title: Post-control surveillance of Triatoma infestans and Triatoma sordida with chemically-baited sticky traps.
abstract: BACKGROUND
  Chagas disease prevention critically depends on keeping houses free of triatomine vectors. Insecticide spraying is very effective, but re-infestation of treated dwellings is commonplace. Early detection-elimination of re-infestation foci is key to long-term control; however, all available vector-detection methods have low sensitivity. Chemically-baited traps are widely used in vector and pest control-surveillance systems; here, we test this approach for Triatoma spp. detection under field conditions in the Gran Chaco.
  
  
  RESULTS
  Using a repeated-sampling approach and logistic models that explicitly take detection failures into account, we simultaneously estimate vector occurrence and detection probabilities. We then model detection probabilities (conditioned on vector occurrence) as a function of trapping system to measure the effect of chemical baits. We find a positive effect of baits after three (odds ratio [OR] 5.10; 95% confidence interval [CI(95)] 2.59-10.04) and six months (OR 2.20, CI(95) 1.04-4.65). Detection probabilities are estimated at p ≈ 0.40-0.50 for baited and at just p ≈ 0.15 for control traps. Bait effect is very strong on T. infestans (three-month assessment: OR 12.30, CI(95) 4.44-34.10; p ≈ 0.64), whereas T. sordida is captured with similar frequency in baited and unbaited traps.
  
  
  CONCLUSIONS
  Chemically-baited traps hold promise for T. infestans surveillance; the sensitivity of the system at detecting small re-infestation foci rises from 12.5% to 63.6% when traps are baited with semiochemicals. Accounting for imperfect detection, infestation is estimated at 26% (CI(95) 16-40) after three and 20% (CI(95) 11-34) after six months. In the same assessments, traps detected infestation in 14% and 8.5% of dwellings, whereas timed manual searches (the standard approach) did so in just 1.4% of dwellings only in the first survey. Since infestation rates are the main indicator used for decision-making in control programs, the approach we present may help improve T. infestans surveillance and control program management.
authors.affiliation: Centro para el Desarrollo de la Investigación Científica, Díaz Gill Medicina Laboratorial/Fundación Moisés Bertoni, Asunción, Paraguay. rojasdearias@gmail.com
authors.forename: Antonieta
authors.initials: A
authors.lastname: Rojas de Arias
authors.forename: Fernando
authors.initials: F
authors.lastname: Abad-Franch
authors.forename: Nidia
authors.initials: N
authors.lastname: Acosta
authors.forename: Elsa
authors.initials: E
authors.lastname: López
authors.forename: Nilsa
authors.initials: N
authors.lastname: González
authors.forename: Eduardo
authors.initials: E
authors.lastname: Zerba
authors.forename: Guillermo
authors.initials: G
authors.lastname: Tarelli
authors.forename: Héctor
authors.initials: H
authors.lastname: Masuh
mesh_terms: D000818:Animals; D014355:Chagas Disease / Q000517:prevention & control*; D004772:Entomology / Q000379:methods*; D005260:Female; D006801:Humans; D007300:Insect Control / Q000379:methods*; D007306:Insecticides / Q000008:administration & dosage*; D012680:Sensitivity and Specificity; D014224:Triatoma / Q000254:growth & development*
chemical_list: D007306:Insecticides