Histological changes of oocytes of the cattle tick Rhipicephalus microplus (Canestrini, 1888) treated with copper solutions

• Published in: Experimental parasitology Vol. 265; p. 108812
• Main Authors: Dolenga, Carla Juliana Ribeiro, dos Anjos, Alan, Yoshitani, Ursula Yaeko, Sanches, Gustavo Seron, Bechara, Gervasio Henrique, Arruda, Eduardo José, Molento, Marcelo Beltrão
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.10.2024
• Subjects: Acaricide resistance; Acaricides - pharmacology; Animals; Bioactive metals; Cattle; Cattle Diseases - drug therapy; Cattle Diseases - parasitology; Cattle-tick; Chlorpyrifos - pharmacology; Copper - pharmacology; Copper chloride; Copper sulfate; Copper Sulfate - pharmacology; Female; Histopathology; Oocytes - drug effects; Ovary - drug effects; Oviposition - drug effects; Pyrethrins - pharmacology; Rhipicephalus - drug effects; Tick Infestations - drug therapy; Tick Infestations - parasitology; Tick Infestations - prevention & control; Tick Infestations - veterinary; Bioactive metals; Acaricide resistance; Histopathology; Cattle-tick; Copper chloride; Copper sulfate
• ISSN: 0014-4894; 1090-2449; 1090-2449
• DOI: 10.1016/j.exppara.2024.108812

Infections caused by the ectoparasite Rhipicephalus microplus can cause major health problems in cattle, including death. Tick control is regularly made using a range of acaricide products. As a consequence, tick populations have been heavily selected for drug resistance. The objective of this work was to determine the in vitro efficacy of copper chloride and sulfate (CuCl2 and CuSO4) solutions against R. microplus. The adult immersion test (AIT), which measures the egg-laying and egg-hatch effects, was used for the Cu-II solutions at 30, 60, 120, 240, 480, and 1000 mM, in triplicates. Distilled water and the combination of cypermethrin 20% and chlorpyrifos 50% were used as controls. Histological sections were performed from the ovaries of adult engorged female ticks treated with 240, 480, and 1000 mM of CuCl2 and CuSO4. We have established a histological index of the damage caused by the solutions to the tick oocytes. The overall efficacy (egg laying & egg hatch) for CuCl2 and CuSO4 was 81.3, 82.5, 89.8, 84.5, 100.0, and 100%, and 61.7, 43.4, 62.5, 93.1, 100.0, and 98.5% respectively. Smaller oocytes were found in the Cu-II groups compared to the negative control. The histological data showed a concentration-dependent degenerative lesion of oocytes, described as cytoplasmic vacuolation and nuclear disorganization. The combination of cypermethrin and chlorpyriphos showed 100% efficacy. Cu-II solutions showed in vitro efficacy against adult engorged ticks being particularly harmful to oocytes. Thus, bioactive metals could be a complementary biofriendly treatment to control R. microplus and these injuries could be responsible for preventing egg hatch, and reducing pasture contamination. Safety studies are underway demonstrating the Cu-II potential in naturally infected cattle and their persistence in the environment. [Display omitted] •CuCl2 and CuSO4 at 480 and 1000 mM had 100% efficacy against adult ticks.•Smaller oocytes were determined in the Cu-II salt groups than in the control.•Cytoplasmic vacuolation and nuclear disorganization of oocytes were observed after copper solutions.•Histological alterations had a concentration-dependent effect.