In Mexico, cattle farmers face a significant issue with tick infestations, particularly from Rhipicephalus microplus and Amblyomma mixtum. To combat these pests, various chemical acaricides have been developed. However, their frequent and improper use has led to the emergence of resistant tick strains. This poses a serious challenge for cattle health and productivity.

The study focused on monitoring the susceptibility or resistance of A. mixtum to commonly used synthetic chemical acaricides. The goal was to identify potential risk factors associated with acaricide resistance in these ticks. Researchers collected fully engorged adult female A. mixtum ticks from twenty different ranches. They then performed larval packet tests (LPT) and larval immersion tests (LIT) using specific doses of various acaricides. The formulations tested included Phenylpyrazole (fipronil), Organophosphates (coumaphos), Formamidine (amitraz), Synthetic Pyrethroids (cypermethrin), and Macrocyclic Lactones (ivermectin).

The results were categorized into three groups: resistant, probable resistant, or susceptible. A strain of A. mixtum from the municipality of Las Choapas showed resistance to multiple acaricides. The mortality levels at the discriminating doses were as follows: fipronil (65. 3%), coumaphos (54. 3%), amitraz (52. 4%), and cypermethrin (35. 5%). However, ivermectin showed probable resistance with a mortality rate of 90. 8%.

Out of the 20 strains collected, 50% (10/20) were resistant to at least one of the acaricides tested. Amitraz showed the highest frequency of resistance among the strains evaluated. Only three strains were found to be susceptible to all the acaricides tested. This information is crucial for refining strategies to effectively control these ectoparasites.

The findings highlight the urgent need for better management practices in the cattle industry. Overuse and misuse of acaricides have led to widespread resistance, making it harder to control tick infestations. This situation calls for a more sustainable approach, possibly involving integrated pest management strategies. Farmers need to be educated on the proper use of acaricides and the importance of rotating different types of chemicals to prevent resistance.

The study also underscores the importance of regular monitoring and testing of tick strains for acaricide resistance. This proactive approach can help in early detection and management of resistant strains, ensuring the health and productivity of cattle. By understanding the resistance patterns, farmers can make informed decisions about which acaricides to use and when to use them.

The battle against acaricide resistance is ongoing, and it requires a collective effort from researchers, farmers, and policymakers. Through better practices and continuous monitoring, it is possible to mitigate the impact of resistant tick strains on the cattle industry. This will not only improve cattle health but also enhance the overall productivity and sustainability of the industry.

Tick Trouble: The Mexican Cattle Industry's Battle Against Acaricide Resistance

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