(Hansen's Disease)

RATIONALE FOR SURVEILLANCE

Leprosy continues to affect a large number of people. In 1997 there were an estimated 1.5 million cases in the world. Control of the disease has improved with the introduction of multidrug therapy (MDT). WHO (9GPW6.2) has targeted the disease for elimination (<1 case/10 000 population) by the year 2000, using a focused flexible approach. This includes making multidrug therapy available to all communities and areas, appropriate and good quality diagnosis and treatment, with evaluation through epidemiological surveillance and programme monitoring.

RECOMMENDED CASE DEFINITION

Clinical description

The clinical manifestations of the disease vary in a continuous spectrum between the two polar forms, lepromatous and tuberculoid leprosy:

 

• In lepromatous (multibacillary) leprosy, nodules, papules, macules and diffuse infiltrations are bilateral symmetrical and usually numerous and extensive; involvement of the nasal mucosa may lead to crusting, obstructed breathing and epistaxis; ocular involvement leads to iritis and keratitis

• In tuberculoid (paucibacillary) leprosy, skin lesions are single or few, sharply demarcated, anaesthesic or hypoaesthesic, and bilateral asymmetrical, involvement of peripheral nerves tends to be severe

• Borderline leprosy has features of both polar forms and is more labile

• Indeterminate leprosy is characterized by hypopigmented maculae with ill-defined borders; if untreated, it may progress to tuberculoid, borderline or lepromatous disease

Laboratory criteria for confirmation

Alcohol-acid-fast bacilli in skin smears (made by the scrape-incision method).

In the paucibacillary form the bacilli may be so few that they are not demonstrable. In view of the increasing prevalence of HIV and hepatitis B infection in many countries where leprosy remains endemic, the number of skin smear sites and the frequency of smear collection should be limited to the minimum necessary.

Case classification

WHO operational definition:

A case of leprosy is defined as a person showing one or more of the following features, and who as yet has to complete a full course of treatment:

 

• hypopigmented or reddish skin lesions with definite loss of sensation
• involvement of the peripheral nerves, as demonstrated by definite thickening with loss of sensation
• skin smear positive for acid-fast bacilli

Classification (microbiological):

 

Paucibacillary (PB): includes all smear-negative cases
Multibacillary (MB): includes all smear-positive cases.

Classification (clinical):

 

Paucibacillary single lesion leprosy: 1 skin lesion.
Paucibacillary leprosy: 2 to 5 patches or lesions on the skin.
Multibacillary leprosy: >5 patches or lesions on the skin.

RECOMMENDED TYPES OF SURVEILLANCE

Individual patient records at peripheral level for investigation and case management.

Routine monthly reporting of aggregated data of all cases from periphery to intermediate level and from intermediate to central level.

International: Quarterly and annual reporting of aggregated data from central level to WHO.

RECOMMENDED MINIMUM DATA ELEMENTS

Individual patient records

Unique identifier, name, sex, age, geographical information, disability grade, laboratory examination, disease classification (multi- or paucibacillary, see case definition), date treatment commenced, treatment outcome (disability, cured, dropout), contacts.

Aggregated data for reporting - essential indicators (endemic countries)

 

• Number of cases registered for treatment at a given time (usually end of year)
• Number of newly detected cases by type of leprosy
• Number of cases treated with multidrug therapy (MDT)
• Number of WHO grade 2 disability* among new cases
• Number of patients cured with MDT
• Number of relapses

 

* See: WHO technical Reports Series N°g 874, Geneva: World Health Organization, 1988: 31-32

Multidrug treatment (MDT) indicators

(see Special Aspects)

MDT supply indicators:

For MB adult cases, MB child cases, PB adult cases, PB child cases:

 

• Number of patients under treatment
• Blister pack utilization (%)

RECOMMENDED DATA ANALYSES, PRESENTATION, REPORTS

Point prevalence, annual detection, MDT coverage, number of patients cured (wherever possible based on cohort reporting), number of cases registered for chemotherapy at the end of the year divided by the population in which the cases have occurred.

Graphs: Prevalence by year, detection by year, number of patients on multidrug therapy (MDT) by year, number of patients cured on MDT by year.

Maps: Number of registered cases, number of new cases, type of treatment, MDT coverage all by geographical area.

Tables: Prevalence, new case detection, percentage of children, percentage of disabled, percentage multibacillary, number cured with MDT.

PRINCIPAL USES OF DATA FOR DECISION-MAKING

 

• Assess the magnitude of the problem
• Identify variations in case detection
• Evaluate the policy of elimination of leprosy
• Plan the distribution of drugs
• Identify technical and operational difficulties faced by the programme
• Identify high risk areas for further targeting intervention
• Evaluate impact of intervention

SPECIAL ASPECTS

 

• Leprosy tends to be underreported. However, there are no reliable cost-effective methods to estimate the real prevalence of the disease accurately

• In endemic countries, essential indicators must be validated through independent mechanisms in order to assess performance of MDT services and progress towards the elimination of the disease at local level

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

Eradication and Elimination of Diseases (CEE/CDS)

 

E-mail: daumeried@who.ch / Surveillancekit@who.ch
Tel: (41 22) 791 3919
Fax: (41 22) 791 4850