Low Microfilaremia Levels in Three Districts in Coastal Ghana with at Least 16 Years of Mass Drug Administration and Persistent Transmission of Lymphatic Filariasis.

Dziedzom De Souza,Edward Dumashie,Samson Otoo,Frances Mccarthy,Kojo Sedzro,Samuel Dadzie,Nana-Kwadwo Biritwum,Joseph Otchere,Dickson Osabutey,Collins Ahorlu,Benjamin Marfo,Sandra King,Odame Asiedu,Joseph Osei,Irene Larbi,Irene Ayi,Susan Adu-Amankwah,Daniel Boakye

doi:10.3390/tropicalmed3040105

Abstract

Ghana has been implementing mass drug administration (MDA) of ivermectin and albendazole for the elimination of lymphatic filariasis (LF) since the year 2000, as part of the Global Programme to Eliminate Lymphatic Filariasis (GPELF). It was estimated that 5–6 years of treatment would be sufficient to eliminate the disease. Tremendous progress has been made over the years, and treatment has stopped in many disease endemic districts. However, despite the successful implementation of MDA, there are districts with persistent transmission. In this study we assessed the epidemiology of LF in three adjoining districts that have received at least 16 years of MDA. The assessments were undertaken one year after the last MDA. 1234 adults and 182 children below the age of 10 years were assessed. The overall prevalence of circulating filarial antigen in the study participants was 8.3% (95% CI: 6.9–9.9), with an estimated microfilaria prevalence of 1.2%. The microfilarial intensity in positive individuals ranged from 1 to 57 microfilariae/mL of blood. Higher antigen prevalence was detected in males (13.0%; 95% CI: 10.3–16.2) compared to females (5.5%; 95% CI: 4.1–7.2). The presence of infection was also highest in individuals involved in outdoor commercial activities, with the risks of infection being four- to five-fold higher among farmers, fishermen, drivers and artisans, compared to all other occupations. Using bednets or participating in MDA did not significantly influence the risk of infection. No children below the age of 10 years were found with infection. Detection of Wb123 antibodies for current infections indicated a prevalence of 14.4% (95% CI: 8.1–23.0) in antigen-positive individuals above 10 years of age. No antibodies were detected in children 10 years or below. Assessment of infection within the An. gambiae vectors of LF indicated an infection rate of 0.9% (95% CI: 0.3–2.1) and infectivity rate of 0.5% (95% CI: 0.1–1.6). These results indicate low-level transmission within the districts, and suggest that it will require targeted interventions in order to eliminate the infection.

Highlights

Lymphatic filariasis (LF) is a common parasitic disease of major public health importance in tropical and subtropical countries, which are economically less endowed
The treatment strategy relies on the assumption that if the microfilaria reservoir in the human host is reduced below a certain threshold, transmission of W. bancrofti by anopheline vectors could be interrupted [5]
This paper presents the baseline epidemiological situation of LF in 18 communities in three endemic districts in Ghana that have received 16 to 18 years of mass drug administration (MDA) without interrupting transmission, prior to randomization and assignment to treatment groups for the evaluation of a twice-yearly treatment regimen with IVM + ALB

Summary

Introduction

Lymphatic filariasis (LF) is a common parasitic disease of major public health importance in tropical and subtropical countries, which are economically less endowed. The treatment strategy relies on the assumption that if the microfilaria (mf) reservoir in the human host is reduced below a certain threshold, transmission of W. bancrofti by anopheline vectors could be interrupted [5] By this strategy it was estimated that five to six rounds of mass drug administration (MDA) will be required to eliminate the disease. Being co-endemic for onchocerciasis, the recommended treatment regimen is IVM + ALB given once a year These drugs mostly target mf in the blood, with limited macrofilaricidal and sterilization effect on the adult worms [7]. Following the baseline parasitological surveys, the data was analyzed to better understand the epidemiology of LF in the study areas The information from this baseline analysis will help to implement targeted interventions, including adequate community sensitization required to achieve maximum impact, as well as monitoring the effects of the interventions

Methods

Results

Conclusion