The recent good rain in the north of the state will have stimulated worm activity, in particular Haemonchus. We have seen a few cases in the New Year where worm egg counts are already at very high levels (3000 epg plus mean), along with an increased number of properties where drench thresholds are being exceeded. Not all sheep producers are finding themselves in the same situation, however. Those that have had consistently low worm burdens over the spring period are typically remaining that way for the moment—it will take a period of time for the worms to reach worrisome levels given the low starting point, particularly when combined with good grazing management. Given the above scenario is not uncommon this season it is important for graziers to establish the current “state of play” within their sheep so that unnecessary drenching can be avoided. The practice of administering drenches, “just in case” also places additional pressure on selection for drench resistance whilst pasture refugia levels are low.
Nematodirus (Thin Necked Intestinal Worm) have been identified in lambs at an increased frequency over the past month following the hatching of their “drought resistant” eggs. Egg output from this worm variety is low, thus drench trigger levels are somewhat less than the major worm species. The highest count identified in the VHR laboratory this season has been a mean WEC of 350 epg, the submission originating from the Coonabarabran district. Heavy infestations of Nematodirus will cause intense scouring in young sheep, often failing to resolve despite effective drenching. Sheep typically develop a strong immunity to this worm species by 18 months of age.
Worm counts have been steadily coming in. There has been some Barber’s pole worm (BPW) picked up in some reports (80–95% on those that have requested typing), with a range of 0–440 epg on reports received to date. No production issues in any of those properties that have had BPW.
We have advised producers to re-test in 4–6 weeks times to ensure that there are no worm build ups at that time.
In the western part of the Riverina LLS there have been mixed counts observed in Wormtests ranging from a 0 egg count to counts as high as 920 (no larval diff available).
Recent scattered storms and mild mid-summer conditions across the area have created short green pick which may lend itself to larval pick-up in sheep and lambs grazing these areas. Producers concerned about growth rates, weight loss or scouring should consider conducting a Wormtest.
One 84 year-old grazier describes it as the best season he's seen; another gave it 11 out of ten. It certainly doesn't look much like our usual summer, with green feed a foot high and showers or heavy dews almost daily. No surprises then that barber's pole worms are going gang-busters. There have been some significant losses where sheep were last drenched in early November. Other producers were misled by low worm egg counts in early December, and returned from a week at the coast over New Year to find crook sheep. There are marked differences between paddocks on properties in the level of contamination and hence re-infection and this is a challenge when it comes to monitoring for worms at present.
Sheep are doing well, with scouring at a low level compared with most years. A couple of cases of scouring weaners were caused by nematodirus (thin necked intestinal worm), another was due to coccidiosis, and another involved a bacterial infection. These are all best diagnosed with a post mortem examination.
"How many of your sheep got flystruck?" has overtaken "How much rain did you get?" as the topic of conversation in the district. An old Ag Department video on fly strike in sheep talked about the "three costly days", the time taken from being struck to serious illness and death from blowflies. It sets the benchmark at present for how frequently you need to be inspecting sheep, if they aren't jetted or "Clik'd". One truck load of crossbred lambs that was weighed and drafted for sale had twelve lambs fly-struck by the time they were transported three days later.
Rams, including polled British breeds, have suffered deep fly-struck wounds after fighting. The fever associated with these infections will cause temporary infertility lasting several weeks. With autumn joining imminent, frequent inspection and preventative treatments are required, especially with those rams that have little or no wool on the poll to aid retention of blowfly chemicals.
Here on the Monaro we have seen very few worm tests done over the summer period. The reason for this, I suspect, is that we have had a remarkably wet summer with mostly mild temperatures—perfect conditions for worms—and most farms are giving a second summer drench routinely.
In the worm tests that have been done we have seen some extremely high egg counts. These tests have been done following the death of several sheep, and the suspicion has been for a Barber’s Pole infestation. On one property that had deaths of several Dorper Cross ewes we found egg counts ranging from zero in the older sheep, up to 37,400 epg in the young sheep. The average for the mob was 5,916 epg with 97% Barber’s Pole worm. A second property that was also experiencing deaths in the Merino ewes and lambs had counts ranging from zero to 21,600 with an average of 3,944 epg. The sheep that were found to have the highest egg counts were post mortemed and huge numbers of barber’s pole worms were seen in the abomasum in both cases. Neither of these properties had conducted a summer drench as they had never experienced a worm problem in summer previously thanks to our normally hot, dry conditions.
We are enjoying the best summer down this way that has been seen for decades according to many producers! Along with the feed, as predicted last month, there is an abundance of Haemonchus.
We have been conducting a drench resistance trial over the last few weeks involving a number of properties. Apart from starting to reveal some concerning responses to drench actives, the testing has also given us some interesting WECs. Mean pre-drench test WECs ranged from 216–2136 epg over 8 properties (individual counts 0–6,040 epg).
Highlighting how pro-active farmers need to be with their worm control in conditions such as these, the repeat WECs on the undrenched group on each property, 2–3 weeks after the initial WECs were done, ranged from mean 657–6,090 epg. (Individuals ranged from 0–18,800 epg). The most dramatic increase was in a mob of 4-month old merino lambs, which had already been drenched at marking. They went from mean WEC 288 epg to 6,090 epg.
The vast majority of the worms are Haemonchus (82–100%), with one property having ~50% Haemonchus/50% Trichostrongylus.
The ensuing discussions with producers have highlighted what can be a significant discrepancy between where producers think their mobs are at, and what WECs reveal. The need to emphasise how important it is to use at least two active ingredients when drenching has also become very evident.
The incidence of fly strike has risen dramatically over the last 2 weeks with a significant proportion of 4–6month old lambs being affected with body strike on some properties. Merinos and Dorpers top the most popular list for flystrike.
The recommendations therefore are: assume nothing, when in doubt, Worm Egg Count; always use multiple actives when drenching; be vigilant with respect to flystrike; and enjoy the feed—we still have February to come!
The early part of the summer in the western part of the Murray region was very hot and dry.
Very few worm egg counts, but they were all low.
Rain in early January may increase the larval availability on pastures but it may also stimulate activity and early death of those larvae.