After severe barber’s pole worm outbreaks earlier in the year, many local producers will be asking: is this the new normal, and how do we avoid these problems in the future?
Despite the spike in problems this year, the perfect storm of conditions for barber’s pole worm typically only occurs every few years and lasts for just a few months.
But before barber’s pole worm numbers start to rise in the spring months, it’s time to plan ahead by following some basic steps: recognise the signs of barber’s pole worm disease; plan an annual preventative and monitoring program; manage drench resistance; seek informed advice.
It’s important to recognise the signs of barber’s pole worm disease, so outbreaks can be quickly confirmed and managed.
As barber’s pole worms suck blood, and large burdens can develop rapidly, sheep deaths often occur with little warning.
Signs in live animals include anaemia (pale gums, skin and eye membranes) and weakness (collapse when driven).
When associated with factors such as the time of year, location and drenching history, experienced producers will suspect a barber’s pole worm problem.
Impending or actual outbreaks can usually be confirmed by the extremely high worm egg counts, seen only with barber’s pole worm.
If worm egg counts cannot be done immediately, a veterinarian can provide rapid confirmation and rule out other causes of sudden death.
As with all worms, long-term barber’s pole control requires a planned annual program, aimed at preventing sheep losses while maintaining the effectiveness of a range of drenches.
Barber’s pole worm numbers should be kept as low as possible before the usual seasonal increases in spring and early summer, to prevent the multiplier effect of large worm numbers.
Minimising worm numbers in ewes is especially important, as their natural worm immunity decreases for some weeks during lactation (a temporary immunological change).
As well as the risk of ewe deaths, the resulting contamination of pasture with worm eggs exposes their lambs to heavy barber’s pole intake.
Experience over some years will indicate whether routine pre-lambing drenching is necessary in a particular location, but a preventative drench is often justified with relatively low counts.
Lambs are especially worm-susceptible, and control programs should aim to keep burdens of all worm species low during the first year of life.
Pasture movements to prevent sheep from grazing pastures with large numbers of worm larvae reduce the need for drenching, but must be practical to implement.
Where options are limited, priority should be given to the most susceptible sheep classes (lactating ewes and young sheep).
The time that paddocks must be spelled before worm larvae will die off varies greatly between environment and seasons.
This may be as little as two months in hot tropical zones to more than six months during temperate winter periods.
In most cases, at least a three-month period is necessary for a worthwhile reduction in barber’s pole larval numbers.Expert local knowledge is needed for an effective annual plan.
Options for spelling that also allow paddock utilisation include cropping, and swapping with mature cattle or sheep confirmed to have low worm egg counts. (WormBoss provides a good discussion.)
Monitoring worm egg counts of sheep during barber’s pole worm risk periods is essential, given the potential for sudden and unpredicted outbreaks of barber’s pole disease.
Monitoring schedules vary with the location, season and sheep class, as well as the drenching and previous worm count history, but high-risk mobs may need checking every 3-4 weeks.
Worm control action for pre-emptive monitoring is indicated at much lower counts than for confirming barber’s pole worm disease, as the aim is to minimise developing worm burdens and prevent heavy pasture contamination by worm eggs.
The barber’s pole worm vaccine, Barbervax, has been especially useful in summer rainfall regions where frequent drenching is common and drench resistance a major limitation.
It is given at approximately six-weekly intervals over the barber’s pole worm risk period (typically five injections), and vaccination from mid-spring provides a significant reduction in worm egg counts over the major risk season.
The effect of the vaccine may be reduced where sheep are exposed to heavy intake of barber’s pole worms, but it has proved highly effective when supported by planned paddock management and monitoring of worm egg counts.
Sheep of all ages are susceptible to barber’s pole worm and deaths may occur in all classes, but sheep in good nutritional condition are more resilient to its effects.
The ability to minimise the adverse effects of all worm species is a further reason for maintaining sheep at Lifetime Wool recommended body condition profiles.
However, resistance to worms is largely genetic, and worm-resistant sheep have been bred or introduced by many producers for some decades.
The permanent reduction in susceptibility to worms (all species) is a sound long-term investment in barber’s pole worm management.
Drench resistance is a major impediment to barber’s pole worm control and, with no new drenches revealed by drug companies to be under development, sustainable control programs should aim to reduce the reliance on drenching.
Resistance has been reported to all drenches and, although this now includes the newer products, it is especially advanced in the older types.
As a general rule, combination products (two or more actives) are recommended, because they are more likely to be effective, and multi-active resistance takes longer to develop.
Of particular note, drench resistance typically reduces the period of effectiveness of long-acting products. (These products have a specific resistance development risk and should only be used with informed advice.)
Patterns of resistance varies greatly between properties, and without knowing the resistance situation on a particular farm, making drench choices is largely flying blind.
Drench resistance tests (comparing several drenches at one time) are recommended at about two-yearly intervals, but DrenchCheck provide a basic guide.
