title: Status of Onchocerciasis transmission after more than a decade of mass drug administration for onchocerciasis and lymphatic filariasis elimination in central Nigeria: challenges in coordinating the stop MDA decision.
abstract: BACKGROUND
  This study was undertaken in five onchocerciasis/lymphatic filariasis (LF) co-endemic local government areas (LGAs) in Plateau and Nasarawa, Nigeria. Annual MDA with ivermectin had been given for 17 years, 8 of which were in combination with albendazole. In 2008, assessments indicated that LF transmission was interrupted, but that the MDA had to continue due to the uncertain status of onchocerciasis transmission. Accordingly, assessments to determine if ivermectin MDA for onchocerciasis could be stopped were conducted in 2009.
  
  
  METHODS
  We evaluated nodule, microfilarial (mf) skin snip, and antibody (IgG4 response to OV16) prevalence in adults and children in six sentinel sites where baseline data from the 1990s were available. We applied the 2001 WHO criteria for elimination of onchocerciasis that defined transmission interruption as an infection rate of <0.1% in children (using both skin snip and OV16 antibody) and a rate of infective (L3) blackflies of <0.05%.
  
  
  RESULTS
  Among adult residents in sentinel sites, mean mf prevalence decreased by 99.37% from the 1991-1993 baseline of 42.95% (64/149) to 0.27% (2/739) in 2009 (p<0.001). The OV16 seropositivity of 3.52% (26/739) among this same group was over ten times the mf rate. No mf or nodules were detected in 4,451 children in sentinel sites and 'spot check' villages, allowing the exclusion of 0.1% infection rate with 95% confidence. Seven OV16 seropositives were detected, yielding a seroprevalence of 0.16% (0.32% upper 95%CI). No infections were detected in PCR testing of 1,568 Simulium damnosum s.l. flies obtained from capture sites around the six sentinel sites.
  
  
  CONCLUSIONS
  Interruption of transmission of onchocerciasis in these five LGAs is highly likely, although the number of flies caught was insufficient to exclude 0.05% with 95% confidence (upper CI 0.23%). We suggest that ivermectin MDA could be stopped in these LGAs if similar results are seen in neighboring districts.
authors.affiliation: The Carter Center, Atlanta, Georgia, United States of America.
authors.forename: Darin S
authors.initials: DS
authors.lastname: Evans
authors.affiliation: The Carter Center Nigeria, Jos, Plateau, Nigeria.
authors.forename: Kal
authors.initials: K
authors.lastname: Alphonsus
authors.affiliation: The Carter Center Nigeria, Jos, Plateau, Nigeria.
authors.forename: Jon
authors.initials: J
authors.lastname: Umaru
authors.affiliation: The Carter Center Nigeria, Jos, Plateau, Nigeria.
authors.forename: Abel
authors.initials: A
authors.lastname: Eigege
authors.affiliation: The Carter Center Nigeria, Jos, Plateau, Nigeria.
authors.forename: Emmanuel
authors.initials: E
authors.lastname: Miri
authors.affiliation: University of Jos, Plateau, Nigeria.
authors.forename: Hayward
authors.initials: H
authors.lastname: Mafuyai
authors.affiliation: Consultant, River Blindness Foundation, Atlanta, Georgia, United States of America.
authors.forename: Carlos
authors.initials: C
authors.lastname: Gonzales-Peralta
authors.affiliation: The Carter Center Nigeria, Jos, Plateau, Nigeria.
authors.forename: William
authors.initials: W
authors.lastname: Adamani
authors.affiliation: Plateau State Ministry of Health, Jos, Plateau, Nigeria.
authors.forename: Elias
authors.initials: E
authors.lastname: Pede
authors.affiliation: Nasarawa State Ministry of Health, Lafia, Nasarawa, Nigeria.
authors.forename: Christopher
authors.initials: C
authors.lastname: Umbugadu
authors.affiliation: Department of Public Health, Federal Ministry of Health, Abuja, FCT, Nigeria.
authors.forename: Yisa
authors.initials: Y
authors.lastname: Saka
authors.affiliation: Department of Public Health, Federal Ministry of Health, Abuja, FCT, Nigeria.
authors.forename: Bridget
authors.initials: B
authors.lastname: Okoeguale
authors.affiliation: The Carter Center, Atlanta, Georgia, United States of America.
authors.forename: Frank O
authors.initials: FO
authors.lastname: Richards
mesh_terms: D000328:Adult; D015766:Albendazole / Q000008:administration & dosage / Q000627:therapeutic use; D000818:Animals; D000871:Anthelmintics / Q000008:administration & dosage / Q000627:therapeutic use; D000906:Antibodies; D000977:Antiparasitic Agents / Q000008:administration & dosage / Q000627:therapeutic use; D002648:Child; D002675:Child, Preschool; D004605:Elephantiasis, Filarial / Q000453:epidemiology / Q000517:prevention & control*; D005260:Female; D006801:Humans; D007559:Ivermectin / Q000008:administration & dosage / Q000627:therapeutic use; D008297:Male; D008842:Microfilariae; D008875:Middle Aged; D009549:Nigeria / Q000453:epidemiology; D009855:Onchocerciasis / Q000188:drug therapy* / Q000453:epidemiology / Q000635:transmission*; D015995:Prevalence; D016036:Seroepidemiologic Studies; D012843:Simuliidae; D055815:Young Adult
chemical_list: D000871:Anthelmintics; D000906:Antibodies; D000977:Antiparasitic Agents; D007559:Ivermectin; D015766:Albendazole