title: Dynamics of antigenemia and transmission intensity of Wuchereria bancrofti following cessation of mass drug administration in a formerly highly endemic region of Mali.
abstract: After seven annual rounds of mass drug administration (MDA) in six Malian villages highly endemic for Wuchereria bancrofti (overall prevalence rate of 42.7%), treatment was discontinued in 2008. Surveillance was performed over the ensuing 5 years to detect recrudescence.
  
  
  
  Circulating filarial antigen (CFA) was measured using immunochromatographic card tests (ICT) and Og4C3 ELISA in 6-7 year-olds. Antibody to the W. 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 with W. bancrofti was determined by dissection and reverse transcriptase polymerase chain reaction (RT-PCR) of mosquito pools.
  
  
  
  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 (trend χ2= 11.85, df =3, P = 0.0006). Wb123 antibody positivity rates in 2013 were similar to the CFA prevalence by ELISA (5/285). Although two W. bancrofti-infected Anopheles 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 (trend χ2= 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.
  
  
  
  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.
authors.affiliation: Filariasis Unit, International Center of Excellence in Research, Faculty of Medicine and Odontostomatology, Point G, Bamako, Mali. yicoulibaly@icermali.org.|Filarial Program Support Unit, Liverpool School of Tropical Medicine, Liverpool, UK. yicoulibaly@icermali.org.
authors.forename: Yaya I
authors.initials: YI
authors.lastname: Coulibaly
authors.affiliation: Filariasis Unit, International Center of Excellence in Research, Faculty of Medicine and Odontostomatology, Point G, Bamako, Mali.
authors.forename: Siaka Y
authors.initials: SY
authors.lastname: Coulibaly
authors.affiliation: Filariasis Unit, International Center of Excellence in Research, Faculty of Medicine and Odontostomatology, Point G, Bamako, Mali.
authors.forename: Housseini
authors.initials: H
authors.lastname: Dolo
authors.affiliation: Filariasis Unit, International Center of Excellence in Research, Faculty of Medicine and Odontostomatology, Point G, Bamako, Mali.
authors.forename: Siaka
authors.initials: S
authors.lastname: Konate
authors.affiliation: Filariasis Unit, International Center of Excellence in Research, Faculty of Medicine and Odontostomatology, Point G, Bamako, Mali.
authors.forename: Abdallah A
authors.initials: AA
authors.lastname: Diallo
authors.affiliation: Filariasis Unit, International Center of Excellence in Research, Faculty of Medicine and Odontostomatology, Point G, Bamako, Mali.
authors.forename: Salif S
authors.initials: SS
authors.lastname: Doumbia
authors.affiliation: Filariasis Unit, International Center of Excellence in Research, Faculty of Medicine and Odontostomatology, Point G, Bamako, Mali.
authors.forename: Lamine
authors.initials: L
authors.lastname: Soumaoro
authors.affiliation: Filariasis Unit, International Center of Excellence in Research, Faculty of Medicine and Odontostomatology, Point G, Bamako, Mali.
authors.forename: Michel E
authors.initials: ME
authors.lastname: Coulibaly
authors.affiliation: Filariasis Unit, International Center of Excellence in Research, Faculty of Medicine and Odontostomatology, Point G, Bamako, Mali.
authors.forename: Ilo
authors.initials: I
authors.lastname: Dicko
authors.affiliation: Filariasis Unit, International Center of Excellence in Research, Faculty of Medicine and Odontostomatology, Point G, Bamako, Mali.
authors.forename: Moussa B
authors.initials: MB
authors.lastname: Sangare
authors.affiliation: Filariasis Unit, International Center of Excellence in Research, Faculty of Medicine and Odontostomatology, Point G, Bamako, Mali.
authors.forename: Benoit
authors.initials: B
authors.lastname: Dembele
authors.affiliation: Filariasis Unit, International Center of Excellence in Research, Faculty of Medicine and Odontostomatology, Point G, Bamako, Mali.
authors.forename: Modibo
authors.initials: M
authors.lastname: Sangare
authors.affiliation: National Lymphatic Filariasis Elimination Program, Bamako, Mali.
authors.forename: Massitan
authors.initials: M
authors.lastname: Dembele
authors.affiliation: Faculty of Medicine and Odontostomatology of Bamako, Bamako, Mali.
authors.forename: Yeya T
authors.initials: YT
authors.lastname: Touré
authors.affiliation: Filarial Program Support Unit, Liverpool School of Tropical Medicine, Liverpool, UK.
authors.forename: Louise
authors.initials: L
authors.lastname: Kelly-Hope
authors.affiliation: Department of Biomedical Sciences, Institute of Tropical Medicine, Antwerp, Belgium.
authors.forename: Katja
authors.initials: K
authors.lastname: Polman
authors.affiliation: Neglected Tropical Diseases Support Center, Task Force for Global Health, Decatur, GA, USA.
authors.forename: Dominique
authors.initials: D
authors.lastname: Kyelem
authors.affiliation: Filariasis Unit, International Center of Excellence in Research, Faculty of Medicine and Odontostomatology, Point G, Bamako, Mali.
authors.forename: Sekou F
authors.initials: SF
authors.lastname: Traore
authors.affiliation: Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, L3 5QA, UK.
authors.forename: Moses
authors.initials: M
authors.lastname: Bockarie
authors.affiliation: Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA.
authors.forename: Amy D
authors.initials: AD
authors.lastname: Klion
authors.affiliation: Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA.
authors.forename: Thomas B
authors.initials: TB
authors.lastname: Nutman
mesh_terms: D000818:Animals; D000852:Anopheles / Q000469:parasitology; D000909:Antibodies, Helminth / Q000097:blood; D000947:Antigens, Helminth / Q000097:blood*; D002846:Chromatography, Affinity; D018562:Disease Transmission, Infectious; D004358:Drug Therapy / Q000379:methods*; D004605:Elephantiasis, Filarial / Q000188:drug therapy / Q000453:epidemiology* / Q000635:transmission*; D004797:Enzyme-Linked Immunosorbent Assay; D062665:Epidemiological Monitoring; D005369:Filaricides / Q000008:administration & dosage*; D006801:Humans; D008302:Mali; D015995:Prevalence; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014958:Wuchereria bancrofti / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification*
chemical_list: D000909:Antibodies, Helminth; D000947:Antigens, Helminth; D005369:Filaricides
keywords: Anopheles gambiae complex; Mass drug administration; Post-MDA surveillance; Transmission assessment survey; Wuchereria bancrofti