Other diseases with symptoms that are similar to the common symptoms of giardiasis include:

• Bacterial infections with salmonella, E. coli, campylobacter, staphylococcus, or shigella. Symptoms of infection with these organisms generally do not last as long as those caused by Giardia lamblia.
• Viral infections. Symptoms of infection with viruses generally do not last as long as those caused by Giardia lamblia.
• Infection with other parasites such as Cryptosporidium, Cyclospora, or Dientamoeba fragilis. Symptoms caused by infection with these organisms last as long or longer than those caused by G. lamblia.
• Appendicitis.

Problems with digestion that can cause giardiasis-like symptoms include:

• Lactose intolerance, which causes symptoms when you drink milk or eat dairy products.
• Irritable bowel syndrome, which causes symptoms that come and go.
• Inflammatory bowel disease (Crohn's disease or ulcerative colitis).
• Celiac sprue (also called celiac disease or nontropical sprue).