Hospital: Report by IDSS, facsimile, mail or phone
Lab: Report by IDSS, facsimile, mail or phone
Physicians: Report by facsimile, mail or phone
Local Public Health Agency (LPHA): Only clusters of cases warrant specific follow-up
Iowa Department of Public Health
Disease Reporting Hotline: (800) 362-2736
Secure Fax: (515) 281-5698
Giardia lamblia is a protozoan parasite that has two forms: cyst (inactive form) and trophozoite (active form). Infected persons can shed both trophozoites and cysts in stool
B. Clinical Description
Symptoms: of giardiasis are variable, and usually asymptomatic, but can include soft, non-bloody, foul-smelling diarrhea. Abdominal cramps and a “bloated” feeling with excess gas often accompany the diarrhea. The diarrhea can be chronic or intermittent and it can be accompanied by fatigue and steatorrhea (fatty stools). Appetite loss combined with malabsorption can lead to significant weight loss, failure to thrive and anemia.
Onset: is usually abrupt. Diarrhea may occur after meals, is non-bloody and is mucous-like 25% of the time.
Complications: are not common. However diarrhea may last 2 - 6 weeks.
Common reservoirs: Humans and some animals (dogs, cats, rodents, cattle, deer, elk, beaver, and muskrats) are reservoirs, although the public health importance of most nonhuman reservoirs is debated. Overall, humans are the most important source of other human infections. Wildlife such as deer, elk, and beaver may be important in contaminating surface water supplies; domestic animals (e.g., dogs) may be a source for some human exposures. The most common source in Iowa is young children, especially those in child care.
D. Modes of Transmission
Spread: Giardia is principally spread person-to-person. Persons become infected by fecal-oral transfer of cysts from the feces of an infected individual, especially in institutions and child care centers. Transmission can also occur person-to-person through certain types of sexual contact (e.g., oral-anal contact. Giardiasis has developed with ingestion with as few as 10 cysts.
Environmental: Localized outbreaks may occur from fecally contaminated water, such as stream and lake waters and swimming pools that are contaminated by human and animal feces. Eating food contaminated by an infected food handler can be a source, but this has been rarely documented. Diapered children using “kiddie” pools filled with tap water without added chlorine or bleach is a high-risk source of transmission.
E. Incubation period
The incubation period can vary from 3 - 25 days (or longer); the median is 7-10 days.
F. Period of Communicability or Infectious Period
The disease is communicable for as long as the infected person excretes the organism, which may be many months. The asymptomatic carrier rate is high.
Giardiasis has a worldwide distribution. Children are infected more frequently than adults. Prevalence is higher in areas of poor sanitation and in institutions with children who are not toilet trained, especially child care centers. It infects nearly 2% of adults and 6% to 8% of children in developed countries worldwide. Nearly 33% of people in developing countries have had giardiasis. In the United States, Giardia infection is the most common intestinal parasitic disease affecting humans. Surveys conducted in the United States have demonstrated prevalence rates of Giardia in stool specimens that range from 1% to 30%, depending on location and age. Cases occur more commonly in the summer and fall months.
H. Bioterrorism Potential
I. Additional Information
The Council of State and Territorial Epidemiologists (CSTE) surveillance case definitions for Giardiasis can be found at: www.cdc.gov/osels/ph_surveillance/nndss/phs/infdis.htm#top
CSTE case definitions should not affect the investigation or reporting of a case that fulfills the criteria in this chapter. (CSTE case definitions are used by the state health department and the CDC to maintain uniform standards for national reporting.)
American Academy of Pediatrics. 2006 Red Book: Report of the Committee on Infectious Diseases, 27th Edition. Illinois, American Academy of Pediatrics, 2006.
CDC Website. Giardiasis www.cdc.gov/parasites/giardia/epi.html
Heymann, D. L. ed. Control of Communicable Diseases Manual, 20th Edition. Washington, DC, American Public Health Association, 2015.
State Hygienic Laboratory, www.shl.uiowa.edu/