RATIONALE FOR SURVEILLANCE

This zoonosis with worldwide distribution occurs seasonally in countries with a humid subtropical or tropical climate. It is often linked to occupation, sometimes in outbreaks. Feral and domestic animal species may serve as sources of infection with one of the Leptospira serovars. Infection is transmitted to humans through direct contact with (the urine of) infected animals or a urine-contaminated environment, mainly surface waters, soil and plants. The course of disease in humans ranges from mild to lethal. Leptospirosis is probably underreported in many countries because of difficult clinical diagnosis and lack of diagnostic laboratory services. Surveillance provides the basis for intervention strategies in human or veterinary public health.

RECOMMENDED CASE DEFINITION

Clinical description

Acute febrile illness with headache, myalgia and prostration associated with any of the following symptoms:

 

• conjunctival suffusion
• meningeal irritation
• anuria or oliguria and/or proteinuria
• jaundice
• haemorrhages (from the intestines; lung bleeding is notorious in some areas)
• cardiac arrhythmia or failure
• skin rash

and a history of exposure to infected animals or an environment contaminated with animal urine.

Other common symptoms include nausea, vomiting, abdominal pain, diarrhoea, arthralgia.

Laboratory criteria for diagnosis

 

• Isolation (and typing) from blood or other clinical materials through culture of pathogenic leptospires

• Positive serology, preferably Microscopic Agglutination Test (MAT), using a range of Leptospira strains for antigens that should be representative of local strains

Case classification

Suspected: A case that is compatible with the clinical description. Probable: Not applicable.

Confirmed: A suspect case that is confirmed in a competent laboratory.

 

Note: Leptospirosis is difficult to diagnose clinically in areas where diseases with symptoms similar to those of leptospirosis occur frequently.

RECOMMENDED TYPES OF SURVEILLANCE

Immediate case-based reporting of suspected or confirmed cases from peripheral level (hospital/general practitioner/laboratory) to intermediate level. All cases must be investigated.

Routine reporting of aggregated data of confirmed cases from intermediate to central level. Hospital-based surveillance may give information on severe cases of leptospirosis. Serosurveillance may give information on whether leptospiral infections occur or not in certain areas or populations.

International: The International Leptospirosis Society* collects worldwide data:

Royal Tropical Institute (KIT), Department of Biomedical Research, NH Swellengrebel Laboratory, Meibergdreef 39,1105 AZ Amsterdam, The Netherlands

 

Tel: 31 20 566 5441
Fax: 31 20 697 1841
E-mail: r.hartskeerl@kit.nl
ILS home page: http://www.med.monash.edu.au/micro/department/adler/ilspage.htm

RECOMMENDED MINIMUM DATA ELEMENTS

Individual patient record for reporting and investigation

 

• Age, sex, geographical information, occupation
• Clinical symptoms (morbidity, mortality)
• Hospitalization (Y/N)
• History and place of exposure (animal contact, environment)
• Microbiological and serological data
• Date of diagnosis
• Rainfall, flooding

Aggregated data for reporting

 

• Number of cases
• Number of hospitalizations
• Number of deaths
• Number of cases by type (causative serovar/serogroup) of leptospirosis

RECOMMENDED DATA ANALYSES, PRESENTATION, REPORTS

Number of cases by: age, sex, occupation, area, date of onset, causative serovars/serogroups, (presumptive) infection source, transmission conditions (graphs, tables, maps).

Frequency distribution of signs and symptoms by case and causative serovar (tables).

Reports of outbreaks, reports of preventive measures, surveillance of the human population and populations of feral and domestic animals.

PRINCIPAL USES OF DATA FOR DECISION-MAKING

 

• Assess the magnitude of the problem in different areas and risk groups/areas/conditions
• Identify outbreaks
• Identify animal sources of infection
• Monitor for emergence of leptospirosis in new areas and new risk (occupational) groups
• Design rational control or prevention methods
• Identify new serovars and their distribution
• Inform on locally occurring serovars for a representative range in the MAT

SPECIAL ASPECTS

Serology by Microscopic Agglutination Test (MAT) may provide presumptive information on causative serogroups. Attempts should be made to isolate leptospires, and isolates should be typed to assess locally circulating serovars.

Questioning the patient may provide clues to infection source and transmission conditions. Animal serology may give presumptive information on serogroup status of the infection Isolation followed by typing gives definite information on serovar.

CONTACT

Regional Offices

See Regional Communicable Disease contacts on section "Communicable disease contacts in Regional Offices".

Headquarters: 20 Avenue Appia, CH-1211 Geneva 27, Switzerland

Communicable Diseases Surveillance and Response (CSR)

 

E-mail: cosivio@who.ch / outbreak@who.ch
Tel: (41 22) 791 2531/4687/2111
Fax: (41 22) 791 4893/0746 attn CSR