A Retrospective Study of the Epidemiology of Leprosy in Cebu: An Eleven-Year Profile

Abstract

BackgroundCebu has been one of the most leprosy endemic areas in the Philippines. Despite the high coverage rates of multiple drug therapy (MDT) and high BCG-vaccine coverage in children, leprosy control authorities believe that leprosy transmission and incidence (as evidence by continuing new case detection in both adults and children) have not declined as expected, once leprosy had been eliminated.In response to the concerns communicated by the authorities regarding ongoing leprosy transmission in Cebu, this study aims to examine the evidence for the hypothesized ongoing transmission, both in children and adults. Furthermore, it will be assessed which groups and areas are experiencing a continuing risk of leprosy infection; this can form a starting point for more targeted approaches to leprosy control.Methodology & Principal FindingsCase records from 2000–2010 were retrospectively collected from the Leonard Wood Memorial Clinic archives, and all other clinics on the island where leprosy was treated. Between 2000 and 2010, 3288 leprosy cases were detected. The overall five year case notification rate (CNR) dropped significantly from 47.35 (2001–2005) to 29.21 cases (2006–2010) per 100.000 population. Smaller CNRs were reported for children; however the decline in child-CNR over the same period was minimal. Furthermore, no increase in median age of notification in children or adults was found between 2000 and 2010. Population-adjusted clustering of leprosy cases was mainly detected in urban and peri-urban areas.Conclusions & SignificanceAlthough the overall CNR declined significantly, CNR seems to be rather static in lower risk populations and areas. Cases are mainly found in urban areas, however CNRs in these areas decline at a much faster rate than in the lower endemic rural areas. A similar situation was found when comparing adults and children: CNRs observed in children were lower than in adults, but further decline (and elimination) of these childhood CNRs was found to be difficult. Moreover, the median age of notification in children has remained stable, suggesting transmission is still on-going.It is unclear why many years of good MDT-coverage and a gradual decline in CNR have not been accompanied by evidence of reduced transmission, especially beyond a certain threshold level of case notification. We believe that a new approach to leprosy control is required to tackle transmission more directly. The most promising approach may involve chemoprophylaxis and/or immunoprophylaxis interventions, targeted at high risk (urban) areas and groups such as household contacts, followed by a different approach once decline in CNR starts to level off. Identified clusters and trends can form the starting point for implementing this approach.

Análise da situação epidemiológica da hanseníase em uma área endêmica no Brasil: distribuição espacial dos períodos 2001 - 2003 e 2010 - 2012

“…In fact, this study showed the overlapping of the clusters in both periods temporally separated in ten years, which reinforces the idea of temporal and geographic persistence of the indicators of the analyzed condition. Other authors have shown the persistence of the geographic distribution of leprosy and its spatial concentration 7,8,10,16,[22][23][24] . For example, the clusters identified for the incidence rate of leprosy and for the incidence rate in adolescents aged less than 15 years are in areas similar to those mentioned in previous studies 7,10,22 .…”

“…The model with the Poisson distribution was used. This model is based on a number of events (cases of leprosy) distributed according to a known population at risk 16,17 . The statistical significance was evaluated considering p ≤ 0.05 (likelihood ratio test).…”

Tendências da hanseníase no Tocantins, um estado hiperendêmico do Norte do Brasil, 2001-2012

“…Tampouco podem ser esperadas mudanças súbitas na sua ocorrência, como por exemplo, redução da incidência 4,6,17 .…”

Trends of main indicators of leprosy in Brazilian municipalities with high risk of leprosy transmission, 2001–2012

“…Despite efforts to reduce the prevalence of the disease, these actions have apparently little effect on the reducing transmission and incidence [4–6]. Use of leprosy prevalence as an indicator has been criticized since it is influenced by factors such as treatment duration and case identification.…”