title: A field trial of alternative targeted screening strategies for Chagas disease in Arequipa, Peru.
abstract: BACKGROUND
  Chagas disease is endemic in the rural areas of southern Peru and a growing urban problem in the regional capital of Arequipa, population ∼860,000. It is unclear how to implement cost-effective screening programs across a large urban and periurban environment.
  
  
  METHODS
  We compared four alternative screening strategies in 18 periurban communities, testing individuals in houses with 1) infected vectors; 2) high vector densities; 3) low vector densities; and 4) no vectors. Vector data were obtained from routine Ministry of Health insecticide application campaigns. We performed ring case detection (radius of 15 m) around seropositive individuals, and collected data on costs of implementation for each strategy.
  
  
  RESULTS
  Infection was detected in 21 of 923 (2.28%) participants. Cases had lived more time on average in rural places than non-cases (7.20 years versus 3.31 years, respectively). Significant risk factors on univariate logistic regression for infection were age (OR 1.02; p = 0.041), time lived in a rural location (OR 1.04; p = 0.022), and time lived in an infested area (OR 1.04; p = 0.008). No multivariate model with these variables fit the data better than a simple model including only the time lived in an area with triatomine bugs. There was no significant difference in prevalence across the screening strategies; however a self-assessment of disease risk may have biased participation, inflating prevalence among residents of houses where no infestation was detected. Testing houses with infected-vectors was least expensive. Ring case detection yielded four secondary cases in only one community, possibly due to vector-borne transmission in this community, apparently absent in the others.
  
  
  CONCLUSIONS
  Targeted screening for urban Chagas disease is promising in areas with ongoing vector-borne transmission; however, these pockets of epidemic transmission remain difficult to detect a priori. The flexibility to adapt to the epidemiology that emerges during screening is key to an efficient case detection intervention. In heterogeneous urban environments, self-assessments of risk and simple residence history questionnaires may be useful to identify those at highest risk for Chagas disease to guide diagnostic efforts.
authors.affiliation: Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, United States of America.
authors.forename: Gabrielle C
authors.initials: GC
authors.lastname: Hunter
authors.forename: Katty
authors.initials: K
authors.lastname: Borrini-Mayorí
authors.forename: Jenny
authors.initials: J
authors.lastname: Ancca Juárez
authors.forename: Ricardo
authors.initials: R
authors.lastname: Castillo Neyra
authors.forename: Manuela R
authors.initials: MR
authors.lastname: Verastegui
authors.forename: Fernando S
authors.initials: FS
authors.lastname: Malaga Chavez
authors.forename: Juan Geny
authors.initials: JG
authors.lastname: Cornejo del Carpio
authors.forename: Eleazar
authors.initials: E
authors.lastname: Córdova Benzaquen
authors.forename: César
authors.initials: C
authors.lastname: Náquira
authors.forename: Robert H
authors.initials: RH
authors.lastname: Gilman
authors.forename: Caryn
authors.initials: C
authors.lastname: Bern
authors.forename: Michael Z
authors.initials: MZ
authors.lastname: Levy
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D014355:Chagas Disease / Q000175:diagnosis* / Q000453:epidemiology*; D002648:Child; D002675:Child, Preschool; D003362:Cost-Benefit Analysis; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D008403:Mass Screening / Q000191:economics / Q000379:methods*; D008875:Middle Aged; D010568:Peru / Q000453:epidemiology; D015995:Prevalence; D012307:Risk Factors; D016353:Self-Examination / Q000379:methods; D014505:Urban Population; D055815:Young Adult