A new benzimidazole anthelmintic, triclabendazole (CGA-89317) was found to be highly efficient against mature and early immature Fasciola hepatica infections in sheep. At the dose rate of 2.5 mg/kg the efficiency was 90 and 98 per cent against flukes aged eight and 12 weeks respectively. At 5 mg/kg the drug was 92 and 98 per cent efficient against flukes aged four and eight weeks respectively and 100 per cent against 12-week-old flukes. An efficiency of 93 and 98 per cent was achieved against one-week-old flukes and 99 to 100 per cent against flukes aged two to four weeks at 10 mg/kg. At this dose rate the drug had 100 per cent efficiency against six-week-old flukes. If the dose was increased to 15 mg/kg, 98 per cent efficiency was achieved one day after infection. Triclabendazole was equally efficient when administered orally or by intraruminal or intra-abomasal injection. The maximum tolerated dose of 200 mg/kg was established.

The efficiency of 2-cyclopropylamino-4, 6-diamino-s-triazine CGA-72662 (proposed common name: cyromazine) for the control of blowfly strike was tested in fly cage and field trials on sheep. The safety to sheep and physico-chemical properties of the compound as they relate to blowfly control were also assessed. When the sheep were thoroughly jetted with a solution of CGA-72662 containing 1g of active ingredient per litre, the mean incidence of fly strike in 7 field trials was reduced from 16.5% to 1.5% over a period of 9 weeks. The incidence of strike in the treated sheep in 2 insectary tests, which imposed levels of fly activity far in excess of that usually encountered in the field, was reduced from 93% and 73% in untreated sheep to 2% and nil respectively over a period of 8 weeks. Jetting with CGA-72662 solutions 100 times greater than the recommended concentration did not produce any side effects in sheep. Three treatments at twice the recommended concentration during the first trimester did not affect pregnant ewes nor their progeny. The compound was safe to use in combination with common anthelmintics and with sheep dips used for control of lice. CGA-72662 was stable in solution. No stripping occurred in dips and it persisted on wool for a considerable period. A satisfactory alternative to the organophosphorus insecticides has been found in CGA-72662, since it provided a substantial increase in residual protection against blowfly strike with a high degree of safety.

SUMMARY: The efficiency of the broad spectrum anthelmintic nitroscanate against tapeworm and nematode infections of dogs was tested in artificially or naturally infected dogs. The safety of the compound was also evaluated in acute, subacute and chronic toxicity tests. At the recommended single dose rate of 50 mg/kg given to the dogs with food, nitroscanate was 98% efficient against Taenia hydatigena, T. ovis and T. pisiformis. The drug was highly efficient against Echinococcus granulosus only at the dose rate of 200 mg/kg given twice but total elimination of worms was not achieved. Natural infections of Dipylidium caninum, Ancylostoma spp and Uncinaria stenocephala were totally eliminated from all dogs at the dose rate of 25 mg/kg or higher. Nitroscanate was 97% efficient against adult Toxocara canis at a single dose of 50 mg/kg. When the dose was repeated 24 hours later total elimination of both mature worms and immature worms in puppies aged 2 weeks was achieved. The repeated dose of 100 mg/kg removed 98% of early immature worms from puppies aged 3 days. The drug was 100% efficient against adult Toxascaris leonina at a single dose of 50 mg/kg and 90.5% efficiency was achieved against early 4th stage larvae by two doses of 50 mg/kg. Nitroscanate was not efficient against Trichuris vulpis. The drug was efficient for the removal of Toxocara cati and Ancylostoma tubaeforme from cats. Nitroscanate caused no serious symptoms of toxicity at dose rates up to 10,000 mg/kg in single or repeated doses in young or older adult dogs. The drug was safely given to dogs during pregnancy, to young puppies and to cats. The regular use of nitroscanate as a broad spectrum anthelmintic for the prevention and control of parasitic infections of dogs is discussed.

In a field experiment, moderate to heavy natural concomitant infections with immature and mature Fasciola hepatica were treated with triclahendazole at a dose rate of 10 mg/kg and an efficiency of 99.8% was achieved. Subsequent treatments of all susceptible farm animals at the same dose rate at intervals of eight to eleven weeks were carried out for 14 months; no patent infections could be detected in sheep and cattle during the whole period. Evidence is presented that pasture contamination with liver fluke was reduced to a negligible level for a further 12 months after the final treatment. It is suggested that, if regular treatments with triclabendazole are given within the pre-patent period of Fasciola hepatica infection for the whole season, the infection can be eradicated or reduced to such a low level that control of the disease could be maintained with less frequent strategic drenching for a considerable period.

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