RATIONALE FOR SURVEILLANCE
The leading principle for sleeping sickness control is the reduction of human reservoir through treatment of infected individuals and the reduction of man-fly contact through adapted vector control. An intercountry approach for surveillance/control activities is essential and supported by WHO. The objective of surveillance is the precise identification and proper epidemiological assessment of all endemic foci.
RECOMMENDED CASE DEFINITION
In the early stages, a painful chancre*, which originates as a papule and evolves into a nodule may be found at the primary site of tsetse fly bite. There may be fever, intense headache, insomnia, painless lymphadenopathy, anaemia, local oedema and rash. In the later stage, there is cachexia, somnolence and signs of central nervous system involvement. The disease may run a protracted course of several years in the case of Trypanosoma brucei gambiense. In case of T. b. rhodesiense, the disease has a rapid and acute evolution. Both diseases are always fatal without treatment.
*The painful chancre is very rare in T. b. gambiense infection.
Laboratory criteria for diagnosis
Presumptive: serological: card agglutination trypanosomiasis test (CATT) for T. b. gambiense only or immunofluorescent assay (IFA) for T. b. rhodesiense mainly and possibly for T. b. gambiense.
Confirmative: parasitological: detection (microscopy) of trypanosomes in blood, lymph nodes aspirates or CSF.
Suspected: A case that is compatible with the clinical description and/or a history of exposure.**
Probable: A case with a positive serology with or without clinical symptoms in persons without previous history of trypanosomiasis diagnosis or treatment.
Confirmed: A case with positive parasitology, with or without clinical symptoms.***
** In the early stage or even early in the late stage of the disease there are often no clinical signs or symptoms which can be associated with the disease. Suspicion is then based on local risk of contracting the disease and local disease historical background.
*** Confirmed positive healthy carriers are a major public health risk. As a reservoir of parasites, they disseminate the disease, and must be treated as soon as possible.
RECOMMENDED TYPES OF SURVEILLANCE
• The surveillance system will use a village-based definition using 4 classes:
• Village of unknown epidemiological status
• Suspected village
• Endemic village
• Disease-free village
• In the context of control programmes, surveillance provides valuable village-based data, with the precise geographic location of each village using global positioning system (GPS). Data are analysed using geographical information systems (GIS)
• In areas not covered by control activities, surveillance provides valuable case-based information. Results of serological surveys based on micro-card agglutination trypanosomiasis tests (micro-CATT) will be indicators of endemicity
• Information collected at village level is aggregated at intermediate/central level and reported to WHO
RECOMMENDED MINIMUM DATA ELEMENTS
In addition to the number of parasitologically confirmed cases (presence of trypanosomes shown), and to the number of probable cases (suspected cases with positive serology), the system should include information on:
• strategy used
• village geographic coordinates (latitude, longitude)
• administrative levels
• village type
• population at last census/date of last census, estimated population
• school (levels)
• health infrastructures (type, activities)
• protected sources of water
RECOMMENDED DATA ANALYSES, PRESENTATION, REPORTS
Mapping: at intermediate and central level: map of villages and their endemic status.
PRINCIPAL USES OF DATA FOR DECISION-MAKING
• Knowledge of endemic and suspected areas to direct control activities
• Epidemiological monitoring of endemic foci
• Assessing impact of control programmes
• Use of Global Positioning System (GPS) to define village geographic coordinates
• Sensitivity of parasitological techniques is low and depends on laboratory facilities and personnel skills
WHO Regional Office for Africa (AFRO)
Dr A. Kabore, A/Director, Prevention and Control of Diseases (DDC)
Direct telephone 1 407 733 92 36,
fax 1 407 733 9009
Dr P. Lusamba, A/Regional Adviser, Emerging and other Communicable
Diseases Control (EMC)
Direct telephone: 1 407 733 9338, 26311 40 38 23
Fax: 1 407 733 9009
SAMBAE@HTSD.COM at INET
Following the temporary closure of the AFRO office in Brazzaville, the above contact information may not be valid; a temporary office is available in Harare
Tel: 263 4 706 951/707 493
Fax: 2634 705619/702 044
Headquarters: 20 Avenue Appia, CH-1211 Geneva 27, Switzerland
Communicable Diseases Surveillance and Response (CSR)
E-mail: firstname.lastname@example.org /Surveillancekit@who.ch
Tel: (41 22) 791 3779
Fax: (41 22) 791 4878