Abstract:Abstract. The value of a semi-quantitative scoring of the filarial antigen test (Binax Now Filariasis card test, ICT) results was evaluated during a field survey in the Republic of Congo. One hundred and thirty-four (134) of 774 tests (17.3%) were clearly positive and were scored 1, 2, or 3; and 11 (1.4%) had questionable results. Wuchereria bancrofti microfilariae (mf) were detected in 41 of those 133 individuals with an ICT test score 1 who also had a night blood smear; none of the 11 individuals with questi… Show more
“…Blood was collected by finger prick to detect CFA using the ICT (100 μL) read after 10 minutes according to the manufacturer's instructions. The result was reported using a semiquantitative score defined according to the relative intensity of test and control lines,10 that is, negative tests with no visible test (T) line were assigned a score of 0, tests with a T line weaker than the control (C) line were assigned a score of 1, tests with a T line approximately as dark as the C line were scored as 2, and cards with a T line darker than the C line were scored as 3. Figure 1.Data collection and main laboratory analysis results.…”
Section: Methodsmentioning
confidence: 99%
“…ELISA = enzyme-linked immunosorbent assay; ICT = immunochromatographic card test.*0 = no test (T) line; 1 = T line thinner than control (C) line; 2 = T line as thick as C line; 3 = T line thicker than C line 10…”
Section: Tablementioning
confidence: 99%
“…*0 = no test (T) line; 1 = T line thinner than control (C) line; 2 = T line as thick as C line; 3 = T line thicker than C line 10…”
Since the mid-2000s, the immunochromatographic card test (ICT), a point-of-care test for detecting Wuchereria bancrofti circulating filarial antigens (CFAs), has been the backbone for mapping and monitoring lymphatic filariasis (LF) worldwide. Recently, there have been instances in which CFA positivity has been associated with Loa loa microfilaremia. Here, we examined the association, at both the community and individual levels, between L. loa and CFA using additional diagnostic tools (quantitative polymerase chain reaction [qPCR], Og4C3 enzyme-linked immunosorbent assay, and IgG4 antibodies to Wb123 assays) to demonstrate the relationship between L. loa microfilaremia and ICT positivity. In May 2013, peripheral blood was collected during the day from 1,812 individuals living in southern Cameroon. ICT tests were done on the spot, and positive individuals were resampled at night. Results of qPCR and Wb123 assays concurred proving the absence of W. bancrofti infection. Og4C3 assays indicate a quantitative relationship between the level of L. loa microfilaremia and that of CFA. This was confirmed by epidemiological analyses, which reveal a strong association between L. loa microfilaremia and ICT positivity, with 50% of ICT reacting to L. loa when its microfilarial density exceeds 30,000 microfilariae/mL. At the community level, the proportion of positive ICT would exceed 2% when the prevalence of L. loa microfilaremia in the total population is above 20%. This has significant implications in terms of mapping and control of LF caused by W. bancrofti in Loa-endemic areas. Cross-reactivity of ICT with L. loa has to be considered in the context of both individual and community diagnostics.
“…Blood was collected by finger prick to detect CFA using the ICT (100 μL) read after 10 minutes according to the manufacturer's instructions. The result was reported using a semiquantitative score defined according to the relative intensity of test and control lines,10 that is, negative tests with no visible test (T) line were assigned a score of 0, tests with a T line weaker than the control (C) line were assigned a score of 1, tests with a T line approximately as dark as the C line were scored as 2, and cards with a T line darker than the C line were scored as 3. Figure 1.Data collection and main laboratory analysis results.…”
Section: Methodsmentioning
confidence: 99%
“…ELISA = enzyme-linked immunosorbent assay; ICT = immunochromatographic card test.*0 = no test (T) line; 1 = T line thinner than control (C) line; 2 = T line as thick as C line; 3 = T line thicker than C line 10…”
Section: Tablementioning
confidence: 99%
“…*0 = no test (T) line; 1 = T line thinner than control (C) line; 2 = T line as thick as C line; 3 = T line thicker than C line 10…”
Since the mid-2000s, the immunochromatographic card test (ICT), a point-of-care test for detecting Wuchereria bancrofti circulating filarial antigens (CFAs), has been the backbone for mapping and monitoring lymphatic filariasis (LF) worldwide. Recently, there have been instances in which CFA positivity has been associated with Loa loa microfilaremia. Here, we examined the association, at both the community and individual levels, between L. loa and CFA using additional diagnostic tools (quantitative polymerase chain reaction [qPCR], Og4C3 enzyme-linked immunosorbent assay, and IgG4 antibodies to Wb123 assays) to demonstrate the relationship between L. loa microfilaremia and ICT positivity. In May 2013, peripheral blood was collected during the day from 1,812 individuals living in southern Cameroon. ICT tests were done on the spot, and positive individuals were resampled at night. Results of qPCR and Wb123 assays concurred proving the absence of W. bancrofti infection. Og4C3 assays indicate a quantitative relationship between the level of L. loa microfilaremia and that of CFA. This was confirmed by epidemiological analyses, which reveal a strong association between L. loa microfilaremia and ICT positivity, with 50% of ICT reacting to L. loa when its microfilarial density exceeds 30,000 microfilariae/mL. At the community level, the proportion of positive ICT would exceed 2% when the prevalence of L. loa microfilaremia in the total population is above 20%. This has significant implications in terms of mapping and control of LF caused by W. bancrofti in Loa-endemic areas. Cross-reactivity of ICT with L. loa has to be considered in the context of both individual and community diagnostics.
“…The development of antibody tests for onchocerciasis with native antigens was hampered by the scarcity of parasite material (adult worms can only be obtained by nodulectomy) and by low specificity [49,50], although this was improved by measuring IgG4 subclass antibodies [51].Assays based on recombinant O. volvulus antigens varied in terms of sensitivity and specificity (Table S1 in Dirofilaria immitis or Wuchereria bancrofti in host blood or serum [64][65][66][67]. In addition, filarial antigen levels have shown to be related to the number of adult filarial parasites in several host-parasite systems [68][69][70] andto the number of Mf in the blood or skin [19,71,72]. Some of these assays are also useful for monitoring the success of macrofilaricidal treatment [73][74][75][76].…”
Onchocerciasis (river blindness) is a major public health problem in sub-Saharan Africa. Major disease-control programs have greatly reduced both disease and infection prevalence by mass distribution of donated ivermectin. Recent studies have shown that local elimination was achieved in some areas following many years of ivermectin. The global health community has recently decided to build on these successes with a new program that aims to eliminate onchocerciasis. Diagnostic tests that were useful for identifying priority areas for disease prevention may not be adequate tools for elimination programs. This paper reviews available and emerging diagnostic tests for onchocerciasis and considers how they might be best employed during different stages of onchocerciasis elimination programs.
“…ICT cards were read at 10 minutes by a single trained operator as previously described. 20 The results were scored semiquantitatively as follows: negative tests with no visible test (T) line were assigned a score of 0, tests with a clearly visible T line that was weaker than the control C line were assigned a score of 1, tests with a T line approximately as dark as the control line were scored as 2, and cards with a T line darker than the C line were scored as 3. All individuals with a positive ICT test (score 1) were invited to return for a second blood sampling between 10:00 PM and 1:00 AM for assessment of W. bancrofti mf.…”
Abstract. Implementation of mass drug administration (MDA) with ivermectin plus albendazole (ALB) for lymphatic filariasis (LF) has been delayed in central Africa because of the risk of serious adverse events in subjects with high Loa loa microfilaremia. We conducted a community trial to assess the impact of semiannual MDA with ALB (400 mg) alone on LF and soil-transmitted helminth (STH) infections in the Republic of Congo. Evaluation at 12 months showed that ALB MDA had not significantly reduced Wuchereria bancrofti antigenemia or microfilaria (mf) rates in the community (from 17.3% to 16.6% and from 5.3% to 4.2%, respectively). However, the geometric mean mf count in mf-positive subjects was reduced from 202.2 to 80.9 mf/mL (60% reduction, P = 0.01). The effect of ALB was impressive in 38 subjects who were mf-positive at baseline and retested at 12 months: 37% had total mf clearance, and individual mf densities were reduced by 73.0%. MDA also dramatically reduced the hookworm infection rate in the community from 6.5% to 0.6% (91% reduction), with less impressive effects on Ascaris and Trichuris. These preliminary results suggest that semiannual community MDA with ALB is a promising strategy for controlling LF and STH in areas with coendemic loiasis.
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