Efficacy of doramectin against experimental infections by some nematode parasites in cattle in New Zealand     

Watson TG  Hosking BC  Hooke FG 《New Zealand veterinary journal》1995,43(2):67-69

A study was undertaken to determine the efficacy of the novel avermectin, doramectin, against experimental larval and adult infections of three species of nematode parasite important to cattle production in New Zealand. Eighteen worm-free dairy bull beef calves were randomly allocated on live weight to three similar treatment groups. Each calf was given 30,000 Ostertagia ostertagi, 20,000 Cooperia spp. and 10,000 Trichostrongylus axei infective larvae as a single dose. One group was treated with doramectin 6 days after infection while the remaining groups received saline or doramectin 27 days after infection. Given as a single subcutaneous injection behind the ear, doramectin at 200 microg/kg removed 99.9-100% of adult and larval stages of O. ostertagi, Cooperia spp. and T. axei when compared to infections established in untreated controls (p<0.001). No adverse reactions were observed following treatment in the doramectin-treated animals. No injection site lesions were found by palpation following treatment or by injection site examination at necropsy.  相似文献   

An acute case of Pimelea elongata toxicity in cattle in western New South Wales     

C Cavanagh  S Parry  C Fraser  BC Dominiak 《Australian veterinary journal》2023,101(1-2):35-40

In May 2019, 96 cattle died from Pimelea toxicity in a period of 19 days after potential exposure, with the first deaths occurring within 5 days. After examining the circumstances, we suspect that several factors contributed to the deaths. These included that recently purchased stock and transported had access to flooded land containing Pimelea elongata. This weed species contains simplexin and 18 other compounds. Roots, flowers and seeds are significantly more toxic than the stem, branches and leaves. We suspect that thirsty and hungry stock consumed seed and roots from flooded pastures and consumed lethal doses of simplexin. Blood tests were not good indicators of the conditions. Management strategies are suggested.  相似文献   

Prevention of blowfly strike on coarse and fine woolled sheep with the insect growth regulator dicyclanil     

Nottingham RM  Hosking BC  Schmid HR  Strehlau G  Junquera P 《Australian veterinary journal》2001,79(1):51-57

OBJECTIVE: To assess a ready-to-use formulation of dicyclanil to prevent blowfly strike on coarse and fine woolled sheep under New Zealand conditions. DESIGN: Randomized clinical field trials. PROCEDURE: In a first field trial, coarse wooled sheep treated with a ready-to-use, 5% dicyclanil formulation were compared with untreated control sheep for up to 21 weeks. In a second field trial, fine woolled sheep, treated with the same dicyclanil formulation, were compared with untreated sheep for up to 19 weeks. Efficacy was assessed by calculating the aggregated cumulative strike rate. RESULTS: For trial 1 (coarse woolled sheep) the aggregated cumulative strike rate at the end of the trial at week 21 after treatment reached 3.9% and 19.1% for treated and untreated sheep, respectively. For the treated animals the aggregated cumulative strike rate reached the 1% and 2% benchmarks between weeks 11 and 12. For trial 2 (fine woolled sheep) the aggregated cumulative strike rate at the end of the trial at week 19 reached 0.6% and 7.5% for treated and untreated sheep, respectively. Wool length at the time of application did not substantially influence the efficacy of dicyclanil. CONCLUSION: Under New Zealand field conditions, a ready-to-use 5% spray-on formulation of dicyclanil protected coarse woolled sheep for at least 12 weeks and fine woolled sheep for at least 19 weeks.  相似文献   

Effects of sodium nitroprusside after load reduction and/or atropine pre-treatment prior to dexmedetomidine administration on cardiovascular variables in dogs     

RD Keegan  SA Greene  BC McKusick 《Veterinary anaesthesia and analgesia》2005,32(4):8-8

The purpose of this study was to determine the cardiovascular effects of sodium nitroprusside (SNP)‐induced after load reduction in dogs administered dexmedetomidine (DEX). Using a randomized crossover design and allowing at least 2 weeks between treatments 12 adult hound dogs of either sex weighing 22 ± 1.7 SD kg were anesthetized by face mask administration of 2.9% ET sevoflurane to facilitate instrumentation prior to administration of treatment drugs. Dogs were intubated and instrumented to enable measurement of heart rate (HR), systolic (SAP), mean (MAP) and diastolic (DAP) arterial pressures, mean pulmonary arterial pressure (PAP), pulmonary capillary wedge pressure (PCWP), central venous pressure (CVP), pulmonary arterial temperature (TEMP), and cardiac output (CO). Systemic (SVR) and pulmonary vascular resistances were calculated. Following completion of instrumentation dogs were allowed to recover for 40 minutes. After collection of baseline data, dogs were administered one of four treatments at T–10 minutes prior to injection of DEX (500? g M^–2 IM): 1) saline (SAL); 2) atropine (ATR, 0.02 [n = 6] or 0.04 [n = 6] mg kg^–1 IM); 3) SAL + SNP (infused at 1–10 ?g kg^–1 minute^–1, IV as needed to maintain MAP between 90–110 mm Hg; or 4) ATR + SNP. Cardiovascular data were collected at T‐20 minutes prior to administration of DEX, T‐5 and at 5, 10, 20, 30, 40, and 60 minutes following DEX. Data were analyzed using anova for repeated measures with post hoc differences between means identified using Bonferroni's method (p < 0.05). Differences in ATR dose were not found to be significant and thus results for ATR dose groups were pooled. Administration of SAL (dexmedetomidine alone) was associated with decreases in HR and CO and increases in SAP, MAP, DAP, CVP, and SVR. Administration of ATR was associated with an increase in HR and CO compared with SAL. Administration of SNP was associated with an increase in HR and CO and a decrease in SVR, MAP and CVP compared with SAL. Administration of SNP + ATR was associated with effects similar to that of SNP or ATR alone and resulted in an additive increase in CO. We conclude that SNP‐induced afterload reduction with or without atropine is effective in mitigating DEX‐induced impairment of cardiovascular function.  相似文献   

Immunolocalization of Aquaporins 1 and 9 in the Ram Efferent Ducts and Epididymis          下载免费PDF全文

BC Schimming  PFF Pinheiro  R de Matteis  CM Machado  RF Domeniconi 《Reproduction in domestic animals》2015,50(4):617-624

Aquaporins (AQPs) are essential membrane protein channels for the transport of water across membranes. Fluid movement in the epididymis is important for modulation of the luminal environment, in which sperm mature and reside. This study was designed to understand the morphology and localization of AQPs in ram efferent ducts (ED) and epididymis. For this purpose, the epididymis of seven animals were removed for histologic and immunohistochemical analyses. AQP1 immunoreactivity was observed in the apex of the ED, and AQP9 was found adjacent to the nuclei of the epithelial cells of the ED. The epithelial lining of ram epididymis is pseudostratified columnar and presents principal, basal, apical and narrow cells. In the initial segment (IS), a moderate reaction for AQP1 was observed in the apical cytoplasm of epithelial cells. An intense reactivity for AQP1 was noted over the microvilli of principal cells and in spermatozoa in the caput. In the corpus and cauda, AQP1 was noted only over the endothelial cells of vascular channels located in intertubular spaces. A weak‐to‐moderate reaction for AQP9 was observed in the nuclei of epithelial cells in the IS, caput and corpus of the epididymis. In the cauda, an intense reaction to AQP9 was observed in the epithelial border. In the IS, caput and corpus, the reactivity for AQP9 differed from those observed in domestic animals. The cauda showed a pattern similar to that previously described. These results indicate that AQPs 1 and 9 have reversed locations and roles in rams, suggesting activity variations related with fluid and solute absorption throughout the epididymis.  相似文献   

Preserving new anthelmintics: a simple method for estimating faecal egg count reduction test (FECRT) confidence limits when efficacy and/or nematode aggregation is high     

Dobson RJ  Hosking BC  Jacobson CL  Cotter JL  Besier RB  Stein PA  Reid SA 《Veterinary parasitology》2012,186(1-2):79-92

As it has been 30 years since a new anthelmintic class was released, it is appropriate to review management practices aimed at slowing the development of anthelmintic resistance to all drug classes. Recommendations to delay anthelmintic resistance, provide refugia and the use of a simulation model were reviewed to find optimum treatment strategies that maintain nematode control. Simulated Australian conditions indicated that a common successful low-risk treatment program was a rapid rotation between a "triple-combination" product (benzimidazole+levamisole+abamectin) and a new high-efficacy drug (monepantel). Where Haemonchus contortus was a threat, moxidectin was required at critical times because of its persistent activity against this parasite. Leaving up to 4% of adult sheep untreated provided sufficient "refugia" for non-selected worms to reduce the risk of selecting for anthelmintic resistance without compromising nematode control. For a new anthelmintic, efficacy estimated by faecal egg count reduction (FECR) is likely to be at or close to 100%, however using current methods the 95% confidence limits (CL) for 100% are incorrectly determined as 100%. The fewer eggs counted pre-treatment, the more likely an estimate of 100% will occur, particularly if the true efficacy is >90%. A novel way to determine the lower-CL (LCL) for 100% efficacy is to reframe FECR as a binomial proportion, i.e. define: n and x as the total number of eggs counted (rather than eggs per gram of faeces) for all pre-treatment and post-treatment animals, respectively; p the proportion of resistant eggs is p = x/n and percent efficacy is 100 ×(1-p) (assuming equal treatment group sizes and detection levels, pre- and post-treatment). The LCL is approximated from the cumulative inverse beta distribution by: 95%LCL=100 ×(1-(BETAINV(0.975, x+1, n-x+1))). This method is simpler than the current method, independent of the number of animals tested, and demonstrates that for 100% efficacy at least 37 eggs (not eggs per gram) need to be counted pre-treatment before the LCL can exceed 90%. When nematode aggregation is high, this method can be usefully applied to efficacy estimates lower than 100%, and in this case the 95% upper-CL (UCL) can be estimated by: 95% UCL = 100 ×(1((BETAINV(0.025, x+1, n-x+1))), with the LCL approximated as described above. A simulation study to estimate the precision and accuracy of this method found that the more conservative 99%CL was optimum; in this case 0.975 and 0.025 are replaced by 0.995 and 0.005 to estimate the LCL and UCL, respectively.  相似文献   

Managing anthelmintic resistance: Modelling strategic use of a new anthelmintic class to slow the development of resistance to existing classes     

DM Leathwick  BC Hosking 《New Zealand veterinary journal》2013,61(4):203-207

AIM: To test the hypothesis that a single strategic treatment with a new class of anthelmintic could slow the development of resistance to existing classes of anthelmintic.

METHODS: An existing model was used to simulate nematode parasite dynamics and the development of anthelmintic resistance. Variations on a five-drench preventive programme of treatments for lambs, in which either zero, the first, third or fifth treatment was substituted with a different class of drug, were compared for the time to reach treatment failure (defined as efficacy <95%). The sensitivity to variations in the death rate of adult worms, that varied from 1 to 5%, and the dominance of resistance genes were also assessed.

RESULTS: Replacing one of the five treatments with a different class of anthelmintic almost always slowed the development of resistance, and was never worse than using the same drug for all treatments. Further, there were large differences in the relative time to treatment failure depending on which treatment was substituted. Changing the first treatment always had the least benefit, whereas changing the fifth treatment always had the greatest. This pattern was independent of the daily death rate of adult worms, and was not influenced by the dominance of resistance under treatment.

CONCLUSIONS: The results indicated that strategic substitution of a single treatment with a new class of anthelmintic, at the end of a series of preventive treatments to lambs using an existing class, could slow the further development of resistance to the latter. This strategic use of a new anthelmintic class has the potential to greatly extend the life of existing anthelmintics if these are still effective.  相似文献   

Dose determination studies for monepantel, an amino-acetonitrile derivative, against fourth stage gastro-intestinal nematode larvae infecting sheep   总被引：2，自引：1，他引：1  

Hosking BC  Stein PA  Mosimann D  Seewald W  Strehlau G  Kaminsky R 《Veterinary parasitology》2008,157(1-2):72-80

Monepantel is the first compound from the recently discovered amino-acetonitrile derivative (AAD) class of anthelmintics to be developed for use in sheep. Three dose determination studies were conducted in Australia and Switzerland to identify the minimum therapeutic dose of monepantel when formulated for the oral treatment of sheep to control fourth stage (L4) gastro-intestinal nematode larvae. In each study, sheep infected with the target nematodes (selected from Haemonchus contortus, Teladorsagia (Ostertagia) circumcincta, Teladorsagia trifurcata, Trichostrongylus axei, Trichostrongylus colubriformis, Trichostrongylus vitrinus, Cooperia curticei, Cooperia oncophora, Nematodirus battus, Nematodirus filicollis, Nematodirus spathiger, Chabertia ovina and Oesophagostomum venulosum) were treated with either 1.25, 2.5 or 5.0mg monepantel/kg liveweight. Following euthanasia and worm counting, efficacy was calculated against worm counts from untreated control groups. Monepantel proved highly effective at 2.5 and 5.0mg/kg, but was only moderately effective against some nematode species (L4 stage) at 1.25mg/kg. The results also confirmed that monepantel will effectively control L4 stages of nematodes resistant to at least some of the currently available broad-spectrum anthelmintic classes (macrocyclic lactone resistant strains were not included in the studies). It was concluded that 2.5mg/kg would be a suitable minimum dose rate for a commercial product. No adverse events related to treatment with monepantel were detected.  相似文献   

MAPP对麦秸纤维-聚丙烯复合材料热力学性能的影响   总被引：1，自引：0，他引：1  

潘明珠  周定国  张述垠  Mosto Bousmina 《北京林业大学学报》2009,31(6):97-102

以麦秸纤维为增强材料、聚丙烯为基体物质、马来酸酐接枝聚丙烯（MAPP）为改性剂,制备麦秸纤维-聚丙烯复合材料。利用DMA、DSC、TG和SEM,探讨了MAPP的添加量（质量百分比1%、2%、5%、10%）和麦秸纤维形态（9、9～28、28～35、35目）对麦秸纤维 聚丙烯复合材料的热力学性能和结晶性能的影响。结果表明:①当MAPP的添加量为2%时,麦秸纤维-聚丙烯复合材料的储能弹性模量减小;当MAPP的添加量增加到5%、10%时,复合材料的储能弹性模量增加。②在麦秸纤维-聚丙烯体系内添加MAPP后,麦秸纤维 聚丙烯复合材料的结晶温度提高约1℃,结晶度增加了4%～8%;麦秸纤维以28～35目的形态作为聚丙烯基体的增强材料时,其复合材料的结晶温度为122.7℃,结晶率达到45.8%。③麦秸纤维-聚丙烯复合材料的热分解峰温分别为355和460℃。④麦秸纤维以纤维束的形态分布在基体聚丙烯中起增强作用,在整个体系内,麦秸纤维局部团聚且断裂明显。添加MAPP后,有利于基体物质在麦秸纤维表面的均匀覆盖。   相似文献   

Effects of Activin A on the In Vitro Development and mRNA Expression of Bovine Embryos Cultured in Chemically‐Defined Two‐Step Culture Medium     

JE Park  HJ Oh  SG Hong  G Jang  MK Kim  BC Lee 《Reproduction in domestic animals》2010,45(4):585-593

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