Spirocal lupi (Stomach Parasite) in Dogs

Unfortunately, there is no approved treatment following the infection from this parasite, therefore prevention is essential.

Spirocerca Lupi is more commonly known as the esophageal worm of dogs and is a parasite found in the southern areas of the USA, commonly found in Alabama, Georgia, and Mississippi as well as throughout tropical and subtropical regions throughout the world. This parasite is known to affect foxes and felines, as well as dogs. The adult worm is blood red in color and has the potential to create serious damage in the canine body due to the formation of granulomas following infection. The worm creates hard, fibrous tumors that fill with cellular debris and exudate, obstructing the esophagus and causing chronic coughing, anorexia, and irritation.

Most dogs who have been infected by this parasite show no symptoms, however, this varies greatly on the location and size of the lesions. As the tumor grows in size the dog may begin to experience difficulty swallowing, vomit while eating, and salivating excessively. This can lead to acute weight loss and depression in the pet. Other signs may include:

• Odynophagia (painful swallowing)
• Melena due to the ulceration of lesions in the esophageal 
• Excessive salivation
• Weakness
• Difficulty breathing and chronic cough due to esophageal obstruction caused by tumors 
• Anorexia
• Lethargy and pale mucous membranes caused by chronic hemorrhagic anemia due to ulceration of esophageal tumor
• Lameness
• Swollen hind limbs
• Diarrhea 

In severe cases, sudden death may occur due to after rupture of the aorta caused by the migrating of developing worms.

Dogs become infected following the accidental ingestion of Spirocerca lupi, usually through the ingestion of an intermediate host such as a beetle, or transport host such as birds infected by the larvae. The larvae are then released into the stomach of the dog and penetrate the gut wall; following this, they travel to the aorta. It is thought that the developing larvae migrate from here to the esophagus via the bloodstream.  Upon reaching the esophagus the larvae form a cystic nodule between the aorta and esophagus. The larvae coil within this cyst which can reach 60 - 70mm in diameter and presents as a hard, fibrous tumor that develops into a sarcoma over time. Eggs are laid within this cyst and are eventually passed out through the feces.

If your suspect your canine may be suffering from infection, contact your veterinarian for a consultation. Your veterinarian will perform a full clinical examination on your dog and discuss your pet’s clinical history with you, particularly episodes of vomiting or anorexia. There are a range of diagnostic tests that may be performed, these include: 

• Diagnosis through fecal examination which may contain larvae or eggs, however these shed sporadically so may not be present despite infestation
• Gastroscopy investigation which may show nodule or an adult worm
• Radiographic examination of the respiratory tract which may show a dense mass in the esophagus indicative of the parasite. 
• Positive-contrast barium study may increase visibility of the mass
• Computed tomography scans may also provide diagnostic assistance 
• Direct visualization of masses under anesthesia using endoscopy 

Unfortunately, infections are often not diagnosed until postmortem investigation that may show evidence of granulomas in the lungs, trachea, stomach wall and heart. In some cases, sarcomas show bone involvement throughout the body.

There are no approved treatments available for this disease and due to the large area that is often affected in the esophagus, surgical removal is often not an option. However, the following treatments have been shown to be effective in some cases and may be recommended by your veterinarian.

Doramectin at a dose of 0.2 mg per kg administered subcutaneously at two weekly intervals for three doses;0.4 mg per kg administered subcutaneously for six doses at 2 week intervals; 0.5 mg per kg administered subcutaneously for two doses 2 weeks apart or; 0.5 mg per kg per day given orally for for 42 days; 0.8 mg per kg, administered subcutaneously for two doses one week apart; combined with the administration of prednisolone.

Nutritional support may be given by providing your pet with liquid gruel provided in an upright position. Blood transfusions may be indicated if your pet has suffered from acute blood loss due to hemorrhage.

The most effective management of this condition is through prevention. In endemic areas, practice careful food hygiene and avoid feeding your pet raw meat that may carry the larvae, particularly raw chicken scraps. To reduce the risk of infestation caused by the ingestion of transport hosts, monitor your pet closely while walking or keep on a short leash. Monthly parasitic treatment using moxidectin/imidacloprid applied topically is an effective and approved preventative treatment for infection, discuss with your veterinarian whether this may be the right option for your dog.