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Cross-Reactivity of Filariais 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.

Wanji S, Amvongo-Adjia N, Koudou B, Njouendou AJ, Chounna Ndongmo PW, Kengne-Ouafo JA, Datchoua-Poutcheu FR, Fovennso BA, Tayong DB, Fombad FF, Fischer PU, Enyong PI, Bockarie M - PLoS Negl Trop Dis (2015)

Bottom Line: No Mf of W. bancrofti were found in the night blood of any individual with a positive ICT result or clinical lymphoedema.Similarly, a strong positive association (Spearman's rho = 0.900; p = 0.037) was observed between the prevalence of L. loa and ICT positivity by area: a rate of 1% or more of positive ICT results was found only in areas with an L. loa Mf prevalence above 15%.These results suggest that the main confounding factor for positive ICT test card results are high levels of L. loa.

View Article: PubMed Central - PubMed

Affiliation: Parasites and Vector Biology research unit (PAVBRU), Department of Microbiology and Parasitology, University of Buea, Buea, Cameroon.

ABSTRACT

Background: Immunochromatographic card test (ICT) is a tool to map the distribution of Wuchereria bancrofti. In areas highly endemic for loaisis in DRC and Cameroon, a relationship has been envisaged between high L. loa microfilaria (Mf) loads and ICT positivity. However, similar associations have not been demonstrated from other areas with contrasting levels of L. loa endemicity. This study investigated the cross-reactivity of ICT when mapping lymphatic filariasis (LF) in areas with contrasting endemicity levels of loiasis and mansonellosis in Cameroon.

Methodology/principal findings: A cross-sectional study to assess the prevalence and intensity of W. bancrofti, L. loa and M. perstans was carried out in 42 villages across three regions (East, North-west and South-west) of the Cameroon rainforest domain. Diurnal blood was collected from participants for the detection of circulating filarial antigen (CFA) by ICT and assessment of Mf using a thick blood smear. Clinical manifestations of LF were also assessed. ICT positives and patients clinically diagnosed with lymphoedema were further subjected to night blood collection for the detection of W. bancrofti Mf. Overall, 2190 individuals took part in the study. Overall, 24 individuals residing in 14 communities were tested positive by ICT, with prevalence rates ranging from 0% in the South-west to 2.1% in the North-west. Lymphoedema were diagnosed in 20 individuals with the majority of cases found in the North-west (11/20), and none of them were tested positive by ICT. No Mf of W. bancrofti were found in the night blood of any individual with a positive ICT result or clinical lymphoedema. Positive ICT results were strongly associated with high L. loa Mf intensity with 21 subjects having more than 8,000 L. loa Mf ml/blood (Odds ratio = 15.4; 95%CI: 6.1-39.0; p < 0.001). Similarly, a strong positive association (Spearman's rho = 0.900; p = 0.037) was observed between the prevalence of L. loa and ICT positivity by area: a rate of 1% or more of positive ICT results was found only in areas with an L. loa Mf prevalence above 15%. In contrast, there was no association between ICT positivity and M. perstans prevalence (Spearman's rho = - 0.200; p = 0.747) and Mf density (Odds ratio = 1.8; 95%CI: 0.8-4.2; p = 0.192).

Conclusions/significance: 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.

No MeSH data available.


Related in: MedlinePlus

Correlation between ICT positivity rate and M. perstans Mf prevalence.
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pntd.0004184.g005: Correlation between ICT positivity rate and M. perstans Mf prevalence.

Mentions: The ICT prevalence was strongly correlated (Spearman’s rho = 0.900; p < 0.05) with the endemicity level of loiasis in the different sites as illustrated in Fig 4. ICT positivity was very rare or low in areas where L. loa Mf prevalence was below 10%. A positive ICT prevalence of ICT up to 0.8% could be seen in areas where the L. loa Mf prevalence ranged between 10–15%. When prevalence rates of L. loa Mf were above 25%, rates of more than 1% of ICT positives were detected. In contrast, there was no significant correlation between the prevalence of positive ICT and M. perstans Mf prevalence (Spearman’s rho = - 0.200; p = 0.747) as illustrated in Fig 5.


Cross-Reactivity of Filariais 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.

Wanji S, Amvongo-Adjia N, Koudou B, Njouendou AJ, Chounna Ndongmo PW, Kengne-Ouafo JA, Datchoua-Poutcheu FR, Fovennso BA, Tayong DB, Fombad FF, Fischer PU, Enyong PI, Bockarie M - PLoS Negl Trop Dis (2015)

Correlation between ICT positivity rate and M. perstans Mf prevalence.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4636288&req=5

pntd.0004184.g005: Correlation between ICT positivity rate and M. perstans Mf prevalence.
Mentions: The ICT prevalence was strongly correlated (Spearman’s rho = 0.900; p < 0.05) with the endemicity level of loiasis in the different sites as illustrated in Fig 4. ICT positivity was very rare or low in areas where L. loa Mf prevalence was below 10%. A positive ICT prevalence of ICT up to 0.8% could be seen in areas where the L. loa Mf prevalence ranged between 10–15%. When prevalence rates of L. loa Mf were above 25%, rates of more than 1% of ICT positives were detected. In contrast, there was no significant correlation between the prevalence of positive ICT and M. perstans Mf prevalence (Spearman’s rho = - 0.200; p = 0.747) as illustrated in Fig 5.

Bottom Line: No Mf of W. bancrofti were found in the night blood of any individual with a positive ICT result or clinical lymphoedema.Similarly, a strong positive association (Spearman's rho = 0.900; p = 0.037) was observed between the prevalence of L. loa and ICT positivity by area: a rate of 1% or more of positive ICT results was found only in areas with an L. loa Mf prevalence above 15%.These results suggest that the main confounding factor for positive ICT test card results are high levels of L. loa.

View Article: PubMed Central - PubMed

Affiliation: Parasites and Vector Biology research unit (PAVBRU), Department of Microbiology and Parasitology, University of Buea, Buea, Cameroon.

ABSTRACT

Background: Immunochromatographic card test (ICT) is a tool to map the distribution of Wuchereria bancrofti. In areas highly endemic for loaisis in DRC and Cameroon, a relationship has been envisaged between high L. loa microfilaria (Mf) loads and ICT positivity. However, similar associations have not been demonstrated from other areas with contrasting levels of L. loa endemicity. This study investigated the cross-reactivity of ICT when mapping lymphatic filariasis (LF) in areas with contrasting endemicity levels of loiasis and mansonellosis in Cameroon.

Methodology/principal findings: A cross-sectional study to assess the prevalence and intensity of W. bancrofti, L. loa and M. perstans was carried out in 42 villages across three regions (East, North-west and South-west) of the Cameroon rainforest domain. Diurnal blood was collected from participants for the detection of circulating filarial antigen (CFA) by ICT and assessment of Mf using a thick blood smear. Clinical manifestations of LF were also assessed. ICT positives and patients clinically diagnosed with lymphoedema were further subjected to night blood collection for the detection of W. bancrofti Mf. Overall, 2190 individuals took part in the study. Overall, 24 individuals residing in 14 communities were tested positive by ICT, with prevalence rates ranging from 0% in the South-west to 2.1% in the North-west. Lymphoedema were diagnosed in 20 individuals with the majority of cases found in the North-west (11/20), and none of them were tested positive by ICT. No Mf of W. bancrofti were found in the night blood of any individual with a positive ICT result or clinical lymphoedema. Positive ICT results were strongly associated with high L. loa Mf intensity with 21 subjects having more than 8,000 L. loa Mf ml/blood (Odds ratio = 15.4; 95%CI: 6.1-39.0; p < 0.001). Similarly, a strong positive association (Spearman's rho = 0.900; p = 0.037) was observed between the prevalence of L. loa and ICT positivity by area: a rate of 1% or more of positive ICT results was found only in areas with an L. loa Mf prevalence above 15%. In contrast, there was no association between ICT positivity and M. perstans prevalence (Spearman's rho = - 0.200; p = 0.747) and Mf density (Odds ratio = 1.8; 95%CI: 0.8-4.2; p = 0.192).

Conclusions/significance: 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.

No MeSH data available.


Related in: MedlinePlus