Dynamics of antigenemia and transmission intensity of Wuchereria bancrofti following cessation of mass drug administration in a formerly highly endemic region of Mali. Issue 1 (December 2016)

• Record Type: Journal Article
• Authors: Coulibaly, Yaya; Coulibaly, Siaka; Dolo, Housseini; Konate, Siaka; Diallo, Abdallah; Doumbia, Salif; Soumaoro, Lamine; Coulibaly, Michel; Dicko, Ilo; Sangare, Moussa; Dembele, Benoit; Sangare, Modibo; Dembele, Massitan; Touré, Yeya; Kelly-Hope, Louise; Polman, Katja; Kyelem, Dominique; Traore, Sekou; Bockarie, Moses; Klion, Amy; Nutman, Thomas
• Is Part Of: Parasites & vectors. Volume 9:Issue 1(2016)
• Page Start: 1
• Page End: 9
• Publication Date: 2016-12
• Subjects: Wuchereria bancrofti -- Transmission assessment survey -- Anopheles gambiae complex -- Mass drug administration -- Post-MDA surveillance; Parasitism -- Periodicals; Parasites -- Periodicals; Vector-pathogen relationships -- Periodicals; Animals as carriers of disease -- Periodicals; Insects as carriers of disease -- Periodicals; 616.96
• DOI: 10.1186/s13071-016-1911-9
• Languages: English
• ISSNs: 1756-3305

Abstract

Abstract Background After seven annual rounds of mass drug administration (MDA) in six Malian villages highly endemic forWuchereria bancrofti (overall prevalence rate of 42.7%), treatment was discontinued in 2008. Surveillance was performed over the ensuing 5 years to detect recrudescence. Methods Circulating filarial antigen (CFA) was measured using immunochromatographic card tests (ICT) and Og4C3 ELISA in 6–7 year-olds. Antibody to theW. bancrofti infective larval stage (L3) antigen, Wb123, was tested in the same population in 2012. Microfilaraemia was assessed in ICT-positive subjects.Anopheles gambiae complex specimens were collected monthly using human landing catch (HLC) and pyrethrum spray catch (PSC).Anopheles gambiae complex infection withW. bancrofti was determined by dissection and reverse transcriptase polymerase chain reaction (RT-PCR) of mosquito pools. Results Annual CFA prevalence rates using ICT in children increased over time from 0% (0/289) in 2009 to 2.7% (8/301) in 2011, 3.9% (11/285) in 2012 and 4.5% (14/309) in 2013 (trendχ 2 = 11.85, df =3, P = 0.0006). Wb123 antibody positivity rates in 2013 were similar to the CFA prevalence by ELISA (5/285). Although twoW. bancrofti -infectedAnopheles were observed by dissection among 12, 951 mosquitoes collected by HLC, none had L3 larvae when tested by L3-specific RT-PCR. No positive pools were detected among the mosquitoes collected by pyrethrum spray catch. Whereas ICT in 6–7 year-olds was the major surveillance tool, ICT positivity was also assessed in older children and adults (8–65 years old). CFA prevalence decreased in this group from 4.9% (39/800) to 3.5% (28/795) and 2.8% (50/1, 812) in 2009, 2011 and 2012, respectively (trendχ 2 = 7.361, df =2, P = 0.0067). Some ICT-positive individuals were microfilaraemic in 2009 [2.6% (1/39)] and 2011 [8.3% (3/36)], but none were positive in 2012 or 2013. Conclusion Although ICT rates in children increased over the 5-year surveillance period, the decrease in ICT prevalence in the older group suggests a reduction in transmission intensity. This was consistent with the failure to detect infective mosquitoes or microfilaraemia. The threshold of ICT positivity in children may need to be re-assessed and other adjunct surveillance tools considered.