Ten years later: Evaluation of the effectiveness of 12.5% amitraz against a field population of Rhipicephalus (Boophilus) microplus using field studies, artificial infestation (Stall tests) and adult immersion tests.

Using field trials, artificial infestations (Stall tests) and in vitro adult immersion tests, the present study evaluated the acaricidal efficacy of 12.5% amitraz administered via whole body spraying against a Rhipicephalus (Boophilus) microplus population that did not have any contact with chemical products belonging to this acaricide family for 10 years (approximately 40 generations). Two natural infestation trials, two artificial infestation trials (Stall tests) and two adult immersion tests were performed in two different stages in 2005 and 2015. Between 2002 and 2015, the bovine herd of this property was formed by approximately 450 animals from the Simmental breed that were divided into nine paddocks formed by Cynodon dactylon (L.) Pers. For the natural infestation experiments in 2005 and 2015, we selected nearly 70 animals naturally infested with ticks from the same herd that belonged to the "São Paulo" farm located in São José do Rio Pardo, São Paulo, Brazil. Field studies were performed in the same paddock (9). To evaluate anti-R. (B.) microplus activity in the artificially infested cattle (Stall tests) and adult immersion tests, two experiments of each methodology were performed at CPPAR (the Center of Research in Animal Health located on the FCAV/UNESP campus in Jaboticabal, São Paulo, Brazil) in 2005 and 2015. R. (B.) microplus used in the artificial infestation, and adult immersion test experiments were obtained from paddocks 1-9 in 2005 and 2015 from the commercial farm where the field studies were performed. Based on the obtained results, it was possible to conclude that amitraz use in rotation with pyrethroids every 28 days for three consecutive years (2002-2004) previous to the beginning of the first trial (2005) was sufficient to generate a R. (B.) microplus strain resistant to amitraz. Moreover, using field trials, artificial infestations (Stall tests) and adult immersion tests, we verified that 40 generations of the tick species with no contact to the aforementioned compound (amitraz) were not sufficient to revert or modify the efficacy/resistance of amitraz for this analyzed R. (B.) microplus strain. The reversion of amitraz efficacy values in R. (B.) microplus may only occur when resistance of the field strain is incipient. Alternatively, the differences in the results may be due to differences in the Rhipicephalus spp. species between current study locations. Therefore, future studies must be performed to prove this hypothesis.

Establishing a total allowable concentration of o-toluidine in drinking water incorporating early lifestage exposure and susceptibility.

o-Toluidine is a monocyclic aromatic amine present in the formulation of some materials that contact drinking water. NSF/ANSI 61 Annex A (2011) and US EPA (2005a) risk assessment guidelines were used to determine an acceptable drinking water level. Occupational exposure to o-toluidine is associated with an increased risk of bladder cancer but human disease rates could not be used to establish risk values due to inadequate exposure data and coexposures in the epidemiology cohorts. Chronic dietary exposure to o-toluidine hydrochloride was associated with benign and malignant tumors in both sexes of F344 rats and B6C3F1 mice. o-Toluidine is genotoxic in vitro and in vivo. A 10(-5) cancer risk level was extrapolated from the human equivalent BMDL(10) of 13mg/kg-day for the combined incidence of papillomas and carcinomas of the bladder transitional epithelium in female rats. Considering varying susceptibility to tumor development at different life stages, the unit risk was modified to incorporate potency adjustments for early-life exposures. A framework for lifestage adjustment is presented that makes assumptions evident. For this assessment, the lifetime unit risk derived was ∼2-fold greater than the unadjusted adult lifetime unit risk, and the resulting Total Allowable Concentration in drinking water is 20µg/L.

Evaluation of the efficacy and safety of a novel formulation of metaflumizone plus amitraz in dogs naturally infested with fleas and ticks in Europe.

The efficacy and safety of a novel spot-on formulation of metaflumizone plus amitraz (ProMeris/ProMeris Duo for Dogs, Fort Dodge Animal Health, Overland Park, KS) was assessed in dogs naturally infested with ticks and/or fleas in a multiregional, clinical field study. Nineteen veterinary clinics in Germany and 11 clinics in France enrolled patients to the study. One hundred eighty one dogs with tick infestation and 170 dogs with flea infestation (plus three dogs harboring both ticks and fleas) qualified as primary patients and were randomly allocated to one of two treatments in a ratio of approximately 2:1 for metaflumizone plus amitraz (minimum dosage of 20 plus 20mg/kg) or fipronil (at the recommended label rate). Clinical examinations and baseline parasite counts were performed on Day 0 prior to treatment. Tick and/or flea counts and safety evaluations were repeated at intervals of about 2 weeks for 8 weeks. Both products resulted in consistent reductions in tick numbers (>81%) throughout the study, with metaflumizone plus amitraz giving consistently higher reductions in tick numbers. The efficacy against tick count compared with Day 0 was 97.6%, 93.5%, 89% and 94% at Day 14, 28, 42 and 56, respectively, for metaflumizone plus amitraz. The corresponding efficacies for fipronil were 86.3%, 81.1%, 84.8% and 86.1%. Within groups, the tick reduction was highly significant (P<0.0001) compared to baseline at all observation periods. Both treatments resulted in consistent (>89%) and highly significant (P<0.0001) reductions in flea numbers relative to the baseline counts throughout the study, although fipronil resulted in numerically higher reductions on each count day. The efficacy against fleas compared to baseline was 91.8%, 88.7%, 91.5% and 92.0% at Day 14, 28, 42 and 56, respectively, for metaflumizone plus amitraz. The corresponding efficacies for fipronil were 98.2%, 96.3%, 95.9% and 96.7%. Metaflumizone plus amitraz was highly effective in controlling existing infestations of fleas and ticks on dogs and was effective against reinfestation for at least 56 days. Metaflumizone plus amitraz showed a good tolerance profile in dogs.

Efficacy of a novel formulation of metaflumizone plus amitraz for the treatment of sarcoptic mange in dogs.

A novel spot-on formulation containing metaflumizone plus amitraz (ProMeris/ProMeris Duo for Dogs, Fort Dodge Animal Health, Overland Park, KS) was evaluated for efficacy against sarcoptic mange mites in naturally infested dogs. Sixteen dogs were allocated to two equal groups and were housed individually. Eight of the dogs were treated topically with metaflumizone plus amitraz at the proposed minimum dose rate (20mg/kg of each of metaflumizone and amitraz, at a dose volume of 0.133ml/kg) on Days 0 and 28. The other eight were treated with metaflumizone plus amitraz at the proposed minimum dose rate on Days 0, 14, 28 and 42. To enumerate Sarcoptes scabiei mites, skin scrapings were taken on each of Days 2, 14, 28, 42 and 56. Clinical signs of mange and the extent of sarcoptic lesions were evaluated on each dog when scrapings were made. Evaluation of the efficacy of the treatment was based on the absence of mites supported by the absence of clinical signs associated with canine sarcoptic mange. Treatment with metaflumizone plus amitraz at the minimum proposed dose rate at monthly (two treatments) or two-weekly (four treatments) intervals resulted in a rapid reduction of mites and improved clinical signs. The overall cure rates at Day 56, based on zero mite counts and/or resolution of clinical signs were 75% and 83% of dogs for the monthly and two-weekly regimens, respectively.

Efficacy of a novel formulation of metaflumizone plus amitraz for the treatment of demodectic mange in dogs.

A novel spot-on formulation containing metaflumizone plus amitraz (ProMeris/ProMeris Duo for Dogs, Fort Dodge Animal Health, Overland Park, KS) was evaluated for efficacy against demodectic mange mites in naturally infested dogs. Sixteen dogs were allocated to two equal groups and individually housed. Eight of the dogs were treated topically with metaflumizone plus amitraz at the proposed minimum dose rate (20mg/kg of each of metaflumizone and amitraz, 0.133ml/kg) on Days 0, 28, and 56. The other eight were treated with metaflumizone plus amitraz at the proposed minimum dose rate on Days 0, 14, 28, 42, 56, and 70. Mite numbers were estimated from skin scrapings taken on Days -3 to -1, 28, 56, and 84. Clinical signs of mange and the extent of demodectic lesions on each dog were evaluated when skin scrapings were conducted. Efficacy of the treatment was based on a reduction in mite numbers and an assessment of the clinical signs associated with canine demodectic mange. Treatment at monthly or two-weekly intervals for 3 months resulted in a rapid reduction in mite numbers (>94 and >99% for the monthly and two-weekly treatments, respectively) and an improvement in clinical signs. Success rates, based on zero mite counts in skin scrapings at Day 84 were 42.9 and 62.5% of dogs for the monthly and two-weekly regimens, respectively.

Chemical composition of Schiff's reagent crystals.

Crystals were prepared by adding 0.04 M sulfuric acid to a Schiff's reagent made with 2.5 g pararosaniline (PR) chloride dissolved in a saturated SO2 solution. Elemental analysis of the crystals gave the composition C19H21N3S2O7.4H2O which corresponds to the sulfate of pararosanilinesulfonic acid (PRSA) tetrahydrate. The moisture content was ca. 5%. A reagent reconstituted by dissolving 0.2 grams of crystals in HCl 0.1 N contains ca. 3.5 x 10(-3) M or 0.11% PR. A solution prepared with 2.5 g PR in 100 ml O.1 N HCl plus 0.04 M M K2S2O5 gave only a few crystals after 0.04 M sulfuric acid was added. The PR content, determined colorimetrically, was 0.25% compared with 1.35% in saturated SO2. The per cent dye loss during charcoal purification was also higher. The low concentration of PR, caused both by the lower solubility and by the larger loss during charcoal purification explains the poor yield of crystals of a reagent prepared in HCl/K2S2O5, compared to a reagent prepared in saturated SO2. After crystallization is complete, the crystals are in equilibrium with a concentration of 0.2% of PR in the supernatant: when the initial concentration is close to this value crystallization is negligible or completely fails.