-from Epidemiological Bulletin, Vol. 23 No. 3, September 2002-
Rationale for surveillance
Visceral leishmaniasis is endemic in over 60 countries. The incidence is estimated
at 500 000 cases each year. It is the most severe form of leishmaniasis and
it can be fatal in the absence of treatment. Deadly epidemics frequently occur
in the anthroponotic foci of Bangladesh, India, Nepal and Sudan, where man is
believed to be the sole reservoir. Surveillance is essential in establishing
disease impact and monitor efforts towards disease control and detecting epidemics.
Recommended case definition
Clinical description
An illness with prolonged irregular fever, splenomegaly and weight loss as its
main symptoms.
Laboratory criteria for diagnosis
– positive parasitology (stained smears from bone marrow, spleen, liver,
lymph node, blood or culture of the organism from a biopsy or aspirated material)
– positive serology (IFA, ELISA).
Case classification
WHO operational definition:
A case of visceral leishmaniasis is a person showing clinical signs (mainly
prolonged irregular fever, splenomegaly and weight loss) with serological (at
geographical area level) and/or parasitological confirmation (when feasible
at central level) of the diagnosis. In endemic malarious areas, visceral leishmaniasis
should be suspected when fever lasts for more than two weeks and no response
has been achieved with anti-malaria drugs (assuming drug-resistant malaria has
also been considered).
Recommended types of surveillance
Routine monthly reporting of aggregated data from periphery to intermediate
and central level.
Active case finding through surveys of selected groups or mass surveys (standardised and periodical) is an alternative to estimate the prevalence of visceral leishmaniasis.
International: annual reporting from central level to WHO (limited number of countries).
Recommended minimum data elements
Individual patient records at peripheral level:
Leishmaniasis data: Clinical features, date of diagnosis, serological/parasitological
diagnosis, Leishmania species, treatment outcome.
Identification data: Unique identifier, age, sex, geographical information, travel history, duration of stay at current residence.
Aggregated data for reporting:
Number of cases by age, sex, type of diagnosis.
Recommended data analysis, presentation, reports
Tables:
Incidence by geographical area, age, sex, type of diagnosis, risk group, by
clinical features, by month/year.
Point prevalence (if active case detection).
Principal uses of data for decision-making
– Evaluate the real extent of the problem and the main populations at risk
– Improve and focus the control activities
– Identify technical and operational difficulties
– Evaluate impact of control interventions
– Anticipate epidemics
Special aspects
Visceral leishmaniasis tends to be largely underreported because most of
the official data are obtained through passive case detection only. The number
of people exposed to infection or infected without any symptoms is much more
important than the number of detected cases.
Source: "WHO Recommended Surveillance Standards, Second edition,
October 1999”, WHO/CDS/CSR/ISR/99.2
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Epidemiological Bulletin, Vol. 23 No. 3, September
2002