M. J. Hutchinson

EVALUATION OF FLEA CONTROL STRATEGIES USING FIPRONIL ON CATS IN A CONTROLLED SIMULATED HOME ENVIRONMENT

Three groups of six cats were kept in similar carpeted pens in which a self-replicating population of Ctenocephalides felis had been established. One group was left untreated, but the other groups were treated every 28th day with 0.5 ml of a 10 per cent fipronil spot-on formulation, and the cats in one of the treated groups also wore a methoprene collar. No fleas were found on any of the treated cats, either during the first 13 weeks of the study, when heavy flea burdens were developing in the control pen, or over the next 11 weeks when a declining number of fleas was present on the control group.

A NOVEL APPROACH TO FLEA CONTROL ON CATS, USING PYRIPROXYFEN

Pyriproxyfen is a new insect growth regulator with potent activity against developing stages of the cat flea, Ctenocephalides felis. To determine its duration of action after application as a spot-on topical treatment, 20 cats were allocated to two groups. One group acted as untreated controls, and each cat in the other was given a single dose of 1 mg/kg pyriproxyfen. Each cat was infected with fleas at weekly intervals and caged. Eggs were collected and their viability determined as a measure of the effect of the agent on adult fleas. The effect of the transfer of pyriproxyfen from each cat to its immediate surroundings was monitored by observing the development of fertile flea eggs placed on samples of blanket taken from each cage. Results from untreated control cats showed that the experimental conditions were favourable for the lifecycle of the flea. Flea reproduction on treated cats was inhibited completely for seven weeks and substantially for at least a further two weeks. Blankets used by cats treated up to two weeks previously prevented flea development entirely and substantial control was still achieved up to four weeks after treatment.

Evaluation of flea control programmes for cats using fenthion and lufenuron

Four groups of six cats were kept in carpeted pens similarly infected with Ctenocephalides felis. One group was left untreated, but the other groups were treated every 28th day with either an insecticide (fenthion at 30 mg); or an inhibitor of insect development (lufenuron at 133 or 266 mg) or with both. A sudden upsurge in the numbers of fleas occurred on the control cats after 50 days. At this time, the three control strategies had reduced the counts by 91.3, 72.5 and 98.6 per cent, respectively. Thereafter, welfare considerations demanded the limitation of the flea burden on the control cats, but conditions were shown to be favourable for flea development throughout the study. The mean numbers of fleas on the treated groups after six months were 1.2, 11.0 and 0.4, respectively. After this, in addition to the fleas acquired in the pen, the cats were each infected weekly with five fleas to mimic roaming animals introducing extraneous fleas into the home. This produced no obvious effect on the counts and the mean values three months later were 0.5, 11.0 and 0.2, respectively. None of the strategies eradicated the flea population but they all reduced the numbers considerably and worked equally well whether or not small numbers of new fleas were introduced into the system. Significantly lower flea counts were maintained in the early and later stages of the study by the strategies including the insecticide.

Studies on the control of Toxocara canis in breeding kennels.

The control of Toxocara canis was investigated in naturally infected unweaned puppies. Anthelmintic treatments were administered to three litters of pups at 2, 4 and 6 weeks of age. When either a new combination anthelmintic containing febantel, pyrantel embonate and praziquantel or fenbendazole was used, the faecal egg output over the first 7 weeks of life was reduced by more than 80% and worm burdens by over 90%. In contrast, piperazine adipate had no appreciable effect on T. canis egg output, even though worm burdens were reduced by 86% by 7 weeks of age. In a further trial using three litters, the worm burden of pups treated with the combination anthelmintic was profiled before and after the 2 week dose and after the 4 week dose. Although worm numbers were substantially reduced by treatment, there was evidence of significant reinfection taking place throughout the control programme. It is concluded that more potent anthelmintics can provide longer term benefits by reducing the numbers of T. canis eggs shed into the environment, but that multiple dosing remains essential for this purpose.

Compatibility of the programmed use of doramectin with lungworm vaccination in calves

DONALDSON, L. E. (1986) Veterinary Record 118, 661 GEISERT, R. D., FOX, T. C., MORGAN, G. L., WELLS, M. E., WETTEMANN, R. P. & ZAVY, M. T. (1991) Journal ofReproduction and Fertility 92,475 HASLER, J. F., BOWEN, R. A., NELSON, L. D. & SEIDEL, G. E. Jr (1980) Journal ofReproduction and Fertility 58, 71 HASLER, J. F., McCAULEY, A. D., LATHROP, W. F. & FOOTE, R. H. (1987) Theriogenology 27, 139 IRELAND, J. J. & ROCHE, J. F. (1982) Journal ofReproduction and Fertility 64, 295 LINDNER, G. M. & WRIGHT, W. Jr (1983) Theriogenology 20,407 LOWMAN, B. G., SCOTT, N. A. & SOMERVILLE, S. H. (1976) Condition scoring of cattle. Revised edition. East of Scotland College of Agriculture, Bulletin 6 NELSON, L. D., ELSDEN, R. P. & SEIDEL, G. E. Jr (1982) Theriogenology 17, 101 (Abstract) NORTHEY, D. L., BARNES, F. L., EYESTONE, W. H. & FIRST, N. L. (1985) Theriogenology 23, 214 (Abstract) REMSEN, L. G., ROUSSEL, J. D. & KARIHALOO, A. K. (1982) Theriogenology 17, 105 (Abstract) ROBINSON, N. A., LESLIE, K. E. & WALTON, J. S. (1989) Journal of Dairy Science 72, 202 ROCHE, J. F. & IRELAND, J. J. (1981) Endocrinology 108, 568 SREENAN, J. M. & DISKIN, M. G. (1983) Veterinary Record 112, 517 WILTBANK, J. N., HAWK, H. W., KIDDER, H. E., BLACK, W. G., ULBERG, L. C. & CASIDA, L. E. (1956) Journal ofDairy Science 39,456 WRIGHT, J. M. (1981) Theriogenology 15,43

Evaluation of the effect of the fenbendazole sustained-release intraruminal device on the immunity of calves to lungworm

Each of 10 set-stocked calves was given a fenbendazole sustained- release intraruminal bolus at turnout for the control of parasitic bronchitis while a group of 10 similar calves was left untreated. The respiratory rates of the control calves were not greatly increased during the grazing season, but persistent coughing was evident from early July when they all had patent lungworm infections. Only occasional coughing was reported from the bolus-treated calves except for a transient increase in its frequency in late September. In mid-August, one of the treated calves was passing lungworm larvae and when they were housed six of the 10 had patent infections. In August tracer calves picked up an average of 23.5 lungworms per day from the control paddock but only 2.1 from the paddock grazed by the treated calves. In September the corresponding figures were 7.6 and 19.2 lungworms per day, respectively, from the control and ‘treated’ paddocks. After housing, the post mortem worm counts after an experimental challenge with Dictyocaulus viviparus larvae were reduced by 99.2 and 98.7 per cent (P<0.0001), respectively, for the control and bolus-treated calves in comparison with weight-matched parasite-naive calves. Thus, despite a relatively low level of challenge during the grazing season, the treated animals had developed a considerable degree of protective immunity.