Bladder Worm Infection in Small Animals
Pearsonema plica (syn Capillaria plica or bladder worm) is a nematode that can uncommonly infect the urinary bladder and occasionally the ureters and renal pelvises of dogs and cats.
Distribution is worldwide, and wild animals appear to be the primary hosts. A similar though even less common organism, Pearsonema feliscati (syn Capillaria feliscati), is also found in cats.
Dogs and cats become infected by eating earthworms that contain the first-stage larvae of Pearsonema spp. Mature nematodes are threadlike, yellowish, and 13–60 mm long. The colorless, operculated eggs have a slightly pitted shell and are 63–68 × 24–27 mcm in size.
Most affected dogs and cats are clinically normal, but some animals may show clinical signs of cystitis.
Urinary capillariasis may be associated with development of renal amyloidosis. The eggs are shed in the urine and may be found in the urine sediment.
No approved treatments exist for Pearsonema spp infections in dogs or cats; however, ivermectin (0.2 mg/kg, SC, for 1 or 2 doses 1 week apart) and fenbendazole (50 mg/kg, PO, every 24 hours for 4–10 days) are reported to be effective and are sometimes used concurrently. Repeated courses of fenbendazole may be needed.
Giant Kidney Worm Infection in Small Animals
The giant kidney worm (Dioctophyma renale) is the largest known nematode. It can parasitize the kidney as well as other organs.
D renale has a worldwide distribution.
Mink are the most common definitive host. Many species, including dogs and humans, can be infected.
The definitive host contracts D renale by ingesting encysted larvae in raw fish (eg, pike, bullhead) or frogs or by ingesting an infected annelid worm. The larvae penetrate the bowel wall and migrate first to the liver (which can cause liver disease or hemoabdomen) and later to the kidneys. In dogs, the parasite often fails to reach the kidneys and may be found free in the abdominal cavity, where it can cause peritonitis.
Kidney worms grow larger in dogs than in mink, reaching up to 103 cm.
Courtesy of Dr. Kevin Kazacos.
Female worms are larger than male worms, and both are blood red. Both male and female worms must be present in the same kidney to complete the life cycle. Barrel-shaped yellow-brown eggs with thick, pitted shells measuring 71–84 × 45–52 mcm are shed into the urine.
In the kidneys, these worms cause obstruction, hydronephrosis, and destruction of the renal parenchyma. The right kidney is most commonly affected. Due to the unilateral nature of the disease, clinical signs may be absent. However, hematuria and/or renal or abdominal pain can be present.
Urinalysis may reveal proteinuria, hematuria, and pyuria. Ultrasonography shows hydronephrosis and the nematodes.
If both sexes of the nematode are present in the kidney and the ureter is patent, parasitic ova may be found in the urine sediment (see D renale eggs, photomicrograph). Alternatively, exploratory laparotomy may reveal worms in the peritoneal cavity, between the hepatic lobes, or within the affected kidney(s) via nephrotomy.
Unilateral nephrectomy is the treatment of choice if the opposite kidney is unaffected. Preventing ingestion of raw fish or other aquatic organisms is recommended in areas where the parasite is known to infect wild animals.
