Banca de DEFESA: JOSE FLAVIO VIDAL COUTINHO

Uma banca de DEFESA de DOUTORADO foi cadastrada pelo programa.
STUDENT : JOSE FLAVIO VIDAL COUTINHO
DATE: 21/10/2025
TIME: 08:00
LOCAL: REMOTA
TITLE:

EFFECTIVENESS OF DELTAMETHRIN-IMPREGNATED COLLARS IN THE CONTROL OF ZOONOTIC VISCERAL LEISHMANIASIS: IMPACT ON CANINE INFECTION CLUSTERS AND LUTZOMYIA LONGIPALPIS ABUNDANCE

KEY WORDS:

Canine visceral leishmaniasis, human leishmaniasis, Leishmania infantum, Deltamethrin-impregnated collars, spatial autocorrelation, Lutzomyia Longipalpis.

PAGES: 182
BIG AREA: Ciências da Saúde
AREA: Medicina
SUMMARY:

Introduction: Zoonotic visceral leishmaniasis (ZVL) is a neglected parasitic disease caused by Leishmania infantum in Latin America and Europe and it is transmitted in the New World by sandflies of the species Lutzomyia longipalpis. The control model adopted in Brazil since the urbanization of ZVL is based on culling of infected canine reservoirs and vector control using residual insecticide. These strategies have systematically failed, leading to the nationwide spread of the pathogen and development of visceral leishmaniasis in both humans and dogs. In this context, the effectiveness of novel strategies has begun to be tested, with a notable emphasis on the large-scale use of insecticide-impregnated collars in dogs.

Methodology: A non-randomized prospective intervention study with 4% deltamethrin-impregnated collars was carried out in two priority areas for the ZVL surveillance and control service in the municipality of Natal, to evaluate the reduction of L. infantum transmission in dogs, comparing the incidence in the intervention area (IA) with that observed in the control area (CA) without collars. Canine serological census surveys were conducted at the beginning of the study (t0), at 6, 12, and 27 months, with euthanasia of infected dogs and placement of collars on the dogs. Two collar replacements were made, one after 6 months and another at 12 months. An analysis of the spatial dynamics of canine L. infantum infection was performed using a Bayesian model, with determination of the spatial association coefficient by Moran's index between neighboring blocks. Entomological monitoring was also carried out in the peridomicile with CDC light traps for 19 months and serological testing for tick-borne pathogens to analyze the association between these and canine L. infantum infection. A cross-sectional study of human L. infantum infection was also conducted at time 0. Results: A total of 11,285 canine evaluations were conducted over 27 months across four serological surveys. Canine L. infantum infection differed between intervention (10%) and control (19.7%) areas at study baseline (OR = 0.454; 95% CI: 0.364-0.566). Human L. infantum infection also showed distinct rates: 4% (intervention) versus 14.3% (control). The odds ratio (OR) of L. infantum infection between dogs and humans was: 2.405 (95% CI: 1.720-3.363) in the intervention area and 1.459 (95% CI: 1.117-1.906) in the control area. Impregnated collars were effective at 6 months (OR = 0.448; 95% CI: 0.343-0.584) but showed no significant differences between areas 12 and 27 months. Leishmania seroconversion was lower in collared animals (p = 0.044), with half the Relative Risk compared to control dogs. Thematic maps of canine L. infantum infection revealed outlier blocks with high infection force and high mean neighborhood incidence (cluster formation) in both intervention (IA) and control (CA) areas. However, the recurrence of outlier blocks between successive periods (0-12 and 12-27 months) was low in IA (18.75% and 6.7%) and CA (7.5% and 6.7%). No significant differences were observed between the global time series of vector numbers (mean difference 3.62; p=0.5281), relative abundance (mean difference 0.29; p=0.625) and household infestation rates (mean difference -11.26; p=0.059) when comparing CA and IA. However, in the 5 IA households with collared dogs, there is a significant reduction in mean Lu. longipalpis numbers (x̅ ± sd: 2.4±2.0) was observed compared to 5 IA households without dogs (x̅ ± sd:: 4.97±4.3). Statistical differences were found between: IA without dogs and CA (Estimate=21.17; p=0.002875) and IA with collared dogs vs without dogs (Estimate=-15.53; p=0.04590). Conclusion: Although collar use proved effective in reducing individual L. infantum infection incidence, the population-level effectiveness of collars was not sustained beyond the initial 6 months. Moderate coverage in initial canine population collaring, high loss to follow-up of collared dogs, elevated collar loss rates, and influx of new susceptible, unprotected dogs into the intervention area were among the main limiting factors for collar effectiveness in reducing ZVL transmission.

COMMITTEE MEMBERS:
Externa à Instituição - DEBORAH BITTENCOURT MOTHE FRAGA - IGM
Externo à Instituição - FILIPE DANTAS TORRES - Fiocruz - PE
Externa ao Programa - 1346630 - LARA DE MELO BARBOSA ANDRADE - nullExterno à Instituição - LUCAS PEDREIRA DE CARVALHO - UFBA
Presidente - 350647 - SELMA MARIA BEZERRA JERONIMO