Mapping lymphatic filariasis in Loa loa endemic health districts naïve for ivermectin mass administration and situated in the forested zone of Cameroon.

BACKGROUND: The control of lymphatic filariasis (LF) caused by Wuchereria bancrofti in the Central African Region has been hampered by the presence of Loa loa due to severe adverse events that arise in the treatment with ivermectin. The immunochromatographic test (ICT) cards used for mapping LF demonstrated cross-reactivity with L. loa and posed the problem of delineating the LF map. To verify LF endemicity in forest areas of Cameroon where mass drug administration (MDA) has not been ongoing, we used the recently developed strategy that combined serology, microscopy and molecular techniques. METHODS: This study was carried out in 124 communities in 31 health districts (HDs) where L. loa is present. At least 125 persons per site were screened. Diurnal blood samples were investigated for circulating filarial antigen (CFA) by FTS and for L. loa microfilariae (mf) using TBF. FTS positive individuals were further subjected to night blood collection for detecting W. bancrofti. qPCR was used to detect DNA of the parasites. RESULTS: Overall, 14,446 individuals took part in this study, 233 participants tested positive with FTS in 29 HDs, with positivity rates ranging from 0.0 to 8.2%. No W. bancrofti mf was found in the night blood of any individuals but L. loa mf were found in both day and night blood of participants who were FTS positive. Also, qPCR revealed that no W. bancrofti but L.loa DNA was found with dry bloodspot. Positive FTS results were strongly associated with high L. loa mf load. Similarly, a strong positive association was observed between FTS positivity and L loa prevalence. CONCLUSIONS: Using a combination of parasitological and molecular tools, we were unable to find evidence of W. bancrofti presence in the 31 HDs, but L. loa instead. Therefore, LF is not endemic and LF MDA is not required in these districts.

First evidence of lymphatic filariasis transmission interruption in Cameroon: Progress towards elimination.

BACKGROUND: Lymphatic filariasis (LF) is among the 10 neglected tropical diseases targeted for control or elimination by 2020. For LF elimination, the World Health Organization (WHO) has proposed a comprehensive strategy including (i) interruption of LF transmission through large-scale annual treatment (or mass drug administration (MDA)) of all eligible individuals in endemic areas, and (ii) alleviation of LF-associated suffering through morbidity management and disability prevention. In Cameroon, once-yearly mass administration of ivermectin and albendazole has been implemented since 2008. The aim of this study was to assess progress towards the elimination goal, looking specifically at the impact of six rounds of MDA on LF transmission in northern Cameroon. METHODOLOGY: The study was conducted in the North and Far North Regions of Cameroon. Five health districts that successfully completed six rounds of MDA (defined as achieving a treatment coverage ≥ 65% each year) and reported no positive results for Wuchereria bancrofti microfilariaemia during routine surveys following the fifth MDA were grouped into three evaluation units (EU) according to WHO criteria. LF transmission was assessed through a community-based transmission assessment survey (TAS) using an immunochromatographic test (ICT) for the detection of circulating filarial antigen (CFA) in children aged 5-8 years old. PRINCIPAL FINDINGS: A total of 5292 children (male/female ratio 1.04) aged 5-8 years old were examined in 97 communities. Positive CFA results were observed in 2, 8 and 11 cases, with a CFA prevalence of 0.13% (95% CI: 0.04-0.46) in EU#1, 0.57% (95% CI: 0.32-1.02) in EU#2, and 0.45% (95% CI: 0.23-0.89) in EU#3. CONCLUSION/SIGNIFICANCE: The positive CFA cases were below WHO defined critical cut-off thresholds for stopping treatment and suggest that transmission can no longer be sustained. Post-MDA surveillance activities should be organized to evaluate whether recrudescence can occur.

Loss of sensitivity of immunochromatographic test (ICT) for lymphatic filariasis diagnosis in low prevalence settings: consequence in the monitoring and evaluation procedures.

BACKGROUND: Diagnostic tools for lymphatic filariasis (LF) elimination programs are useful in mapping the distribution of the disease, delineating areas where mass drug administrations (MDA) are required, and determining when to stop MDA. The prevalence and burden of LF have been drastically reduced following mass treatments, and the evaluation of the performance of circulating filarial antigen (CFA)-based assays was acknowledged to be of high interest in areas with low residual LF endemicity rates after multiple rounds of MDA. The objective of this study was therefore to evaluate the immunochromatographic test (ICT) sensitivity in low endemicity settings and, specifically, in individuals with low intensity of lymphatic filariasis infection. METHODS: To perform this study, calibrated thick blood smears, ICT and Og4C3 enzyme-linked immunosorbent assay (ELISA) were carried out by night to identify Wuchereria bancrofti microfilarial and circulating filarial antigen carriers. A threshold determination assay regarding ICT and ELISA was performed using serial plasma dilutions from individuals with positive microfilarial counts. RESULTS: All individuals harbouring microfilariae (positive blood films) were detected by ICT and ELISA, but among individuals positive for ELISA, only 35.7 % of them were detected using ICT (Chi square: 4.57; p-value = 0.03), indicating a moderate agreement between both tests (kappa statistics = 0.49). Threshold determination analyses showed that ELISA was still positive at the last plasma dilution with negative ICT result. CONCLUSIONS: These findings suggest a loss of sensitivity for ICT in low endemicity settings, especially in people exhibiting low levels of circulating filarial antigen, raising serious concern regarding the monitoring and evaluation procedures in the framework of LF elimination program.

Mapping of Bancroftian Filariasis in Cameroon: Prospects for Elimination.

BACKGROUND: Lymphatic filariasis (LF) is one of the most debilitating neglected tropical diseases (NTDs). It still presents as an important public health problem in many countries in the tropics. In Cameroon, where many NTDs are endemic, only scant data describing the situation regarding LF epidemiology was available. The aim of this study was to describe the current situation regarding LF infection in Cameroon, and to map this infection and accurately delineate areas where mass drug administration (MDA) was required. METHODOLOGY: The endemicity status and distribution of LF was assessed in eight of the ten Regions of Cameroon by a rapid-format card test for detection of W. bancrofti antigen (immunochromatographic test, ICT). The baseline data required to monitor the effectiveness of MDA was collected by assessing microfilariaemia in nocturnal calibrated thick blood smears in sentinel sites selected in the health districts where ICT positivity rate was ≥ 1%. PRINCIPAL FINDINGS: Among the 120 health districts visited in the eight Regions during ICT survey, 106 (88.3%) were found to be endemic for LF (i.e. had ICT positivity rate ≥ 1%), with infection rate from 1.0% (95% CI: 0.2-5.5) to 20.0% (95% CI: 10-30). The overall infection rate during the night blood survey was 0.11% (95% CI: 0.08-0.16) in 11 health districts out of the 106 surveyed; the arithmetic mean for microfilaria density was 1.19 mf/ml (95% CI: 0.13-2.26) for the total population examined. CONCLUSION/SIGNIFICANCE: ICT card test results showed that LF was endemic in all the Regions and in about 90% of the health districts surveyed. All of these health districts qualified for MDA (i.e. ICT positivity rate ≥ 1%). Microfilariaemia data collected as part of this study provided the national program with baseline data (sentinel sites) necessary to measure the impact of MDA on the endemicity level and transmission of LF important for the 2020 deadline for global elimination.

Prevalence of trachoma in the north region of Cameroon: results of a survey in 15 health districts.

BACKGROUND: To estimate the prevalence of trachoma in the North Region of Cameroon in order to facilitate the planning of trachoma control activities in this region, a survey was carried out in 2011 and 2012 in 15 health districts (HDs). METHODOLOGY: A cross-sectional, two-stage cluster random sampling survey was carried out. The survey focused on two target populations: children aged 1 to 9 years for the prevalence of Trachomatous Inflammation-Follicular (TF) and those aged 15 and over for the prevalence of Trachomatous Trichiasis (TT). The sample frame was an exhaustive list of villages and neighborhoods of HDs. The World Health Organization simplified trachoma grading system was used for the recognition and registration of cases of trachoma. PRINCIPAL FINDINGS: 30,562 children aged 1 to 9 years and 24,864 people aged 15 and above were examined. In children aged 1-9 years, the overall prevalence of TF was 4.2% (95% confidence intervals (CI): 4.0-4.5%). Three (3) of 15 HDs in the region showed TF prevalence of ≥ 10% (Poli, Rey Bouba, and Tcholliré). The overall TT prevalence was 0.25% (95% CI: 0.20-0.33%). There were estimated 1265 TT cases in the region. The prevalence of blindness was 0.01% (95% CI: 0.00-0.03%), low vision was 0.11% (95% CI: 0.07-0.17%), and corneal opacity was 0.22% (95% CI: 0.17-0.29%). CONCLUSIONS/SIGNIFICANCE: This survey provides baseline data for the planning of activities to control trachoma in the region. The overall prevalence of TF in the region is 4.2%, and that of TT is 0.2%; three HDs have a TF prevalence ≥ 10%. These three HDs are eligible for mass drug administration with azythromycin, along with the implementation of the "F" and "E" components of the SAFE strategy.

Absence of an association between Plasmodium falciparum infection and post-ivermectin Loa-related non-neurologic serious adverse events.

Although ivermectin treatment can induce serious adverse events (SAEs) in individuals harboring high Loa loa microfilaremia (mf), not all patients with high mf levels develop such reactions, suggesting that cofactors may be involved. A study was conducted in Cameroon to investigate the possible role of Plasmodium coinfection at the time of ivermectin treatment in the development of SAEs. Before their first ivermectin treatment, thick smears were obtained from 4,175 individuals to determine the burden of Plasmodium sp., L. loa, and Mansonella perstans. After treatment, 18 (4.3 per 1,000) patients developed a non-neurologic SAE. Logistic regression analysis, adjusting for age, sex, P. falciparum infection, and M. perstans infection intensities, confirmed that L. loa mf was the main risk factor for SAEs. We found no evidence that coinfection with P. falciparum at the time of ivermectin treatment was associated with the occurrence of Loa-related SAEs in this population.

Mapping of schistosomiasis and soil-transmitted helminthiasis in the regions of centre, East and West Cameroon.

BACKGROUND: Schistosomiasis and soil-transmitted helminthiasis (STH) are widely distributed in Cameroon. Although mass drug administration (MDA) of mebendazole is implemented nationwide, treatment with praziquantel was so far limited to the three northern regions and few health districts in the southern part of Cameroon, based on previous mapping conducted 25 years ago. To update the disease distribution map and determine where treatment with praziquantel should be extended, mapping surveys were conducted in three of the seven southern regions of Cameroon, i.e. Centre, East and West. METHODOLOGY: Parasitological surveys were conducted in April-May 2010 in selected schools in all 63 health districts of the three targeted regions, using appropriate research methodologies, i.e. Kato-Katz and urine filtration. PRINCIPAL FINDINGS: The results showed significant variation of schistosomiasis and STH prevalence between schools, villages, districts and regions. Schistosoma mansoni was the most prevalent schistosome species, with an overall prevalence of 5.53%, followed by S. haematobium (1.72%) and S. guineensis (0.14%). The overall prevalence of schistosomiasis across the three regions was 7.31% (95% CI: 6.86-7.77%). The prevalence for Ascaris lumbricoides was 11.48 (95% CI: 10.93-12.04%), Trichuris trichiura 18.22% (95% CI: 17.56-18.90%) and hookworms 1.55% (95% CI: 1.35-1.78%), with an overall STH prevalence of 24.10% (95% CI: 23.36-24.85%) across the three regions. STH was more prevalent in the East region (46.57%; 95% CI: 44.41-48.75%) in comparison to the Centre (25.12; 95% CI: 24.10-26.17%) and West (10.49%; 95% CI: 9.57-11.51%) regions. CONCLUSIONS/SIGNIFICANCE: In comparison to previous data, the results showed an increase of schistosomiasis transmission in several health districts, whereas there was a significant decline of STH infections. Based on the prevalence data, the continuation of annual or bi-annual MDA for STH is recommended, as well as an extension of praziquantel in identified moderate and high risk communities for schistosomiasis.

Programmatic and Communication Issues in Relation to Serious Adverse Events Following Ivermectin Treatment in areas Co-endemic for Onchocerciasis and Loiasis.

In areas co-endemic for loiasis and onchocerciasis, the classic Community-Directed Treatment using ivermectin (Mectizan(R)) must be adapted as additional program activities, better communication and tighter control of ivermectin stocks are required to minimize risk and manage serious adverse events following ivermectin treatment in patients co-infected with Loa loa. The importance of these serious adverse events on community participation in onchocerciasis control efforts has not been adequately studied. Program implementers do not as of yet fully understand the psychological impact of serious adverse events on communities and therefore have not designed communication strategies that adequately address the real concerns of community members. It is clear, however, that along with an effective case detection and management strategy, a reinforced communication strategy will be required to motivate at least 65% of the total population in onchocerciasis and loiasis co-endemic areas to participate in the treatment program and to take ivermectin over an extended period. This strategy must be based on research undertaken at the community level in order to address the concerns, fears and issues associated with adverse events due to ivermectin - to ensure that communities believe that the benefits of taking ivermectin outweigh the risks. In addition to an overall increase in the time required to sustain onchocerciasis control programs in co-endemic areas, each aspect of the reinforced program and communication strategy - rapid epidemiological assessments, materials development, training, advocacy, community sensitization and mobilization, case management and counselling, supervision, monitoring and evaluation will require additional resources and support from all stakeholders concerned.