The cause of this wide range in severity of symptoms is not fully known but the intestinal flora of the infected host may play a role. Diarrhea is less likely to occur in people from developing countries.Symptoms typically develop 9–15 days after exposure, but may occur as early as one day. The most common and prominent symptom is chronic diarrhea, which can occur for weeks or months if untreated. Diarrhea is often greasy and foul-smelling, with a tendency to float. This characteristic diarrhea is often accompanied by a number of other symptoms, including gas, abdominal cramps, and nausea or vomiting. Some people also experience symptoms outside of the gastrointestinal tract, such as itchy skin, hives, and swelling of the eyes and joints, although these are less common. Fever occurs in only about 15% of people, in spite of the nickname "beaver fever".Prolonged disease is often characterized by diarrhea, along with malabsorption of nutrients in the intestine. This malabsorption results in fatty stools, substantial weight loss, and fatigue. Additionally, those with giardiasis often have difficulty absorbing lactose, vitamin A, folate, and vitamin B12. In children, prolonged giardiasis can cause failure to thrive and may impair mental development. Symptomatic infections are well recognized as causing lactose intolerance, which, while usually temporary, may become permanent. Cause
Giardiasis 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.
Surveillance data (for 2013 and 2014) reports six outbreaks (96 cases) of waterborne giardiasis contracted from rivers, streams or springs and less than 1% of reported giardiasis cases are associated with outbreaks.Person-to-person transmission accounts for the majority of Giardia infections, and is usually associated with poor hygiene and sanitation. Giardia is often found on the surface of the ground, in the soil, in undercooked foods, and in water, and on hands that have not been properly cleaned after handling infected feces. Water-borne transmission is associated with the ingestion of contaminated water. In the U.S., outbreaks typically occur in small water systems using inadequately treated surface water. Venereal transmission happens through fecal-oral contamination. Additionally, diaper changing and inadequate handwashing are risk factors for transmission from infected children. Lastly, food-borne epidemics of Giardia have developed through the contamination of food by infected food-handlers. Vaccine
There are no vaccines for humans yet, however there are several vaccine candidates in development. They are targeting: recombinant proteins, DNA vaccine, variant-specific surface proteins (VSP), cyst wall proteins (CWP), giadins and enzymes.At present, one commercially available vaccine exists – GiardiaVax, made from G. lamblia whole trophozoite lysate. It is a vaccine for veterinary use only in dogs and cats. GiardiaVax should promote production of specific antibodies. Treatment
Treatment is not always necessary as the infection usually resolves on its own.