Published in BMC Infectious Diseases, this study by P. Bermudi, D. N. C. C. Costa, and colleagues examined a complex zoonotic system: the transmission of Leishmania infantum from infected dogs to humans via sandfly vectors. Visceral leishmaniasis (VL) is a severe, often lethal disease when untreated, and controlling canine infection is central to disrupting transmission.
The researchers analyzed data from 2006 to 2015 in two endemic urban municipalities—Araçatuba and Birigui in São Paulo State, Brazil. They assessed seroprevalence in dogs and the coverage of major control strategies: canine serological surveys, culling of infected dogs, and insecticide spraying. All data were georeferenced to examine spatial and temporal dynamics.
Using latent Gaussian Bayesian models with spatio-temporal structure—specifically Besag-York-Mollie models for spatial effects and AR(1) models for temporal effects—the authors evaluated how control measures correlated with human disease incidence across time. Both immediate and lagged effects (one- and two-year delays) were tested using INLA-based deterministic modeling.
Control activity coverage was generally low across the decade. The temporal trends in human VL differed between municipalities, but both showed an overall decline in incidence. Notably, the canine serological surveys demonstrated a protective association only in the two-year lag model, meaning reduced human cases were detectable two years after screening and culling efforts were implemented.
The authors interpret this delayed effect as evidence that even low-intensity dog serosurveys combined with culling can contribute to reducing human VL by gradually lowering the reservoir of infected dogs. However, the study acknowledges the ethical and logistical challenges of dog culling and the need for integrated, humane, and effective vector-control strategies.
Source: Bermudi, P., Costa, D. N. C. C., Chiaravalloti-Neto, F., et al. (2020). Canine Serological Survey and Dog Culling and Its Relationship with Human Visceral Leishmaniasis in an Endemic Urban Area. BMC Infectious Diseases. Published February 21, 2020.
