A common protozoal infection of the small intestine, spread via conatminated food and water and direct person-to-person contact.
Giardiasis is an infection of the small intestine caused by Giardia lamblia (also known as G. intestinalis), a flagellate protozoan. Giardiasis is the most commonly reported pathogenic protozoan disease in the United States. Travelers are the largest risk group for giardiasis infection, especially those who travel to the developing world. Giardiasis is prevalent among hikers and campers, people who swim in public pools, children who attend daycare, and in homosexual males. Others at high risk include close contacts of infected people and those who have contact with infected animals.
Giardiasis is spread via the fecal-oral route. Most people contract the disease by ingesting contaminated water or food, or by not washing their hands after touching something contaminated with Giardia cysts. Although humans are the main reservoir of the parasite, a variety of domestic and wild animals, such as dogs, cats, cattle, beavers and deer carry Giardia species and can infect humans.
Prevalence rates for giardiasis range from 2-7% in developed countries and 20-30% in most developing countries. The CDC estimates there are an upwards of 2.5 million cases of giardiasis annually.
The most common symptoms of Giardia infection include diarrhea for a duration of more than 10 days, abdominal pain, flatulence, bloating, vomiting, and weight loss. Symptoms vary from person to person, often depending on number of organisms ingested, duration of infection, and individual host and parasite factors. Approximately 50% of infections are characterized as asymptomatic. Children usually become less ill than adults and frequently develop asymptomatic infections.
Giardiasis is diagnosed by the detection of cysts or trophozoites in the feces, trophozoites in the small intestine, or by the detection of Giardia antigens in the feces.
Giardiasis has been associated with several gastrointestinal disorders, including irritable bowel syndrome, inflammatory bowel disease and biliary tract dysfunction. Case reports indicate that giardiasis may also be involved with other health complications such as reactive arthritis and urticaria/pruritus or other dermatologic disorders.
Approved therapies currently available in the United States include tinidazole and nitazoxanide. Giardiasis cure rates with single-dose tinidazole therapy range from 80-100%.