Determination of Fipronil and Fipronil-Sulfone in Surface Waters of the Guandu River Basin by High-Performance Liquid Chromatography with Mass Spectrometry.

Fipronil (FIP) is a broad-spectrum insecticide used in the industrial, residential and agricultural sectors, which presents environmental and human health risks. Studies report its presence in aquatic environments in several countries, but in Brazil reports are scarce. The aim of this work was to evaluate the presence of fipronil and fipronil sulfone in surface waters through a validated analytical method by LC-MS according to INMETRO and USEPA in eight sampling sites in two seasons (summer and autumn, 2020) in Guandu River basin, in the state of Rio de Janeiro. FIP was quantified in the concentration range of 0.132-2.44 µg/L, while FIP-S was detected in most samples. This is the first study on the occurrence of FIP and FIP-S in the Guandu River basin, presenting values high enough to justify the need for monitoring studies in a region of great importance for the city of Rio de Janeiro.

Evaluation of pyriproxyfen in cattle by oral treatment: An alternative to control Haematobia irritans.

The horn fly, Haematobia irritans, is a bovine ectoparasite that causes large losses to cattle breeders, through lower meat and milk production and hide damage. Currently, the control of this parasite is mainly through chemicals. However, the indiscriminate use of these substances generates resistance. Pyriproxyfen belongs to an insect growth disruptors class with mechanisms of action for the control of immature forms of the insect. The aim of this study was to investigate the potential of pyriproxyfen administered orally to cattle for the control of the horn fly. In vitro bioassays were carried out by evaluating the number of adults emerged from 30 eggs per replicate, in triplicate, added in a substrate (fresh cattle feces) spiked with pyriproxyfen solutions in the concentration range of 2-130 ppb (ng.g-1). Probit analysis estimated LC50 value of 7.89 ppb and LC90 value of 70.08 ppb. The doses used in the in vivo evaluation were established based on the LC90 values and the anatomical and physiological aspects of the bovine digestive tract. Capsules containing pyriproxyfen at doses of 2.5 mg (G2.5) and 40 mg (G40) were produced and administered orally by bolus applicator for 12 days. The efficacy of pyriproxyfen against the immature forms of H. irritans was determined by incubating eggs in vitro in the feces collected on days 0, +3, +6, +10 and +13. Quantification of pyriproxyfen in feces was performed by UPLC-MS/MS, finding concentrations ranging from 13.4 to 22.6 ppb for G2.5 and between 268.5 to 509.0 ppb for G40. Pyriproxyfen administered orally is eliminated in the active form in the fecal mass and at a dose of 40 mg.day-1 (0.1 mg/kg/day) generates fecal concentrations able to produce 100 % prevention of adults emergence of H. irritans.

Chitosan gels for buccal delivery of Schinus molle L. essential oil in dogs: characterization and antimicrobial activity in vitro.

Periodontal disease is considered the main oral cavity disorder in dogs. Essential oils have the potential for use in the prevention and treatment of oral diseases. The antimicrobial activity of Schinus molle L. essential oil (SMEO) has already been reported. Chitosan, a natural product with antimicrobial activity and good biocompatibility has potential in biodental applications. In this study, we evaluated the in vitro antimicrobial activity of SMEO against bacteria associated with periodontal disease in dogs, developed and evaluated the physicochemical properties of a novel chitosan-based buccal delivery system containing SMEO. SMEO showed antimicrobial activity against Gram positive and Gram negative bacteria associated with canine periodontitis, with MIC values of 750 µg.mL-1 for Staphylococcus spp. and Streptococcus spp, 1000 µg.mL-1 for Corynebacterium spp. and 1250 µg.mL-1 for Pseudomonas spp. All formulations evaluated presented adequate physicochemical properties, good stability, and pH values close to buccal pH (5.0-7.0). Chitosan gel loaded with SMEO showed potential as a SMEO delivery system, having the ideal physicochemical and rheological properties (pseudoplastic and apparent viscosities) required for application on buccal tissue. Thus, we can conclude that formulation has the potential to be used for buccal mucosa delivery in the prevention and treatment of periodontal disease in dogs.

Evaluation of pharmacokinetics and efficacy of ivermectin following oral administration in dogs against experimental infection of Ctenocephalides felis felis and Rhipicephalus sanguineus.

With the increasing number of pets in home the human-animal relationship is increasingly close and care about control disease growing. Ivermectin (IVM) is frequently used because its proven safety. IVM is recommended for the treatment of demodectic scabies and prevention of heartworm in dogs, but informally is extremely used to control of Ctenocephalides felis felis and Rhipicephalus sanguineus. The aim of this study is evaluate the use of IVM in dogs, by the oral route at 0.6µg/kg dose, against experimental infection of these parasites using the construction of the plasma concentration curve and efficacy study. A IVM quantification method in canine plasma using HPLC-FL was developed and validated based on RE n°899/03 ANVISA. The samples collected during the efficacy test was analyzed by this validated method and prove Cmax of 350ng/mL at 4h (tmax) and AUC of 8411ng/h/mL. Spite of formulation have shown good absorption, the highest efficiency values found for Rhipcephalus sanguineus and Ctenocephalides felis felis were very low, 35% and 67% respectively, demonstrating this not be the most appropriate treatment for the control of these parasites.

Injectable fipronil for cattle: Plasma disposition and efficacy against Rhipicephalus microplus.

Fipronil is a phenylpyrazole class insecticide. It is widely used as an insecticide in agriculture and in the control of ectoparasites in veterinary medicine. The application of fipronil in an injectable form (subcutaneously) becomes an innovation, since there is no commercially available preparation containing fipronil herein. The present study aimed at fipronil usage, applied subcutaneously in cattle, to control Rhipicephalus microplus. The assessing criteria used in the research have been the construction of the plasma concentration curve and efficacy studies. A method using High Performance Liquid Chromatograph with ultraviolet detection was developed for determination of fipronil in bovine plasma samples, providing a fast and simple process with good reproducibility and low limit of quantification. The validation of the analytical method showed linearity, selectivity, precision, accuracy, sensitivity and stability, thus proving it as suitable for routine analysis. This method showed to be an important investigative tool in the analysis of fipronil plasma concentration in cattle. Fipronil administered via subcutaneous in bovine reached the systemic circulation (Cmax=378.06±137.44 ng/mL), was quickly absorbed (t(max)=10±0.87 h), and its elimination occurred slowly (t(1/2)=12 days), while maintaining quantifiable blood plasma levels (23.79±12.16 ng/mL) for up to 21 days after the treatment with a 1 mg/kg dosage. The in vivo efficacy tests proved that fipronil applied subcutaneously in a single dose of 1 mg/kg in cattle exhibited a mean efficacy of 82.41% against R. microplus. The potential of subcutaneous injection as an alternative treatment route in cattle encourage the development of an injectable formulation of fipronil.

In vitro efficacy of essential oils and extracts of Schinus molle L. against Ctenocephalides felis felis.

Extracts and essential oils from plants are important natural sources of pesticides. These compounds are considered an alternative to control ectoparasites of veterinary importance. Schinus molle, an endemic species of Brazil, produces a high level of essential oil and several other compounds. The aim of this work was to determinate the chemical composition of extracts and essential oils of S. molle and further to evaluate the activity against eggs and adults of Ctenocephalides felis felis, a predominant flea that infests dogs and cats in Brazil. In an in vitro assay, the non-polar (n-hexane) extract showed 100% efficacy (800 µg cm(-2); LD50 = 524·80 µg cm(-2)) at 24 and 48 h. Its major compound was lupenone (50·25%). Essential oils from fruits and leaves were evaluated, and had 100% efficacy against adult fleas at 800 µg cm(-2) (LD50 = 353·95 µg cm(-2)) and at 50 µg cm(-2) (LD50 = 12·02 µg cm(-2)), respectively. On the other hand, the essential oil from fruits and leaves was not active against flea eggs. This is the first study that reports the insecticidal effects of essential oils and extracts obtained from Schinus molle against Ctenocephalides felis felis.