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.
However, if the illness is acute or symptoms persist and medications are needed to treat it, a nitroimidazole medication is used such as metronidazole, tinidazole, secnidazole or ornidazole.The World Health Organization and Infectious Disease Society of America recommend metronidazole as first line therapy. The US CDC lists metronidazole, tinidazole, and nitazoxanide as effective first-line therapies; of these three, only nitazoxanide and tinidazole are approved for the treatment of giardiasis by the US FDA. A meta-analysis done by the Cochrane Collaboration found that compared to the standard of metronidazole, albendazole had equivalent efficacy while having fewer side effects, such as gastrointestinal or neurologic issues. Other meta-analyses have reached similar conclusions. Both medications need a five to 10 day long course; albendazole is taken once a day, while metronidazole needs to be taken three times a day. The evidence for comparing metronidazole to other alternatives such as mebendazole, tinidazole or nitazoxanide was felt to be of very low quality. While tinidazole has side effects and efficacy similar to those of metronidazole, it is administered with a single dose.Resistance has been seen clinically to both nitroimidazoles and albendazole, but not nitazoxanide, though nitazoxanide resistance has been induced in research laboratories. The exact mechanism of resistance to all of these medications is not well understood. In the case of nitroimidazole-resistant strains of Giardia, other drugs are available which have showed efficacy in treatment including quinacrine, nitazoxanide, bacitracin zinc, furazolidone and paromomycin.