1. Reason for surveillance
2. Case definition
3. Notification criteria and procedure
4. The disease
5. Managing single notifications

1. Reason for surveillance

• To identify the source of the infection and to prevent further cases
• To monitor the epidemiology to inform the development of better prevention strategies.

2. Case definition

Confirmed case

A confirmed case requires laboratory definitive evidence.

Laboratory definitive evidence

Detection of Giardia lamblia.

Factors to be considered in case identification

Laboratory diagnosis of giardiasis usually involves isolation of Giardia lamblia cysts or trophozoites from stool samples, samples of duodenal contents or occasionally a small intestinal biopsy. NAT or antigen detection kits for faeces are available. Giardia lamblia is also known as Giardia duodenalis and Giardia intestinalis.

3. Notification criteria and procedure

Giardiasis is to be notified by laboratories on diagnosis (ideal reporting by routine mail).

Only confirmed cases should be entered onto NCIMS.

4. The disease

Infectious agent

The flagellate protozoan Giardia duodenalis.

Mode of transmission

Giardiasis is transmitted by the faecal oral route:

• From person-to-person, by hand-to-mouth transfer of cysts from infected faeces
• By ingestion of faecally contaminated water.

Timeline

The typical incubation period is usually 3 to 25 days or longer; the median is 7 to 10 days. Giardia is infectious for the duration of excretion of the organism, which may be months.

Clinical presentation

Giardiasis is frequently asymptomatic, but may present as acute or chronic diarrhoea, steatorr​hoea, bloating, abdominal cramps, fatigue and malnutrition.

5. Managing single notifications

Response time

Investigation

Within 1 working day of notification of a cluster of confirmed cases begin follow-up investigation. Cases that do not form part of a cluster are followed up at the discretion of the local PHU Director.

Data entry

Within 3 working days of notification enter confirmed cases on NCIMS.

Response procedure

The response to a notification will normally be carried out in collaboration with the case's health carers. But regardless of who does the follow-up, PHU staff should ensure that action has been taken to:

• Confirm the onset date and symptoms of the illness
• Confirm results of relevant pathology tests, or recommend the tests be done
• Find out if the case or relevant care-giver has been told what the diagnosis is before beginning the interview
• Seek the doctor's permission to contact the case or relevant care-giver
• Review case and contact management
• Identify and control the likely source of a cluster.

Case management

Investigation and treatment

Refer to Therapeutic Guidelines: Antibiotic.

Education

The case or relevant care-giver should be informed about the nature of the infection and the mode of transmission. Emphasise the importance of hygienic practices, particularly hand washing before eating and preparing food and after going to the toilet.

Isolation and restriction

Children with diarrhoea should not attend childcare for 24 hours after diarrhoea has ceased.

Environmental evaluation

Where a water-borne source is suspected, collect samples for analysis, and discuss with the Water Unit.

Contact management

Identification of contacts

Not applicable.

Investigation and treatment

When a cluster has been identified in a childcare centre, the director of the facility should be asked to telephone the PHU immediately if new cases of diarrhoea are reported. The facility should be telephoned or visited at least once a week for 2 weeks after onset of the last case to verify that surveillance and appropriate preventive measures are being carried out.

Public warnings

Where an ongoing source of infection is suspected, discuss further public health actions with the Communicable Diseases Branch.