Giardiasis

Victorian statutory requirement

Giardiasis (Group B disease) must be notified in writing within five days of diagnosis.

School exclusion: exclude cases from child care and school until diarrhoea has ceased or until a medical certificate of recovery is produced.

Infectious agent

Giardia lamblia is a flagellate protozoan which lives in the duodenum and jejunum.

Identification

Clinical features
Giardia infection is usually asymptomatic but may present as acute or chronic diarrhoea associated with abdominal cramps, bloating, nausea, vomiting, fever, fatigue and weight loss. Fat malabsorption may lead to steatorrhoea. Symptoms usually last one to two weeks or months. The rate of asymptomatic carriage may be high.

Method of diagnosis
Stool microscopy for cysts or trophozoites can be used for diagnosis of Giardia however a negative test does not preclude infection.

Incubation period

The incubation period is usually one to three weeks but it can be longer. It is on average seven to ten days.

Public health significance & occurrence

Occurrence is worldwide and endemic in most regions. Over 800 cases are reported in Victoria each year. Infection is detected more frequently in children than adults. It is readily transmitted in institutions such as day care centres among children who are not toilet trained. Other risk factors for infection include travel to high risk areas, immunosuppression, male to male sexual intercourse and achlorhydria.

Reservoir

Reservoirs include humans and animals as well as contaminated waters.

Mode of transmission

Transmission occurs person to person and animal to person via hand to mouth transfer of cysts from infected faeces or faecally contaminated surfaces. Water-borne outbreaks may occur due to faecal contamination of public water supplies or recreational swimming areas.

Period of communicability

It is communicable for the entire period of cyst excretion.

Susceptibility & resistance

Everyone is susceptible to infection. Relapses may occur.

Control measures

Preventive measures
Preventative measures include:

educating families and personnel of day care centres in personal hygiene such as the need for hand washing before meals, after toilet use and changing nappies
protecting public water supplies against faecal contamination
educating travellers about the need for safe food and water consumption.

Control of case
Symptomatic cases are usually treated with metronidazole or tinidazole. Consult the current version of Therapeutic guidelines: antibiotic (Therapeutic Guidelines Limited). Treatment of asymptomatic carriers is rarely warranted.

Dispose of faeces in a sanitary and hygienic manner and disinfect soiled clothing and other articles concurrently.

School exclusion criteria apply until diarrhoea has ceased or until a medical certificate of recovery is produced. Food handlers should not attend work until diarrhoea 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 diarrhoea has ceased.

Control of contacts
The diagnosis should be considered in symptomatic contacts. Active case finding among contacts is rarely indicated.

Control of environment
Disinfection of contaminated areas or water sources is required. Particular attention should be paid to potentially contaminated surfaces in child care centres.

Outbreak measures

Two or more related cases may indicate an outbreak and requires prompt reporting to the Department of Human Services. Attempt to identify a potentially common exposure such as child care attendance or exposure to farm animals and recreational swimming areas. Epidemiological, environmental and laboratory investigations may be warranted as per the Department’s Guidelines for the investigation of gastrointestinal illness.

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