Optimizing long-acting antiparasitics use for integrated tick management of Rhipicephalus australis infesting cattle in New Caledonia

Authors: HUE, THOMAS - Agronomic Institute Of New Caledonien; FONTFREYDE, CHLOE - Agronomic Institute Of New Caledonien; WANG, HSIAO-HSUAN - Texas A&M University; GRANT, WILLIAM - Texas A&M University; PETE, TEEL - Texas A&M University; Perez De Leon, Adalberto - Beto

Submitted to: Tropical Animal Health and Production
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/18/2021
Publication Date: N/A
Citation: N/A

Interpretive Summary: Ticks are economically important external parasites of cattle that affect their health and production directly through their parasitic lifestyle and indirectly as vectors of pathogens causing animal diseases several of which can be transmitted to humans through the bite of infected ticks. In New Caledonia, the tick scientifically known as Rhipicephalus australis causes major health problem among cattle herds. Veterinary drugs including synthetic acaricides and antiparasitics that can also kill ticks have been used to treat cattle infested with this tick. However, the intense application of this type of veterinary drugs selected for cattle tick populations that became resistant to them. Research to optimize the use of long-acting antiparasitics with acaricidal properties is needed. This will help realize the use of these long-acting acaricides as part of integrated tick management strategies that combine practices to maximize the use of pastures to raise cattle. This study reports the implementation of a method involving pasture and herd management, with minimal strategic use of long-acting acaricides, in several New Caledonian farms over a five-year period. Longer larval acaricidal effect was achieved with one of the two commercial long-acting acaricides tested. Pasture and herd management allowed an increase in the delay between a long-acting acaricide application and the subsequent acaricide treatment from 11.0 weeks to 17.7 weeks. However, if ticks were detected and reported by producers on the day of a long-acting acaricide application, the delay to the following treatment was reduced from 18.5 weeks to 11.2 weeks. Optimizing the strategic use of long-acting acaricides and combining this approach with pasture and herd management reduced chemical use that can delay the development of acaricide resistance. These findings provide science-based evidence to cattle producers for adaptive integrated tick management. Consolidation of this information with other livestock husbandry studies contribute to the advancement of cattle breeding under changing agroecological conditions in New Caledonia.

Technical Abstract: The tick Rhipicephalus australis is the most economically important ectoparasite of livestock in New Caledonia affecting cattle health and production. Decades of control attempts based on the application of chemical acaricides exerted a strong selective pressure for R. australis populations some of which evolved resistance to these treatments. Research to optimize the use of long-acting antiparasitics with acaricidal properties is needed. This will help realize the use of these long-acting acaricides as part of integrated R. australis management strategies that combine practices to maximize the use of pastures to raise cattle. This study reports the implementation of a method involving pasture and herd management, with minimal strategic use of long-acting acaricides, defined as having substantial efficacy against larvae for weeks, in 33 New Caledonian farms over a five-year period. Diverse parameters concerning the utilisation of long-acting acaricides in association with pasture and herd management were analysed to optimize their strategic use. Longer larval acaricidal effect was achieved with a commercial pour-on formulation of fluazuron than with the commercial injectable (subcutaneous) formulation containing 3.15% ivermectin tested. Pasture and herd management allowed an increase in the delay between a long-lasting acaricide application and the subsequent acaricide treatment from 11.0 weeks to 17.7 weeks. However, if ticks were detected and reported by producers on the day of a long-acting acaricide application, the delay to the following treatment was reduced from 18.5 weeks to 11.2 weeks. The impact of a long-acting acaricide treatment on larval populations in pastures was greatest with a stocking rate of 5 animals per hectare during one week. Optimizing the strategic use of long-acting antiparasitics with acaricidal properties and combining this approach with pasture and herd management reduced chemical use that can delay the development of acaricide resistance. These findings provide science-based evidence to cattle producers for adaptive integrated tick management. Consolidation of this information with other livestock husbandry studies contribute to the advancement of cattle breeding under changing agroecological conditions in New Caledonia.