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Beng AA, Esum ME, Deribe K, Njouendou AJ, Ndongmo PWC, Abong RA, Fru J, Fombad FF, Nchanji GT, Amambo G, Gandjui NTV, Biholong B, Nko'Ayissi G, Mbia P, Akame J, Enyong PI, Reid SD, Tougoue JJ, Zhang Y, Wanji S. Mapping lymphatic filariasis in Loa loa endemic health districts naïve for ivermectin mass administration and situated in the forested zone of Cameroon. BMC Infect Dis 2020; 20:284. [PMID: 32299374 PMCID: PMC7164349 DOI: 10.1186/s12879-020-05009-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2020] [Accepted: 04/01/2020] [Indexed: 11/21/2022] Open
Abstract
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.
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Affiliation(s)
- Andrew A Beng
- Department of Microbiology and Parasitology, Parasites and Vector Biology Research Unit (PAVBRU), University of Buea, Buea, Cameroon
- Research Foundation in Tropical Diseases and the Environment (REFOTDE), Buea, Cameroon
| | - Mathias E Esum
- Department of Microbiology and Parasitology, Parasites and Vector Biology Research Unit (PAVBRU), University of Buea, Buea, Cameroon
- Research Foundation in Tropical Diseases and the Environment (REFOTDE), Buea, Cameroon
| | - Kebede Deribe
- Centre for Global Health Research, Brighton and Sussex Medical School, Brighton, BN1 9PS, UK.
- School of Public Health, College of Health Sciences, Addis Ababa University, P.O. Box 9086, Addis Ababa, Ethiopia.
| | - Abdel J Njouendou
- Department of Microbiology and Parasitology, Parasites and Vector Biology Research Unit (PAVBRU), University of Buea, Buea, Cameroon
- Research Foundation in Tropical Diseases and the Environment (REFOTDE), Buea, Cameroon
| | - Patrick W C Ndongmo
- Department of Microbiology and Parasitology, Parasites and Vector Biology Research Unit (PAVBRU), University of Buea, Buea, Cameroon
- Research Foundation in Tropical Diseases and the Environment (REFOTDE), Buea, Cameroon
| | - Raphael A Abong
- Department of Microbiology and Parasitology, Parasites and Vector Biology Research Unit (PAVBRU), University of Buea, Buea, Cameroon
- Research Foundation in Tropical Diseases and the Environment (REFOTDE), Buea, Cameroon
| | - Jerome Fru
- Department of Microbiology and Parasitology, Parasites and Vector Biology Research Unit (PAVBRU), University of Buea, Buea, Cameroon
- Research Foundation in Tropical Diseases and the Environment (REFOTDE), Buea, Cameroon
| | - Fanny F Fombad
- Department of Microbiology and Parasitology, Parasites and Vector Biology Research Unit (PAVBRU), University of Buea, Buea, Cameroon
- Research Foundation in Tropical Diseases and the Environment (REFOTDE), Buea, Cameroon
| | - Gordon T Nchanji
- Department of Microbiology and Parasitology, Parasites and Vector Biology Research Unit (PAVBRU), University of Buea, Buea, Cameroon
- Research Foundation in Tropical Diseases and the Environment (REFOTDE), Buea, Cameroon
| | - Glory Amambo
- Department of Microbiology and Parasitology, Parasites and Vector Biology Research Unit (PAVBRU), University of Buea, Buea, Cameroon
- Research Foundation in Tropical Diseases and the Environment (REFOTDE), Buea, Cameroon
| | - Narcisse T V Gandjui
- Department of Microbiology and Parasitology, Parasites and Vector Biology Research Unit (PAVBRU), University of Buea, Buea, Cameroon
- Research Foundation in Tropical Diseases and the Environment (REFOTDE), Buea, Cameroon
| | | | | | | | - Julie Akame
- Helen Keller International, Yaoundé, Cameroon
| | - Peter I Enyong
- Department of Microbiology and Parasitology, Parasites and Vector Biology Research Unit (PAVBRU), University of Buea, Buea, Cameroon
- Research Foundation in Tropical Diseases and the Environment (REFOTDE), Buea, Cameroon
| | | | | | - Yaobi Zhang
- Helen Keller International, New York, NY, USA
- Helen Keller International, Regional Office for Africa, Dakar, Senegal
| | - Samuel Wanji
- Department of Microbiology and Parasitology, Parasites and Vector Biology Research Unit (PAVBRU), University of Buea, Buea, Cameroon
- Research Foundation in Tropical Diseases and the Environment (REFOTDE), Buea, Cameroon
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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. 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. PLoS Negl Trop Dis 2015; 9:e0004184. [PMID: 26544042 PMCID: PMC4636288 DOI: 10.1371/journal.pntd.0004184] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2015] [Accepted: 09/30/2015] [Indexed: 12/05/2022] Open
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. Mapping of lymphatic filariasis (LF) caused by W. brancrofti 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 W. bancrofti 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 W. bancrofti during night TBF examination, as well as by parasite DNA detection. The possibility of ICT cross-reacting with L. loa antigen was envisaged, but so far associations between ICT positivity and L. loa endemicity levels and loads of Mf in day blood have not yet been established. Moreover, M. perstans another filaria with blood dwelling Mf, that is often sympatric with L. loa, could contribute to the observed ICT cross-reactivity. The authors investigated the cross-reactivity of ICT in areas with contrasting endemicity levels of L. loa and M. perstans in Cameroon. Results incriminated L. loa 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). M. perstans 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.
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Affiliation(s)
- Samuel Wanji
- Parasites and Vector Biology research unit (PAVBRU), Department of Microbiology and Parasitology, University of Buea, Buea, Cameroon
- Research Foundation for Tropical Diseases and the Environment (REFOTDE), Buea, Cameroon
- * E-mail:
| | - Nathalie Amvongo-Adjia
- Research Foundation for Tropical Diseases and the Environment (REFOTDE), Buea, Cameroon
- Laboratory of Parasitology and Ecology, Department of Animal Biology and Physiology, University of Yaoundé 1, Yaounde, Cameroon
| | - Benjamin Koudou
- Centre for Neglected Tropical Diseases (incorporating the Lymphatic Filariasis Support Centre), Liverpool School of Tropical Medicine, Liverpool, United Kingdom
| | - Abdel Jelil Njouendou
- Parasites and Vector Biology research unit (PAVBRU), Department of Microbiology and Parasitology, University of Buea, Buea, Cameroon
- Research Foundation for Tropical Diseases and the Environment (REFOTDE), Buea, Cameroon
| | - Patrick W. Chounna Ndongmo
- Parasites and Vector Biology research unit (PAVBRU), Department of Microbiology and Parasitology, University of Buea, Buea, Cameroon
- Research Foundation for Tropical Diseases and the Environment (REFOTDE), Buea, Cameroon
| | - Jonas A. Kengne-Ouafo
- Parasites and Vector Biology research unit (PAVBRU), Department of Microbiology and Parasitology, University of Buea, Buea, Cameroon
- Research Foundation for Tropical Diseases and the Environment (REFOTDE), Buea, Cameroon
| | | | | | - Dizzle Bita Tayong
- Parasites and Vector Biology research unit (PAVBRU), Department of Microbiology and Parasitology, University of Buea, Buea, Cameroon
- Research Foundation for Tropical Diseases and the Environment (REFOTDE), Buea, Cameroon
| | - Fanny Fri Fombad
- Parasites and Vector Biology research unit (PAVBRU), Department of Microbiology and Parasitology, University of Buea, Buea, Cameroon
- Research Foundation for Tropical Diseases and the Environment (REFOTDE), Buea, Cameroon
| | - Peter U. Fischer
- Infectious Diseases Division, Department of Internal Medicine, Washington University School of Medicine, St. Louis, Missouri, United States of America
| | - Peter I. Enyong
- Parasites and Vector Biology research unit (PAVBRU), Department of Microbiology and Parasitology, University of Buea, Buea, Cameroon
- Research Foundation for Tropical Diseases and the Environment (REFOTDE), Buea, Cameroon
| | - Moses Bockarie
- Centre for Neglected Tropical Diseases (incorporating the Lymphatic Filariasis Support Centre), Liverpool School of Tropical Medicine, Liverpool, United Kingdom
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