Canine Visceral Leishmaniasis in Rio Grande do Norte State, Northeastern Brazil - Spatial analysis

Abstract

Background: Human visceral leishmaniasis (HVL) is a potentially fatal disease with a worldwide distribution, being endemic in 12 countries in the Americas. The main reservoir in the urban environment is the dog, whose cases precede the disease in humans. For the control of HVL, the Ministry of Health of Brazil recommends efficiency in the notification of human cases, control of sandflies, elimination of reservoirs and health education, in addition to the interruption in the transmission of the disease by the intensification of surveillance and control of priority areas based on identification by spatial analysis. The objective of the study was to investigate the spatial distribution of canine visceral leishmaniasis (CVL) in the state of Rio Grande do Norte, Brazil, determining areas of risk by identifying spatial clusters, with a view to monitoring and implementing preventive actions.
Materials, Methods & Results: Secondary data from sample and/or routine serological surveys for serological diagnosis of LVC in the period from 2011 to 2018 were used. The inclusion of animals in the routine diagnosis per municipality resulted from demands of veterinarians, veterinary clinics, dog tutors, zoonoses control centers and environmental surveillance. The spatial statistical analysis was performed with SatScan software version 9.6 for the detection of spatial clusters, based on using the statistical scan method. Of the total of 231,123 dogs tested in the period, 24,642 (10.6%) were seroreactive for CVL. During the study, the municipalities with the highest number of cases were Natal and Mossoró, with 9,671 and 4,514 cases, respectively. During the years 2011 to 2018, 38 significant clusters (P < 0.05) were identified that included one or more municipalities.
Discussion: The state of Rio Grande do Norte has an urban environment susceptible to the occurrence of CVL, with climate and topography that favor the proliferation of the vector and housing in precarious socio-sanitary conditions. The high number of CVL cases in Natal can be explained by the fact that the city is considered endemic for CVL, characterized as an area of intense transmission of the disease, according to the Ministry of Health. In addition, public infrastructure in
some locations is deficient and living conditions are unfavorable, so that there is a need to invest in effective protection measures for vector control, as well as a focus on health education, whose HVL control measures in the municipality need to be readjusted. The high rate of cases and the constant presence of clusters in the municipality of Açu can be explained by the increasing degradation of the Caatinga biome, evidenced by the removal of firewood for use in the ceramist pole, whose activity is concentrated on a large scale in the use of raw material and energy, through the production of charcoal, for agricultural and livestock fronts, putting species of fauna and flora at risk. It is also noteworthy that this fact contributes to the destruction of wild ecotopes, resulting in the search for the vector for other sources of human and animal food, allowing an increase in the number of cases of the disease. It’s concluded that canine visceral leishmaniasis is distributed in a large part of the state of Rio Grande do Norte. The underreporting and/or deficiency in the disclosure of data by some municipalities represents a challenge in complying with the actions of the Visceral Leishmaniasis Surveillance and Control Program, and attention should be paid to the monitoring and inspection of the execution actions of municipal managers, as well as how to train professionals who are part of the service.

Keywords: georeferencing, public health, zoonoses, leishmaniasis, epidemiology.