February 2023

In this VETgirl online veterinary continuing education blog, Dr. Amy Kaplan, CVMA, DACVECC, MRCVS reviews a case of Physaloptera, a rare cause of gastric ulcers in dogs. Never heard of this rare nematode? Tune in to learn more!

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Physaloptera Nematode Causing Gastric Ulcers in a Dog

OK, as an emergency critical care specialist, I see a whole lot of vomiting at Urgent Pet Care. Vomiting in dogs. Vomiting in cats. All day vomiting. Well, this case here was about an 18-week-old, intact female, mixed breed presented to the veterinary ER for guess what? Vomiting for a week, always immediately after eating food. Earlier that week, the puppy was seen at her primary care veterinarian, who had taken radiographs to rule out a gastrointestinal (GI) foreign body; the dog was treated outpatient with maropitant (Cerenia), a bland diet, and an anthelmintic, pyrantel pamoate, for empiric treatment of GI parasites.

The client reported that the vomiting was perhaps less frequent after outpatient treatment, but since the puppy still had a good appetite, they decided to see if it would resolve through the week. However, over the weekend (of course – always the weekend!), the vomiting progressed to increased frequency and the dog was presented to the local veterinary ER hospital. Routine diagnostics included a CBC (with no significant findings), a biochemistry panel (all within normal limits aside from a mild hyperglycemia at 140 mg/dL [7.8 mmol/L, reference range 75-125 mg/dL / 4.2-6.9 mmol/L]), and a barium series (to look for presence of foreign material/obstruction or delayed gastric emptying). No barium retention was seen through the study; all barium was observed in the colon at the final 8hr check. As there was no radiographic signs of GI obstruction and after successfully holding down some food, the dog was discharged.

Cutest vomiting puppy ever! Photo by Dr. Amy Kaplan, CVMA, DACVECC, MRCVS

Three days later, a follow-up phone call revealed that the puppy was still occasionally vomiting after eating, but remained in good spirits with normal energy and activity. Approximately 2 weeks after her ER visit, the puppy re-presented to the ER for mild hematemesis, despite being on a bland diet (e.g., boiled chicken/rice). The puppy was still BAR (bright, alert and response), and still showed interest in eating and drinking, but the hematemesis really concerned the owners.

Repeat diagnostics were normal (e.g., CBC, chemistry) aside from a mild hypokalemia of 3.6 mEq/L (3.8-5.3 mEq/l), presumptively secondary to the vomiting of gastric fluid and lack of nutritional intake secondary to the vomiting. PT/PTT times and platelet count were within normal limits, and a snap cPL was normal, helping rule out pancreatitis as an underlying cause for the vomiting. A parvovirus snap test was performed (despite diarrhea not being present to be really sure all bases were covered); this was negative. Abdominal radiographs showed no suggestion of a GI obstruction nor any foreign material lingering in the stomach.

Due to lack of access to a diagnostic abdominal ultrasound over the weekend, the ER veterinarian offered to perform a surgical explore to look for any abnormalities that may be causing the vomiting. During the abdominal explore, the intestines appeared normal in color and motility, but the stomach had an area of visible bruising. Suspecting this was a deep ulcer, the ER clinician resected the affected stomach tissue only to reveal…

Gastric ulcer found in the puppy’s stomach due to Physaloptera Photo by Dr. Amy Kaplan, CVMA, DACVECC, MRCVS

a live and wriggling worm attached to the inside of the stomach in the gastric ulcer!

The Physaloptera worm found in the gastric ulcer in this dog. Photo by Dr. Amy Kaplan, CVMA, DACVECC, MRCVS

Yuck (but oh so cool too)! Knowing there could be more of these worms present, the ER clinician visually and palpably examined the interior of the stomach to the best of their capabilities (being such a tiny puppy stomach!). After not finding any other worms or ulcers, the stomach and surgical sites were closed. The worm was not submitted for identification, but based on the finding of only one live worm and the associated stomach ulcer it caused, the suspicion was raised for the stomach worm being Physaloptera. Also, as worm appeared to be resistant to the recently administered anthelminthic medication, the index of suspicion was even higher for Physaloptera.

So, what exactly is Physaloptera?

Physaloptera, a nematode, can be found worldwide and can affect both cats and dogs. Once an infected insect, mouse, or potentially even frog is ingested, the nematode larva then grows to full adulthood within the stomach of the dog or cat (1). Adult worms can be anywhere from 1 to 6 cm in length and mainly attach in the stomach, but proximal duodenal attachment has also been reported (2).

Diagnosing stomach worms can be super tricky! So, how do we identify Physaloptera? Infected cats and dogs tend to show only vague signs of intermittent vomiting (and possibly regurgitation), but often maintain a good appetite and energy level. Some dogs and cats may completely asymptomatic too. Worm burdens in infected patients are super low – generally less than only 5 worms. Physaloptera produce fewer eggs than other common canine and feline nematodes and their eggs often sink in fecal flotations. This makes detection of Physaloptera eggs by our common routine fecal screening incredibly difficult. You may get more yield of the heavier eggs on fecal sedimentation, but there’s still just SO few eggs produced from the adult worms (as they are so few) that it’s easy to miss them.

Sometimes animals may vomit a worm or two, but more often the worms are firmly attached to the gastric mucosa where they cause ulceration of the stomach and potentially even of the duodenum. These worms can evade our routine anthelminthics and monthly preventatives, so just because our pets are treated, that doesn’t mean they’re protected or “treated.” Some reports suggest successful treatment of Physaloptera with longer courses of high-dose fenbendazole in conjunction with pyrantel pamoate (2). However, the most effective way to rid these worms to date is to physically extract the buggers through endoscopy or surgery (2).

So, back to this poor pup. After recovery from surgery, the dog was started on gastroprotectant medications (e.g., specifically sucralfate and famotidine, an H2 blocker) to treat the remaining ulcers and potential gastritits. (Due to the patient’s small size, omeprazole was not readily available OTC, but would have been preferred based on stronger efficacy for the treatment of gastric ulcers). This dog recovered uneventfully and bounced out of the hospital as happy as she came in, but with no further vomiting. The pet owners were warned that reinfection with Physaloptera was possible, if the nematode was residing in the local environment. At a 21-day check, the dog remained happy and healthy, gaining appropriate weight, while no longer vomiting/regurgitating.

I feel like at this stage in my career, the vague vomiting workup is almost reflexive at this point with a CBC, chemistry, UA, radiographs, fecal, and + parvo test (depending on vaccine status). And I think we generally do get an answer from just the first-tier or maybe even the second-tier diagnostics.

Do we routinely jump to surgery in the vomiting dog? Abdominal explores can be powerful diagnostic tools, but we have to weigh the risks of anesthesia and surgery, and generally when we’re reaching for this diagnostic, it’s because we have exhausted our common, less invasive, vomiting workup tools and still not found an answer. For this pup, surgical exploratory not only found her answer, but also was the means for treatment. So often we workup puppies with vague signs of vomiting that end up being from common issues like diet change or dietary indiscretion. While this patient’s signs were vague, appropriate work up revealed her diagnosis was a bit more of a “zebra.” Even though it’s ingrained in us from vet school to look for horses when you hear hoofbeats, sometimes you do truly find those zebras! Or worms in this case… Ew.

Sometimes you get a zebra when you hear hoofbeats! Image by Pfüderi from Pixabay

1. Peregrine, AS. Physaloptera spp in Small Animals. Merck Manual. Last revised Oct 2022. Accessed https://www.merckvetmanual.com/digestive-system/gastrointestinal-parasites-of-small-animals/physaloptera-spp-in-small-animals.
2. Soderman L, Harkin KR, Gastric Physaloptera Infection in 27 Dogs (1997-2019). J Am Anim Hosp Assoc 2021;57(1):8-14.

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