Analysis of Seasonality, Tendencies and Correlations in Human and Canine Visceral Leishmaniasis

Background: Leishmaniosis are a chronic disease complex, which may vary from simple cutaneous lesions to a fatal visceral form, with elevated expansion within the urban centers. Fortaleza is an endemic area for VL and it has been presenting registers of human death in the past decade. The HVL seasonality, the HVL and CVL tendencies have been evaluated, along with the correlation and influence of the seroreactive dogs, of the euthanized dogs, of the abiotic environmental factors and the human and canine population over the coefficient of the HVL incidence, in the Fortaleza town between 2006 and 2012. Materials, Methods & Results: The experimental protocol was approved by the Ethics Committee for the State University of Ceara Animal Use (CEUA/UECE), protocol no 08622833-1. As a data source for the analysis of HVL and CVL, the monthly quantitative of notified and registered cases in the State of Ceara Health Secretariat (SESA) and in the Fortaleza Zoonosis Control Center (CCZ) was utilized respectively from 2006 to 2012. Fortaleza's population estimate during and after the census period, the rainfall average monthly rate (mm), the air relative humidity (%) and the temperature (degrees C), were provided, at the same period, by the Brazilian Institute of Geography and Statistics (IBGE)., The data were analyzed by ANOVA followed by Tukey, linear regression and Spearman correlation test. The monthly average of HVL registered cases, between 2006 and 2012, did not differ significantly between the months of the year. The HVL incidence coefficient, per 100.000 inhabitants, presented a negative tendency, while the human lethality and mortality coefficients and the percentage of seroreactive dogs presented a positive, stationary and negative tendency, respectively. The percentage of euthanized dogs presented a slight correlation and did not influence the HVL incidence coefficient. On the other hand, the percentage of seroreactive dogs presented correlation and positive influence over the HVL incidence coefficient. The human population presented negative influence over the HVL, furthermore, the canine population also presented negative influence over the number of visceral leishmaniasis (VL) human cases over the evaluated period. The average monthly values of the rainfall rate, of the air humidity and of the temperature demonstrate correlation, having the rainfall rate not presenting influence over the HVL incidence coefficient. On the other hand, the relative air humidity and the average temperature negatively influenced the LVH incidence coefficient. Discussion: In this study, a direct dependency between the canine and human cases according to the percentage of seroreactive dogs, a non-relation with the percentage of euthanized dogs and an inverse relation with the human and canine populations and the abiotic environmental factors (relative air humidity and average temperature) were observed. Therefore, it was concluded, that the seroreactive canine population control has influence over the HVL. This research creates perspectives for the identification of other factors that may influence the incidence of canine and human cases, such as vector density and the participation of other possible reservoirs within the domestic disease cycle. Furthermore, a deeper evaluation of the native vegetation, appointed by human action, is suggested.