Developing a practice

Trials were carried out on 11 farms to assess the effectiveness of 2.5 per cent w/v cypermethrin pour-on for the control of ticks on sheep. Treatment at the rate of 5 ml/10 kg bodyweight gave 92 per cent control of ticks on ewes for up to nine weeks and 88 per cent control on lambs for up to eight weeks.     

Intraruminal controlled release of cyromazine for the prevention of Lucilia cuprina myiasis in sheep

The efficacy of cyromazine, continuously released from intraruminal capsules at dose rates from 0.5 to 2 mg kg-1 d-1, was evaluated against implants of eggs and first instar larvae of Lucilia cuprina on Merino sheep. Estimates from the non-linear relationship between the success of implants and plasma concentrations showed that 95 per cent protection of sheep could be achieved at a mean release rate of 1.39 mg kg-1 d-1 cyromazine which gave rise to a mean plasma concentration of 0.26 mg litre-1. Present formulations allowed protection for about 90 days in a 40 kg sheep. The 'square wave' type of release profile provided negligible suboptimal dosing thus limiting the potential for selection of resistance. Systemic application of cyromazine provides control of covert and overt strike among sheep and could be used in ecologically based strategies for the control of L. cuprina populations.     

Efficacy of an oxibendazole-trichlorfon paste formulation against third stage larvae of Gasterophilus intestinalis and its safety in horses

A paste formulation containing 14.3 per cent of oxibendazole and 44 per cent of trichlorfon was administered to 33 ponies and horses. The dose rate used was equivalent to 10 mg and 30 mg/kg bodyweight, of oxibendazole and trichlorfon respectively. After treatment 25 animals passed between one and 82 third stage larvae of Gasterophilus intestinalis in their faeces. Dosing with 0.2 mg ivermectin/kg bodyweight three weeks later resulted in six animals expelling between one and four bots. The efficacy of the oxibendazole-trichlorfon paste was on average 96.2 per cent. This drug combination given to 52 ponies and horses at the indicated dose rate and to six ponies at twice that dose was tolerated without side effects except transient softening of the faeces in several animals and mild symptoms of colic in two horses.     

Efficacy of ivermectin against induced gastrointestinal nematode infections in goats

The efficacy of ivermectin (0.08 per cent w/v oral solution) at different dose levels was evaluated against induced infections of adult Haemonchus contortus (21 days old) and Trichostrongylus colubriformis (21 days old) and fourth stage larvae of Oesophagostomum columbianum (17 days old), Ostertagia circumcincta (five days old) and Strongyloides papillosus (five days old). Twenty-five Boergoats (mutton goats) were randomly allocated by bodyweight within each sex to an untreated control group and four ivermectin treatment groups; ivermectin was administered at either 25, 50, 100 or 200 micrograms/kg orally, once. The goats were killed and processed for worm recovery 25 to 27 days after treatment. At 25 micrograms/kg the efficacy of ivermectin varied from 43 per cent for adult T colubriformis to more than 99 per cent for fourth larval stage O columbianum. Ivermectin at 50 micrograms/kg or higher was 99 per cent or more effective against all induced parasite infections with the exception of ivermectin at 50 micrograms/kg against S papillosus (97 per cent). For all parasites there was a statistically significant (P less than 0.05) difference between the control group and the pooled treated groups. No adverse reactions to ivermectin treatment were observed in the goats.     

The ability of diamphenethide to control immature Fasciola hepatica in sheep at a lower than standard dose level

Groups of eight Welsh Mountain sheep were dosed with diamphenethide at the rate of 70 mg/kg bodyweight at either one, four, six or eight weeks after artificial infection with approximately 300 Fasciola hepatica metacercariae. Comparisons were made with similarly infected but undosed sheep and with sheep which were neither infected nor dosed. The good clearance of flukes up to six weeks of age (above 97 per cent on pooled data) was reflected in the plasma concentrations of the accepted liver damage marker enzymes glutamate dehydrogenase and gamma-glutamyl transpeptidase. Highly significant correlations were demonstrated between the numbers of flukes recovered, the plasma levels of these enzymes and haemoglobin and plasma albumin values. At 70 mg/kg, diamphenethide was shown to be able to control F hepatica populations of up to six weeks of age. The systematic use of diamphenethide at this dose level at intervals of up to six weeks during the period of metacercarial challenge should prevent ovine fascioliasis.     

Efficacy of eprinomectin pour-on against gastrointestinal nematodes and the nasal bot fly (Oestrus ovis) in sheep

The efficacy of the pour-on formulation of eprinomectin, at a dose rate of 0.5 mg/kg bodyweight, was assessed in sheep against three main species of gastrointestinal nematodes and against the nasal bot fly, Oestrus ovis, and some pharmacokinetic parameters were determined for 21 days after the treatment. By comparison with untreated control sheep, infected experimentally with Haemonchus contortus, Teladorsagia circumcincta and Trichostrongylus colubriformis, eprinomectin was 100 per cent effective against the two abomasal species and 99.5 per cent effective against T. colubriformis. In ewes naturally infected with the nasal bot fly, the efficacy of the drug against O. ovis was 97.7 per cent. The mean (se) systemic area under the curve (AUC) was 56.0 (26.2) ng/day/ml and the mean residence time was 5.3 (1.0) days, but there were wide variations between individual sheep.     

Upper gastrointestinal examinations: a radiographic study of clinically normal beagle puppies

A total of 24 upper gastrointestinal examinations were performed on four weanling beagle puppies over six weeks, using liquid barium (10 ml/kg bodyweight of 60 per cent w/v barium sulphate suspension] and barium food (8 g/kg of crushed kibble dog food and 7 ml/kg bodyweight of 60 per cent w/v barium sulphate suspension) as contrast media. The radiographic appearance was similar to that noted in adult dogs except for the consistent location of the pylorus on or near the midline. Duodenal pseudoulcers were seen more often with liquid barium and the caecal shadows were identified more often with the longer examination time with barium food. The stomach of the puppies appeared to have discriminatory emptying function; that is, semi-solid food was emptied from the stomach at a slower rate (210 to 450 minutes) than liquid (60 to 90 minutes). Solid meals emptied faster in puppies than in adult dogs. Dosages of 13 to 15 mg/kg bodyweight for the liquid barium examination and 14 g of ground kibble and 16 ml of barium sulphate suspension per m² of body surface area for the barium food examination are suggested as more appropriate for contrast studies in puppies.     

Comparative efficacy of triclabendazole, nitroxynil and rafoxanide against immature and mature Fasciola hepatica in naturally infected cattle

In two trials the fasciolicidal activities of triclabendazole, nitroxynil and rafoxanide were assessed in cattle naturally infected with predominantly immature stages of Fasciola hepatica. Tablets containing 900 mg triclabendazole were administered orally at a dose rate of 12 mg/kg bodyweight. Rafoxanide and nitroxynil were used at a dose rate of 10 mg/kg, rafoxanide being given orally and nitroxynil by subcutaneous injection. Based on faecal egg counts nine weeks after treatment the efficacies were calculated to be 100 per cent for triclabendazole and 95.0 per cent for nitroxynil in the first trial and 98.4 per cent for triclabendazole and 52.9 per cent for rafoxanide 15 weeks after treatment in the second trial. In the first trial five animals from each of the three groups were slaughtered and their fluke burdens counted. Compared with the untreated control group the reductions in the fluke burdens were 96.9 per cent in triclabendazole treated cattle and 76.4 per cent in the nitroxynil treated group.     

Field evaluation of the efficacy of fenbendazole in captive wild ruminants

The efficacy of in-feed fenbendazole at a dose rate of 7.5 mg/kg bodyweight for three consecutive days was assessed in five Arabian oryx (Oryx leucoryx), six scimitar-horned oryx (Oryx dammah), 14 slender-horned gazelles (Gazella leptoceros), eight Soay sheep (Ovis aries aries soay), 13 alpine ibex (Capra ibex ibex), six red deer (Cervus elaphus hippelaphus) and 11 Nelson's elk (Cervus elaphus nelsoni) kept in five herds in a zoo. The efficacy was assessed by means of repeated faecal egg count reduction (fecr) tests and in vitro egg hatch assays. Fenbendazole was highly effective against nematodes in five of the seven species, consistently reducing egg shedding by more than 90 per cent. In the egg hatch assays of the five herds, 50 per cent inhibition of hatching (ld50) was observed at a concentration of thiabendazole below 0.1 microg/ml. In the Arabian oryx and alpine ibex the efficacy of fenbendazole was less than 90 per cent, and the ld50 in the egg hatch assays was between 0.1 and 0.2 microg/ml thiabendazole.     

Analgesic and spasmolytic effects of dipyrone, hyoscine-N-butylbromide and a combination of the two in ponies.

The analgesic and spasmolytic effects of dipyrone (Novalgin) (2500 mg/100 kg bodyweight) hyoscine-N-butylbromide (Buscopan) (20 mg/100 kg bodyweight) and a combination of both drugs were evaluated in a balloon-induced model of colic, using five ponies with caecal fistulae. The drugs were given intravenously and 0.9 per cent sodium chloride solution (5 ml/100 kg bodyweight) was used as a control. The physiological saline solution and dipyrone had no effect on caecal contractions. After the injection of hyoscine-N-butylbromide and the drug combination caecal contractions ceased within 30 seconds and for 20 and 24 minutes, respectively (P less than 0.05). The results on pain relief were not statistically significant for any of the drugs. Dipyrone had a good analgesic effect in only two of the ponies, starting after eight to 10 minutes and lasting for 50 minutes. The drug combination relieved pain within 30 seconds after injection and the relief lasted for 50 minutes in three of the ponies and for 20 minutes in the other two. Hyoscine-N-butylbromide alone produced an analgesic effect within 30 seconds after injection which lasted for 20 minutes.     

Seasonal comparisons of anthelmintic activity of levamisole pour-on in cattle in the USA

Anthelmintic activity of a pour-on formulation of levamisole, applied during warm weather (16 degrees to 36 degrees C) at 10 mg/kg bodyweight, was evaluated in groups of naturally parasitised calves. This activity was compared to that obtained in similar groups of calves treated in the winter (-4 degrees to +7 degrees C). Controlled efficacy of the pour-on formulation was determined for each season by comparing mean worm burdens in treated calves sacrificed seven to nine days after treatment to non-treated controls. In these trials, burdens of Bunostomum phlebotomum, Cooperia species, Haemonchus placei, Nematodirus species, Oesophagostomum radiatum, Ostertagia ostertagi and Trichostrongylus axei in treated calves were reduced by 83.3 to 100 per cent in the summer and 89.2 to 100 per cent in the winter. Field investigations at nine locations across the USA compared changes in faecal egg counts for cattle treated and evaluated during warm summer months (27 degrees to 36 degrees C) to those treated during cold winter months (-18 degrees to +10 degrees C). Overall, faecal egg counts were reduced by 90.2 per cent in the summer trials and 94.0 per cent in the winter trials. The results of these trials indicate that there is no seasonal variation in the anthelmintic activity of this pour-on formulation of levamisole.     

Effectiveness of a mixture of cyromazine and diazinon for controlling flystrike on sheep

Objective To determine whether there is any need for woolgrowers to add diazinon to cyromazine jetting fluid to control active flystrike on sheep.
Method Larval implants were placed on 143 sheep and allowed to develop for 2 days. Groups of 47 or 48 of these struck sheep were jetted with cyromazine at 1000 mg/L, diazinon at 400 mg/L, or a mixture of the two. After treatment, the implants were assessed daily for 3 days for the presence of feeding larvae.
Results When checked 1 day after treatment, there was a 62% reduction in flystrike in the diazinon treated sheep compared to only 12% reduction on the cyromazine treated sheep. Flystrike reduction on the sheep jetted with the mixture of cyromazine and diazinon was 69%. Three days after treatment flystrike control was 97 to 99% in the latter two groups.
Conclusion Diazinon provided a faster resolution of strikes but by 3 days after treatment there was no significant difference in the number of implants remaining active on the sheep treated with cyromazine or with the mixture of cyro-mazine and diazinon.     

Pharmacokinetics and pharmacodynamics of piroxicam in dogs

Piroxicam was administered to beagle dogs intravenously and orally at a dose rate of 0.3 mg/kg bodyweight. It had an elimination half-life of 40.2 hours, a volume of distribution of 0.29 +/- 0.02 litres/kg and a body clearance rate of 0.066 litres/hour. When administered orally it was 100 per cent bioavailable and maximum plasma concentrations were achieved quickly (3.1 +/- 1.0 hours). Piroxicam inhibited the generation of thromboxane B2 in the blood of dogs by more than 70 per cent and more than 50 per cent inhibition was maintained in most animals for 48 hours.     

Comparison of the efficacy of dermal formulations of ivermectin and levamisole for the treatment and prevention of Dictyocaulus viviparus infection in cattle

Four groups of six parasite-naive calves were infected at seven day intervals with three doses of infective larvae of Dictyocaulus viviparus. Twenty-one days after the first dose three of the groups were treated either with an injectable formulation of ivermectin at a dose rate of 200 micrograms/kg bodyweight, or with pour-on preparations of levamisole at 10 mg/kg or ivermectin at 500 micrograms/kg. On day 28 two calves from each group were slaughtered and their burdens of lungworms counted. On day 35 the remaining calves were reinfected with D viviparus infective larvae at a rate of 80 L3/kg. The levamisole preparation was 94.6 per cent effective and both ivermectin preparations were 100 per cent effective against the initial infections. The ivermectin-treated calves were protected from the reinfection which subsequently became patent in the levamisole-treated and control calves.     

The efficacy of in-feed medication with fenbendazole against gastrointestinal nematodes of sheep, with particular reference to inhibited larvae.

Anthelmintic activity of fenbendazole in a feed formulation was tested against nematode parasites of sheep. Dose rates ranging from 1.4 mg per kg for four days to 0.4 mg per kg for 14 days removed 98 to 100 per cent of the total gastrointestinal worm burden, including large numbers of inhibited fourth stage larvae of Ostertagia circumcincta. One hundred per cent effectiveness against adult Dictyocaulus filaria was also recorded.     

An evaluation of the efficacy of oxfendazole against the common nematode parasites of the horse.

In a controlled trial in naturally-infected young ponies, oxfendazole administered orally at dose-rates of 10 mg per kg and 50 mg per kg resulted in complete elimination of Trichostrongylus axei, Parascaris equorum, Oxyuris equi and adult Strongylus vulgaris. Also, all migrating Strongylus edentatus larvae recovered from the subperitoneal tissues of the flank were found to be dead. Minimum efficiencies of 99.8 per cent and 99.1 per cent were obtained against adult small strongyles (Trichonema spp) and 97.6 per cent and 100 per cent of developing small strongyle larvae at dose-rates of 10 mg per kg and 50 mg per kg respectively. Although the arterial lesions caused by migrating S vulgaris larvae were less severe in the treated compared with the untreated animals, reductions in mean larval numbers over controls were only in the region of 49 to 59 per cent.     

Efficacy of oxfendazole against inhibited larvae of Ostertagia ostertagi in naturally infected calves in the southern USA

Forty yearling calves were assigned to four equal groups; three of the groups were treated with oxfendazole at dose rates of 6.75 mg/kg, 4.50 mg/kg, or 2.25 mg/kg bodyweight while the fourth group served as an untreated control. The calves were native to north-east Mississippi, USA, and harboured natural infections of gastrointestinal nematodes. The study was conducted during July when inhibited early fourth-stage larvae may be found in large numbers after their acquisition in the spring. The calves were maintained in separate groups on concrete-floored pens for 17 days before the intraruminal administration of oxfendazole. Seven days after treatment, the calves were slaughtered and the gastrointestinal parasites counted. At all the dose rates examined oxfendazole exhibited an efficacy of at least 99.4 per cent against adults of Haemonchus placei, Trichostrongylus axei, Bunostomum phlebotomum, Cooperia species, T colubriformis, Oesophagostomum radiatum, and Trichuris ovis. The efficacy against adult Ostertagia ostertagi was at least 99.4 per cent at dose rates of 6.75 and 4.50 mg/kg bodyweight, but decreased to 93.7 per cent at 2.25 mg/kg. The efficacy of oxfendazole against inhibited larvae of O ostertagi decreased with dose rate from 78.8 per cent at 6.75 mg/kg, to 58.9 per cent at 4.50 mg/kg and 20.3 per cent at 2.25 mg/kg bodyweight.     

Failure of a single treatment with ivermectin to control sheep scab (Psoroptes ovis) on artificially infested sheep

Ivermectin at 200 micrograms/kg bodyweight given either as a single subcutaneous injection or as an oral drench failed to eradicate Psoroptes ovis from artificially infested sheep. The oral drench reduced the mite populations by 43 per cent within 24 hours but no further significant decline was recorded over 38 days. The subcutaneous injection reduced the mite populations by 90 per cent after 10 days but live P ovis were present on all the treated animals 84 days after treatment. The efficacy of treatment was less the higher the initial mite burden. The injection had no effect on clinical sheep scab, and the disease continued to progress despite the mite mortality.     

The treatment of bovine sarcoptic mange (Sarcoptes scabiei var. bovis) using eprinomectin extended-release injection

The efficacy of eprinomectin in an extended-release injection (ERI) formulation was evaluated in cattle harbouring induced infestations of Sarcoptes scabiei var. bovis (sarcoptic mange) in three studies conducted in Germany (two studies) and Austria (one study). A total of 44 cattle were included in the studies, 12 in one study and 16 in each of the other two studies. Approximately eight weeks following initial induced infestation, cattle in each study were formed into replicates of two animals each on the basis of pre-treatment bodyweights. Within replicates the animals were randomly allocated to one of two treatments: ERI vehicle (control) or Eprinomectin 5% (w/v) ERI (1.0 mg eprinomectin/kg). Treatments were administered at 1 mL/50 kg bodyweight by subcutaneous injection in front of the shoulder once on day 0. The number of live mites in skin scrapings was determined prior to treatment and at weekly intervals for eight weeks after treatment. Severity of skin lesions was evaluated and scored when skin scrapings were taken. In all studies, animals were weighed before infestation and again prior to and at 56 days after treatment.     

The efficacy of oxfendazole administered as a bolus compared with a drench formulation

Summary

In a flock of 40 ewe lambs of the Texel breed the anthelmintic oxfendazole was tested in two different formulations, a 2.265 per cent suspension and a 4 gram bolus containing 151 mg active ingredient. All treatments were based on a dose rate of 5 mg / kg body weight. Faecal examinations and larval differentiations were carried out on the day of treatment and two and seven days later. No differences in efficacy were apparent between the two treated groups.

Oxfendazole in either formulation was 100 per cent effective in removing the major strongylids and trichostrongylids.

A lower activity was seen against Strongyloides papillosus.