Giardiasis

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 and 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. Waterborne 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 and 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.

sources of information

·         The blue book: Guidelines for the control of infectious diseases