Summer 2019 – Faecal egg count reduction testing time!

By Ginny Dodunski

Drench resistance testing can feel like those health checks we avoid or ‘defer’ for ourselves: It is not a pleasant job, we might not like the results and the changes we may have to make might be unpalatable.

But like those personal health check-ups, when you let them slide there is always that bit of doubt in the back of your mind, wondering what is really going on unseen, and the long-term cost of not knowing where you’re at?

And isn’t it a relief when you finally do get around to getting yourself looked at; the majority of the time the situation isn’t as bad as you might have feared, and even if it is, at least you now have a plan and course of action to get on with, instead of just worry.

So if you’ve not completed a faecal egg count reduction test on your place, or it’s been over 5 years since the last one, why not make 2019 the year that you ditch the niggling worry and get on with it!

Since the early 2000s, NZ researchers have led the way in studying drench resistance and how to manage it. We now have clear, practical strategies to help reduce further development of resistance on individual farms, but these do vary according to the start point: On farms with minimal resistance, continuing to use combination drenches with minimal changes to other practices may be entirely justifiable. On others, with impending severe resistance, simply switching products may not be enough.

It is near impossible to pick which of these categories a farm falls into just by the look or performance of their stock. Testing is essential.

The first step is to talk to your friendly sheep vet about getting started!

You will need to set aside a group of lambs to leave undrenched for a while to let their faecal egg counts build up to a reasonable level. They should not be left so long that they become noticeably ill thrifty; as long as all lambs have a positive egg count and most are into the mid-hundreds the test can commence.

In many areas it is important to hit the right time of the year for this work – in the mid and upper North Island if you wait until too far into the summer the worm species balance gets swamped by Barbers Pole worm. In most parts of the country, Trichostrongylus will dominate in later in the autumn. It is a waste of time and money to go through the whole process only to find you have no information about other the other worm species on your farm. Ostertagia (Teladorsagia) has been the most common drug-resistant worm nationally; this tends to predominate from the pre-lamb period until early summer.

In some North Island districts, you may be better to defer this year’s test from now until late November or early December, to hit the ideal period to get the worm species balance right.

Different veterinarians will have slightly different variations on the actual protocol of the test. The number one requirement is that larval cultures are performed on the pre-drench samples (to establish the species balance present at the start). Larval cultures should also be repeated on samples from all the groups of lambs where worm eggs were present after drenching, to see which species are surviving your drench treatment.

Once the results are in, your vet/animal health advisor will interpret the results and help you make a plan to keep protecting the status of the drenches you are using on your farm.