Physalopterosis in Dogs

There is no breed, age, or sex predisposition to a stomach worm infection. If your pet has a history of consuming insects or vertebrate prey and is suffering from persistent vomiting, physalopterosis should be considered. Your dog becomes infected when he ingests the host (for example cockroach or bird), and the larva matures to an adult nematode, which then adheres to the stomach mucosa.

Physaloptera are stomach worms that attach to the gastric mucosa of your dog. The worms can cause chronic vomiting, and lead to further complications. The presence of even one worm can be harmful; they are quite large. Some canines remain asymptomatic while others become very ill with a physaloptera infestation.

Many canines are asymptomatic with a physaloptera infection. Others will present with the following symptoms.

• Regurgitation
• Chronic or intermittent vomiting
• A single, or multiple whole worms may be seen in vomitus
• Loss of appetite
• Dark feces
• Diarrhea
• Lethargy

If the infection is severe, there can be additional signs.

• Anemia
• Weight loss
• Dehydration
• Malnourishment

Types

There are several species of physaloptera. The males are 30mm (about 1 inch) in size, and the female can grow to 40mm (around 2 inches). They are usually found in the anterior portion of the duodenum (first part of the small intestine immediately beyond the stomach) and the stomach.

The life cycle, simply put, is as described.

• Larvated eggs are passed in the feces of definitive hosts (coyote, skunk)
• The intermediate host (cricket, beetle) consumes feces or something in the environment contaminated by fecal matter
• Paratenic host will eat the insect, and the nematode (worm) will remain as third stage larva in the host (bird, snake) tissue
• The dog will eat the cricket or bird to complete the life cycle when the adult grows to maturity and attaches to the stomach wall

Many factors contribute to the prevalence of the stomach worm.

• The dog must ingest the host (grub, beetle, bird, mouse)
• Once matured in the stomach and attached to the mucosal wall, the worm will feed by sucking blood and eating stomach tissue
• The worm will cause bleeding as it moves, along with erosion as it feeds
• Stomach wall thickening can result as the cells try to repair the mucosa
• Physaloptera are most common the Midwest of the United States but are found everywhere in North America
• A dog who likes to eat insects, or hunts rodents or birds will be more likely to contract the infection
• Access to the outdoor habitat of raccoon, cougar, fox, and badger will increase risk

The diagnosis of the cause for your dog’s vomiting can be complex. You may have seen the presence of a worm in the vomitus of your pet. If not, be certain to describe to the veterinarian the feeding and vomiting pattern of your canine family member. Does he vomit immediately after eating? Is this a chronic problem?

Your veterinary caregiver will do a direct fecal smear under the microscope or a fecal sedimentation to look for eggs. The eggs are very small and thick shelled but are not always detected.

The best method for determining the presence of the physaloptera is through endoscopic exam of the stomach and duodenum. Through the use of the tube, light and camera, stomach worms are sometimes visible. They may be hard to detect because they can become hidden in the mucus. However, evidence of hemorrhage areas where the worm has attached previously may be evident. In many instances, the worms can be removed during the endoscopy.

The veterinarian may have removed a worm from your pet’s stomach during the diagnostic process of gastroscopy; though this is fortunate, a deworming should be done as well.

Oral medication, called anthelmintics, are given every two weeks for three treatments orally. Studies show that the medication, Pyrantel, has an excellent efficacy of 80%. This should eliminate the stomach worm.

If your canine family member had a severe case of physalopterosis, a gastroprotectant may be prescribed, as well as corticosteroids to promote healing. The shedding of worms in vomit or feces and symptoms of diarrhea or vomiting should cease within two weeks after treatment.

As with any medication, continue the course as prescribed. Do not stop the treatment early, even if your pet appears to be cured.

You will need to bring your furry family member for a follow-up fecal exam. If eggs are present, a repeat of the treatment will need to be done. Your veterinary team will also examine your dog to determine his present state of health in regards to weight and appetite, and to verify with you that the vomiting or diarrhea has ended.

As a precaution against reinfection, do not allow your pet to free roam or hunt for insects and small animals such as rodents.