Research into a vaccine against worm parasites to reduce reliance on chemical control has been carried out for a number of decades, however it is especially important in today’s era when drench resistance to barber’s pole worm in some parts of Australia has compromised the effectiveness of present control methods.
Barber's pole worm is considered the most significant parasite of sheep and goats globally, and is a major cause of sheep mortalities in summer rainfall and tropical climatic regions. Research at the Moredun Research Institute in Edinburgh (United Kingdom) has demonstrated that high levels of protection against barber's pole worm can be obtained from immunity induced using an antigen derived from gut proteins of the worm, but it has not proved possible to produce this antigen by recombinant DNA-based technology.
Importing this type of vaccine into Australia is not possible due to biosecurity risks, so the Department of Primary Industries and Regional Development, Western Australia’s Albany laboratories has developed a feedlot system where large numbers of lambs are deliberately 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 laboratories. All processes - field and laboratory - operate under the audit-backed Good Manufacturing Practice system for manufacturing. Barbervax is now being exported to South Africa.
Use of Barbervax
Barbervax is now registered for use in lambs, hoggets and ewes. Before the high risk barber's pole season starts, sheep are given three ‘priming’ vaccinations three to four weeks apart to confer immunity, and then a series of vaccinations six weeks apart over the barber's pole worm-risk season (in the New South Wales Tablelands, generally December to April) to maintain that protection. Usually for lambs the first vaccination will be given at lamb marking, and the second injection three to four weeks later, and the third generally at weaning. Protection against the development of significant barber's pole burdens will then last for six weeks, when another vaccination will be needed. In most cases, a drench at weaning would also be given, to ensure that the vaccine is not overwhelmed by existing barber's pole burdens, and to control other scour worms such as Black Scour Worm (Trichostrongylus), and Brown Stomach Worm (Teladorsagia).
For older sheep vaccinated as lambs, some immune memory persists so that the first injection in the second year restores the immunity gained from lamb vaccination, with six-weekly boosters from then on. With ewes not previously vaccinated, pre-lambing vaccinations are required to ‘prime’ the immune system as for lambs.
Extensive trial work funded by Meat and Livestock Australia (MLA) shows that the vaccine provides between 75 and 95% protection. In trials in New South Wales (NSW) and Western Australia (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 would have died of anemia 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 five month season typically reduces the need for two to five short acting drenches or one long-acting drench.
The vaccine does not 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. Sheep in poor body condition or showing signs of worms may not respond fully to vaccination, and may require additional support.
Production of Barbervax
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.
Consequently, a manufacturing system was developed using a feedlot to produce large quantities of barber's pole worm in lambs at slaughter, with no ill-effects regarding their health, and then produce a barber's pole worm vaccine product for purchase by sheep producers, at the Albany laboratories. 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.
For more information go to barbervax.com.au