Joseph B. Koroma

Mapping, monitoring, and surveillance of neglected tropical diseases: towards a policy framework

As national programmes respond to the new opportunities presented for scaling up preventive chemotherapy programmes for the coadministration of drugs to target lymphatic filariasis, onchocerciasis, schistosomiasis, soil-transmitted helminthiasis, and trachoma, possible synergies between existing disease-specific policies and protocols need to be examined. In this report we compare present policies for mapping, monitoring, and surveillance for these diseases, drawing attention to both the challenges and opportunities for integration. Although full integration of all elements of mapping, monitoring, and surveillance strategies might not be feasible for the diseases targeted through the preventive chemotherapy approach, there are opportunities for integration, and we present examples of integrated strategies. Finally, if advantage is to be taken of scaled up interventions to address neglected tropical diseases, efforts to develop rapid, inexpensive, and easy-to-use methods, whether disease-specific or integrated, should be increased. We present a framework for development of an integrated monitoring and evaluation system that combines both integrated and disease-specific strategies.

Geographical Distribution of Intestinal Schistosomiasis and Soil-Transmitted Helminthiasis and Preventive Chemotherapy Strategies in Sierra Leone

Background A national baseline mapping of schistosomiasis and soil-transmitted helminthiasis (STH) was performed in Sierra Leone. The aim was to provide necessary tools for the Ministry of Health and Sanitation to plan the intervention strategies in the national integrated control program on neglected tropical diseases according to the World Health Organization (WHO) guidelines for preventative chemotherapy (PCT) and for future monitoring and evaluation. Methodology/Principal Findings 53 primary schools were randomly selected through a two-staged random sampling throughout the country. Approximately one hundred children aged 5–16 years of age were systematically selected from each school and their stool samples examined in a field laboratory. A total of 5,651 samples were examined. Data were analyzed with multivariable logistic regression models using model-based geostatistics. Spatial analysis predicted that S. mansoni infection was positively associated with population density and elevation and that there was a large cluster of high risk of S. mansoni infection (prevalence >70%) in the north and most of the eastern areas of the country, in line with the observed prevalence in Kono (63.8–78.3%), Koinadugu (21.6–82.1%), Kailahun (43.5–52.6%), Kenema (6.1–68.9%) and Tonkolili (0–57.3%). Hookworm infection was negatively associated with population density and land surface temperature, and was high across Sierra Leone with a large cluster of high infection risk (prevalence >70%) in the north-eastern part of the country. Remarkably low prevalence of Ascaris lumbricoides (7.2%) and Trichuris trichiura (3.3%) was recorded when compared with results published in the 1990s. Conclusions/Significance Results justify PCT for schistosomiasis for school age children and at-risk adults every year in high-risk communities in five districts and every two years in moderate-risk communities in one more district. The high prevalence of STH, particularly hookworm, coupled with widespread anemia according to a national report in Sierra Leone, suggests all but one district justifying biannual PCT for STH for pre-school children, school age children, and at-risk adults. PCT for STH in the remaining district, Kono is justified annually.

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

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.

Neglected tropical disease control in post-war Sierra Leone using the Onchocerciasis Control Programme as a platform

Strategic investments in the control of neglected tropical diseases (NTD) spearheaded by the US Government, the British Government and other bilateral donors such as foundations and key pharmaceutical partners have enabled the treatment of millions of people for the five targeted debilitating diseases (lymphatic filariasis, onchocerciasis, schistosomiasis, soil-transmitted helminthiasis and trachoma), paving the way for the potential elimination as public health problems of some of these diseases. Like many other countries, Sierra Leone has a high burden of these major NTDs. Despite the fragile infrastructure of a health system emerging from a devastating 10-year civil war, the country has successfully implemented the National NTD Control Programme, reaching national coverage in 2010. The NTD Control Programme uses the existing Onchocerciasis Control Programme as a platform and involves primary health workers. The programme has provided extensive training opportunities to health workers at national, district and community levels. The country currently has 31 161 trained community volunteers treating a population of five million people. It is shown that the investments in NTD control are not only to control NTDs but also to strengthen health systems, particularly at the primary level, through extensive capacity building of frontline health workers and community-directed distributors.

Impact of three rounds of mass drug administration on lymphatic filariasis in areas previously treated for onchocerciasis in Sierra Leone.

Background 1974–2005 studies across Sierra Leone showed onchocerciasis endemicity in 12 of 14 health districts (HDs) and baseline studies 2005–2008 showed lymphatic filariasis (LF) endemicity in all 14 HDs. Three integrated annual mass drug administration (MDA) were conducted in the 12 co-endemic districts 2008–2010 with good geographic, programme and drug coverage. Midterm assessment was conducted 2011 to determine impact of these MDAs on LF in these districts. Methodology/Principal Findings The mf prevalence and intensity in the 12 districts were determined using the thick blood film method and results compared with baseline data from 2007–2008. Overall mf prevalence fell from 2.6% (95% CI: 2.3%–3.0%) to 0.3% (95% CI: 0.19%–0.47%), a decrease of 88.5% (p = 0.000); prevalence was 0.0% (100.0% decrease) in four districts: Bo, Moyamba, Kenema and Kono (p = 0.001, 0.025, 0.085 and 0.000 respectively); and seven districts had reductions in mf prevalence of between 70.0% and 95.0% (p = 0.000, 0.060, 0.001, 0.014, 0.000, 0.000 and 0.002 for Bombali, Bonthe, Kailahun, Kambia, Koinadugu, Port Loko and Tonkolili districts respectively). Pujehun had baseline mf prevalence of 0.0%, which was maintained. Only Bombali still had an mf prevalence ≥1.0% (1.58%, 95% CI: 0.80%–3.09%)), and this is the district that had the highest baseline mf prevalence: 6.9% (95% CI: 5.3%–8.8%). Overall arithmetic mean mf density after three MDAs was 17.59 mf/ml (95% CI: 15.64 mf/ml–19.55 mf/ml) among mf positive individuals (65.4% decrease from baseline of 50.9 mf/ml (95% CI: 40.25 mf/ml–61.62 mf/ml; p = 0.001) and 0.05 mf/ml (95% CI: 0.03 mf/ml–0.08 mf/ml) for the entire population examined (96.2% decrease from baseline of 1.32 mf/ml (95% CI: 1.00 mf/ml–1.65 mf/ml; p = 0.000)). Conclusions/Significance The results show that mf prevalence decreased to <1.0% in all but one of the 12 districts after three MDAs. Overall mf density reduced by 65.0% among mf-positive individuals, and 95.8% for the entire population.

Combined spatial prediction of schistosomiasis and soil-transmitted helminthiasis in Sierra Leone: a tool for integrated disease control

Background A national mapping of Schistosoma haematobium was conducted in Sierra Leone before the mass drug administration (MDA) with praziquantel. Together with the separate mapping of S. mansoni and soil-transmitted helminths, the national control programme was able to plan the MDA strategies according to the World Health Organization guidelines for preventive chemotherapy for these diseases. Methodology/Principal Findings A total of 52 sites/schools were selected according to prior knowledge of S. haematobium endemicity taking into account a good spatial coverage within each district, and a total of 2293 children aged 9–14 years were examined. Spatial analysis showed that S. haematobium is heterogeneously distributed in the country with significant spatial clustering in the central and eastern regions of the country, most prevalent in Bo (24.6% and 8.79 eggs/10 ml), Koinadugu (20.4% and 3.53 eggs/10 ml) and Kono (25.3% and 7.91 eggs/10 ml) districts. By combining this map with the previously reported maps on intestinal schistosomiasis using a simple probabilistic model, the combined schistosomiasis prevalence map highlights the presence of high-risk communities in an extensive area in the northeastern half of the country. By further combining the hookworm prevalence map, the at-risk population of school-age children requiring integrated schistosomiasis/soil-transmitted helminth treatment regimens according to the coendemicity was estimated. Conclusions/Significance The first comprehensive national mapping of urogenital schistosomiasis in Sierra Leone was conducted. Using a new method for calculating the combined prevalence of schistosomiasis using estimates from two separate surveys, we provided a robust coendemicity mapping for overall urogenital and intestinal schistosomiasis. We also produced a coendemicity map of schistosomiasis and hookworm. These coendemicity maps can be used to guide the decision making for MDA strategies in combination with the local knowledge and programme needs.

No Evidence for Lymphatic Filariasis Transmission in Big Cities Affected by Conflict Related Rural-Urban Migration in Sierra Leone and Liberia

Background In West Africa, the principal vectors of lymphatic filariasis (LF) are Anopheles species with Culex species playing only a minor role in transmission, if any. Being a predominantly rural disease, the question remains whether conflict-related migration of rural populations into urban areas would be sufficient for active transmission of the parasite. Methodology/Principal Findings We examined LF transmission in urban areas in post-conflict Sierra Leone and Liberia that experienced significant rural-urban migration. Mosquitoes from Freetown and Monrovia, were analyzed for infection with Wuchereria bancrofti. We also undertook a transmission assessment survey (TAS) in Bo and Pujehun districts in Sierra Leone. The majority of the mosquitoes collected were Culex species, while Anopheles species were present in low numbers. The mosquitoes were analyzed in pools, with a maximum of 20 mosquitoes per pool. In both countries, a total of 1731 An. gambiae and 14342 Culex were analyzed for W. bancrofti, using the PCR. Two pools of Culex mosquitoes and 1 pool of An. gambiae were found infected from one community in Freetown. Pool screening analysis indicated a maximum likelihood of infection of 0.004 (95% CI of 0.00012–0.021) and 0.015 (95% CI of 0.0018–0.052) for the An. gambiae and Culex respectively. The results indicate that An. gambiae is present in low numbers, with a microfilaria prevalence breaking threshold value not sufficient to maintain transmission. The results of the TAS in Bo and Pujehun also indicated an antigen prevalence of 0.19% and 0.67% in children, respectively. This is well below the recommended 2% level for stopping MDA in Anopheles transmission areas, according to WHO guidelines. Conclusions We found no evidence for active transmission of LF in cities, where internally displaced persons from rural areas lived for many years during the more than 10 years conflict in Sierra Leone and Liberia.

Managing the Fight against Onchocerciasis in Africa: APOC Experience

Due to the socioeconomic impact of human onchocerciasis (commonly referred to as river blindness) in West Africa, the Onchocerciasis Control Programme in the Volta River Basin (OCP) was instituted [1]. This initial programme started in 1975 and covered seven West African countries: Benin, Burkina Faso, Cote d’Ivoire, Ghana, Mali, Niger, and Togo. However, later evidence indicated that endemic areas outside the initial area posed a threat to the achievement of the OCP and, hence, the Programme was extended southward and westward to include four additional countries, bringing the total number of countries covered by OCP to eleven. The formal name was then changed to the Onchocerciasis Control Programme in West Africa, retaining the acronym OCP. OCP used aerial larviciding as its principle strategy to control the vectors of human onchocerciasis, members of the Simulium damnosum complex, in the absence of a safe drug for mass treatment against the parasites [2]. Efforts to control onchocerciasis evolved in 1987 when ivermectin was donated to kill the juvenile worms that cause the various symptoms associated with the disease. As a result of the donation, OCP instituted a new strategy of chemotherapy in combination with vector control. In the 11 countries covered by OCP, this two-prong approach led to the virtual elimination of onchocerciasis as a public health problem and as an obstacle to socioeconomic development. The availability of a donated drug effective against the parasite and safe for mass drug administration, coupled with evidence that other pathological effects of onchocerciasis were equally important socioeconomic threats, led to the decision that onchocerciasis should be controlled in all endemic countries in Africa (Fig 1). Open in a separate window Fig 1 Onchocerciasis-endemic countries in Africa, showing countries covered by the OCP and initially by APOC. Map from 2010. Note that South Sudan gained independence in 2011, becoming the 20th APOC country.

Costs of Transmission Assessment Surveys to Provide Evidence for the Elimination of Lymphatic Filariasis

Background To reach the global goal of elimination of lymphatic filariasis as a public health problem by 2020, national programs will have to implement a series of transmission assessment surveys (TAS) to determine prevalence of the disease by evaluation unit. It is expected that 4,671 surveys will be required by 2020. Planning in advance for the costs associated with these surveys is essential to ensure that the required resources are available for this essential program activity. Methodology and Findings Retrospective cost data was collected from reports from 13 countries which implemented a total of 105 TAS surveys following a standardized World Health Organization (WHO) protocol between 2012 and 2014. The median cost per survey was

The epidemiology of trachoma in the five northern districts of Sierra Leone.

21,170 (including the costs for rapid diagnostic tests [RDTs]) and