title: Relationship between oral declaration on adherence to ivermectin treatment and parasitological indicators of onchocerciasis in an area of persistent transmission despite a decade of mass drug administration in Cameroon.
abstract: BACKGROUND
  Onchocerciasis control for years has been based on mass drug administration (MDA) with ivermectin (IVM). Adherence to IVM repeated treatment has recently been shown to be a confounding factor for onchocerciasis elimination precisely in rain forest areas where transmission continues and Loa loa co-exists with Onchocerca volvulus. In this study, participants' oral declarations were used as proxy to determine the relationship between adherence to IVM treatment and parasitological indicators of onchocerciasis in the rain forest area of Cameroon with more than a decade of MDA.
  
  
  METHODS
  Participants were recruited based on their IVM intake profile with the aid of a semi-structured questionnaire. Parasitological examinations (skin sniping and nodule palpation) were done on eligible candidates. Parasitological indicators were calculated and correlated to IVM intake profile.
  
  
  RESULTS
  Of 2,364 people examined, 15.5% had never taken IVM. The majority (40.4%) had taken the drug 1-3 times while only 18% had taken ≥ 7 times. Mf and nodule prevalence rates were still high at 47%, 95% CI [44.9-49.0%] and 36.4%, 95% CI [34.4-38.3%] respectively. There was a treatment-dependent reduction in microfilaria prevalence (rs =-0.986, P = 0.01) and intensity (rs =-0.96, P = 0.01). The highest mf prevalence (59.7%) was found in the zero treatment group and the lowest (33.9%) in the ≥ 7 times treatment group (OR = 2.8; 95% CI [2.09-3.74]; P < 0.001). Adults with ≥ 7 times IVM intake were 2.99 times more likely to have individuals with no microfilaria compared to the zero treatment group (OR = 2.99; 95% CI [2.19-4.08], P < 0.0001). There was no clear correlation between treatment and nodule prevalence and intensity.
  
  
  CONCLUSIONS
  Adherence to ivermectin treatment is not adequate in this rain forest area where L. loa co-exists with O. volvulus. The prevalence and intensity of onchocerciasis remained high in individuals with zero IVM intake after more than a decade of MDA. Our findings show that using parasitological indicators, reduction in prevalence is IVM intake-dependent and that participants' oral declaration of treatment adherence could be relied upon for impact studies. The findings are discussed in the context of challenges for the elimination of onchocerciasis in this rain forest area.
authors.affiliation: Parasite and Vectors Research Unit, Department of Microbiology and Parasitology, University of Buea, P.O.Box 63, Buea, Cameroon. swanji@yahoo.fr.|Research Foundation for Tropical Diseases and Environment, P.O.Box 474, Buea, Cameroon. swanji@yahoo.fr.
authors.forename: Samuel
authors.initials: S
authors.lastname: Wanji
authors.affiliation: Parasite and Vectors Research Unit, Department of Microbiology and Parasitology, University of Buea, P.O.Box 63, Buea, Cameroon. arnaudkengne@yahoo.com.|Research Foundation for Tropical Diseases and Environment, P.O.Box 474, Buea, Cameroon. arnaudkengne@yahoo.com.
authors.forename: Jonas A
authors.initials: JA
authors.lastname: Kengne-Ouafo
authors.affiliation: Parasite and Vectors Research Unit, Department of Microbiology and Parasitology, University of Buea, P.O.Box 63, Buea, Cameroon. mathias_mesum@yahoo.fr.|Research Foundation for Tropical Diseases and Environment, P.O.Box 474, Buea, Cameroon. mathias_mesum@yahoo.fr.
authors.forename: Mathias E
authors.initials: ME
authors.lastname: Esum
authors.affiliation: Parasite and Vectors Research Unit, Department of Microbiology and Parasitology, University of Buea, P.O.Box 63, Buea, Cameroon. ndongmopatrick@yahoo.com.|Research Foundation for Tropical Diseases and Environment, P.O.Box 474, Buea, Cameroon. ndongmopatrick@yahoo.com.
authors.forename: Patrick W N
authors.initials: PW
authors.lastname: Chounna
authors.affiliation: Parasite and Vectors Research Unit, Department of Microbiology and Parasitology, University of Buea, P.O.Box 63, Buea, Cameroon. adzemye@gmail.com.|Research Foundation for Tropical Diseases and Environment, P.O.Box 474, Buea, Cameroon. adzemye@gmail.com.
authors.forename: Bridget F
authors.initials: BF
authors.lastname: Adzemye
authors.affiliation: Research Foundation for Tropical Diseases and Environment, P.O.Box 474, Buea, Cameroon. jeebanga@yahoo.com.|Department of Biological Sciences, Faculty of Science, University of Bamenda, P.O. Box 39, Bambili, North West Region, Cameroon. jeebanga@yahoo.com.
authors.forename: Joan E E
authors.initials: JE
authors.lastname: Eyong
authors.affiliation: Tropical Medicine Research station, P.O. Box 55, Kumba, Cameroon. jatojatoisaac@yahoo.com.
authors.forename: Isaac
authors.initials: I
authors.lastname: Jato
authors.affiliation: Parasite and Vectors Research Unit, Department of Microbiology and Parasitology, University of Buea, P.O.Box 63, Buea, Cameroon. fabriceroberto@yahoo.fr.|Research Foundation for Tropical Diseases and Environment, P.O.Box 474, Buea, Cameroon. fabriceroberto@yahoo.fr.
authors.forename: Fabrice R
authors.initials: FR
authors.lastname: Datchoua-Poutcheu
authors.affiliation: Parasite and Vectors Research Unit, Department of Microbiology and Parasitology, University of Buea, P.O.Box 63, Buea, Cameroon. abongr@gmail.com.|Research Foundation for Tropical Diseases and Environment, P.O.Box 474, Buea, Cameroon. abongr@gmail.com.
authors.forename: Raphael A
authors.initials: RA
authors.lastname: Abong
authors.affiliation: Parasite and Vectors Research Unit, Department of Microbiology and Parasitology, University of Buea, P.O.Box 63, Buea, Cameroon. enyongap@gmail.com.|Tropical Medicine Research station, P.O. Box 55, Kumba, Cameroon. enyongap@gmail.com.
authors.forename: Peter
authors.initials: P
authors.lastname: Enyong
authors.affiliation: Division of Infection and Pathway Medicine, School for Biomedical Studies, University of Edinburgh, 49 Little France Crescent, Edinburgh, EH16 4SB, UK. David.W.Taylor@ed.ac.uk.
authors.forename: David W
authors.initials: DW
authors.lastname: Taylor
mesh_terms: D000818:Animals; D000871:Anthelmintics / Q000627:therapeutic use*; D002163:Cameroon / Q000453:epidemiology; D006801:Humans; D007559:Ivermectin / Q000627:therapeutic use*; D055118:Medication Adherence; D017181:Onchocerca volvulus / Q000302:isolation & purification*; D009855:Onchocerciasis / Q000188:drug therapy* / Q000453:epidemiology*; D015995:Prevalence; D012867:Skin / Q000469:parasitology / Q000473:pathology; D011795:Surveys and Questionnaires
chemical_list: D000871:Anthelmintics; D007559:Ivermectin