WE can no longer manage worms just by using drenches; pasture management is key.

Monitoring worm egg counts and drenching only when required reduces the exposure of the parasite to the drenches that still work. We know what drenches still work against the parasites in our animals by doing a faecal egg count reduction test (FECRT) every 3-5 years.

Using an effective drench like Tridectin reduces the number of worm eggs deposited on pasture by treated animals. The difference between 98 percent efficacy (average Tridectin efficacy), and 93pc efficacy (average abamectin-triple drench efficacy)¹ results in 3.5 times more resistant eggs on pasture. With a worm egg count of 1200 eggs per gram of faeces, a mob of 250 ewes (70 kg) will produce 42 million more eggs per day if treated with the drench that’s only 93pc effective¹.

Every time we use a drench we inadvertently select for resistant worms that survive the drench. To delay the onset of resistance, we’ve increased the use of combination drenches. Unfortunately most of these combination drenches contain Abamectin (table 1)², increasing the selection pressure for resistance against this molecule.

Avoiding the inclusion of the same active (eg abamectin) repeatedly in the program may require using more than one drench at the same time (concurrently), going down the race twice and including Tridectin, the only three way combination drench containing moxidectin controlling barber’s pole and small brown stomach worms for 14 days after drenching due to the persistency of moxidectin³.

For more information visit portal.tridectin.com.au and contact your local area sales manager from Virbac to assist you to design your worm management program.

References:
1: Skirting The Issues, Spring 2022; portal.tridectin.com.au (Virbac FECRT data 2018-2023)
2: APVMA Pubcris
3: Tridectin 3-Way Oral Drench for Sheep – label, APVMA Approval number: 83241

Table 1: