Leprosy Case Detection Research Articles

Rapid survey on case detection of leprosy in a low endemic situation, Zhucheng County, Shandong Province, The People’s Republic of China

The prevalence of leprosy fell below 1 per 100,000 in Shandong province in 1994. Since then, a few incident leprosy cases have been reported each year over the past 10 years. In order to explore whether or not the reduction in case detection in the province was due to the stopping of active case-finding activities, a rapid village survey was conducted in a formerly endemic county, using skin disease service. Ninety-one villages in 23 townships, covering a total population of 104,885, were surveyed. No leprosy case was detected. The results of the survey, along with other evidences, such as higher MB/PB ratio among newly detected cases and late onset of the disease, suggest that leprosy is dying out as a disease in the county as well as in Shandong. The efforts of the leprosy control programme should shift to other services such as prevention of disability and care for the disabled.

High prevalence of non-leprotic hypochromic patches among children in a rural area of Mali, West Africa

The identification of one or several hypochromic patches (HP) on the skin is a key stage in the diagnosis of leprosy on dark skin. However, HP are often caused by other disorder than leprosy. A study to determine the prevalence and causes of HP among children was carried out in a rural area of Mali in November 2001. All children under 15 years of age in two villages in an endemic area were screened by two dermatologists. Among the 1729 children seen, HP were identified in 71 patients, with a prevalence of 4.1%. The most common cause of HP was tinea versicolor, which was present in 39.4% of children with HP, followed by pityriasis alba in 31%, naevus achromicus in 24% and vitiligo in 5.6%. No case of leprosy was detected. Our study raises several points with practical consequences for the detection of leprosy cases: the high prevalence of non-leprous HP compared to leprosy, the reliability of the clinical diagnosis of leprosy, and the role of general health care workers in the detection of leprosy cases. Helping those who should be involved in that detection in distinguishing true cases from other hypochromic disorders appears to be a priority.

Modeling of Under-detection of Cases in Disease Surveillance

Accurate epidemiological surveillance of leprosy is a matter of international public health concern. It often suffers, however, from potential problems of under-registration of reported cases, particularly in poorer and more socially deprived areas. Such problems also apply in the surveillance of many other communicable or transmissible diseases. We develop a Bayesian model for small-area disease rates that allows for censoring of case detection in suspect districts and can therefore be used to estimate under-reporting of cases in a given study region. Such methods are applied to leprosy incidence in a municipality of Pernambuco State in North Eastern Brazil, using a social deprivation indicator as the basis for considering data from certain districts to be censored. The time period we consider was immediately prior to an extension of the coverage and efficacy of the control program and model predictions concerning under reporting can therefore be compared with more reliable data subsequently collected from the same region. The proposed method produces informative estimates of under detection of leprosy cases in the defined study region and these estimates compare well, both in size and in geographical location, with the numbers of cases subsequently detected. As illustrated by the application discussed in this article, the proposed model provides a general tool that may be used in spatial epidemiological surveillance situations where the available data is suspected to contain significant under-registrations of cases in certain geographical areas.

Analysis on the detection of new leprosy cases before, during and after the year of leprosy elimination campaigns

To analyse the impact on of case finding of leprosy elimination campaigns (LECs), data on newly detected leprosy cases in a leprosy endemic area were collected before, during and after the year of LEC. The number of new leprosy cases detected during the year of LEC was significantly higher than previously. The number of newly detected cases after the year of LEC was similar to that of detected before the year of LEC in counties with persisting case finding activities. However, the number of newly detected cases after the year of LEC significantly decreased in counties without active case finding activities. The average distance from the homes of leprosy cases detected during LEC to the leprosy control unit at the count town was 62.8 km, which is farther than that of other leprosy cases detected before and after the year of LEC. The average time from disease onset to diagnosis of leprosy cases detected after the year of LEC shortened. The results also showed that carrying out LECs is unlikely to have a significant impact on the trend of case finding within a short time in local areas, but it may improve some indicators of leprosy patients and so promote leprosy control in local areas.

Trends in leprosy case detection worldwide since 1985

Trends in case detection and case detection rate (CDR) since 1985 are described at regional and national levels. Annual case detection by WHO Region was available for 1994-2000. Using different sources, complete time series for case detection were constructed for 1985-1998 for a group of 33 endemic countries cumulatively (top 33), and for 14 individual countries (top 14). Population statistics were used to derive CDRs. India contributed 79% to global case detection in 1998. Africa, the Americas and South-East Asia each contributed about 30% when India is excluded. During 1994-2000, case detection did not decrease in these three WHO Regions. The 33 countries contributed 99% and 98% to global case detection in 1994 and 1998, respectively. Cumulative case detection for the top 33 minus India gradually increased, overall almost doubling. The contribution of the top 14 to case detection of the top 33 hardly changed over time, equalling 96% in 1998 (81% when India is excluded). In terms of annual case detection, Brazil was always ranked second after India; it accounted for 27% of 1998 case detection in the top 33 except India. In 1998, seven of the top 14 countries--including India and Brazil--had CDRs above 2 per 10,000. The CDR did not exceed 1 per 10,000 for the other half. Decreasing tendencies in CDR, either for the whole period or in the 1990s, are observed for four of the top 14 countries (Guinea and three Western Pacific countries: China, Vietnam and the Philippines). In conclusion, there is no general decline in case detection to date, and several important countries still have high CDRs. Prevalence is an irrelevant indicator for monitoring epidemiological changes in leprosy. Trends in the transmission and incidence of leprosy are still completely unclear, necessitating further research. The target to eliminate leprosy as a public health problem, defined as a prevalence of less than 1 per 10,000, is therefore also an inadequate yardstick for decision making on leprosy control.

Increase in leprosy detection rates in São Luís, Maranhão, Brazil, from 1993 to 1998: is the endemic expanding?

A descriptive epidemiologic study on the detection of new leprosy cases was conducted in São Luís, Maranhão, Brazil, from 1993 to 1998. A database was created for the purpose, covering 2,796 reported cases. General detection rates were calculated, as well as specific rates by gender, clinical type, and age group. Linear, exponential, geometric, and log adjustment models were performed to analyze time trends in the disease. An increase in detection was observed, involving mostly female and paucibacillary cases, mainly of tuberculoid leprosy. The increase in detection was most evident in the 15 to 19 year-old population. The percentage of detection under 15 indicated the need for active case search in this group.

Developing and using a PCR test to detect subclinical Mycobacterium leprae infection

While the prevalence of leprosy has declined around the world, there has not been a corresponding decrease in its incidence, thus indicating that it has not been possible to prevent transmission of the disease. Despite the small number of patients with lepromatous leprosy, the majority of the inhabitants of endemic areas show signs of exposure to Mycobacterium leprae, which could be explained by the presence of subclinical bacilliferous infections in the community. The objective of this study was to investigate the use of a polymerase chain reaction (PCR) test to detect M. leprae in samples of nasal mucus from asymptomatic household contacts of patients with leprosy. We standardized and optimized a PCR technique to amplify a 321 base pair DNA fragment, using a pair of primers complementary to a segment of an LSR/A15 gene that codes for the 15 kDa M. leprae antigen. We investigated the optimal concentrations of all the test components. We used dimethyl sulfoxide (DMSO) to achieve a more specific amplification. We applied the PCR test to 70 healthy household contacts of leprosy patients from eight municipalities in Colombia where there was a high prevalence of the disease. The test's detection limit was 100 fg of DNA. With the optimized technique, bacillus was detected in the nasal mucus samples of 9 (12.8%) of the 70 household contacts. The 3 PCR-positive household contacts of paucibacillary cases were from municipalities with very high prevalence levels. In comparison to contacts who were PCR-negative, the contacts who were PCR-positive had spent significantly less time, as a proportion of their age, living with a patient (P = 0.028). This finding demonstrates the test's capacity for early detection. The PCR test that we developed is useful as a tool for detection and early follow-up of possible leprosy cases. It can be used to monitor high-risk populations and also to maintain the achievements of leprosy elimination programs in countries where the disease's prevalence has been significantly reduced.

Studies on mode of detection of leprosy in China during the years 1981-1998.

Along with the nationwide economic reform initiated in the early 1980s and the rapid decrease of leprosy endemic after the implementation of multi-drug therapy (MDT), the leprosy programme changed from 'vertical' to 'horizontal'. An evolution in the mode of detection of leprosy cases has consequently taken place. Based on the nationwide registration of newly detected cases, the profile of patients at detection has been studied. The proportions of cases corrected significantly with calendar years in detection by dermatological clinics, contact checks, 'clue survey' and mass survey, showing a significant increase in percentage of cases detected through dermatological clinics and contact checks, and decreases through 'clue survey' and mass survey. Detection of cases through dermatological clinics and voluntary reporting have become the main modes of case-finding during 1997-1998, accounting for 37.3% and 28.6%, respectively, where contact check accounts for only 9.1%. In areas with good dermatological services, a significantly higher proportion (75.9%) of cases was detected through dermatological clinics, where voluntary reporting and 'clue survey' were the main modes of detection in endemic areas. As regards confirmation of diagnosis, the great majority of cases were confirmed by leprosy units, even though they were detected in various other situations. Only 6.5% of leprosy cases were detected and subsequently confirmed by doctors in dermatologic clinics. The present modes of detection and their relation to demographical, epidemiological, clinical factors and health services are discussed. This study emphasizes the cardinal importance of the dermatological clinics in the detection of leprosy cases in China at the present time and hence the need to strengthen the training of doctors in these clinics, while continuously encourage their involvement in leprosy control.

Detection of new leprosy cases at a walk‐in skin clinic in Cebu City, Philippines, highlights surveillance: Roberto Cortés Franco, MD, Editor

Detection of new leprosy cases at a walk‐in skin clinic in Cebu City, Philippines, highlights surveillance: Roberto Cortés Franco, MD, Editor