The global distribution of lymphatic filariasis, 2000–18: a geospatial analysis

Abstract

Summary Background Lymphatic filariasis is a neglected tropical disease that can cause permanent disability through disruption of the lymphatic system. This disease is caused by parasitic filarial worms that are transmitted by mosquitos. Mass drug administration (MDA) of antihelmintics is recommended by WHO to eliminate lymphatic filariasis as a public health problem. This study aims to produce the first geospatial estimates of the global prevalence of lymphatic filariasis infection over time, to quantify progress towards elimination, and to identify geographical variation in distribution of infection. Methods A global dataset of georeferenced surveyed locations was used to model annual 2000–18 lymphatic filariasis prevalence for 73 current or previously endemic countries. We applied Bayesian model-based geostatistics and time series methods to generate spatially continuous estimates of global all-age 2000–18 prevalence of lymphatic filariasis infection mapped at a resolution of 5 km 2 and aggregated to estimate total number of individuals infected. Findings We used 14 927 datapoints to fit the geospatial models. An estimated 199 million total individuals (95% uncertainty interval 174–234 million) worldwide were infected with lymphatic filariasis in 2000, with totals for WHO regions ranging from 3·1 million (1·6–5·7 million) in the region of the Americas to 107 million (91–134 million) in the South-East Asia region. By 2018, an estimated 51 million individuals (43–63 million) were infected. Broad declines in prevalence are observed globally, but focal areas in Africa and southeast Asia remain less likely to have attained infection prevalence thresholds proposed to achieve local elimination. Interpretation Although the prevalence of lymphatic filariasis infection has declined since 2000, MDA is still necessary across large populations in Africa and Asia. Our mapped estimates can be used to identify areas where the probability of meeting infection thresholds is low, and when coupled with large uncertainty in the predictions, indicate additional data collection or intervention might be warranted before MDA programmes cease. Funding Bill & Melinda Gates Foundation.

High-resolution age-specific mapping of the two-week illness prevalence rate based on the National Health Services Survey and geostatistical analysis: a case study in Guangdong province, China

“…Other environmental and socio-economic factors with potential effects on the outcomes were extracted from different open-access sources (Additional file 1 : Table S1, Figure S1). As communities/villages in China usually cover areas larger than 1km 2 and many risk mapping studies usually took the spatial resolution of 5 × 5 km 2 [ 20 , 33 , 34 ], we adopted this resolution for this risk mapping study. We aligned the covariate data over a regular grid of 5 × 5 km 2 spatial resolution and further assigned to the survey villages/communities.…”

“…Most previous statistical models addressed the age effect on disease risk either using a linear or categorical form of age as a fixed effect, or applying spline methods [ 32 – 34 ]. However, such models are not able to deal with situations where the age-prevalence relationship differs across the study region.…”

“…Parsaeian et al used area-specific exponential functions to account for the variation of disease burden with age [ 36 ], which may call for high computational burden when interaction with space at high resolution. Based on the Bayesian geostatistical modeling framework, setting and projecting mesh knots is a considerable method to lower the computational burden for space-factor interaction [ 34 ].…”

Progress in the elimination of lymphatic filariasis in the Western Pacific Region: successes and challenges

“…By 2020, 85% of the originally endemic IUs stopped MDA and the number of people requiring MDA for LF in the Western Pacific Region was reduced by 72% from 2000 to 2018. 28 The success and progress of LF elimination in the region to date is attributed to a combination of strategic, programmatic and epidemiological factors, as described below.…”

Drug Resistance in Filarial Parasites Does Not Affect Mosquito Vectorial Capacity

“…Vector-borne diseases remain an important challenge for public health globally, and contribute to over 17% of the global estimated burden of all infectious diseases [1]. Recent few decades have seen encouraging progress in the control of some important mosquitoborne diseases including malaria [2,3] and filariasis [4]. However, continued success in controlling these diseases faces numerous challenges, with the evolution of resistance against anti-parasitic drugs being one of the most important [5][6][7].…”