A comprehensive assessment of lymphatic filariasis in Sri Lanka six years after cessation of mass drug administration.
BACKGROUND
The Sri Lankan Anti-Filariasis Campaign conducted 5 rounds of mass drug administration (MDA) with diethycarbamazine plus albendazole between 2002 and 2006. We now report results of a comprehensive surveillance program that assessed the lymphatic filariasis (LF) situation in Sri Lanka 6 years after cessation of MDA.


RESULTS
Transmission assessment surveys (TAS) were performed per WHO guidelines in primary school children in 11 evaluation units (EUs) in all 8 formerly endemic districts. All EUs easily satisfied WHO criteria for stopping MDA. Comprehensive surveillance was performed in 19 Public Health Inspector (PHI) areas (subdistrict health administrative units). The surveillance package included cross-sectional community surveys for microfilaremia (Mf) and circulating filarial antigenemia (CFA), school surveys for CFA and anti-filarial antibodies, and collection of Culex mosquitoes with gravid traps for detection of filarial DNA (molecular xenomonitoring, MX). Provisional target rates for interruption of LF transmission were community CFA <2%, antibody in school children <2%, and filarial DNA in mosquitoes <0.25%. Community Mf and CFA prevalence rates ranged from 0-0.9% and 0-3.4%, respectively. Infection rates were significantly higher in males and lower in people who denied prior treatment. Antibody rates in school children exceeded 2% in 10 study sites; the area that had the highest community and school CFA rates also had the highest school antibody rate (6.9%). Filarial DNA rates in mosquitoes exceeded 0.25% in 10 PHI areas.


CONCLUSIONS
Comprehensive surveillance is feasible for some national filariasis elimination programs. Low-level persistence of LF was present in all study sites; several sites failed to meet provisional endpoint criteria for LF elimination, and follow-up testing will be needed in these areas. TAS was not sensitive for detecting low-level persistence of filariasis in Sri Lanka. We recommend use of antibody and MX testing as tools to complement TAS for post-MDA surveillance.
Department of Internal Medicine, Infectious Diseases Division, Washington University School of Medicine, St. Louis, Missouri, United States of America.
Ramakrishna U
RU
Rao
Anti Filariasis Campaign, Sri Lanka Ministry of Health, Colombo, Sri Lanka.
Kumara C
KC
Nagodavithana
Anti Filariasis Campaign, Sri Lanka Ministry of Health, Colombo, Sri Lanka.
Sandhya D
SD
Samarasekera
Anti Filariasis Campaign, Sri Lanka Ministry of Health, Colombo, Sri Lanka.
Asha D
AD
Wijegunawardana
Anti Filariasis Campaign, Sri Lanka Ministry of Health, Colombo, Sri Lanka.
Welmillage D Y
WD
Premakumara
Anti Filariasis Campaign, Sri Lanka Ministry of Health, Colombo, Sri Lanka.
Samudrika N
SN
Perera
Anti Filariasis Campaign, Sri Lanka Ministry of Health, Colombo, Sri Lanka.
Sunil
S
Settinayake
Division of Biostatistics, Washington University School of Medicine, St. Louis, Missouri, United States of America.
J Phillip
JP
Miller
Department of Internal Medicine, Infectious Diseases Division, Washington University School of Medicine, St. Louis, Missouri, United States of America.
Gary J
GJ
Weil
D000293:Adolescent; D000328:Adult; D015766:Albendazole / Q000627:therapeutic use*; D000818:Animals; D000871:Anthelmintics / Q000008:administration & dosage*; D000909:Antibodies, Helminth / Q000097:blood; D000947:Antigens, Helminth / Q000097:blood; D002648:Child; D003430:Cross-Sectional Studies; D003465:Culex / Q000469:parasitology; D018509:DNA, Helminth / Q000302:isolation & purification; D004049:Diethylcarbamazine / Q000627:therapeutic use*; D060740:Disease Eradication; D004605:Elephantiasis, Filarial / Q000188:drug therapy / Q000453:epidemiology*; D005260:Female; D005369:Filaricides / Q000627:therapeutic use; D006801:Humans; D007303:Insect Vectors / Q000469:parasitology; D008137:Longitudinal Studies; D008297:Male; D008842:Microfilariae / Q000276:immunology / Q000302:isolation & purification; D008875:Middle Aged; D015995:Prevalence; D013188:Sri Lanka / Q000453:epidemiology; D055815:Young Adult
D000871:Anthelmintics; D000909:Antibodies, Helminth; D000947:Antigens, Helminth; D018509:DNA, Helminth; D005369:Filaricides; D015766:Albendazole; D004049:Diethylcarbamazine