The symptoms may last for weeks, and weight loss can occur in many people infected with the parasite. Loss of appetite is common. Anyone can get giardiasis, although there is an increased risk of infection in children and those who may have a compromised immune system. Even though children may be more likely to acquire the acute infection, chronic infection is more common in adults. Definite diagnosis can be made by a laboratory test in which the microscopic forms of the parasite are seen in stool samples.
More exotic tests are available but are expensive.
The usual adult dose is 250 mg tablets three times daily for 7-10 days. Chronic cases may require larger doses or treatment for a longer period of time. Metronidazole is available in most countries, and is relatively inexpensive. Prevention of infection is primarily that of avoiding contaminated water and food. All vegetables and fruits that are to be eaten with cooking should be washed with safe water.