ObjectiveTo evaluate the efficacy of a synthetic sex-aggregation pheromone of the sand fly vector Lu. longipalpis, co-located with residual insecticide, to reduce the infection incidence of Leishmania infantum in the canine reservoir.MethodsA stratified cluster randomised trial was designed to detect a 50% reduction in canine incident infection after 24 months in 42 recruited clusters, randomly assigned to one of three intervention arms (14 cluster each): synthetic pheromone + insecticide, insecticide-impregnated dog collars, or placebo control. Infection incidence was measured by seroconversion to anti-Leishmania serum antibody, Leishmania parasite detection and canine tissue parasite loads. Changes in relative Lu. longipalpis abundance within households were measured by setting three CDC light traps per household.ResultsA total 1,454 seronegative dogs were followed-up for a median 15.2 (95% C.I.s: 14.6, 16.2) months per cluster. The pheromone + insecticide intervention provided 13% (95% C.I. 0%, 44.0%) protection against anti-Leishmania antibody seroconversion, 52% (95% C.I. 6.2%, 74·9%) against parasite infection, reduced tissue parasite loads by 53% (95% C.I. 5.4%, 76.7%), and reduced household female sand fly abundance by 49% (95% C.I. 8.2%, 71.3%). Variation in the efficacy against seroconversion varied between trial strata. Equivalent protection attributed to the impregnated-collars were 36% (95% C.I. 14.4%, 51.8%), 23% (95% C.I. 0%, 57·5%), 48% (95% C.I. 0%, 73.4%) and 43% (95% C.I. 0%, 67.9%), respectively. Comparison of the two interventions showed no statistically consistent differences in their efficacies; however, the errors were broad for all outcomes. Reductions in sand fly numbers were predominant where insecticide was located (chicken and dog sleeping sites), with no evidence of insecticide-induced repellence onto humans or dogs.ConclusionThe synthetic pheromone co-located with insecticide provides protection particularly against canine L. infantum parasite transmission and sand fly vector abundance. The effect estimates are not dissimilar to those of the insecticide-impregnated collars, which are documented to reduce canine infection incidence, human infection and clinical VL disease incidence, in different global regions. The trialled novel lure-and-kill approach is a low-cost potential vector control tool against ZVL in the Americas.

BackgroundDespite large-scale reductions in Chagas disease prevalence across Central and South America, Trypanosoma cruzi infection remains a considerable public health problem in the Gran Chaco region where vector-borne transmission persists. In these communities, peridomestic animals are major blood-meal sources for triatomines, and household presence of infected dogs increases T. cruzi transmission risk for humans. To address the pressing need for field-friendly, complementary methods to reduce triatomine infestation and interrupt T. cruzi transmission, this study evaluated the systemic activity of three commercial, oral, single dose insecticides Fluralaner (Bravecto®), Afoxolaner (NexGard®) and Spinosad (Comfortis®) in canine feed-through assays against Triatoma infestans, the principal domestic vector species in the Southern Cone of South America.MethodsTwelve healthy, outbred dogs were recruited from the Zoonosis Surveillance and Control Program in Santa Cruz, Bolivia, and randomized to three treatment groups, each containing one control and three treated dogs. Following oral drug administration, colony-reared second and third stage T. infestans instars were offered to feed on dogs for 30 min at 2, 7, 21, 34 and 51 days post-treatment.ResultsEighty-five per cent (768/907) of T. infestans successfully blood-fed during bioassays, with significantly higher proportions of bugs becoming fully-engorged when exposed to Bravecto® treated dogs (P < 0.001) for reasons unknown. Exposure to Bravecto® or NexGard® induced 100% triatomine mortality in fully- or semi-engorged bugs within 5 days of feeding for the entire follow-up period. The lethality effect for Comfortis® was much lower (50–70%) and declined almost entirely after 51 days. Instead Comfortis® treatment resulted in substantial morbidity; of these, 30% fully recovered whereas 53% remained morbid after 120 h, the latter subsequently unable to feed 30 days later.ConclusionsA single oral dose of Fluralaner or Afoxolaner was safe and well tolerated, producing complete triatomine mortality on treated dogs over 7.3 weeks. While both drugs were highly efficacious, more bugs exposed to Fluralaner took complete blood-meals, and experienced rapid knock-down. Coupled with its longer residual activity, Fluralaner represents an ideal insecticide for development into a complementary, operationally-feasible, community-level method of reducing triatomine infestation and potentially controlling T. cruzi transmission, in the Gran Chaco region.

Background: Screening for Trypanosoma cruzi infection was performed amongst children in a rural community in the Bolivian Chaco, an area known for high prevalence. The force of infection (FOI) was estimated. Methods: A total of 423 children attending the local school were screened using the Chagas Detect Plus (CDP) rapid test (InBios International, Inc.). CDP-positive specimens were further tested by indirect haemagglutination assay (IHA) and Wiener Recombinante v3.0 ELISA. A catalytic model was used to estimate FOI. Results: Confirmed seroprevalence was 0.22, rising steeply with age. The mean age of seropositive individuals was 13 years. The calculated specificity of the rapid test was 91.9%. The annual incidence estimated from the FOI was 0.021. Conclusions: This study demonstrates persistent transmission and continuing high levels of T. cruzi infection in the Bolivian Chaco, and highlights the practicality of school-based screening.

BackgroundIndoor Residual Spraying (IRS) of insecticides is a key method to reduce transmission by Triatoma infestans, vector of Chagas disease in a large part of South America. However, the successes of IRS in the Gran Chaco region straddling Bolivia, Argentina and Paraguay, have not equalled those in other Southern Cone countries.AimsThis study evaluated routine IRS practises and insecticide quality control in a typical endemic community in the Bolivian Chaco.MethodsAlpha-cypermethrin active ingredient (a.i.) concentrations captured onto filter papers fitted to sprayed wall surfaces, and in prepared spray tank solutions, were measured using an adapted Insecticide Quantification Kit (IQK™). The results were analysed by negative binomial GLM regression in relation to the time (minutes) spray teams spent treating houses, spray rates (surface area to spray [m2/minute]), householder compliance to empty houses for IRS delivery, and the visual presence/absence of filter papers. The IQK™ assays developed for these samples were validated against HPLC quantification methods. Results: Substantial variations in the delivered a.i. concentrations were observed; only 10.4% (50/480) of filter papers, and 8.8% (5/57) of houses received the target concentration. The delivered concentrations were not related to those in the matched spray tank solutions. The sedimentation of a.i. in the surface solution of prepared spray tanks was rapid, resulting in a 29% loss of a.i. content within 5 minutes, and 48.5% after 15 minutes. The delivered concentrations were positively associated with the time spent spraying the house, and inversely related to the spray rate, but showed weak correlations in both cases. The influence of householder compliance on spray rates were significant, though associated differences in delivered concentrations were not detected. No differences were observed in spray rates between houses fitted with filter papers and houses without.ConclusionsSuboptimal delivery of IRS is partially attributed to the insecticide physical characteristics, and the need for revision of insecticide delivery methods, which includes training of IRS teams and community education to encourage compliance. The IQK™ is a necessary field-friendly tool to improve IRS quality, and to facilitate health worker training and decision making by the Chagas disease vector control managers.

The aim of this study was to describe the phlebotomine sand fly fauna and its respective ecological indexes in risk zones of cutaneous leishmaniasis (CL). The study was carried out in the Municipality of Santarém, Pará State, Brazil. From the total of 102 records of CL patients in 2010 and 2011, infected with different Leishmania species, 31 were selected. Kernel density analysis was performed. CDC light traps were placed (6 p.m.-6 a.m., three nights, height of 1.5 m) in the identified risk zones (indoors, chicken sheds and surrounding forest) in two occasions: rainy and dry seasons of 2012. Shannon traps were installed in the forest during 3 h (7 p.m.-9 p.m., one night). Shannon (H'), Pielou (J') and Dominance (D) indexes were calculated and two spatial clusters (SC) of CL, SC1 (urban-rural) and SC2 (rural farm), were identified. Phlebotomines were sampled in SC1 (243) and SC2 (174). In the whole sample (417) there were 24 species of 10 genera, but only 12 species were found in both risk zones. Ecological indexes varied widely (H' = 0.5-1.72; J = 0.44-0.78; D = 0.46-0.91). The highest D values in the forest (≥ 0.75) were associated to Psychodopygus complexus during both seasons in SC1 and Psychodopygus davisi during the rainy season in SC2. Other CL vectors were identified in smaller frequence. A great diversity of phlebotomine species was described in each risk zone. The CL vectors sampled were well-matched with the Leishmania species infecting the patients. The epidemiological importance of dominant species may vary with climatic seasons and risk zones in Santarém.

Running head: cluster randomised trial against leishmaniasis 1 2 Sand fly synthetic sex-aggregation pheromone co-located with 3 insecticide reduces canine Leishmania infantum infection incidence: a 4 stratified cluster randomised trial 5 6 7 41 42 43 *corresponding authors 44 orin.courtenay@warwick.ac.uk 45 j.g.hamilton@lancaster.ac.uk 46 47 48 49 50 Abstract 70 71 Objective 72 To evaluate the efficacy of a synthetic sex-aggregation pheromone of the 73 sand fly vector Lu. longipalpis, co-located with residual insecticide, to reduce 74 the infection incidence of Leishmania infantum in the canine reservoir, and to 75 reduce sand fly vector abundance. To compare the outcomes to those 76 resulting from fitting deltamethrin-impregnated collars to the canine reservoir. 77 Methods 78 A stratified cluster-randomised trial was designed to detect a 50% reduction 79 in canine incident infection after 24 months in 42 recruited clusters, randomly 80 assigned to one of three intervention arms (14 cluster each): pheromone + 81 insecticide, insecticide-impregnated dog collars, or placebo control. Infection 82 incidence was measured by seroconversion to anti-Leishmania antibody, 83 Leishmania parasite detection and canine tissue parasite loads. Changes in 84 relativeLu. longipalpis abundance within households were measured by 85 setting three CDC light traps per household. 86 Results 87 A total 1,454 seronegative dogs were follow-up for a median 15.2 (95% C.I.s: 88 14.6, 16.2) months per cluster. The pheromone + insecticide intervention 89 provided 13% (95% C.I. 0%, 44.0%) protection against anti-Leishmania 90 antibody seroconversion, 52% (95% C.I. 6.2%, 74·9%) against parasite 91 infection, reduced tissue parasite loads by 53% (95% C.I. 5.4%, 76.7%), and 92 reduced household female sand fly abundance by 49% (95% C.I. 8.2%, 93 71.3%). Variation in the efficacy against seroconversion varied between trial 94 4 strata. Equivalent protection attributed to the impregnated-collars were 36% 95 (95% C.I. 14.4%, 51.8%), 23% (95% C.I. 0%, 57·5%), 48% (95% C.I. 0%, 96 73.4%) and 43% (95% C.I. 0%, 67.9%), respectively. Comparison of the 97 outcomes of the two interventions showed no statistically consistent 98 differences in their efficacies; however, the errors were broad for all 99 outcomes. Reductions in sand fly numbers were predominant where 100 insecticide was located (chicken and dog sleeping sites), with no evidence of 101 insecticide-induced repellency onto humans or dogs.102 Conclusion. 103 The synthetic pheromone lure-and-kill approach provides protection 104 particularly against L. infantum parasite transmission and sand fly vector 105 abundance. The effect estimates are not dissimilar to those of the insecticide-106 impregnated collars, which are documented to reduce canine infection 107 incidence, and human infection and clinical VL disease incidence, in different 108 global regions. As a low-cost alternative or complimentary vector control tool, 109 optimisation of best community deployment of the pheromone + insecticide 110 a...

Background The rising incidence of visceral leishmaniasis due to Leishmania infantum requires novel methods to control transmission by the sand fly vector. Indoor residual spraying of insecticide (IRS) against these largely exophilic / exophagic vectors may not be the most effective method. A synthetic copy of the male sex-aggregation pheromone of the key vector species Lutzomyia longipalpis in the Americas, was co-located with residual pyrethroid insecticide, and tested for its effects on vector abundance, hence potential transmission, in a Brazilian community study. Methods Houses within eight defined semi-urban blocks in an endemic municipality in Brazil were randomised to synthetic pheromone + insecticide or to placebo treatments. A similar number of houses located >100m from each block were placebo treated and considered as “True Controls” (thus, analysed as three trial arms). Insecticide was sprayed on a 2.6m2 surface area of the property boundary or outbuilding wall, co-located within one metre of 50mg synthetic pheromone in controlled-release dispensers. Vector numbers captured in nearby CDC light traps were recorded at monthly intervals over 3 months post intervention. Recruited sentinel houses under True Control and pheromone + insecticide treatments were similarly monitored at 7–9 day intervals. The intervention effects were estimated by mixed effects negative binomial models compared to the True Control group. Results Dose-response field assays using 50mg of the synthetic pheromone captured a mean 4.8 (95% C.L.: 3.91, 5.80) to 6.3 (95% C.L.: 3.24, 12.11) times more vectors (female Lu. longipalpis) than using 10mg of synthetic pheromone. The intervention reduced household female vector abundance by 59% (C.L.: 48.7, 66.7%) (IRR = 0.41) estimated by the cross-sectional community study, and by 70% (C.L.: 56.7%, 78.8%) estimated by the longitudinal sentinel study. Similar reductions in male Lu. longipalpis were observed. Beneficial spill-over intervention effects were also observed at nearby untreated households with a mean reduction of 24% (95% C.L.: 0.050%, 39.8%) in female vectors. The spill-over effect in untreated houses was 44% (95% C.L.: 29.7%, 56.1%) as effective as the intervention in pheromone-treated houses. Ownership of chickens increased the intervention effects in both treated and untreated houses, attributed to the suspected synergistic attraction of the synthetic pheromone and chicken kairomones. The variation in IRR between study blocks was not associated with inter-household distances, household densities, or coverage (proportion of total households treated). Conclusions The study confirms the entomological efficacy of the lure-and-kill method to reduce the abundance of this important sand fly vector in treated and untreated homesteads. The outcomes were achieved by low coverage and using only 1–2% of the quantity of insecticide as normally required for IRS, indicating the potential cost-effectiveness of this method. Implications for programmatic deployment of this vector control method are discussed.

objective Failure to control domestic Triatoma infestans in the Chaco is attributed to vulnerable adobe construction, which provides vector refuges and diminishes insecticide contact. We conducted a pilot to test the impact of housing improvement plus indoor residual spraying (IRS) on house infestation and vector abundance in a rural community in the Bolivian Chaco. methods The intervention included three arms: housing improvement + IRS [HI], assisted IRS [AS] in which the team helped to clear the house pre-IRS and routine IRS [RS]. HI used locally available materials, traditional construction techniques and community participation. Vector parameters were assessed by Timed Manual Capture for 2 person-hours per house at baseline and medians of 114, 173, 314, 389 and 445 days post-IRS-1. A second IRS round was applied at a median of 314 days post-IRS-1.results Post-intervention infestation indices and abundance fell in all three arms. The mean odds of infestation was 0.29 (95% CL 0.124, 0.684) in the HI relative to the RS arm. No difference was observed between AS and RS. Vector abundance was reduced by a mean 44% (24.8, 58.0) in HI compared to RS, with no difference between AS and RS. Median delivered insecticide concentrations per house were lower than the target of 50 mg/m 2 in >90% of houses in all arms.conclusion Housing improvement using local materials and community participation is a promising strategy to improve IRS effectiveness in the Bolivian Chaco. A larger trial is needed to quantify the impact on reinfestation over time.