Impacto da pulverização residual domiciliar no controle da leishmaniose visceral em uma área urbana no sudeste do Brasil

Abstract

Visceral leishmaniasis (VL) is considered a neglected zoonosis of great importance to public health worldwide. In Brazil, it is caused by the protozoan Leishmania infantum and transmitted by the sandfly Lutzomyia longipalpis. The canine form of the disease, the main reservoir in the urban VL cycle, is known as canine visceral leishmaniasis (CVL). The VL control program in Brazil involves diagnosing human cases, as well as controlling reservoirs and vectors. Indoor residual spraying is an integrated strategy in the program, consisting of applying long-acting insecticides in the environment to target adult vectors. Given this context, the objective was to establish a historical series model to test and evaluate the impact of indoor spraying on canine visceral leishmaniasis in the municipality of Belo Horizonte (BH), the capital of the state of Minas Gerais (MG). A retrospective longitudinal observational time-series study was conducted from 2006 to 2018, using secondary data from the Municipal Health Department of Belo Horizonte, Minas Gerais. A database containing records of indoor spraying and another with the results of canine CVL surveys were provided. Monthly calculations were performed for the proportion of seroreactive dogs (PSC = [seropositive dogs/tested dogs × 100]) and the spraying success rate (SSR = [number of completed sprays/total of scheduled sprays × 100]). The time- series analysis was conducted using Gretl software. The results of the ARMAX model demonstrated a temporal relationship between the PSC and SSR variables. Furthermore, PSC showed a temporal relationship with a one-month lag (76.8%) and a seven-month lag (20%). Regarding PSC and SSR, the temporal relationship had a lag at time t (5%) and another with a three-month lag (-5%). Additionally, outliers were detected in January 2011, December 2014, August 2015, November 2018, and an intervention point in October 2013. Based on these results, the findings suggest evidence of the effectiveness of chemical control, reducing CVL cases by 0.06% for each additional unit of SSR. Although the influence was shown to be low, indoor spraying appears capable of inducing a reduction in the proportion of positive dogs. Attention must be paid to various factors affecting this correlation. This study contributed to a better understanding of chemical control for VL, as well as to improving control measures, using this municipality as a model.