<unk>  is caused by the protozoan Giardia duodenalis. The infection occurs in many animals, including beavers, other rodents, cows, and sheep. Animals are believed to play a role in keeping infections present in an environment. G. duodenalis has been sub-classified into eight genetic assemblages (designated A–H). Genotyping of G. duodenalis isolated from various hosts has shown that assemblages A and B infect the largest range of host species, and appear to be the main and possibly only G. duodenalis assemblages that infect humans. Risk factors According to the United States Centers for Disease Control and Prevention (CDC), people at greatest risk of infection are: * People in childcare settings * People who are in close contact with someone who has the disease * Travelers within areas that have poor sanitation * People who have contact with feces during sexual activity * Backpackers or campers who drink untreated water from springs, lakes, or rivers * Swimmers who swallow water from swimming pools, hot tubs, interactive fountains, or untreated recreational water from springs, lakes, or rivers * People who get their household water from a shallow well * People with weakened immune systems * People who have contact with infected animals or animal environments contaminated with feces Factors that increase infection risk for people from developed countries include changing diapers, consuming raw food, owning a dog, and travelling in the developing world. However, 75% of infections in the United Kingdom are acquired in the UK, not through travel elsewhere. In the United States,<unk>  occurs more often in summer, which is believed to be due to a greater amount of time spent on outdoor activities and traveling in the wilderness. Transmission<unk>  is transmitted via the fecal-oral route with the ingestion of cysts. Primary routes are personal contact and contaminated water and food. The cysts can stay infectious for up to three months in cold water. Many people with Giardia infections have no or few symptoms. They may, however, still spread the disease.
Giardiasis
Irritable bowel syndrome
Cryptosporidiosis
Cyclosporiasis
Eosinophilic gastroenteritis
Dientamoebiasis
Opisthorchiasis
Amoebiasis