Diagnostic exercise: chronic vomiting in a dog.

An approximately one-and-a-half-year-old, neutered male, mixed-breed dog was presented for a chronic history of vomiting. Profuse diarrhea was also noted during examination. An exploratory laparotomy was performed, bone chips were removed from the stomach, and a raised, circular area of gastric mucosa was biopsied. Histologically, there was severe gastric cryptosporidiosis as well as numerous spiral bacteria, consistent with Helicobacter spp. Polymerase chain reaction revealed visible bands for the 18S ribosomal RNA gene for Cryptosporidium spp. The polymerase chain reaction product was sequenced and was found to be most similar to Cryptosporidium muris. Both the gastric location and the species of Cryptosporidium are unusual in a dog.