03464nas a2200277   4500000000100000008004100001100001200042700002000054700001300074700001700087700002300104700002000127700002500147700001600172700001400188700001400202700001500216700001300231700001500244245021800259856007900477300001300556490000600569520259700575022001403172       2015                            d1 aWanji S1 aAmvongo-Adjia N1 aKoudou B1 aNjouendou AJ1 aChounna Ndongmo PW1 aKengne-Ouafo JA1 aDatchoua-Poutcheu FR1 aFovennso BA1 aTayong DB1 aFombad FF1 aFischer PU1 aEnyong P1 aBockarie M00aCross-reactivity of filariasis ICT cards in areas of contrasting endemicity of Loa loa and Mansonella perstans in Cameroon: Implications for shrinking of the lymphatic filariasis map in the Central African Region.  uhttp://journals.plos.org/plosntds/article?id=10.1371/journal.pntd.0004184   ae00041840 v93 a<p>Author Summary:</p>

<p>Mapping of lymphatic filariasis (LF) caused by <em>W</em>. <em>brancrofti</em> is usually done by employing a rapid diagnostic test that permits the detection of worm antigen in daytime blood. This is sometimes combined with a thick blood film (TBF) for microscopic examination, as confirmatory tool for detecting <em>W</em>. <em>bancrofti</em> Mf in peripheral night blood. During recent epidemiological surveys using immunochromatographic card test (ICT) to map LF in areas highly endemic for loiasis, positive card tests were observed in individuals’ amicrofilaremic for <em>W</em>. <em>bancrofti</em> during night TBF examination, as well as by parasite DNA detection. The possibility of ICT cross-reacting with <em>L</em>. <em>loa</em> antigen was envisaged, but so far associations between ICT positivity and <em>L</em>. <em>loa</em> endemicity levels and loads of Mf in day blood have not yet been established. Moreover, <em>M</em>. <em>perstans</em> another filaria with blood dwelling Mf, that is often sympatric with <em>L</em>. <em>loa</em>, could contribute to the observed ICT cross-reactivity. The authors investigated the cross-reactivity of ICT in areas with contrasting endemicity levels of <em>L</em>. <em>loa</em> and <em>M</em>. <em>perstans</em> in Cameroon. Results incriminated <em>L</em>. <em>loa</em> as the major confounder in ICT cross-reactivity, with significant association between ICT positivity and loiasis both at individual level (load of Mf/ml of blood) and endemicity level (Mf prevalence). <em>M</em>. <em>perstans</em> displayed no association with ICT positivity. The findings raised concerns about the specificity of the whole blood ICT used for LF mapping in loiasis co-endemic areas. The development of an algorithm for LF mapping in loiasis co-endemic areas will be important to validate the LF map obtained using ICT in Central Africa.</p>

<p>CONCLUSIONS/SIGNIFICANCE<strong>: </strong>This study has confirmed the strong association between the ICT positivity and L. loa intensity (Mf/ml of blood) at the individual level. Furthermore, the study has demonstrated that ICT positivity is strongly associated with high L. loa prevalence. These results suggest that the main confounding factor for positive ICT test card results are high levels of L. loa. The findings may indicate that W. bancrofti is much less prevalent in the Central African region where L. loa is highly endemic than previously assumed and accurate re-mapping of the region would be very useful for shrinking of the map of LF distribution.</p>
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