Assessing trends in ectoparasiticidal drugs used to control ticks and flies in farm animals: A four-year analysis reveal differences between epidemiological zones at country level in Uruguay

The use of ectoparasiticides is a major concern in the control of parasites. In this study, we examined the trends and patterns of veterinary medicines use comparing between a high-risk epidemiological zone (HRZ) and a low-risk epidemiological zone (LRZ) for ectoparasites over a four-year period (2017-2020) at country level data. The objective of this study was to analyze the patterns of ectoparasiticide use in Uruguayan cattle, using the Anatomical Therapeutic Chemical Classification System for Veterinary Drugs (ATCvet) and dose indicators to consider regional variations in the animal population and production intensity. A total of 222 registered products classified as acaricides and/or insecticides based on 21 different active ingredients were grouped into 8 ATCvet level 4 categories. The annual consumption of active ingredients in ectoparasiticides averaged 40.6 tons. The total volume in the HRZ was 693 % higher than in the LRZ. The most sold ATCvet groups were Amidines (55.9 %), Pyrethrins/Pyrethroids (20.7 %), and Organophosphate Compounds (7 %). We calculated four different indicators with the resulting median values for entire country: 89.3 Technical Units per 1000 kg (IQR range of 10.5), 0.15 mg/kg of dosing biomass, 45.7 mg/ha of dose grazing area, and 3.09e+ 10 mg/LU/ha, respectively. Amidines were the most used group in the HRZ across all indicators, while Carbamates and Pyrethrins/Pyrethroids dominated in the LRZ. Cypermethrin, Amitraz, and Ethion were predominant in the HRZ, while Cypermethrin, Carbaryl, and Diazinon were common in the LRZ. The analysis of the four mixed Generalized Linear Models revealed significant differences in the use of veterinary medicines between zones with varying levels of epidemiological risk for parasitic diseases, with certain categories showing consistent patterns between indicators and zones. These results highlight the complexity of a veterinary medicine usage and the need for specialized strategies in veterinary medicine to address regional differences in the use of parasitic agents.