Lymphatic filariasis mapping by Immunochromatographic Test cards and baseline microfilaria survey prior to mass drug administration in Sierra Leone

Abstract

BackgroundNational mapping of lymphatic filariasis (LF) was conducted using Immunochromatographic tests (ICT) in 2005 to determine endemicity and geographic spread of the disease. A baseline microfilaria survey was then conducted to determine LF prevalence and microfilaria intensity.MethodsIn 2005 1,982 persons of 15 years and over from 14 health districts were selected and fingertip blood samples were tested with ICT cards. In 2007-8 blood samples were taken between 10 p.m. and 2 a.m. and examined for microfilaria (mf) from 9,288 persons from 16 sentinel sites representing each district and 2 additional sites for districts with populations over 500,000 (Bo and Kenema).ResultsThe overall LF prevalence by ICT cards was 21% (males 28%, females 15%). All districts had a prevalence of Wuchereria bancrofti antigen > 1%. Distribution of LF prevalence showed a strong spatial correlation pattern with high prevalence in a large area in the northeast gradually decreasing to a relatively low prevalence in the southwest coast. High prevalence was found in the northeast, Bombali (52%), Koinadugu (46%), Tonkolili (37%) and Kono (30%). Low prevalence was found in the southwest, Bonthe (3%) and Pujehun (4%). The mf prevalence was higher in the northeast: Bombali, 6.7%, Koinadugu 5.7%, Port Loko 4.4% and Kono 2.4%. Overall there was a significant difference in mf prevalence by gender: males 2.9%, females 1.8% (p = 0.0002) and within districts in Kailahun, Kono, Port Loko, Moyamba and Koinadugu (all p < 0.05). The mf prevalence was higher in people > 20 years (2.5%) than in people ≤ 20 years (1.7%) (p = 0.043). The overall arithmetic mean mf density was 50.30 mf/ml among mf-positive individuals and 1.19 mf/ml in the population examined which varied significantly between districts.ConclusionsThe ICT results showed that LF was endemic nationwide and that preventive chemotherapy (PCT) was justified across the country. Both the ICT and microfilaraemia surveys found that prevalence was greater in males than females. The increase in microfilaraemia prevalence by age was evident when grouped as ≤ 20 versus > 20 years demonstrating early exposure. Baseline LF microfilaria load will be used to monitor PCT program progress.

The global distribution and transmission limits of lymphatic filariasis: past and present

“…Alternatively, the presence of W. bancrofti antigenaemia can be detected using the ICT card test [33][34][35] and presence of specific IgG4 antibodies to Brugia spp can be detected using the Brugia Rapid™ test [36][37][38]. Surveys for the mapping of LF have been based on a variety of sampling designs, including the rapid geographical assessment of Bancroftian filariasis (RAGFIL) method [29,63], lot quality assurance sampling [64,65], population-based household surveys [66] and sentinel site surveys [43,67,68], with the choice of survey methodology dependent on available resources and the stage of the control programme [69].…”

“…By the end of 2012, 59 out of the 72 endemic countries had completed national mapping surveys [39]. The results of these surveys highlight the marked withincountry geographical heterogeneity [26,[40][41][42][43][44][45][46]. LF mapping is ongoing in the remaining endemic countries except Eritrea, where it has not started yet [2].…”

Entomological determinants of insecticide-treated bed net effectiveness in Western Myanmar

“…Anopheles epiroticus (n = 1469) was the most commonly caught Anopheles species in human bait catches (48%) in both areas and, as in other coastal areas of South-East Asia, is likely to be an important malaria vector in this area [5,11-13]. The Rakhine state is composed of a network of inland seawater rivers and streams and tidal creeks along these rivers.…”

“…Among these, Anopheles dirus and Anopheles minimus were identified as the primary vector species complexes, as in many other parts of the country, while Anopheles annularis, Anopheles subpictus, Anopheles epiroticus (previously called Anopheles sundaicus ), Anopheles aconitus, Anopheles hyrcanus, Anopheles culicifacies, Anopheles maculatus , Anopheles varuna, Anopheles jeyporensis, Anopheles sinensis and Anopheles philippinensis have all been identified as secondary vectors [3-5]. In the nearby Chittagong Hill Tracts in Bangladesh, Anopheles umbrosus, Anopheles barbirostris, Anopheles nigerrimus , Anopheles nivipes, Anopheles kochi , and Anopheles vagus have also been identified as vectors [6].…”

Fifteen years of programme implementation for the elimination of Lymphatic Filariasis in Ghana: Impact of MDA on immunoparasitological indicators

“…However, in some cases, additional data needed to be collected for more reliable estimates. The availability of funding determines the ability to undertake surveys [14]. It is hoped that the financial commitments by international partners such as United States Agency for International Development (USAID), Department for International Development (DFID), World Bank, the Bill & Melinda Gates Foundation following the London Declaration (2012), and the subsequent meeting in Paris (2014) will see major improvements in the funding needs of control programmes [15,16].…”