Estudo dos fatores climáticos e ambientais associados à ocorrência de carrapatos Amblyomma sculptum (Acari: Ixodidae) adultos na mesorregião metropolitana do Rio de Janeiro

Abstract

This study evaluates the influence of climatic variables on the occurrence distribution of Amblyomma sculptum adult ticks in four sample areas in Seropédica and Mangaratiba, two municipalities in Rio de Janeiro Metropolitan mesoregion. The data used is relative to tick sampling between the spring of 2008 and the winter of 2012. The climatic variables included in the study were mean temperature, relative humidity and rainfall, in the day of sampling and in the 15 days prior to each sampling. For the statistical analysis, four types of generalized linear models were used: Poisson, Negative Binomial, Quasi Poisson (μ2) and Zero Inflated Poisson (ZIP). A total of 574 ticks were found, most of them in the autumn. The bivariate analysis between each one of the independent variables and the response variable, tick count, showed seven variables that were significant at least in two types of models (being ZIP one of them): temperature in the day before sampling, temperature between the 4th and 6th days prior to sampling, temperature between the 11th and 15th days prior, humidity in the day before sampling, humidity in 5th day before, humidity between the 9th and 12th days prior and rainfall in the 12th day prior to sampling. These variables were combined in the multivariate analysis, therewith, nine models were fitted. Analyzing the prevalence ratio (PR), Akaike Information Criterion (AIC), mean square of residuals (MSR) and correlation between expected Y and observed Y (Corr), the best model was chosen, with the following variables (PR [CI 90%]): temperature between the 11th and 15th days prior to sampling (1,06 [1,01; 1,11]), humidity in the day before (1,04 [1,02; 1,05]) and rainfall in the 12th day prior to sampling (0,97 [0,94; 0,99]). Regarding the fitted models, it was possible to notice that the most satisfactory parameters were presented by ZIP models, in which the MSR values were the lowest and Corr values were the highest. The bivariate analyzes performed as of ZIP models contrasted the fact that temperature acts as a protection factor for the occurrence of A. sculptum adult ticks in the day of sampling and in the two days before, but it acts as a risk factor form the 3rd to the 15thday before. Humidity and rainfall act as protection factors for tick occurrence as from the 3rd and the 5th day prior to sampling, respectively. In the days closer to sampling, these two latter variables did not show a definite conduct of risk or protection with respect to the studied tick occurrence. Within this context, we conclude that understanding the parameters responsible for controlling the life cycle of A. sculptum is essential to generate risk models of disease transmission