The release in October 2014 of the new ‘Barbervax’ vaccine against barber’s pole worm gives the sheep industries a new weapon in the fight against an old foe. This provides a major alternative to drench-based control, and will help manage drench resistance. After many years of research in Scotland by the Moredun Research Institute, and recent collaboration with the Department of Agriculture and Food in Western Australia, the world’s first sheep worm vaccine, and the first vaccine for a gut dwelling worm parasite of livestock, has been produced.
Barbervax will be of particular benefit in the major barber’s pole-endemic regions, where frequent drenching is usually necessary to prevent sheep deaths, and where anthelmintic resistance has severely reduced drench options. The vaccine was launched in mid-October 2014 in Armidale in the NSW Northern Tablelands, where resistance to the majority of drench classes occurs on most properties, and long-acting drench types often no longer provide prolonged protection.
Barbervax is now registered for use in lambs (editor's note, December 2015—the vaccination is now registered for sheep of all ages), and is given as a series of 4–5 subcutaneous injections of 1 ml, at approximately 6-week intervals to cover the barber’s pole worm-risk season (in the Tablelands, generally December to April).
In lambs , It is important to understand that the first two vaccinations are not able to provide protection, but they prime the lamb’s immune system so that protection occurs following the third vaccination, and lasts for at least 6 weeks. Further vaccinations need to be given each 6 weeks while there is a barber’s pole worm risk.
In most cases, the first vaccination will be given at lamb marking, and the second injection 3–5 weeks later. The third vaccination is generally at weaning, in most cases with a drench to ensure that the vaccine is not over-whelmed by existing barber’s pole burdens, and to control other worms such as Trichostrongylus (black scour worm). Two more vaccinations are given at 6-weekly intervals after the third vaccination.
Extensive trial work funded by Meat and Livestock Australia shows that the vaccine provides between 75 and 95% protection. In trials in NSW and WA, vaccinated sheep maintained low barber’s pole worm egg counts over summer and autumn, when worm egg counts in unvaccinated control sheep reached many thousands of eggs per gram, and many controls (unvaccinated lambs) would have died of anaemia without a salvage drench. Because the number of barber’s pole worm larvae on the pasture remains low due to the reduced worm egg output, even the small percentage of sheep that do not respond to vaccination (as occurs with all vaccines) are not faced with significant worm larval intake. Computer modelling indicates that provided the vaccine is more than about 70% effective, and the priming vaccinations are given before heavy barber’s pole burdens develop, the vaccine course over a 5-month season typically reduces the number of drenches needed; 2–5 less short acting drenches or one less long-acting drench would be given.
The vaccine does not completely replace the need for drenches, or the need for programs to control scour worms. Worm egg counts should be used to check that heavy barber’s pole burdens are not present when vaccine protection is being established at the second or third injection, and monitored periodically to ensure low counts are maintained. Pasture planning to avoid significant barber’s pole intake will further enhance the effectiveness of vaccination, and breeding for worm resistant sheep provides longer-term worm control. Sheep in poor body condition or showing signs of worms may not respond fully to vaccination, and may require additional support.
Vaccines against livestock worms have been a major research subject for many decades, and the only other anti-worm vaccine available is against the lungworm of cattle, developed in the 1950s. Research at the Moredun Research Institute over more than 20 years showed that injecting proteins (worm antigens) extracted from the intestinal membranes of barber’s pole worm into sheep could provide high levels of protection against barber’s pole infections. However, the protective effects could not be reproduced when the specific proteins were produced in DNA (recombinant) systems, which are used for modern vaccine production.
The question then was: is it feasible to produce the large quantities of adult worms needed for a commercial vaccine by deliberately infecting sheep? Work at the Department of Agriculture and Food WA’s Albany laboratories has led to a feedlot system where large numbers of lambs are infected with barber’s pole larvae—with no ill-effects on the sheep. The worms are extracted from the gut after the lambs are sent for slaughter, and protein antigens from the worms are used to produce the vaccine in the Albany laboratory. All processes—field and laboratory—operate under the audit-backed Good Manufacturing Practice system for manufacturing.
Barbervax production will be increased in coming years from the first 300,000 doses (sufficient for 60,000 lambs, of which all has been sold), for use in Australia. Eventually, the vaccine will be marketed overseas for situations where barber’s pole cannot be easily or sustainably controlled without the excessive use of drenches. Registration to use the vaccine in yearling and adult sheep will also be sought (editor's note, December 2015—the vaccination is now registered for sheep of all ages). Trials indicate that some immune memory persists so that the first injection in the second year restores the immunity gained from lamb vaccination, with 6-weekly boosters from then on. Trials are proceeding in goats to confirm previous encouraging results. The vaccine will not be a ‘silver bullet’, but used in a monitored control program it is expected to provide a significant new approach—at a competitive cost—to control of a very significant parasite.