Pesquisa e desenvolvimento de um novo antiparasitário para administração oral em cães

Abstract

Nitazoxanide (NTZ) is an antiparasitic that has an important and wide action against microbial agents, helminths (such as Toxocara sp. and Ancylostoma sp.) and protozoa (such as Giardia sp.). However, in Brazil so far there are no formulations that make use of this molecule in the treatment of these parasites in animals. Bearing in mind that the parasites are part of the zoonotic chain, arousing concern within the clinical and epidemiological scope of veterinary medicine due to its wide infectious potential and also due to the increasing resistance to standard medications used in the treatment of these infections, the importance of research on safe antiparasitics with low capacity for resistance development. The objective of this work was to evaluate the toxicity and efficacy of nitazoxanide alone and associated with ivermectin, pyrantel, febantel and praziquantel in vitro, ex vivo and in vivo. In vitro efficacy tests were carried out on eggs of Ancylostoma sp., Toxocara sp and Giardia sp by filtering methodology and recovery of parasitic structures and test of toxicity and degradation of the cell tapetum in kidney MDCK and MDBK cells with degradation reading by spectrophotometry. A hemotoxicity test was performed to assess hemolysis, using a detergent solution as a positive control and an alkaline solution as a negative control to assess the potential for degradation of red blood cells. To carry out the ex vivo experiment, the model of ocular irritability in chicken eyes was used, being computed at different times, the level of irritability of the eyeballs on the instillation of NTZ associated and isolated, being used as a negative control saline solution. In the in vivo tests in a murine model, the analysis of the efficacy of the product in the therapeutic dosage was carried out by reducing the parasitic contamination of eggs of Ancylostoma sp., Toxocara sp and Giardia sp. The analysis of acute and chronic toxicity was performed by administering the product at a therapeutic dose, overdose and underdose, evaluating clinical signs, behavioral assessment and changes in renal and hepatic biochemical parameters. Statistical analysis was performed using percentage, egg reduction count for determination and Kruskal-Wallis. In vitro cytotoxicity studies demonstrated that the higher the dose of NTZ, the greater the renal cell destruction in MDCK cells. Concentrations above 30mg/kg showed high control potential (98%) but with high (97%) cellular toxicity. Thus, the concentration of NTZ was reduced, like the 10mg/kg used in the product proposed here, in which we obtained high efficacy, and a decrease in in vitro toxicity to 25%. The data expressed by the use of isolated NTZ in the control of Giardia sp, were very expressive, since they reached the level of 99%, followed by 98% for Toxocara sp and 86% against Ancylostoma sp. The toxicity tests suggested that the product at therapeutic concentrations, tested, projects great safety since it did not show toxicity. The in vitro efficacy tests demonstrated that the proposed product (NTZ, pyrantel, febantel, praziquantel and ivermectin) obtained a high potential of efficacy in the control of nematodes, reaching levels that varied from 95% (Ancylostoma sp) to 98% (Toxocara sp) . Against Giárdia sp, it reached the mark of 99% of effectiveness, while the positive control of the study represented by the associated use of pyrantel, febantel, praziquantel (antiparasitic of conventional use for dogs) obtained levels of nematode control of 73% for Ancylostoma sp , 85% for Toxocara sp and against Giardia sp 75%. It was concluded that the action of NTZ as a symbiotic agent with other antiparasitics was extremely remarkable, to the point of being considered as an excellent parasiticide even in tests with the target species, mainly due to its capacity to eliminate the different structures of nematodes and protozoa. In this sense, NTZ can become an excellent alternative for antiparasitic control.