Control Strategies for the Tick Rhipicephalus Microplus (Canestrini, 1888) on Cattle: Economic Evaluation and Report of a Multidrug-Resistant Strain

PURPOSE

The aim of this study was to evaluate four strategies for application of acaricides to control the tick Rhipicephalus microplus among infested cattle, and to show which of these has the best cost-benefit ratio.

METHODS

For this, 72 cattle were selected and divided into four groups: Group 1 (G1): fipronil, pour-on; Group 2 (G2): fluazuron, pour-on; Group 3 (G3): moxidectin, injectable; and Group 4 (G4): chlorpyrifos 30 g, cypermethrin 15 g and fenthion 15 g, spraying (atomizing chamber). Every seven days, the numbers of semi-engorged females were counted and laboratory tests were conducted using different commercial technical-grade products for resistance monitoring.

RESULTS

G4 showed the best percentage reduction, with the highest rate on the seventh day post-treatment (DPT) (83.23%). G3 was the second best strategy, with a percentage of inverse reduction such that the best results were on the 28th DPT (82.85%), while G1 and G2 reached their best results on the 21st DPT (32.63% and 2.79%).

CONCLUSION

It was noteworthy that the formulation used in G4 was the only one that was efficient for strategic control and that, based on the economic analysis, was shown to be economically viable over the medium term due to the need for investment. The presence of a multidrug-resistant strain in the state of Mato Grosso do Sul in vitro, for the chemical bases amitraz, cypermethrin and cypermethrin + DDVP, is reported here for the first time.

Economic performance evaluation of Brangus and Nellore cattle breed naturally infested with Rhipicephalus microplus in an extensive production system in Central-West Brazil

The objective of the present study was to evaluate the performance of Brangus and Nellore cattle in an extensive production system. Sixty growing bulls, 30 of the Brangus and 30 of the Nellore breeds that were naturally infested with Rhipicephalus microplus were subdivided into four groups: control Nellore (15 animals), treated Nellore (15), control Brangus (15), and treated Brangus (15). The animals in the treated groups underwent acaricidal treatments for 1 year. Tick counts, acaricidal treatments and animal weighing were performed every 18 days, and the costs of acaricidal, anti-myiasis, and preventive treatments for tick fever were recorded for cost evaluation. The treated Brangus and Nellore groups did not show a significant difference in weight gain, whereas Nellore weight gain was superior in the control groups. The cost of acaricidal treatment throughout the experimental period was $494 US. The costs of the preventive treatment for tick fever and myiasis were $98 US and $15 US, respectively. The highest rates of tick infestation were found in the control group of the Brangus animals, which served as the basis for the suggested implementation of a strategic control program for animals in the growth phase. Nellore animals showed low rates of infestation. Under the conditions of this study, the Nellore animals were more efficient than the Brangus animals because they achieved satisfactory weight gain, similar to the Brangus, and a low tick count even in the control group. This finding demonstrates that expenses related to the acaricidal, anti-myiasis and tick fever treatments are unnecessary in Nellore cattle, making these animals more profitable.

Lactate and glucose minimum speeds and running performance

This study aimed to analyse the validity of glucose minimum speed (GMS) for lactate minimum speed (LMS) assessment during running and their relationship to endurance performance. Eight male trained runners (28.7 +/- 9.0 years) volunteered to take part in this study and underwent an official 10-km road race and a track lactate minimum test (LMT) (0.5-km sprint plus 6 x 800 m from 87 to 98% of maximal 3-km speed). Lactate and glucose minimum speeds were considered those related to the minimum blood lactate and glucose concentrations respectively attained during the graded phase of LMT. Significant correlations (p < 0.05) were found between LMS and GMS (r = 0.72) and LMS and 10-km performance (r = 0.83), but not between GMS and 10-km performance (r = 0.49). No significant differences (p > 0.05) were found between LMS (4.75 +/- 0.08 m/s), GMS (4.73 +/- 0.07 m/s) and 10-km mean speed (4.79 +/- 0.17 m/s). In conclusion, we found GMS to be a good predictor of LMS during track LMT, LMS being well related to endurance running performance.