LEPTOSPIROSIS

Last updated: 06 September 2004

1. Reason for surveillance

• To monitor the epidemiology to inform the development of better prevention strategies.

2. Case definition

A confirmed case requires laboratory definitive evidence only.

Laboratory definitive evidence

• Isolation of pathogenic Leptospira species, or

• A fourfold or greater rise in Leptospira agglutination titre between acute and convalescent phase sera obtained at least two weeks apart and preferably conducted at the same laboratory, or

• A single Leptospira micro agglutination titre greater than or equal to 400 supported by a positive EIA IgM result.

Clinical evidence
Not applicable

Epidemiological evidence
Not applicable

3. Notification criteria and procedure

Leptospirosis is to be notified by:

• Laboratories on microbiological confirmation (ideal reporting by routine mail).

Only confirmed cases should be entered onto NDD.

4. The disease

Infectious agent
Leptospira interrogans spirochetes.

Mode of transmission
Leptospirosis is transmitted by direct contact with the urine or tissues of infected animals. It can also be transmitted to humans who are in contact with water, soil or mud contaminated with infected urine, or who ingest contaminated water.

Human-to-human transmission occurs only rarely (e.g., sexual transmission, transplacental transmission, transmission via breast milk). Blood is potentially infectious in the first week of the disease and urine is infectious from the end of the first week and can remain infectious for months. The route of infection is typically via skin cuts and abrasions or through direct contact with mucous membranes.

Often there is a history of contact with animals or exposure to environments where potentially infected animals are present. Many animals can carry leptospira and may be completely asymptomatic. Commonly implicated animals are cattle, pigs, sheep, dogs and rats.

Timeline
The typical incubation period is 5 to 14 days (range 2 to 30 days).

Clinical presentation
The usual clinical presentation is fever, chills, headache, severe myalgia, (particularly of the calves, thighs and lumbar region) and conjunctival suffusion. Severity varies with the infecting serovar.

About 10% of cases progress to severe disease:

• Weil's (syndrome jaundice, renal failure, haemorrhage and myocarditis)

• Meningitis and meningoencephalitis

• Pulmonary haemorrhage and ARDS.

Case fatality rate increases with increasing age and comorbidities.

5. Managing single notifications

Response times
Investigation
Within 3 working days of a confirmed case begin follow-up investigation.

Data entry
Within 5 working days of notification enter confirmed cases on NDD.

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

• Seek the doctor's permission to contact the case or relevant care-giver

• Find out if the case or relevant care-giver has been told what the diagnosis is before beginning the interview

• Identify the likely source of infection.

Case management
Treatment and Investigation
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. To avoid future infection cases should be advised to avoid urine or tissues of infected animals and avoid swimming in potentially contaminated water or walking barefoot in mud or moist soil that may have been contaminated with animal urine.

If direct or indirect contact with urine or infected animal tissues is anticipated, skin abrasions should be covered with an occlusive dressing and gloves and other protective clothing should be worn.

Exposure Investigation
A history of possible exposures should be sought. Attempt to identify the source of infection, such as exposure to urine or tissues of infected animals or contaminated drinking or recreational water.

It is important to determine:

• An occupational history (farmers, abattoir workers, vets, army personnel, miners, sewer workers)

• Recreational exposures (water sports, caving, white-water rafting, triathlon, gardening)

• A history of contact with common host animals (especially cattle, pigs, sheep, dogs and rodents)

• Travel history (especially travel to Queensland and other tropical regions).

Isolation and restriction
Although person-to-person transmission is rare, it is prudent to give advice to cases about using condoms, avoiding breastfeeding and using standard precautions when handling urine for several months following onset of leptospirosis.

Environmental evaluation
If the case has occupational risk factors such as working in an abattoir, discuss with WorkCover and/or the Senior Animal Regulatory Officer at the Department of Agriculture. Control contaminated waters if feasible.

Contact management
Identification of contacts
Contacts are those who may have been exposed to the same source as the case. Action to detect cases among defined contacts should be considered.