Risk of relapse among non-lepromatous patients released from treatment after dapsone monotherapy.

Information on 14,625 non-lepromatous patients released from treatment after dapsone monotherapy and followed up to a maximum of 15 years at the ILEP project. Dharmapuri, India, was analysed to study the pattern of relapses. The overall relapse rate was 5/1000 person years. Males had a higher relapse rate than females. The risk of relapse increased with age, number of lesions and duration of treatment. The risk for relapse remained constant over several years after release from treatment. Even though the absolute risk for relapse after MDT may be different, the pattern of relapses and the factors affecting it may be similar to what has been shown in this study.

Selection of MDT strategies through epidemiometric modeling.

The epidemiometric model of leprosy, built on Polambakkam, India, data, is used to compare the impact on incidence of dapsone and different multidrug therapy (MDT) strategies. The simulations show that generalization of MDT could have a dramatic impact on transmission of the disease. Relapses after MDT, although important from an individual point of view, have a negligible influence on the incidence. Introduction of MDT requires investments that, during the first few years of the program, are much greater than for dapsone monotherapy. These are, however, rapidly absorbed due to the rapidly declining number of new cases, particularly when MDT is not limited to multibacillary cases but is administered to all patients.

Registration of the number of macules in paucibacillary leprosy for evaluation of early diagnosis and individual prognosis.

The number of macules is usually registered at diagnosis in the first clinical examination of leprosy patients. The question studied here is whether this practice is of any interest as an indicator of the precocity of detection of the prognosis. The study is based on the 26,996 paucibacillary patients detected from 1957 to 1982 in Polambakkam Leprosy Centre (South India) for whom the number of macules and disability status are assessed and registered. Several observations suggest that the proportion of single-macule patients among the newly detected cases is a more sensitive indicator than the proportion of new patients with disabilities for the evaluation of the delay between onset of the disease and detection. Its use could be especially helpful for programmes running for several years, when it becomes difficult to observe significant variations in the proportion of patients with disabilities. Regarding the prognosis value of the number of macules, inactivation and relapse probabilities were calculated. Regularity of treatment is found to be a better predictor of early inactivation than the number of macules, while relapse probabilities are more affected by the number of macules.

Rate and time distribution of relapses in multibacillary leprosy.

Of the 47,068 patients registered in the Polambakkam Leprosy Center between 1955 and 1982, we selected 1886 cases having shown bacteriological positivity at any time during this period, whatever their classifications at registration, and subsequently found bacteriologically negative. After an average follow-up period of 10 years, 243 relapses were observed, giving a crude relapse rate of 12.8 per person-years of observation and a cumulative probability of relapse of 18.9%. Relapse rates were found to be dependent on regularity during smear-positive and -negative periods; a regularity greater than 75% in the smear-positive period proved to be particularly important. The results show no evidence that relapses occurring after 3 years of negativity could be reinfections, and that the relapse rate was still affected by regularity 7 years after negativation. The median delay of relapses was found to be 4.4 years and was not affected by the regularity of treatment.

Simulation of vaccination and resistance in leprosy using an epidemiometric model.

Epidemiometric models are useful in studying disease dynamics in populations. Such a model was developed for leprosy and proved useful, but did not take into account age- and sex-specific incidence rates. This paper presents a new version of the model which makes provisions for age and sex differential rates according to the type of leprosy and which includes more realistic parameters for death rates, population variations, and natural growth rates. This new version of the epidemiometric model was used to stimulate the effects of various vaccines and drug resistance on the incidence of leprosy in a population.

[Absenteeism during treatment for leprosy. Analysis of causes as apparent from a survey in southern India]. / L'absentéisme au cours du traitement de la lèpre. Analyse des causes révélées par une enquête en Inde du Sud.

The reasons for absenteeism during leprosy treatment were investigated in a rural area of southern India. 120 patients known as "absents" to most controls were first interviewed and the major causes for absenteeism thus determined. A questionnaire was then elaborated in view to reveal these principal causes with efficiency and was applied by 8 investigators to 1200 patients, mostly absents or irregular to medical visits. 620 were selected at random for computer analysis. Results suggest that anxiety for loss of income while attending the medical control and erroneous impression of cure as soon as skin lesions have improved could be of first importance. Nevertheless no relation appears between absenteeism and income level, number of persons depending on the patient, or type of leprosy. Adverse reactions attributed to DDS are also frequently reported, especially fever, because of confusion with leprosy reactions, malaria and any other febrile condition. Assiduity to medical visits could be determined during the year following this study in 1191 of the 1200 patients showing clear beneficial effect over this period.

Application of an economic model to the study of leprosy control costs.

The effectiveness of various control methods for reducing the incidence of leprosy have been tested over 20 years and compared with predictions made using the present current control method (early diagnosis and mass treatment). Specific vaccination of the whole population, a control measure yet to be developed, has been identified as the most effective strategy in the long run. A cost-effectiveness analysis has been carried out for three indicators, annual incidence, annual prevalence and cumulative prevalence at 20 years, using cumulative costs. The analysis indicates that specific vaccination at high levels of coverage is the most effective method for controlling incidence in the long term. Provided the cost of the vaccination campaign during the first years (roughly fourfold the funds required for carrying out the current strategy) can be supported, specific vaccination is also the most cost-effective method where a high level of effectiveness is required. Specific vaccination is still the most advantageous method if prevalence or cumulative prevalence are taken to indicate the effectiveness of leprosy control. The BCG-type of vaccination is not only less effective, it is also less cost-effective. Reducing the rate of abandonment of treatment (which in the model has been simulated by increasing the rate of resuming treatment) and earlier detection both appear as useful methods under conditions of severe budgetary constraints. Their ultimate effectiveness in terms of incidence reduction is, however, very small. As expected, segregation is costly and ineffective compared with other methods. In each simulation, the cost of treating the backlog of patients already ill or infected (incubating) at the time the control measures are initiated is high. Methods aimed at reducing transmission, such as vaccination, early treatment or segregation, have long-delayed effects on the cost even if incidence is reduced. The major cost item in these control measures is the prolonged or even life-long treatment of patients. The development of fast-acting, effective treatment is likely to be the only way to reduce the cost in the short term. Thus, in addition to research aimed at developing a vaccine for leprosy, resources should also be allocated for developing new therapeutics.