Treatment of natural infestations of the biting louse (Werneckiella equi) on horses using triflumuron, a benzoylurea derivative insect growth regulator

The implication of ROS production on triflumuron-induced oxidative stress and genotoxicity in human colon carcinoma (HCT-116) cells

The aim of this study is to evaluate the cytotoxic and the genotoxic effects of triflumuron (TFM) on human colon carcinoma cells (HCT-116). Indeed, TFM is used to protect vegetables, fruits, and domestic animals against a large spectrum of parasites causing animal and human disorders. However, studies revealing its toxicity and its mode of action in mammalian systems remain very limited. We monitored our work with the cytotoxicity assay starting with the cell viability test, the ROS generation, the malondialdehyde (MDA) production, the DNA fragmentation, and the measurement of some antioxidant enzymes activities such as catalase, superoxide dismutase, and the glutathione S-transferase. Also, we measured the mitochondrial transmembrane potential. We showed that TFM induced a dose-dependent cell death. This decrease in cell viability was accompanied by a significant reduction in the mitochondrial membrane potential. We also have shown that TFM induced oxidative stress as revealed by the generation of reactive oxygen species, the increase of the MDA levels, and the activation of the antioxidant enzymes. Moreover, our results indicated that TFM induced DNA damage in HCT-116 cells as monitored by the comet assay. We demonstrate, for the first time, the cytotoxic and the genotoxic potentials of TFM on human cultured cells.

Ectoparasites of feral horses [Equus ferus caballus (Linnaeus., 1758)] on Karadağ Mountain, Karaman, Turkey

Approximately 250 feral horses [Equus ferus caballus (Linnaeus, 1758)] living on Karadağ Mountain near Karaman City were caught by Kazakh horse herdsmen with permission of the Turkish Ministry of Agriculture and Forestry and brought to a farm in Karkın village in Konya Province, 70 km from Karadağ, in November, 2017. This study was carried out to determine the presence of ectoparasites infesting a subsample of 36 feral horses. The horses were visually inspected, and then their bodies were checked by hand for ectoparasites. Thirty-five (97.2%) were infested with at least one of five species of ectoparasites: Bovicola equi (Linnaeus, 1758), Hippobosca equina (Linnaeus, 1758), Haemaphysalis parva (Neuman, 1897), Hyalomma excavatum (Koch, 18449), Dermacentor marginatus (Sulzer, 1776). Most of the horses were coinfested with two ectoparasite species. Prevalence of infestation with H. equina was 80.6% and with B. equi 72.2%. In addition, prevalence of Ha. parva was 25.0%, Hy. excavatum 13.9%, and D. marginatus was 5.6%. This is the first systematic examination for external parasites of feral horses in Turkey. Further studies are needed to determine ectoparasites of greater numbers of feral horses in different localities.

A review on the treatment and control of ectoparasite infestations in equids

Ectoparasites infestations are a growing concern to horse owners and equine veterinarians alike. Ectoparasites cause significant health and welfare issues and can potentially can serve as vectors for a variety of pathogens. The prevalence of ectoparasites increases around the world, and especially in horses information on the successful prevention and treatment of ectoparasite infestations in scarce and in many instances anecdotal. This poses a challenge to the equine veterinarian and off-label use of drugs can lead to detrimental effects in horses. In this review we describe the current available evidence for the prevention and treatment of ectoparasite infestations in horses. Only a very limited number of products is approved for the use in horses and fortunately many of the other products that are used in an off-label manner appear to be safe in horses. Future research in this area should aim at providing PK/PD modelling data to assure appropriate and safe dose regimen to prevent and treat ectoparasite infestations in horses.

Triflumuron induces genotoxicity in both mice bone marrow cells and human Colon cancer cell line

Triflumuron (TFM) is an insect growth regulator (IGR), an insecticide commonly used over the world. It is known for its several toxic manifestations, such as reprotoxicity, immunotoxicity and hematotoxicity, which could affect public health. However, studies that reveal its toxic effects on mammalians are limited. To reach this purpose, our study aimed to elucidate the eventual genotoxic effects of TFM in mice bone marrow cells and in HCT 116 cells after a short term exposition. TFM was administered intraperitoneally to Balb/C male mice at doses of 250, 350 and 500 mg/kg bw for 24 h. Genotoxicity was monitored in bone marrow cells using the comet test, the micronucleus test and the chromosome aberration assay. Our results showed that TFM induced DNA damages in a dose-dependent manner. This genotoxicity was confirmed also in vitro on human intestinal cells HCT 116 using the comet test. It was then asked whether this genotoxicity induced by TFM could be due to an oxidative stress. Thus, we found that TFM significantly decreased HCT 116 cell viability. In addition, it induced the generation of reactive oxygen species (ROS) followed by lipid peroxidation as revealed by the increase in the malondialdehyde (MDA) levels. Similarly, the activation of the antioxidant enzymes (catalase and superoxide dismutase) was also observed. Our results indicated that, in our experimental conditions, TFM had a genotoxic effect on bone morrow cells and in HCT 116 cells. Moreover, we demonstrated that this genotoxicity passes through an oxidative stress.

Triflumuron induces cytotoxic effects on hepatic and renal human cell lines

Insect growth regulator insecticides are a new class of pesticides, commonly used around the world to control insect damages. Among those compounds, we focused our interest on triflumuron (TFM), which is less toxic than other conventional insecticides. However, not much is known about its toxic effects on mammalian systems. Therefore, our study aimed toward evaluating the cytotoxic and genotoxic effects of TFM using two different cell lines, the human renal embryonic cells (HEK 293) and hepatocytes (Hep G2). We showed, according to the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, that TFM reduced significantly the cell viability and increased the reactive oxygen species generation, malondialdehyde levels, and mitochondrial membrane potential in both cell lines. The antioxidant system was disturbed as assessed by the increased activities in both catalase and superoxide dismutase. We demonstrated also, that TFM is an inductor of DNA damages quantified by the comet assay. Moreover, we showed an overexpression of proapoptotic Bax and a decrease in antiapoptotic Bcl-2 expression. As a conclusion, we demonstrate that the liver presents the major target organ to TFM, in which the cytotoxicity and the genotoxic effects were significantly higher in hepatic cells than in renal cells and by consequence its uses must be controlled.

Protective effects of fennel essential oil against oxidative stress and genotoxicity induced by the insecticide triflumuron in human colon carcinoma cells

The increased use of pesticides is the origin of multiple damages to the environment and to humans; thus, the search for new strategies to reduce or even protect the toxic effects caused by these synthetic products became a necessity. In this context, our study attempted to evaluate the protective effects of fennel essential oil (FEO), the main essential oil extracted from Faeniculum vulgare Mill., a plant with aromatic, flavorful, and medicinal uses, against toxicity induced by an insecticide-triflumuron (TFM)-in human carcinoma cells (HCT116). Our methodological approach consists of the cytotoxicity assay starting with the cell viability test, the ROS generation, the malondialdehyde (MDA) production, the DNA fragmentation, and the measurement of some antioxidant enzymes activities such as catalase (CAT) and superoxide dismutase (SOD). Also, we measured the mitochondrial transmembrane potential. The outcome of the current study showed clearly that after 2 h of HCT 116 cell pretreatment with FEO, there were increase in cell viability, reduction in ROS generation, and modulation in CAT and SOD activities induced by TFM. In the same manner, significant decreases in MDA levels were found. Mainly, the results indicated a perceptible decrease in DNA damages and a significant reduction in the mitochondrial membrane potential loss. Our work demonstrates that FEO can be an important protector against toxic effects induced by TFM in HCT 116 cells.

Progress and prospects of arthropod chitin pathways and structures as targets for pest management

Chitin is a structural component of the arthropod cuticular exoskeleton and the peritrophic matrix of the gut, which play crucial roles in growth and development. In the past few decades, our understanding of the composition, biosynthesis, assembly, degradation, and regulation of chitinous structures has increased. Many chemicals have been developed that target chitin biosynthesis (benzoyphenyl ureas, etoxazole), chitin degradation (allosamidin, psammaplin), and chitin regulation (benzoyl hydrazines), thus resulting in molting deformities and lethality. In addition, proteins that disrupt chitin structures, such as lectins, proteases, and chitinases have been utilized to halt feeding and induce mortality. Chitin-degrading enzymes, such as chitinases are also useful for improving the efficacy of bio-insecticides. Transgenic plants, baculoviruses, fungi, and bacteria have been engineered to express chitinases from a variety of organisms for control of arthropod pests. In addition, RNA interference targeting genes involved in chitin pathways and structures are now being investigated for the development of environmentally friendly pest management strategies. This review describes the chemicals and proteins used to target chitin structures and enzymes for arthropod pest management, as well as pest management strategies based upon these compounds, such as plant-incorporated-protectants and recombinant entomopathogens. Recent advances in RNA interference-based pest management, and how this technology can be used to target chitin pathways and structures are also discussed.

Benzoylphenyl ureas as veterinary antiparasitics. An overview and outlook with emphasis on efficacy, usage and resistance

Six benzoylphenyl ureas are currently used in formulations approved as veterinary medicines: diflubenzuron for fly control mainly on cattle, lice and blowfly strike control on sheep, and lice control on farmed salmonids; lufenuron for flea control on dogs and cats and for lice control on farmed salmonids; triflumuron for lice and blowfly strike control on sheep; fluazuron for tick control on cattle; teflubenzuron for lice control on farmed salmon; and novaluron for fly and tick control on cattle and for flea control on dogs. Resistance to diflubenzuron and triflumuron has already been reported for sheep body lice and blowflies, and to fluazuron in cattle ticks. These and other minor veterinary usages, as well as the current status of resistance, are reviewed and perspectives for future opportunities are discussed based on unexplored potentials and threats posed by future resistance development.

Control of lice infestation in horses using a 10 mg/mL deltamethrin topical application

Background

Two open-controlled studies evaluated the tolerance and the efficacy of a 10 mg/mL deltamethrin-based pour-on solution (Deltanil®; Virbac, France) in treating (study 1) and preventing (study 2) natural Damalinia equi infestations in horses. In study 1, seven adult horses received 10 mL of the solution from mane to tail head on day 0 (D0). Four adult horses, living separately, served as non-treated controls. All were naturally infected. Lice burden was recorded by counting the number of live parasites, bilaterally, over seven anatomic regions. Lesional score was based on alopecia, crusts, papules/pustules, nodules/plaques, scales and wounds, each assessed on a 0–3 scale. Evaluation was performed on D0 and subsequently weekly until D56 in treated horses and on D0 and D56 in control horses. In study 2, six adult horses free of parasites were similarly treated on D-2 and D30. Two adult horses, naturally infested with D. equi and left untreated, were mixed with the treated horses from D0 to D60. Evaluation was performed similarly to study 1 on all horses, fortnightly until D60.

Results

No adverse event was recorded in either study. In study 1, parasite and lesional scores of control horses were maintained on D56. Parasite scores of the treated horses were reduced by 98% on D7 and 100% from D15 to D56 (mean [SD]: D0 44 [58.4]). Lesional score in treated horses was reduced by 24, 82, 47, 91, 96, 93, 93 and 100% on D7, 15, 21, 28, 35, 42, 50 and 56, respectively (mean [SD]: D0 3.1 [1.8]).

In study 2, the lice populations remained high in the two control horses throughout the study (max mean [SD]: D0 159 [151.3], min D45 34 [39.6]). On treated animals, all parasite counts were negative except on D15 (one louse found). The protection rate was 99.7% on D15 and 100% from D30 to D60.

Conclusions

A single application of the 10 mg/mL deltamethrin preparation was effective and safe in the treatment and in the prevention of lice infestation in these horses. It was also effective in preventing new infestations for one month.

Pyrethroid tolerance in the chewing louse Bovicola (Werneckiella) ocellatus

Equine pediculosis is a significant health and welfare issue, particularly in elderly and chronically debilitated animals. Currently infestation is controlled predominantly using topically applied pyrethroid insecticides, allowing limited scope for the rotation of drugs and increasing the risk of selection for resistance. Here the insecticidal efficacies of two pyrethroid-based products against the louse Bovicola (Werneckiella) ocellatus collected from donkeys were examined in vitro. The products were cypermethrin (Deosect™, Pfizer Ltd., 5% (w/v) cypermethrin, cutaneous spray) and permethrin (Switch™, VetPlus Ltd., 4% (w/v) permethrin, pour-on). The pyrethroid efficacy was contrasted with that of the organophosphate diazinon, since the louse populations examined were unlikely to have had prior exposure to this compound. The efficacy of diluted pure permethrin, the excipient, butyl dioxitol and the synergist piperonyl butoxide in the presence of the pyrethroids, were also considered. At the concentrations recommended for animal application, neither 4% (w/v) permethrin, nor 0.1% (w/v) cypermethrin had any significant effect on the mortality of B. ocellatus and neither induced significantly more mortality than an acetone-only control. In contrast, 0.04% diazinon caused 70% mortality within 4h and 100% mortality after 24h exposure. The addition of a potential pyrethroid synergist, piperonyl butoxide, in combination with cypermethrin and permethrin, resulted in no significant increase in mortality. It is concluded that the population of lice tested display a high level of pyrethroid tolerance which is likely to reflect the development of resistance. Twenty-four hours after routine treatment of 10 donkeys with a pour-on permethrin product (Switch™, VetPlus Ltd., 4% (w/v) permethrin, pour-on) hair tufts taken from their flanks were not significantly insecticidal compared with hair from the midline application site, implying a low level of insecticide distribution. Such a distribution pattern is likely to create an insecticide concentration gradient over the body and further facilitate selection for resistance.