Worm egg count results from the New England region over the last month continue to remain in the low to moderate range in the majority of cases, however some properties have recorded high mean counts (in excess of 1000 epg). Haemonchus are typically the predominant species in culture results. Daytime temperatures are now favourable for larval development; however the lack of rain to date will have prevented this process from taking place. A meaningful rain event (15 mm plus), combined with warm days and absence of frosts will kick-start worm activity and pasture growth. Let’s hope that happens sooner rather than later!
Liver fluke assessment and treatment should be made over the August/September period on those properties known to have a history of the parasite. Triclabendazole (TCBZ) is the treatment of choice in sheep (only drug effective against all stages of liver fluke), however there has been a number of properties identified in the last few years in the New England with genuine TCBZ resistance within the resident liver fluke population. This is obviously of great concern to the affected graziers (chemical control now limited to closantel and Nilzan®, both ineffective against early immature fluke), however producers “downstream” are also at risk of acquiring this drug resistant parasite, along with those purchasing stock from affected properties. Graziers need to be mindful of this fact – if they have any suspicion that TCBZ may not be effective, or wish to confirm efficacy, then a pre and post treatment fluke egg count should be performed.
Repeated sole use of TCBZ is ultimately very selective for drug resistance. In circumstances where multiple fluke treatments are required over the course of the year in sheep I suggest that producers consider the use of closantel in Spring, when immature fluke are of lesser concern.
Worm tests have been far and few for this past month.
The few properties that have tested have reported counts less than 300 epg. All of the larval differentiation has come back to the black scour worm and oesphagostomum.
One producer had experienced some deaths in some of his 3 year old ewes due to trichostrongylus but the problem was soon alleviated with the aid of a suitable drench.
Producers have been made aware via a regular animal health radio update to be mindful of worms and to move mobs as necessary, along with undertaking wormtest counts to avoid any issues this spring.
In the Narrandera and Hay areas over the past month, there has been a variety of results. The worst counts seen were in lambing ewes with egg counts of 5600. This was associated with scouring, weakness and death. In general, counts have been low, but the variations seen underpin the need for individual farm monitoring and advice rather than relying on generalisations.
With a mild end to winter and a warm, wet start to spring, producers have started doing worm egg counts in earnest. Egg counts are on the rise, most counts have been between 200 and 500 eggs per gram, although one property had a count of 1720 in their weaners. Despite these moderate to high counts, most producers are reporting that their sheep and lambs are in good condition, and are rarely reporting any scouring, weight loss or deaths. I suspect that this is due largely to the good feed most producers had in their pastures over winter, giving animals more resilience to their worm burdens.
I would recommend that those producers who are planning on doing a worm test are also requesting a larval differential. In those tests that have had differentials done we have seen Haemonchus (Barber's Pole Worm) counts of up to 85% on some properties. Given the mild, wet conditions this spring has brought, I expect we will see more reports like this.
I am still looking for Monaro producers to participate in our drench resistance trials, especially in the Bombala region. We are looking for farms with at least 90 weaners of an even line that have not received any drench or a recent drench. We provide the testing kits, drench, labour and the tests are performed free of charge. Please call either the Bombala or Cooma LLS office if you are interested.
After a brief winter respite, barber's pole worms are again affecting adult ewes. The current cases have occurred in mobs that showed typical barber's pole worm symptoms in the autumn, and have continued to graze on the same pastures. A pre-lambing drench with closantel suppressed the worm during lambing, but symptoms were again apparent seven weeks later. While this current worm infestation is due to larvae that survived the winter on pasture, average daily temperatures will now allow any eggs being pumped out to hatch. If you had trouble with barber's pole in the autumn, keep a close watch on those mobs, and on any sheep now grazing paddocks you know were contaminated at that time.
Apart from those properties with this history of barber's pole in autumn/early winter, worms continue to lay low on most properties. Black scour worms now make up the majority of the larvae hatched from faecal samples, but the overall worm egg counts are low. Most avoided the need to give a drench at lamb marking, and will next handle the drench gun for a first summer drench.
Only a few properties have checked on liver fluke lately, with fluke egg counts nil to low. This probably reflects the amount of closantel used for barber's pole control in the autumn (closantel kills late immature and mature liver fluke as well), plus our bumper autumn and early winter when sheep were able to avoid grazing low-lying, fluke-prone areas.
A run of warm spring days and a forecast of imminent rain signals the need to apply blowfly control chemicals during lamb marking and mulesing. The first cases of lambs struck after mulesing are about a fortnight earlier than usual.
While not strictly a parasite issue, selenium deficiency is causing widespread concern in lambs this spring, associated with lush clover pastures. Selenium in drenches and vaccines only gives about six weeks protection. Selenium deficiency may interfere with immunity to worms in young sheep.
After a dry finish to the winter there are not the clinical problems with parasites that we might have expected.
There are a few more merinos with scours than crossbreds.
Worm egg counts are variable but mostly are fairly low, particularly in sheep that had an effective summer drench or were monitored with low count counts. The odd high counts include some very high levels.