Synergism of thymol, carvacrol and eugenol in larvae of the cattle tick, Rhipicephalus microplus, and brown dog tick, Rhipicephalus sanguineus.

The effects of combinations of the monoterpenes thymol and carvacrol and the phenylpropanoid eugenol in larvae of Rhipicephalus microplus (Canestrini, 1888) (Acari: Ixodidae) and Rhipicephalus sanguineus sensu lato (s.l.) (Acari: Ixodidae) were assessed by the larval packet test. The CompuSyn program was used to make qualitative assessments of the effects (synergistic, additive and antagonistic) of the associations. The effects of all combinations tested against R. microplus larvae were synergistic, with combination indices (CIs) <0.70. When tested against R. sanguineus, eight of the mixtures showed a synergistic effect (CI < 0.70); only the carvacrol + thymol mixture at LC50 presented a moderate synergistic effect, with CIs between 0.70-0.90. This study is the first to determine the effects of the interactions of these substances in the control of these two tick species. The combinations of carvacrol + thymol, carvacrol + eugenol and thymol + eugenol have synergistic effects in R. microplus and R. sanguineus s.l. larvae.

Characterization of the microbial community in a lotic environment to assess the effect of pollution on nitrifying and potentially pathogenic bacteria.

This study aimed to investigate microbes involved in the nitrogen cycle and potentially pathogenic bacteria from urban and rural sites of the São Pedro stream. Water samples were collected from two sites. A seasonal survey of bacterial abundance was conducted. The dissolved nutrient content was analysed. PCR and FISH analysis were performed to identify and quantify microbes involved in the nitrogen cycle and potentially pathogenic bacteria. The seasonal survey revealed that the bacterial abundance was similar along the year on the rural area but varied on the urban site. Higher concentration of dissolved nutrients in the urban area indicated a eutrophic system. Considering the nitrifying microbes, the genus Nitrobacter was found, especially in the urban area, and may act as the principal bacteria in converting nitrite into nitrate at this site. The molecular markers napA, amoA, and nfrA were more accumulated at the urban site, justifying the higher content of nutrients metabolised by these enzymes. Finally, high intensity of amplicons from Enterococcus, Streptococcus, Bacteroides/Prevotella/Porphyromonas, Salmonella, S. aureus, P. aeruginosa and the diarrheagenic lineages of E. coli were observed at the urban site. These results indicate a change in the structure of the microbial community imposed by anthrophic actions. The incidence of pathogenic bacteria in aquatic environments is of particular importance to public health, emphasising the need for sewage treatment to minimise the environmental impacts associated with urbanisation.