High Worm Egg Counts
Sara Sutherland, BVSc, MSc, BSc (Agr)
The very unexpected rain in February was welcomed by all our farmers, even if it wasn’t welcomed by the organisers of Wings over Wairarapa. It should increase feed levels and keep crops going. The unusual moisture is also welcomed by some less desirable acquaintances, including parasites, flystrike, and fungal toxins.
Worm egg counts that we have done in clinic recently have been high. Warm, wet conditions favour the survival of worm larvae. This means that parasite levels can increase very quickly at this time of year. The infamous “Barber’s Pole worm” (Haemonchus contortus) is one species that can be particularly problematic under these conditions. In the Wairarapa, unlike other parts of New Zealand, we see Barber’s Pole in some years and not others. Unlike other worms that affect sheep, Barber’s Pole worm sucks blood directly, causing anaemia, weakness, lethargy and death. Female Barber’s Pole worms lay a lot of eggs, and it doesn’t take very long for those eggs to develop into adult worms.
Worm egg counts from faecal samples will tell you whether worms are present. We do these to see whether a group of animals needs drenching, or after drenching to make sure that your drench was effective. Unfortunately, worm egg counts will not tell you which worm species are present. This requires a larval culture which takes 7-10 days.
Worm resistance to drenches is common in New Zealand sheep and cattle. This makes it harder to control worms. The only way to tell which drenches are effective on your farm is to do a Faecal Egg Count Reduction Test (FECRT). These should be done every three to five years. Proper preparation is essential to get the most out of this test. Once you know which drenches are effective, your vet can help you make a plan of how best to control parasites, protect production and reduce costs.
Published Tuesday 28th of March 2017