Toltrazuril + fenbendazole for cattle: Pharmacokinetics and efficacy against Eimeria spp. and gastrointestinal nematodes.

The present work evaluated the pharmacokinetics and efficacy of the association of 15cmg/kg toltrazuril +5cmg/kg fenbendazole against Eimeria spp. and gastrointestinal nematodes (GINs) in calves of different regions of Brazil (Center-West, Southeast, and South). A total of seven experiments were carried out, five of which determined formulation efficacy against Eimeria spp., considering the following aspects: therapeutic, preventive, metaphylactic, and residual efficacy. Therapeutic efficacy experiments for GINs were carried out by parasitological necropsy. The toltrazuril + fenbendazole association demonstrated ≥95% efficacy against Eimeria spp. for 21 days post-treatment (DPT). When used preventively and metaphylatically, the same association demonstrated ≥97% efficacy against E. zuernii, E. ellipsoidalis, E. cylindrica, E. bovis, E. wyomingensis and E. auburnensis. Toltrazuril + fenbendazole administered seven days before challenge was 100% effective against all these Eimeria species. Results of therapeutic, preventive, metaphylactic and residual efficacies can be related to the pharmacokinetic results, especially considering toltrazuril sulfone, which was detected in animal plasma for a longer period than the parent compound. Toltrazuril + fenbendazole achieved 100% anthelminthic efficacy against the GINs Haemonchus placei (L4), Cooperia pectinata and Oesophagostomum radiatum; 99.94% against adult H. placei; and 99.98% against C. puntacta. The association of toltrazuril + fenbendazole, associated with other measures, is an important and suitable tool for the control and treatment of Eimeria spp. and GINs in young cattle.

First report of the efficacy of a fluralaner-based pour-on product (Exzolt® 5%) against ectoparasites infesting cattle in Brazil.

BACKGROUND: This study describes the effectiveness of a novel active pharmaceutical ingredient, fluralaner (isoxazoline class), against important ectoparasites infesting cattle in Brazil. METHODS: A total of 13 studies involving a 5% fluralaner-based pour-on formulation (Exzolt 5%; further referred to as Exzolt) were conducted. Specifically, the effectiveness of this formulation was studied against Rhipicephalus microplus (6 studies), Cochliomyia hominivorax larvae (4 studies), Dermatobia hominis larvae (1 study) and Haematobia irritans flies (2 studies). RESULTS: The therapeutic efficacy of Exzolt was found to exceed 98% at 4 days post treatment (DPT), while persistent efficacy (> 90% efficacy) against repeated infestations of R. microplus was observed for up to 79 DPT. In field studies, ≥ 98% therapeutic efficacy was demonstrated at all study sites by 7 DPT, and a persistent efficacy (> 90% efficacy) was observed for 42, 49 or 56 DPT. Exzolt prevented C. hominivorax eggs from developing to the larval stage, thus mitigating the development of myiasis in cattle naturally and artificially infested with this screworm. The efficacy of Exzolt against D. hominis larvae was 98% at 3 DPT, while persistent efficacy (> 90% effectiveness) was found to last for up to 70 DPT. Against H. irritans, Exzolt showed therapeutic efficacy (≥ 90%) within the first day of treatment at both study sites, while persistent efficacy (≥ 90%) was observed for 7 DPT at one site and for 21 DPT at the other site. CONCLUSIONS: Overall, the results from these studies confirm that Exzolt is therapeutically efficacious against the most important ectoparasites infesting cattle in Brazil. The novel active pharmaceutical ingredient, fluralaner, provides a new treatment option for farmers to control cattle ectoparasites, especially where there is resistance to other chemical classes. In addition, an effective control of ectoparasites will improve overall cattle health and well-being as well as production.

The effectiveness of a fixed-dose combination pour-on formulation of 1.25% fipronil and 2.5% fluazuron against economically important ectoparasites and associated pharmacokinetics in cattle.

The present work consisted of eight studies to evaluate the ectoparasiticidal spectrum and determine the pharmacokinetic parameters of a pour-on combination of fipronil 1.25mg/kg+fluazuron 2.5mg/kg for cattle against Rhipicephalus microplus, Haematobia irritans and the larvae of Dermatobia hominis and Cochliomyia hominivorax. The analysis fipronil and fluazuron were performed by liquid chromatography using a mass detector for the detection and quantification of analytes (LC-MS/MS). Additionally, in two of these studies, the animals were artificially infested with R. microplus ticks (stall tests), and the efficacy of this formulation was compared with that of two other standalone pour-on formulations of fipronil 1.0mg/kg and fluazuron 2.5mg/kg. In the two stall studies, 28 calves were artificially infested with 5000 R. microplus (different strains), and daily collections of all of the engorged female ticks that detached from each calf were performed until 60 and 100days post-treatment (dpt). For the R. microplus field trials, 20 bovines were selected by counting the semi-engorged females, and the therapeutic and residual efficacy was evaluated by taking tick counts at 3, 7, 14, 21, 28, 35, 42, 49 and 56dpt. Forty bovines that were naturally infested with Dermatobia hominis larvae were selected, and the numbers of larvae were counted by visual and tactile inspection on 3, 7, 14, 28, 35, 42 and 49dpt. To address the efficacy on C. hominivorax larvae, two circular skin incisions (one on each side of the body) measuring approximately 4cm in diameter each were made in 12 crossbred calves, and the natural exposure of the lesions to C. hominivorax infestations was then allowed. The incisions from the 12 animals were carefully examined daily from 1 to 10dpt. Based on the PK results obtained for this pour-on combination containing fipronil 1.25mg/kg+fluazuron 2.5mg/kg, the maximum concentrations (Cmax) and the half-lives (T1/2) of these two active ingredients were detected on days 2, 5/6 and 19 (±2)/24, 4 (±3.5) days for fipronil and fluazuron, respectively. Furthermore, the combination showed higher therapeutic and residual efficacy against R. microplus (P≤0.05) when compared with commercial standalone formulations that were administered separately. A high efficacy for this new combination was also found against C. hominivorax and D. hominis larvae (efficacy≥99%). This study's results show that the combination of these two active ingredients, as opposed to their separate use, could represent a tool for extending the life cycle of these two molecules against cattle ectoparasites, especially R. microplus. Further studies would be desirable to further confirm this.