12 April 1996


A RECENT study directly comparing the persistence of Ivomec Pour-on and Cydectin Injectable under the same conditions showed little difference between the two despite the claim of longer persistence for Cydectin, reports Signets Beef and Sheep Notes.

Furthermore, a recent study conducted in South America comparing injectable Ivomec, Dectomax, Abamectin and Cydectin under real farm conditions concluded there was no practical difference in the persistence activity between any of these products as judged by reduced faecal worm egg counts. The issue of persistence is complicated probably because no standard protocol exists to test the persistence of these products.

All products (see Table 2) have the same mode of action against the parasites and are considered to be in the same anthelmintic group – the avermectins.

Always use these products in accordance with the data sheet and seek vet advice. For all programmes in the Table 2 animals must be set-stocked, all in the group treated, and no untreated animals added to the group.

lImmunity to worms depends on adequate exposure to infection. The continuous prolonged treatment with ivermectin may in-crease the vulnerability to re-infection once the bolus expires because of a failure to develop adequate immunity. Animals may be at risk if they are grazed on heavily contaminated pasture the following year. Manufacturers of Dectomax warn that should lungworm occur late in the season, then 0 and 8 week treatments may not be protective.n