[en] [en] INTRODUCTION: Amblyomma cajennense sensu lato represents a significant challenge for sustainable tick control in tropical cattle systems due to its ecological adaptability, wide host range, and frequent co-occurrence with Rhipicephalus microplus. This study evaluated the occurrence of acaricide resistance in A. cajennense s.l. populations collected from cattle farms in coastal Ecuador.
METHODS: A cross-sectional field assessment was conducted on seven farms (Esmeraldas, n = 2; Manabí, n = 5) that met the minimum requirement of 30 engorged A. cajennense s.l. females per farm for resistance testing. Tick larvae were subjected to larval packet tests to determine susceptibility to three commonly used acaricides: amitraz, ivermectin, and alpha-cypermethrin.
RESULTS: Phenotypic resistance to at least one acaricide was detected on all evaluated farms. Resistance prevalence was 43% for amitraz, 86% for ivermectin, and 100% for alpha-cypermethrin. Multi-resistance occurred on 86% of farms. Estimated lethal dose values revealed extremely high LD₉₀ and LD₉₉ levels, frequently exceeding recommended commercial concentrations by several orders of magnitude. Exploratory screening suggested that extensive cattle production systems and the presence of alternative hosts, particularly horses and other equids, may contribute to resistance emergence and persistence.
DISCUSSION: The results are particularly relevant because A. cajennense s.l. frequently co-occurs with R. microplus on cattle farms, although the two species differ substantially in ecology, host use, and life cycle. Control strategies primarily designed for R. microplus, such as whole-animal acaricide treatments, may have limited impact on Amblyomma populations maintained through wildlife hosts and environmental stages. This study provides the first evidence of acaricide resistance in A. cajennense s.l. in Ecuador and highlights the need for species-specific management strategies, improved resistance monitoring, and integrated tick control programs adapted to multi-species infestations in tropical livestock systems.
Disciplines :
Veterinary medicine & animal health
Author, co-author :
Pérez-Otáñez, Ximena; Facultad de Medicina Veterinaria y Agronomía, Universidad UTE, Quito, Ecuador ; Grupo de Investigación CABSAC, Facultad de Medicina Veterinaria y Agronomía, Universidad UTE, Quito, Ecuador ; Instituto de Investigación en Zoonosis (CIZ), Universidad Central del Ecuador, Quito, Ecuador
Vanwambeke, Sophie O; Georges Lemaitre Centre for Earth and Climate Research, Earth and Life Institute, UCLouvain, Louvain-la-Neuve, Belgium
Paucar-Quishpe, Valeria; Instituto de Investigación en Zoonosis (CIZ), Universidad Central del Ecuador, Quito, Ecuador ; Facultad de Medicina Veterinaria y Zootecnia, Universidad Central del Ecuador, Quito, Ecuador
Pérez, Cecilia; Facultad de Medicina Veterinaria y Zootecnia, Universidad Central del Ecuador, Quito, Ecuador
Grijalva-Olmedo, Jorge; Facultad de Medicina Veterinaria y Zootecnia, Universidad Central del Ecuador, Quito, Ecuador
Cepeda-Bastidas, Darío; Facultad de Ciencias Agrícolas, Universidad Central del Ecuador, Quito, Ecuador
Orozco, Geoconda; Facultad de Medicina Veterinaria y Zootecnia, Universidad Central del Ecuador, Quito, Ecuador
Enríquez Morillo, Sandra; Instituto de Investigación en Zoonosis (CIZ), Universidad Central del Ecuador, Quito, Ecuador
Saegerman, Claude ; Université de Liège - ULiège > Département des maladies infectieuses et parasitaires (DMI) > Epidémiologie, analyse de risques et biosécurité appliquées aux sciences vétérinaires
Ron-Garrido, Lenin; Instituto de Investigación en Zoonosis (CIZ), Universidad Central del Ecuador, Quito, Ecuador ; Facultad de Medicina Veterinaria y Zootecnia, Universidad Central del Ecuador, Quito, Ecuador
Rodríguez-Hidalgo, Richar; Instituto de Investigación en Zoonosis (CIZ), Universidad Central del Ecuador, Quito, Ecuador ; Facultad de Medicina Veterinaria y Zootecnia, Universidad Central del Ecuador, Quito, Ecuador
Language :
English
Title :
Acaricide resistance in Amblyomma cajennense s.l. and implications for integrated tick control in Ecuadorian cattle systems.
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