The Control of Human Visceral Leishmaniasis in an Urban Center: Impact of Two Intervention Strategies in Domestic Dogs in an Urban Area in Northeast Brazil

Visceral leishmaniasis (VL) is an important global public health problem, affecting survival and quality of life of affected individuals. Several control strategies focus on reservoir control and reducing sand fly infestation. The impact of deltamethrin-impregnated collars on human infection has been described in isolated experiences with small samples. Here, we describe an experience in an endemic area in Northeast Brazil using a strategy of culling infected dogs and a second intervention using deltamethrin-impregnated canine collars. In the first intervention, intervention areas were defined where dogs were tested and infected dogs were eliminated. Diagnosis was performed using a rapid test. In the second intervention, the impact of using deltamethrin-impregnated collars on the human infection rate was assessed, measured by serology for leishmaniasis with recombinant rK39 antigen. Between 1,090 and 1,197 people were included annually across three serological surveys. The canine collar consisted of a 20g PVC strip impregnated with 40 mg/g of deltamethrin. Participation required explicit consent from both the individual and dog owners. In the first intervention, culling seropositive dogs reduced canine infection prevalence from 35% to 10% over two years, remaining stable for two additional years of follow-up, and reduced incidence from 36% to 6% (p<0.001) over the same period. The second intervention, using deltamethrin-impregnated collars, showed a reduction in human seroconversion incidence to 1% in the intervention area (where domestic dogs wore impregnated collars), which was lower than the 3.2% incidence in the control area. This difference in incidence was statistically significant (p=0.009). Strategies involving the elimination of diseased animals face high social rejection. In contrast, the use of impregnated collars has good acceptability. This study included 1,090 to 1,197 people annually in three serological surveys, representing the largest sample size among reports of this type of intervention and demonstrating a reduction in human disease. These data suggest that this strategy may be effective in reducing visceral leishmaniasis transmission with good societal acceptance.