Leptospirosis
Page content: Victorian statutory requirement | Infectious agent | Identification | Incubation period | Public health significance & occurrence | Reservoir | Mode of transmission | Period of communicability | Susceptibility & resistance | Control measures | Outbreak measures | Additional sources of information
Victorian statutory requirement
Leptospirosis (Group B disease) must be notified in writing within five days of diagnosis.
School exclusion is not applicable.
Infectious agent
Leptospires are members of the order of Spirochaetes. Pathogenic leptospires belong to the species Leptospira interrogans which is subdivided into serovars. In Australia, the most common serovar is L. interrogans serovar hardjo.
Identification
Clinical features
This group of zoonotic bacterial diseases may present in a variety of manifestations. Common clinical features include fever (which may be biphasic), headache, chills, a rash, myalgia and inflamed conjunctivae. In endemic areas, many infections are either asymptomatic or too mild to be diagnosed.
More severe manifestations occur rarely and include, meningitis, haemolytic anaemia, haemorrhage into skin and mucous membranes, hepatorenal failure, jaundice, mental confusion, respiratory distress and haemoptysis.
The acute illness may lasts from a few days to three weeks or more, with full recovery often taking several months.
Method of diagnosis
Leptospires may be isolated from the blood (days 0 to 7), CSF (days 4 to 10) during the acute illness, and from the urine after 10th day.
The diagnosis is more commonly confirmed serologically by the demonstration of a fourfold or greater rise in Leptospira antibody in paired sera taken in the acute phase and at least two weeks later. A single Leptospira micro agglutination titre of 400 or greater is also highly suggestive of acute infection.
Incubation period
Typically 10 to 12 days, with a range of four to 19 days.
Public health significance & occurrence
Leptospirosis occurs worldwide in developed and developing countries in both rural and urban settings. The disease is an occupational hazard for farmers, sewer workers, miners, dairy and abattoir workers and fish workers. It is a recreational hazard to bathers, campers and some sportspeople in infected areas.
Farmers, farm workers and meat industry workers in Victoria are the occupational groups most commonly affected by leptospirosis.
Reservoir
Serovars vary with the wild and domestic animal affected. Animal hosts in Victoria include rats, cows and pigs. Asymptomatic kidney infections in carrier animals can lead to prolonged and sometime lifelong excretion of leptospires in the urine.
Mode of transmission
Primarily through contact of skin with water, moist soil or vegetation contaminated with the urine of infected animals. The infection may also be transmitted through direct contact with urine or tissues of infected animals or by the inhalation of aerosols of contaminated fluids, such as may occur in abattoirs. Ingestion of foods contaminated with urine of infected rats is an occasional route of infection.
Period of communicability
Direct transmission from person to person is rare. Leptospires may be excreted in the urine for a month, but urinary excretion in humans and animals for up to 11 months has been reported.
Susceptibility & resistance
Immunity to the specific serovar follows infection, but may not protect against infection with a different serovar.
Control measures
Preventive measures
There is no human vaccine available.
General preventive measures include:
- education for the public on modes of transmission, for example advise to avoid swimming or wading in potentially contaminated waters and to use appropriate personal protection when work requires such exposure
- protecting workers in hazardous occupations with boots and gloves
- rodent control around human habitations
- prompt treatment and isolation of infected domestic animals
The Department of Primary Industries can be consulted for advice on herd immunisation.
Control of case
The usual treatment is doxycycline or benzylpenicillin. Consult the current version of the Therapeutic guidelines: antibiotic (Therapeutic Guidelines Limited) or seek specialist infectious disease advice.
Although person to person transmission is rare, cases should be nursed with blood and body fluid precautions. Any articles soiled with urine should be disinfected and the patient should be advised that they may continue to excrete leptospires in the urine for a month or more after the acute infection.
Control of contacts
Not applicable.
Control of environment
The exposure history of each case should be investigated to identify and control possible sources of infection such as exposure to infected animals and potentially contaminated bodies of water. Environmental control measures may include environmental clean-ups, and draining or restricting access to potentially contaminated water bodies.
The Department of Primary Industries investigates suspected animal industry sources such as dairies and piggeries, and may recommend animal vaccination or other disease control measures.
Outbreak measures
See Control measures, above.
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