Avaliação do impacto do controle químico na ecologia da população de Rattus norvegicus de uma comunidade urbana de Salvador-BA.

Abstract

The urbanization has favored the establishment of opportunistic species, such as the synanthropic rodent Rattus norvegicus. The presence of this rodent in urban environments generates high costs of prophylaxis and control, due to the impacts on human health. These impacts may result from the environmental transmission of the pathogenic spirochete Leptospira interrogans, which causes leptospirosis. One of the main strategies of the Ministry of Health to prevent leptospirosis is to control rodent reservoir species, and chemical control is the most widely used method to eliminate them on a large scale. This study aimed to evaluate the differences in R. norvegicus population characteristics after a chemical control campaign, analyzing relative abundance, sex structure, body mass and age of the population, and, consequently, the effectiveness of the control program. This study was carried out in the neighborhood of Pau da Lima, Salvador, in Bahia state, Brazil, where individuals of R. norvegicus were systematically captured before (Oct-Dec 2014) and after (Nov-Dec 2015 and Apr-May 2016) a chemical control campaign performed by the Zoonotic Control Center. During the chemical intervention, 939 households were visited in 2 valleys of the study area. In the pre-intervention campaign, an effort of 310 trap-nights resulted in 43 rodents captured, and in the post-intervention campaign an effort of 312 trap-nights resulted in 47 rodents captured and 324 traps-nights with 36 rodents captured. We utilized a success rate of capture to estimate relative abundance, we also employed Anova tests to compare means of age, body mass, number of embryos and age of pregnant females. We also used binomial tests to verify if the sex ratio differed from 1:1 between the campaigns and determine whether the variation between the proportions of infestation was significant. The results showed that there was no difference in capture success and demographic characteristics of the rodent population before and after the intervention. These results suggest that the campaign analyzed was not effective in impacting the population of R. norvegicus, and provide evidence of the need for reevaluation of rodent control practices.