Ma Fisher

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.

Effect of sub-lethal doses of albendazole on the fecundity of Dictyocaulus viviparus

During an evaluation of the efficacy of prolonged low-dose albendazole therapy on nematode infections in calves, it was observed that a dose-rate of 2 mg kg-1 given daily for 10 days was highly effective at expelling Dictyocaulus viviparus, but smaller doses suppressed the faecal output of larvae without killing the lungworms. A more detailed study with four experimentally infected calves given 1 mg kg-1 day-1 for 10 days showed that faecal output of larvae ceased after six to eight days but resumed four to six days after the withdrawal of the drug. The albendazole-induced sterility was therefore reversible. A subsidiary study showed that the strain of parasite used was fully susceptible to albendazole.