The mass use of deltamethrin collars to control and prevent canine visceral leishmaniasis: A field effectiveness study in a highly endemic area

Abstract

BackgroundVisceral leishmaniasis (VL) is a zoonosis of great importance. Limitations in current VL control measures compromise efficacy, indicating the need to implement new strategies. The aim of this study was to evaluate the effectiveness of the mass use of deltamethrin-impregnated collars in dogs as a public health measure to control and prevent canine visceral leishmaniasis (CVL).MethodologyAn interventional study was implemented in two endemic areas in the district of Monte Gordo (Bahia-Brazil): an intervention area, in which VL seronegative dogs were collared, and a control area in which only conventional CVL control measures were applied. At baseline, seropositive dogs were removed and seronegative dogs were included. Dogs were then reevaluated every 7–8 months for almost two years. At each time point, dogs in the intervention area that remained seronegative received new collars and newly identified seronegative dogs were included and collared. The local zoonosis control authorities were notified of any dogs that tested seropositive in both areas, which were subsequently marked for euthanasia as mandated by the Brazilian Ministry of Health.Principal findingsIn the first serological survey, seroprevalence was similar in both areas. At the second evaluation, significant reductions in seroprevalence were seen in both areas, while seroprevalence in the intervention area reduced to 6.0% during the final evaluation versus an increase of 11.0% in the control area. This significant increase and the estimated relative risk (RR = 0.55) indicated protection against CVL in the intervention area. Although CVL incidence did not differ significantly between the areas, an increased tendency was observed in the control area, which could be due to low seroconversion rates throughout the study or a high loss to follow-up.Conclusions/SignificanceAlthough our evaluation of the effectiveness of deltamethrin-impregnated collars as a community-wide public health control measure was inconclusive, this measure likely provides protection over time. In endemic areas of Brazil, this strategy represents an operational challenge for local zoonosis control authorities, indicating the need for adjustments, including improved collar design.

Laboratory assessment of the anti-feeding effect for up to 12 months of a slow release deltamethrin collar (Scalibor®) against the sand fly Phlebotomus perniciosus in dogs

“…Therefore, a deltamethrin collar maintained on a dog for one year could prevent or reduce the risk of transmission of L. infantum for this extended period. These results help to explain the reported reductions in L. infantum infections from two-season field studies in which dogs received collars in consecutive years and were exposed to natural challenge [ 10 – 15 ].…”

“…Of the seroconverting dogs in that study, clinical signs of canine leishmaniosis were significantly more frequent and rapidly progressive in control than in collared dogs. A study conducted in Brazil between January 2014 and November 2015 compared Leishmania infection rates in seronegative dogs from two neighboring endemic areas; dogs in one area received deltamethrin collars, those in the other area did not [ 15 ]. Despite the many limitations involved in an extended large-scale field study involving roaming domestic dogs, the results from serology testing showed a tendency for the deltamethrin collar to provide population-based protection against infection with Leishmania .…”

“…Numerous publications have demonstrated that the pyrethroid deltamethrin, impregnated into a collar and worn by dogs during the sand fly exposure season, reduces the incidence of Leishmania seroconversion under natural challenge conditions [ 10 – 15 ]. While these field reports, as well as two small-scale laboratory-challenge studies [ 16 , 17 ] suggest that the anti-feeding activity of this collar is season-long, there is a need for well-controlled studies to investigate the specific duration of the period over which the collar prevents sand fly feeding, and the degree to which feeding is prevented.…”

An Overview of Immunotherapeutic Approaches Against Canine Visceral Leishmaniasis: What Has Been Tested on Dogs and a New Perspective on Improving Treatment Efficacy

“…During VL urbanization (Da Silva et al, 2017), dogs became responsible for spreading the disease throughout the Brazilian countryside, resulting in a rising number of human VL cases (Reis et al, 2010). Notably, cases of canine visceral leishmaniasis (CVL) precede human cases (Leite et al, 2018).…”

Leishmaniose visceral canina nos municípios de Araçatuba e Birigui, estado de São Paulo, Brasil

“…Estudos recentes têm verificado a efetividade do uso de coleiras impregnadas com deltametrina no controle da infecção canina (Kazimoto et al, 2018;Silva et al, 2018). Espera-se que a associação das estratégias do uso de coleiras impregnadas com inseticida com a eutanásia de cães positivos seja mais efetiva no controle da doença tanto em cães como em humanos (Leite et al, 2018).…”