Estimated number of leprosy cases in the world.

Planning for disease control requires estimates of the number of leprosy patients from local to global levels. From the mid-sixties to the mid-eighties, global estimates appeared to be constant at between 10 and 12 million. The introduction of multidrug therapy (MDT) in many countries and the consequent reduction of prevalence of the disease has necessitated a reassessment of the global estimate. Based on available information and its interpretation, the number of leprosy cases in the world in 1991 has been estimated at 5.5 million. The number of individuals with deformities due to leprosy, including persons now cured of the disease, has been estimated at between two and three million.

Estimated number of leprosy cases in the world.

Planning for leprosy control requires estimates of the number of leprosy patients at different levels. During the period between the mid-1960s and the mid-1980s, global estimates had remained constant at between 10 and 12 million. The introduction of multidrug therapy (MDT) in many countries and the consequent reduction of the disease's prevalence has necessitated a reassessment of this. Based on available information and its interpretation, the number of leprosy cases in the world for 1991 has been estimated at 5.5 million. The number of individuals deformed by leprosy, including those cured of the disease, has been estimated at between 2 and 3 million.

Issues involved in the rapid assessment of the leprosy problem.

Sample surveys for estimation can prove very expensive and time-consuming because of the enormous sample sizes usually required. Where sample surveys have to be undertaken, diagnoses should be limited to detecting a case of leprosy, without attempting skin smears etc. in order to classify by types. Usually enough knowledge is available on the approximate proportion of multibacillary (MB) cases in most communities, and this knowledge could be utilized for estimating the caseload by types of leprosy. Again intensive tracing of nonrespondents could be limited to either males or females depending on convenience, and well-known sex ratios among patients utilized for deriving estimates for the other sex. The type of rapid methods of estimation depend on three types of situations: (1) before multidrug therapy (MDT); (2) 5 years or more after MDT; and (3) less than 5 years after MDT. In the first situation one or more of the following methods are suggested: (i) extrapolation from registered cases; (ii) extrapolation from child prevalence; and (iii) conducting rapid village surveys. In situations where MDT has been introduced for 5 years or more the registered cases plus a small number, depending on local experience, would seem to be adequate. When MDT was introduced less than 5 years before, it is suggested that the prevalence rates be obtained by statistical interpolation drawing on the experience from areas which have had more than 5 years of MDT.

Estimated number of leprosy cases in the world.

Planning for disease control requires estimates of the number of leprosy patients from local to global levels. From the mid-sixties to the mid-eighties, global estimates appeared to be constant at between 10 and 12 million. The introduction of multidrug therapy (MDT) in many countries and the consequent reduction of prevalence of the disease has necessitated a reassessment of the global estimate. Based on available information and its interpretation, the number of leprosy cases in the world in 1991 has been estimated at 5.5 million. The number of individuals with deformities due to leprosy, including persons now cured of the disease, has been estimated at between 2 and 3 million.

PIP: World leprosy estimates are discussed and generated for 1991. In an effort to identify 5.5 million registered leprosy cases in the world for 1991 it was found that there also are 2-3 million people with deformities due to leprosy. The rehabilitative requirements of this population need to be served in addition to the continued multidrug therapy (MDT) needed to control prevalence. Successful leprosy control has led to a reduction from prior estimates of 10-12 million cases. There are many problems in estimating because of the low frequency of occurrence and its uneven distribution. Well-planned sample surveys are practical and cost effective only in limited areas, rather than for countries as a whole, and also include nonsampling errors. Multimethods were used to derive the world estimates, and the estimates have been adequate for planning purposes. The magnitude of the problem was addressed in 1966 by the WHO which reported 10,786,000 cases which remained stable through 1972. A 1983 estimate by the WHO Study Group on Epidemiology of Leprosy in Relation to Control was 11,525,000 cases. 95% of registered cases are from 25 countries, of which 5 countries contribute 82% (Nigeria, Brazil, Myanmar, Indonesia, and Bangladesh). The current estimates focused on these countries. In the 5 countries, not only were correction factors applied to registered cases, but intensive reviews of all available information and discussions with relevant program managers were conducted. Correction factors for each region were used unless more reliable information was available. The correction factor was calculated as the ratio of registered cases in the top 25 countries in the region to earlier country estimates. There were 5 reasons why estimates in 1991 were significantly lower: 1) cases cured through MDT, 2) removal of cases not fitting the WHO definition which requires a case to be someone receiving MDT treatment or needing treatment, 3) late effects of an intensive dapsone-based control effort, 4) strengthened control activities, and 5) natural declining trends. The patients needing rehabilitation were estimated by considering the past case records over 50 years and the proportion with deformities, the survival rate of those deformed, and the nature of control activity. Estimates and registration of cases is given for 25 countries.

BCG vaccination of children against leprosy: fourteen-year findings of the trial in Burma.

The value of BCG vaccination in preventing leprosy among children was studied in an area of high leprosy endemicity in Burma through a controlled trial; one group of 13 066 children received BCG and another group of 13 176 served as controls. The overall protective effect of BCG, which was only about 20% over the 14-year period, was found to vary with the batch of vaccine, as well as age, sex, and contact status of the children. BCG protection was found to be independent of the initial tuberculin status of the children. The protective effect of BCG against the lepromatous type of leprosy could not be measured because of the low incidence. Protection was observed throughout the fourteen years of the study except for the first year. The results are compared with those of three other major BCG trials in leprosy. The trial has shown that BCG provides only a very modest level of protection and that BCG vaccination is not likely to be an important solution for leprosy control.

BCG vaccination of children against leprosy: fourteen-year findings of the trial in Burma

The value of BCG vaccination in preventing leprosy among children was studied in an area of high leprosy endemicity in Burma through a controlled trial; one group of 13066 children received BCG and another group of 13176 served as controls. The overall protective effect of BCG, which was only about 20% over the 14-year period, was found to vary with the batch of vaccine, as well as age, sex, and contacts status the children. The protective effect of BCG against the lepromatous type of leprosy could not be measured because of the low incidence. Protection was observed throught the fourteen years of the study except for the firts year. The results are compared with those of three other major BCG trials in leprosy. The trial has shown that BCG provides only a very modest level of protection and that BCG vaccination is not likely to be an important solution for leprosy control.