Effectiveness of control strategies against visceral leishmaniasis in Brazil: there is no silver bullet

Resumen

Control of zoonotic visceral leishmaniasis has been a deceiving effort for Brazilian public health officers and researchers. Since the implementation of the Brazilian program for visceral leishmaniasis control (PVLC) in the beginning of the 1960s, the disease has undergone a notable process of urbanization and geographical dissemination and the epidemiological situation is far from showing any substantial progress. The main strategies to reduce transmission proposed by the current PVCL still are vector control with residual insecticides and culling of seropositive dogs. However, few well- designed epidemiological studies give support for their wide-scale use, most showing limited effectiveness and only in specific settings. Novel promising approaches have been advocated such as dog vaccines, insecticide-impregnated dog collars, treatment of infected dogs, and topical insecticides, but there are still many doubts about their effectiveness. The few available effectiveness estimates are not high, suggesting that no intervention would alone solve the problem. There is no simple solution but considering the heterogeneous spatial pattern of disease distribution and the lack of high levels of effectiveness for individual interventions, there is probably no means to reduce transmission without using a combination of interventions delivered according to the different transmission scenarios, preferably targeting areas at highest risk.