Prevention of canine visceral leishmaniasis in Brazil: a prospective study for evaluating the impact and operational difficulties of mass use of deltamethrin impregnated collars in Minas Gerais

BackgroundCanine visceral leishmaniasis (CVL) remains a major public health challenge in Brazil, where domestic dogs are primary urban reservoirs of Leishmania infantum. Traditional control strategies, such as euthanasia of seropositive dogs, face operational limitations and ethical concerns. Insecticide-impregnated collars, particularly those containing 4% deltamethrin (DMC), have emerged as a promising alternative for reducing transmission. Methodology/Principal FindingsA prospective cohort study was conducted in Montes Claros, Minas Gerais, from August 2021 to August 2023, involving 296 dogs divided into two groups: DMC and DMC plus reinforcement device (DMC+RD). Follow-up evaluations occurred every six months over four cycles. The DMC+RD group showed a 41% reduced chance of infection (OR = 0.59; 95% CI: 0.27-1.31) compared to the DMC group. Loss of follow-up was frequent, with 38% overall loss after 24 months, and 50% of owners unable to identify when the loss occurred. Although no statistically significant differences in collar retention were observed, the reinforced device showed a trend toward improved collar permanence. Conclusions/SignificanceHigh effectiveness of DMC applied in a mass population control program was observed, as well that the improvement of the collar design could contribute to reducing the loss of collars and increase the protection. Nevertheless, other factors related to the owners engagement, operational difficulties, and dog population dynamic, can influence the outcomes of the implementation strategy. These results contribute to optimizing CVL control programs and support the scalability of collar-based interventions in endemic regions. Author SummaryIn Brazil, canine visceral leishmaniasis (CVL) remains a major public health challenge due to its role in maintaining the transmission of Leishmania infantum, the parasite responsible for visceral leishmaniasis in humans. To address this, our study evaluated the effectiveness of collars impregnated with 4% deltamethrin in preventing infection in dogs, and tested a reinforcement device designed to reduce collar loss. We followed a cohort of dogs over two years in an endemic urban area, comparing those using the standard collar with those using the reinforced version. Our findings showed that both collar types helped reduce infection rates, but dogs with the reinforced collar had a lower chance of losing it, although the difference was not statistically significant. We also observed that many dog owners were unaware of when collars were lost, highlighting the need for better community engagement. This study provides valuable insights into the operational challenges of implementing this strategy at scale and suggests that improving collar design and owner participation could enhance the success of CVL prevention programs.