(Mite-borne typhus, Tsutsugamushi disease)
RATIONALE FOR SURVEILLANCE
Scrub typhus (mite-borne typhus, Tsutsugamushi disease) is an acute infectious disease that is emerging and re-emerging in South-East Asia and the south-western Pacific region. It can have a case-fatality rate of up to 30% if untreated. Epidemics occur when susceptible individuals are brought into endemic areas (e.g., during military operations). In some countries (e.g., Japan) it is a notifiable disease. Multi-drug resistance has been documented in Thailand.
Surveillance is essential to a better understanding of the epidemiology of the disease and to the detection of outbreaks. Training in diagnostic techniques is often required.
RECOMMENDED CASE DEFINITION
A disease with a primary "punched out" skin ulcer (eschar*) where the bite(s) occurred, followed by acute onset fever after several days, along with headache, profuse sweating, conjunctival injection and lymphadenopathy. Within a week, a dull maculo-papular rash** appears on the trunk, extends to the extremities and disappears in few days. Cough is also common. Defervescence within 48 hours following tetracycline therapy strongly suggests a rickettsial etiology.
* Eschar may be absent in some geographic areas and in highly endemic areas where reinfection is frequent.
** Rash may be overlooked in patients with dark or sunburned skin.
Laboratory criteria for diagnosis
Isolation of Orientia* tsutsugamushi by inoculation of patient blood in white mice (preferably treated with cyclophosphamide at 0.2 mg/g intraperitoneally or intramuscularly on days 1,2 and 4 after inoculation).
* Formerly Rickettsia.
Detection of specific IgM
at 1:100 or higher by Enzyme Immunoassay (EIA)
or 1:32 dilution or higher by Immunoperoxidase (IP)
or 1:10 dilution or higher by Indirect Immunofluorescence (IF).
Suspected: A case that is compatible with the clinical description.
Confirmed: A suspected case with laboratory confirmation.
Note: Serological tests are complicated by the antigenic differences between various strains of the causal agent.
RECOMMENDED TYPES OF SURVEILLANCE
Immediate case-based reporting of all suspected cases from the peripheral level to the intermediate and central level. All suspected cases and outbreaks must be confirmed. A parallel laboratory surveillance system reports all confirmed cases to central level.
RECOMMENDED MINIMUM DATA ELEMENTS
Case-based data to report
• Case classification (suspected/confirmed)
• Unique identifier, age, sex, geographical information
• Date of report
• Hospitalization (Y/N)
• Response to tetracycline therapy
Aggregated data to report
• Number of cases by case classification, age, sex, geographical information, date of report
• Number of hospitalizations
• Number of deaths
RECOMMENDED DATA ANALYSES, PRESENTATION, REPORTS
Graphs: Number of cases by date of report.
Tables: Number of cases by age, geographical area.
Maps: Number of cases, and if appropriate, deaths, by geographical area.
PRINCIPAL USES OF DATA FOR DECISION-MAKING
• Detect outbreaks
• Monitor trends in endemic disease
• Monitor changes in epidemiology and pattern of disease
The distribution of O. tsutsugamushi extends north to Japan, Russia, and the Primorske Karai region in the Russian Far East, south to northern Australia and the western Pacific islands, and west to Afghanistan, Pakistan, and areas bordering the Central Asian Republics.
Human O. tsutsugamushi occurs widely in these regions, but not everywhere.
Scrub typhus is probably one of the most underdiagnosed and underreported febrile illnesses requiring hospitalization in the region. The absence of definitive signs and symptoms combined with a general dependence upon serological tests make the differentiation of scrub typhus from other common febrile diseases such as murine typhus, typhoid fever and leptospirosis quite difficult.
Regional Offices WHO Regional Office for South-East Asia (SEARO)
Dr Vijay Kumar, Director, Integrated Control of Diseases (ICD)
Tel: 00 91 11 331 7804 ext 523/524
Fax: 00 91 11 331 8412
Dr M.V.H. Gunaratne, Regional adviser on Communicable Diseases (CDG)
Tel: 91 11 3318412
Fax: 91 11 331 8607
Dr A.G. Andjaparidze, Regional Adviser on Communicable Diseases (CDA)
Tel: 00 91 11 331 7804 to 7823
Fax: 00 91 11 331 8412
Dr Deoraj (Harry) CAUSSY, Regional Epidemiologist
Tel: 00 9111 331 7804 to 7823
Fax: 00 9111 331-8412 and 8607
Should you experience difficulties in reaching the above, call Fax 91 11 332 7972
WHO REGIONAL OFFICE FOR THE WESTERN PACIFIC (WPRO)
A/Regional Adviser in Communicable Diseases, CDS (Dr Chris Maher)
Tel: 00 632 522 9964
Fax: 00 632 528 1036
Dr Reiko Muto, Associate Professional Officer, CDS
Headquarters: 20 Avenue Appia, CH-1211 Geneva 27, Switzerland
Communicable Diseases Surveillance and Response (CSR)
E-mail: email@example.com / firstname.lastname@example.org
Tel: (41 22) 791 2658/2636/2111
Fax: (41 22) 791 4878