Persistent efficacy of abamectin and doramectin against gastrointestinal nematodes of cattle

Objective To assess the persistent activity of injectable formulations of abamectin and doramectin against gastrointestinal nematodes of cattle.
Design Controlled slaughter study assessing residual efficacy.
Procedure Nematode-free calves were treated with abamectin or doramectin (each at a dose of 200 μg/kg) and infections then induced with repeated doses of infective larvae of Trichostrongylus axei, Haemonchus placei, Ostertagia ostertagi and Cooperia species. The duration of challenge ranged from 14 to 28 days. The calves were slaughtered at either 38/39 or 45/46 days after the treatments and nematodes recovered from the gastro-intestinal tract.
Results Significant reductions in numbers of O ostertagi occurred for both abamectin and doramectin treatments (> 93%) relative to counts in untreated calves, when challenge was administered up to 21 days after treatment. For T axei and Cooperia spp significant reductions occurred when the challenge occurred for 14 days after treatment (99%). Although differences from untreated animals were not significant, the results for H placei suggested high efficacy (> 85%) for up to 21 days for doramectin and up to 28 days for abamectin.
Conclusion There was no significant difference between abamectin and doramectin for any parasite at any challenge point, indicating that there is equivalent persistent activity of doramectin and abamectin against important gastrointestinal nematodes of cattle.     

Analytical determination of the distribution of flumethrin on the body surface of cattle following topical pour-on application.

By means of chemical analysis, the distribution behaviour of flumethrin was determined in the hair coat of cattle following topical pour-on application. Flumethrin was applied at 1 mg active ingredient (a.i.) kg-1 body weight along the backline of cattle. It was demonstrated that this compound could be recovered from all hair samples taken on Day 1 following application from dorsal, lateral, ventral and distal body regions in concentrations ranging from 670 to 1 micrograms a.i. g-1 hair, depending on the distance from the site of application. On Days 3, 5 and 10 after treatment, the corresponding concentrations were 125.0-1.5, 23.0-1.0, and 44.0-0.9 micrograms a.i. g-1 hair, respectively. When correlating these values to the body surface of cattle, it is evident that on all sample days and body regions, a concentration of more than 0.01 microgram a.i. cm-2 body surface was present. This amount of active substance is sufficient for effective acaricidal action, as shown by laboratory and field data.     

Titres After Leptospiral Vaccines

Abstract

Extract

Sir, — It appears that Drs Marshall et al.⁽¹⁾ Marshall, R.B., Manktelow, B.W. and Scholium, L.M. 1982. Standardisation of serology for leptospirosis. N.Z. vet. J., 30: 126–126. [Taylor &; Francis Online], [Web of Science ®] , [Google Scholar] have missed the cardinal point of our paper on an unusual serological response in calves after use of a leptospiral vaccine. ⁽²⁾ Marshall, R.B., Manktelow, B.W. and Scholium, L.M. 1982. Standardisation of serology for leptospirosis. N.Z. vet. J., 30: 126–126. [Taylor &; Francis Online], [Web of Science ®] , [Google Scholar] That point, of course, was that after use of one leptospiral vaccine, but not another, post-vaccination microscopic agglutination titres of calves were indistinguishable from post-infection titres, whatever the actual titres may have been.     

Leptospira interrogans serovar pomona vaccines with different adjuvants in cattle

Three groups of four heifers were vaccinated twice, 11 weeks apart. One group received a commercial pomona vaccine with aluminium hydroxide adjuvant, the second a similar experimental vaccine, and the third a Freund's compete adjuvant (FCA) vaccine. After 47 weeks, the heifers were challenged with at least 65 × 10⁸ virulent serovar pomona organisms.

All vaccinated animals resisted the challenge, and leptospirae were only found in urine from unvaccinated controls.

The outcome of the challenge was not predictable from microscopic agglutination, cold and warm complement fixation, and growth inhibition titres.

The FCA vaccine gave rise to considerably higher antibody responses than the two aluminium hydroxide vaccines, which gave similar responses.     

A comparison of diagnostic methods for the detection of bovine respiratory syncytial virus in experimental clinical specimens.

Virus shedding was monitored in nasal secretions of 12 calves experimentally infected with bovine respiratory syncytial virus (BRSV) using an antigen capture enzyme-linked immunosorbent assay (ELISA) detecting the nucleoprotein (NP) antigen of BRSV, by a polymerase chain reaction (PCR) amplifying the fusion protein of BRSV, and by a microisolation assay combined with immunoperoxidase staining for the F protein of BRSV. Under the conditions of this study, similar limits of detection and quantitative results were obtained from all three assays. BRSV was detected in nasal secretions of all calves for a minimum of 4 d. Virus shedding began on Day 2 after infection, peaked on Days 3-5, and was cleared in most calves by Day 8. The PCR, and to a lesser extent the ELISA, may detect virus shedding for a longer period after infection than virus isolation, possibly due to neutralization of the virus by rising mucosal antibody. Simulated environmental conditions likely to be experienced during transport of clinical field specimens markedly reduced the sensitivity of virus isolation but had a minimal effect on the results of the NP ELISA. Actual field transport conditions (overnight on ice) had minimal apparent effect on the results of the PCR assay. The less stringent specimen handling requirements, combined with low limits of detection, of both the nucleoprotein ELISA and PCR, indicate either of these assays are more suitable for diagnostic applications than virus isolation.     

Efficacy of moxidectin and other anthelmintics against small strongyles in horses

Objective To compare the efficacy of moxidectin to ivermectin, oxibendazole and morantel against some gastrointestinal nematodes in horses.
Design Faecal egg count reduction after treatment.
Procedure A farm was selected where the population of small strongyles in horses was known to be resistant to oxibendazole. Horses were allocated to treatment groups based on faecal egg counts. After treatment, faecal samples were taken up to 109 days after treatment and faecal egg counts estimated. Faecal cultures were used to estimate the contribution of small and large strongyles to the faecal egg counts at each sampling.
Results Moxidectin (0.4 mg/kg) suppressed faecal egg counts for 109 days after treatment in most horses compared to 40 days with ivermectin (0.2 mg/kg), 13 days with morantel (9.4 mg/kg) and less than 13 days with oxibendazole (10 mg/kg). Most of the faecal egg count was attributable to small strongyles based on faecal culture, although Strongylus vulgaris was present in some samples in low numbers. Oxibendazole resistance in small strongyles was confirmed and a less than expected efficacy of morantel was also seen.
Conclusion Moxidectin was highly effective in reducing faecal egg counts after treatment for at least 12 weeks and up to 16 weeks in most horses. These horses were infected with a population of small strongyles known to be resistant to oxibendazole and possibly morantel. The duration of the reduction in faecal egg counts after treatment with moxidectin (0.4 mg/kg) was at least twice that of ivermectin (0.2 mg/kg) and greater than four times that for morantel and oxibendazole.