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Giardia

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G. intestinalis trophozoites in a Giemsa stained mucosal imprint. Photo credit: DPDx, CDC

Giardia trophozoites stained with trichrome. Credit: Waterborne Disease Prevention Branch, CDC

Giardiasis is the most frequently diagnosed intestinal parasitic disease in the United States and among travelers with chronic diarrhea^[1]. Signs and symptoms may vary and can last for 1 to 2 weeks or longer^[2,5]. In some cases, people infected with Giardia have no symptoms^[2-4].

Acute symptoms include^[2,4,6]:

Diarrhea
Gas
Greasy stools that tend to float
Stomach or abdominal cramps
Upset stomach or nausea/vomiting
Dehydration (loss of fluids)

Other, less common symptoms include itchy skin, hives, and swelling of the eye and joints^[2,7,8]. Sometimes, the symptoms of giardiasis might seem to resolve, only to come back again after several days or weeks. Giardiasis can cause weight loss and failure to absorb fat, lactose, vitamin A and vitamin B12^[2,4,9-12].

In children, severe giardiasis might delay physical and mental growth, slow development, and cause malnutrition^[2,11,13-17].

Reference

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Nash TE, Herrington DA, Losonsky GA, Levine MM. Experimental human infections with Giardia lamblia. J Infect Dis. Dec 1987;156(6):974-984.
Gardner TB, Hill DR. Treatment of giardiasis. Clin Microbiol Rev. Jan 2001;14(1):114-128.
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Hill DR. Giardia lamblia. In: Gillespie SH, Pearson RD, eds. Principles and practice of clinical parasitology. Chisester, England: Joan Wiley & Sons; 2001.
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Farthing MJ. Giardia comes of age: progress in epidemiology, immunology and chemotherapy. J Antimicrob Chemother. Nov 1992;30(5):563-566.
Solomons NW. Giardiasis: nutritional implications. Rev Infect Dis. Jul-Aug 1982;4(4):859-869.
Sullivan PB, Marsh MN, Phillips MB, et al. Prevalence and treatment of giardiasis in chronic diarrhoea and malnutrition. Arch Dis Child. Mar 1991;66(3):304-306.
Farthing MJ, Mata L, Urrutia JJ, Kronmal RA. Natural history of Giardia infection of infants and children in rural Guatemala and its impact on physical growth. Am J Clin Nutr. Mar 1986;43(3):395-405.
Berkman DS, Lescano AG, Gilman RH, Lopez SL, Black MM. Effects of stunting, diarrhoeal disease, and parasitic infection during infancy on cognition in late childhood: a follow-up study. Lancet. Feb 16 2002;359(9306):564-571.
Newman RD, Moore SR, Lima AA, Nataro JP, Guerrant RL, Sears CL. A longitudinal study of Giardia lamblia infection in north-east Brazilian children. Trop Med Int Health. Aug 2001;6(8):624-634.
Botero-Garces JH, Garcia-Montoya GM, Grisales-Patino D, Aguirre-Acevedo DC, Alvarez-Uribe MC. Giardia intestinalis and nutritional status in children participating in the complementary nutrition program, Antioquia, Colombia, May to October 2006. Rev Inst Med Trop Sao Paulo. May-Jun 2009;51(3):155-162.