Giardiasis

 

Literature Recommendations

Exclusion-Case in SOS*
(Symptomatic)

Yes [1,2,3,4,5,6,7,9,15]
Grade I-A

Exclusion-Case in SOS*
(Asymptomatic or previously symptomatic but now recovered)

No [15]
Clearance required in SOS* [9b ]
Exclusion in Special Cases [4a]
Grade I-A

Clearance-Case in SOS*

Disagreement exist between sources on clearnace and exclusion c
Grade I-A

Exclusion of Contact
(Symptomatic)

Yes [1,2,3,4,5,6,7,9,15]
Grade I-A

Exclusion of Contact
(Asymptomatic)

No [15]
Clearance required in SOS* [9b]
Exclusion in Special Cases [4a]
Grade I-A

Exclusion-Case in Children
(Group setting with children ≤ 5 years of age)
(Symptomatic)

Yes [1,2,3,5,6,9,15]
Grade I-A

Exclusion-Case in Children
(Group setting with children ≤ 5 years of age)
(Asymptomatic or previously symptomatic but now recovered)

No [15]
Clearance required [9b]
Grade I-A

◊ Applicable Code

None
* SOS (Sensitive Occupations or Situations) is not defined precisely in either the Code of Regulations or Health & Safety Code. See Attachment 2 for the definition of food workers.
◊ See California Code of Regulations, Attachment 1, for details.
+ Local health departments may elect to follow more restrictive exclusion and clearance criteria

a See number three under the Preventive Measures Exclusions.
b See number six under the Preventive Measures Exclusions.
c Three sources [4, 9, 15] state that 2 stools/24 hours apart (taken minimum of 48 hours after stopping antibiotic) but two sources [5, 6] state that only 24 hrs from last episode of diarrhea without any stool clearance.

Disease Trends in the U.S.:

According to the Red Book published by AAP, these are trends of giardiasis in United States: [2]

  • Surveys conducted in the United States have demonstrated prevalence rates of Giardia organisms in stool specimens that range from 1% to 20%, depending on geographic location and age. Duration of cyst excretion is variable but can be months. The disease is communicable for as long as the infected person excretes cysts.
  • Numerous risk factors have been identified for giardiasis.  A telephone survey of patients with giardiasis showed that in comparison with controls, they were more likely to drink water from surface or shallow wells, have family members in day care or with a diagnosis of giardiasis or to have gone camping or traveled out of the country.  A study of 133 patients with giardiasis found that 108 (81%) had a history of travel, mostly to developing areas, and that the remainder either were male homosexuals (14%) or had immunodeficiency (3%). 
  • Over 20,000 cases per year have been reported in the U.S. since 1998, but because of underreporting, the true numbers are much higher. The number of cases reported from June through October is twice as high as the number reported for the remainder of the year. In general, the infection rate is higher in the northern states. These observations may reflect the ability of cysts to survive for prolonged periods of time in colder drinking and recreational water.”

According to the Giardiasis Surveillance program these are trends in United States from 1992-2005. It should be kept in mind that these are only a small fraction of the cases that are reported to Center for Disease Control and Prevention (CDC) through passive surveillance systems. If one were to take into account 1) asymptomatic cases, 2) symptomatic cases that do not seek medical care, 3) diarrheal illnesses that are treated without stool confirmation and 4) not all positive laboratory results are reported to public health officials, the estimated cases of Giardiasis per year would be much higher.  It should also be noted that there was a bimodal age distribution in giardiasis rates.  The highest rates of giardiasis occurred among children aged 0-9 years and followed by persons in their early 30’s to early 40’s. [11, 12, 13]

  • According to the 1992-1997 Giardiasis Surveillance, in 1992, a total of 12,793 cases of giardiasis were reported. The number of reported cases eventually doubled by 1994. Between 1994 and 1997, case reporting plateaued at 25,389–27,778 cases reported per year, with sex distribution being approximately equal. [11]
  • According to the 1998-2002 Giardiasis Surveillance, the total number of reported cases of giardiasis decreased from 24,226 from 1998 to 19,708 for 2001 and then increased to 21, 300 for 2002. [12]
  • According to the Giardiasis Surveillance of 2003-2005, the total number of reported cases of giardiasis remained relatively stable.  Case reports increased 4.4% from 20,084 for 2003 to 20,962 for 2004 and then decrease 4.2% to 20,075 for 2005. [13]

Outbreaks

  1. Daniels et al. examined outbreaks in the primary and secondary schools, colleges and universities from January 1, 1973 to December 31, 1997.  The local health departments reported 604 outbreaks of foodborne disease in the schools. In 60% of the outbreaks an etiology was not determined, and in 45% specific food vehicle of transmission was not determined.  The most commonly reported food preparation practices that contributed to these school-related outbreaks were improper food storage and holding temperatures and food contaminated by a food handler.  Only 1% of the total outbreaks with known etiology were linked to parasites.  Only two outbreaks with known etiology were linked to Giardia lamblia in United States schools from 1973 to 1989.  [7]
  2. According to Hlavsa et al. “although giardiasis cases can occur sporadically, outbreaks are well documented. During 1991–2000, Giardia was identified as a causal agent of 9.4% (10 of 106) of reported recreational water-associated and 16.2% (21 of 130) of reported drinking water-associated outbreaks of gastroenteritis of known or suspected infectious etiology. Additionally, foodborne outbreaks of giardiasis linked to infected foodhandlers and uninfected foodhandlers who diapered infected children have been reported. Outbreaks resulting from person-to-person transmission in child care centers also have been reported.” [12]
  3. According to Yoder et al. “although giardiasis cases occur sporadically, outbreaks are well documented. During 1995-2004, Giardia was identified as a causal agent of five (3.7%) of 136 reported cases of recreational water-associated gastroenteritis outbreaks and of 14 (13%) of 108 reported cases of drinking water-associated gastroenteritis outbreaks.  In addition, foodborne outbreaks of giardiasis linked to infected foodhandlers and to uninfected foodhandlers who diapered infected children prior to handling food have been reported. Outbreaks resulting from person-to-person transmission in child care centers also have been reported.  Communitywide outbreaks might be waterborne initially but spread subsequently through the community by person-to-person transmission. Few direct animal-to-human outbreaks have been documented although linkages have been identified between canine and human transmission. In addition, animal contamination of water (e.g., an infected dead beaver in a water system intake) has been associated with drinking water outbreaks. However, the zoonotic transmission of giardiasis is not believed to play a major role in human disease.” [13]
  4. Katz et al. conducted a retrospective cohort study to determine the source for an outbreak that occurred from June-December 2003 at a country club in a suburb of Boston, Massachusetts.  What he found was two modes of transmission, one linked to the children’s pool at the country club and other person-to-person spread in the community. This evidence is shown by a cluster of 30 primary cases and 105 secondary cases with an overall attack rate of 25%.[14]
  5. Bartlett et al. conducted a prospective randomized controlled trial comparing three strategies for control of Giardia in infant-toddler day care centers: Group 1, exclusion and treatment of symptomatic and asymptomatic infected children; Group 2, exclusion and treatment of symptomatic infection only; Group 3, exclusion and treatment of symptomatic infection, treatment of asymptomatic infection in the center. The study included 31 day care centers with 4180 child-months of observation.  Giardia prevalence was determined before intervention and 1, 2, 4, and 6 months later; new infants and toddlers were tested on admission. Initial Giardia prevalence was 18% to 22% in the three groups. Giardia was identified in 10.5% of 676 new infants and toddlers entering study day care centers during the 6-month follow-up. Giardia prevalence by intervention group was 8%, 12%, and 7% at 1 month, and 7%, 8%, and 8% at 6 months. Bartlett et al. concluded that the stricter intervention resulted in greater cost in terms of child day care and parents' work days lost, but did not result in significantly better control of Giardia infections in this day care environment. [15]

Giardiasis is the most common parasitic cause of diarrhea in the United States. It is an acute symptomatic infection that causes a broad spectrum of clinical manifestations. Children can have occasional days of acute watery diarrhea with abdominal pain, or they may experience a protracted, intermittent, often debilitating disease, which is characterized by passage of foul-smelling stools associated with flatulence, abdominal distention, and anorexia. Anorexia combined with malabsorption can lead to significant weight loss, failure to thrive, and anemia. Asymptomatic infection is common. [1, 2, 5, 10]

Organism: Giardia intestinalis (syn. Giardia lamblia) is a flagellate protozoan which lives in the duodenum and jejunum in the form of a trophozoite and cyst; the infective form is the cyst. Infection is limited to the small intestine and biliary tract. [1, 2]

Reservoir of infection: Humans are the principal reservoir of infection, but dogs, cats, beavers, and other animals can be the source.  These animals can contaminate water with feces containing cysts that are infectious for humans. [1, 2, 8, 10]

Modes of transmission:

  • People become infected directly by hand-to-mouth transfer of cysts from feces of an infected person or indirectly by ingestion of fecally contaminated water or food. Many people who become infected are asymptomatic. Most community-wide epidemics have resulted from a contaminated water supply. Epidemics resulting from person-to-person transmission occur in child care centers and in institutions for people with developmental disabilities. Staff and family members in contact with people in these settings occasionally become infected. [1,2,3,5,8,10]
  •  According to Hlavsa et al. “persons at increased risk for infection include 1) travelers to disease-endemic areas; 2) children in child care settings; 3) close contacts of infected persons (e.g., those in the same family or household or in the child care setting); 4) persons who ingest contaminated drinking water; 5) persons who swallow contaminated recreational water (e.g., water in lakes, rivers, and pools); 6) persons taking part in outdoor activities (e.g., backpacking and camping) who consume unfiltered, untreated water or who fail to practice hygienic behaviors (e.g., hand washing); 7) persons who have contact with infected animals; and 8) men who have sex with men. The relative contribution of person-to-person, animal-to-person, foodborne, and waterborne transmission to sporadic human giardiasis in the United States is unknown.” [12]

Attack rates:            

  • Child Care Setting attack rate specific to giardiasis including clinical and subclinical cases [10]
    • 17%  to 47% among attendees
    • 10%  to 35% adult workers
    • 5%  to 25% one or more of family member will become infected
  • A multicenter study identified Giardia as the cause of diarrhea in 15% of non-dysenteric children examined in outpatient clinics. Investigation of a giardiasis outbreak in a day care facility determined that 47% of ill children transmitted the infection to more than one household contact [13]
Infectious dose

  •  Fewer than 100 organisms (cysts) can cause giardiasis in a healthy volunteer. [10]
  • The infectious dose is low; ingestion of 10 cysts has been reported to cause infection. Infected persons have been reported to shed <1000000000 cysts in their stool per day and to excrete cysts for months [12,14]

Incubation Period – Average of 9 days (range= 7 hours-14 days) [10, 14]

Infectious Period: The disease is communicable for as long as the infected person excretes cysts. [8] Shedding of the organism can be seen from 3 weeks to 6 month [10]

Asymptomatic state:

  • Many people who become infected with Giardia remain asymptomatic. [8]
  • Katz et al. found in his retrospective cohort study of Boston, Massachusetts that 32 % of confirmed infections were asymptomatic.[14]

Diagnosis: Identification of trophozoites or cysts in direct smear examination or immunofluorescent antibody testing of stool specimens or duodenal fluid is diagnostic. A single direct smear examination of stool has a sensitivity of 75% to 95%. Sensitivity is higher for diarrheal stool specimens, because these contain a higher concentration of organisms. Sensitivity is increased by examining 3 or more specimens collected every other day. The specificities of the ELISA and DFA tests have also been near 100% with the caveat that there is no true gold standard for the diagnosis of giardiasis, which makes determination of sensitivity and specificity difficult. The DFA may be the most sensitive test, but it requires fluorescent microscopy. All of the immunodetection assays offer the advantage over standard fecal microscopy (O and P) that the sensitivity is probably as high with one specimen as for three O and P specimens. However, fecal microscopy must still be done if other parasites are suspected. [1, 2, 8, 10]

Preventive Measures
Exclusions:

  1. Australian Blue Book suggests that school exclusion criteria apply until diarrhea has ceased or until a medical certificate of recovery is produced. Food handlers should not attend work until diarrhea has ceased and strict hygienic food preparation practices should be maintained.  It is also recommended that health care workers or child care workers do not attend work until diarrhea has ceased. [1] Guidelines and Consensus Document {Grade III-A}
  2. The Red Book advises day care workers to follow good hand washing techniques while caring for children, especially after changing diapers.  Rationale based on the fact that in the United States and other developed countries, the day care setting is one of the leading sources of transmission of giardiasis. Evident by the fact that giardiasis is a common problem in day care centers. An investigation of an outbreak of diarrhea identified Giardia cysts in 26 (54%) of 48 children tested. Surveys of two other day care centers identified Giardia in 29% to 38% of children compared to a background prevalence of 2%, whereas a study of children from 118 day care centers in Denver identified a prevalence of 16% compared to a background prevalence of 9%.  Secondary transmission rate among households with infected child were 47 %. [2] Guidelines and Consensus Document {Grade III-A}
  3. A guideline produced by Ontario Medical Association and the Ontario Hospital Association states following exclusion in outbreak situations: [4] Guidelines and Consensus Document {Grade III-A}
    1. Food handlers and epidemiologically-linked patient care workers may be asked to submit stools for examination. Symptomatic persons must remain off work until two stool specimens are negative for the outbreak pathogen; the stools must be collected at least 24 hours apart, with the first being collected following at least 24 hours without diarrhea. If the individual has been treated with antibiotics, the first stool must not be submitted until at least 48 hours following cessation of the antibiotic.
    2. Asymptomatic persons should not work during an outbreak if their stool specimens are positive for the outbreak pathogen. Once the outbreak is declared over by the Medical Officer of Health, asymptomatic carriers of the outbreak pathogen may return to work. Prior to returning to work, all staff must be assessed and instructed in personal hygiene and high-risk food preparation, either by hospital staff, or by public health inspection staff.
  4. Daniels et al. states that “several outbreaks in schools have been attributed to contamination of food by food-handlers who worked while ill or had poor personal hygiene.  In our review of reported foodborne outbreaks in school, 57% of outbreaks were attributed to likely contamination by a food-handler. The adoption of a work policy that includes paid leave for food handlers with gastroenteritis would probably increase compliance with illness related work exclusion policies. Training and certifying all food handlers in school cafeterias in specific techniques, such as good personal hygiene, adequate hand washing, proper cooling and reheating of foods and methods of preventing cross-contamination between cooked and raw foods, would also likely reduce the incidence of foodborne disease outbreaks.” [7] Review of Outbreaks and Epidemiology {Grade III-A}
  5. Dennehy suggest that asymptomatic carriers should not be treated except to prevent spread in situations where they are in close contact with immunocompromised patients. [8] Evidence Based Literature. {Grade III-A}
  6. Guerrant et al. suggest two preventive measures in the guidelines for the management of infectious diarrhea. [9] Evidence based reviews with guidelines formed out of reviewed literary sources {Grade III-A}
    1. Diagnostic fecal testing for Public Health reasons.
      • Diagnostic testing of stool specimens is indicated for certain groups of people who are not themselves patients. Food-handlers in food service establishments and health care workers involved in direct patient care should be tested for bacterial pathogens if they have diarrhea because of their potential to transmit infection to large numbers of persons. Similarly, diarrheal illness in a day-care attendee, day-care employee, or resident of an institutional facility (e.g., psychiatric hospital, prison, or nursing home) should be evaluated for bacterial or parasitic infection because gastrointestinal illnesses in these settings may indicate that a disease outbreak is occurring.
    2. Follow-up testing
      • In certain situations, assurance should be obtained that a patient with a laboratory-confirmed bacterial or parasitic diarrheal disease has been cured or is no longer a fecal carrier. Because food-handlers and health care workers can transmit bacterial and parasitic diseases even if they are asymptomatic, it is recommended that before returning to their jobs these persons have 2 consecutive negative stool samples taken 24 h apart and at least 48 h after resolution of symptoms. If the patient has received antimicrobial therapy, the first stool specimen should be obtained at least 48 h after the last dose. Furthermore, if food-handlers or health care workers are symptomatic, they should be excluded from directly handling food and from caring for high-risk patients.
  7. Katz et al. suggests that to prevent future outbreaks we need to focus on proper pool maintenance, including close monitoring of disinfection levels and implementing protocols to respond to contamination events.  In addition, patron education should address refraining from swimming while ill with gastrointestinal symptoms, use of appropriate swim nappies for young children (or exclusion of children requiring nappies), and appropriate hand washing. [14] Review of Outbreaks and Epidemiology {Grade II-A}
  8. Bartlett et al. concluded that the stricter intervention (exclusion and treatment of symptomatic and asymptomatic infection) resulted in greater cost in terms of child day care and parents' work days lost, but did not result in significantly better control of Giardia infections in this day care environment. [15] Review of Outbreaks and Epidemiology {Grade I-A}

References:

  1. The Communicable Diseases Section, Public Health Group, Victorian Department of Human Services, Australia.  Blue book - Guidelines for the control of infectious diseases Revised edition 2005. Guidelines and Consensus document
  2. American Academy of Pediatrics. Red Book – The Report of the Committee of Infectious Diseases. 2006 Edition.  Guidelines and Consensus document
  3. PHLS Advisory Committee on Gastrointestinal infections. Preventing Person to Person Spread Following Gastrointestinal Infections: Guidelines for Public Health Physicians and Environmental Health officers. Communicable Disease and Public Health 2004; 7(4):362-384. Guidelines and Consensus Document
  4. Ontario Medical Association and the Ontario Hospital Association. Enteric Diseases Surveillance Protocol for Ontario Hospitals. Published November 1989/Revised/ Reviewed June 2005 Guidelines and Consensus Document
  5. UK’s Health Protection Agency.  Guidelines on the Management of Communicable Diseases in School and Nurseries.  Accessed at http://www.hpa.org.uk/infections/topics_az/schools/schools.pdf  Guidelines and Consensus Document
  6. Richardson M, Elliman D, Maguire H, et al. Evidence base of incubation periods, periods of infectiousness and exclusion policies for the control of communicable diseases in schools and preschools. Pediatric ID Journal Vol. 20 April 2001; 380-391. Evidence based reviews with guidelines formed out of reviewed literary sources
  7. Daniels NA, Mackinnon L, et al. Foodborne disease outbreaks in United States schools. Pediatr Infect Dis J, 2002; 21:623-8. Review of Outbreaks and Epidemiology
  8. Dennehy, PH. Acute Diarrheal Disease in Children: Epidemiology, Prevention, and Treatment. Infect Dis Clin N Am 19 (2005) 585-602 Evidence Based Literature
  9. Guerrant, RL, Gilder TV, Steiner TS.  Practice Guidelines for the Management of Infection Diarrhea. CID 2001;32:331-50 Evidence based reviews with guidelines formed out of reviewed literary sources
  10. Musher DM, Musher BL. Contagious Acute Gastrointestinal Infections. N Engl J Med 2004;351:2417-27 Evidence Based Literature
  11. CDC. Giardiasis Surveillance – United States, 1992-1997.  MMWR August 11, 2000, Vol. 49 / No. SS-7 Review of Outbreaks and Epidemiology
  12. CDC. Giardiasis Surveillance – United States, 1998-2002. MMWR January 28, 2005, Vol. 54 / SS-1 Review of Outbreaks and Epidemiology
  13. CDC. Giardiasis Surveillance – United States 2003-2005.  MMWR September 7, 2007 / 56(SS07);11-18 Review of Outbreaks and Epidemiology
  14. Katz DE, Heisey-Grove D, Beach M, et al. Prolonged outbreak of giardiasis with two modes of transmission. Epidemiol. Infect. (2006) , 134, 935-941 Review of Outbreaks and Epidemiology
  15. Bartlett AV, Englender SJ, Jarvis BA, et al. Controlled Trial of Giardia lamblia: Control Strategies in Day Care Centers. American Journal of Public Health, June 1991, Vol. 81, No. 6 Review of Outbreaks and Epidemiology