worm larvae. Once eaten, the larvae are released inside your dog’s digestive tract and, from there, the larvae migrate through the intestinal wall to the blood stream.

First stop is the aorta (large blood vessel that carries blood from the heart to the rest of the body). In the aorta the larvae mature into young adult worms. This takes about three months from infection. Adult worms are 4-7cm long.

From the aorta, the worms migrate through the chest to the oesophagus (slukderm). Once in the oesophagus they form a sizable nodule. Female worms live in the nodule and lay eggs. This starts about 5-6 months from infection. Adult worms can live in the oesophagus for more than two years.

The eggs are released into the digestive tract through a small opening in the nodule. Eventually the eggs are passed out of the dog via its poop. The little dung-beetle eats the eggs in the dog’s poop, eggs turn into larvae in the dung-beetle, dog eats dung-beetle with larvae and so the cycle continues. Your dog can also get infected when it eats a lizard, bird or other small mammal (paratenic host) that’s eaten the infected dung-beetle.

Two large veterinary surveys of South African vets in the past decade or so have shown that Spirocerca lupi occurs all over the country. It showed that vets in Gauteng and KwaZulu-Natal come across the condition more than vets in the Eastern Cape. However, with people buying dogs from breeders in different provinces and the fact that many dogs travel with their owners or move house, we can expect to see Spirocerca lupi anywhere.

What does this mean for your dog?

Many dogs with a Spirocerca lupi infection don’t show any signs. When there are clinical signs, these are dependent on where and what is causing the problem:

Nodule in the oesophagus:

  • Vomiting/regurgitation/gagging and repeated swallowing
  • Breathing problems (coughing, panting)
  • Weight loss
  • Fever
  • Weakness/lethargy
  • Pale gums (anaemia caused by bleeding from the nodules)
  • Increased salivation and enlarged salivary glands

Migration through the body:

  • Fever
  • Coughing/pneumonia
  • Secondary bacterial infections
  • Rupture of blood vessels – a rupture of the aorta (aortic aneurism) could result in sudden death

Larvae and adult worms forming nodules in the wrong places:

  • Coughing
  • Paralysis (nodule in spinal cord)
  • Raised liver blood levels (nodule in liver)

If untreated, the parasitic nodules in the oesophagus can become tumorous. The cancer can spread (metastasise) through the body, especially to the lungs, and can cause thickening of the long bones in the legs, leading to oedema (Marie’s disease).

How is it diagnosed?

As you can see, the symptoms (coughing, vomiting, weight loss) are very non-specific, and Spirocerca lupi can be difficult to diagnose.

If your vet suspects Spirocerca lupi, an x-ray of your dog’s chest may show the nodules in the oesophagus. If the x-ray isn’t conclusive, oesophagoscopy is the next step. This involves your dog undergoing a general anaesthetic to pass a small camera with light source (a “scope”) via the mouth into your dog’s oesophagus. This allows your vet to see the nodules and sometimes the actual worms, making the diagnosis very definite.

Looking for eggs under a microscope in your dog’s poop can sometimes be helpful. Eggs are excreted in the stool intermittently and aren’t always seen on a single faecal exam. Repeated exams are necessary to see the Spirocerca lupi eggs. Occasionally the worms (4-7cm; red colour) are brought up in the dog’s vomit

Can it be treated?

If Spirocerca lupi is diagnosed early, veterinary treatment can be successful. It generally involves a repeated deworming regime using a drug that’s not licensed for use in dogs, but is used for deworming livestock (sheep, etc.). There are certain breeds of dogs (especially Collies) that can have a genetic predisposition against this drug (it’s toxic for them), so your vet may need to use an alternative drug.

In more severe cases, treatment will include antibiotics for the secondary infections, ways of feeding your dog to minimise regurgitation, and pain relief if the disease has become cancerous.

It’s not uncommon for the dog to be presented at an advanced stage of the disease where treatment isn’t successful and the focus is on keeping your pet comfortable.

Prevention is better than cure!

Poop-scoop to the rescue! Daily removal (and suitable disposal) of dog poop from your yard can prevent those dung-beetles (and other small critters) from keeping the cycle going.

Suitable food and training of your pup can reduce the likelihood of transmission.

Speak to your vet about products that can help prevent Spirocerca lupi from setting up home in your dog.

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