Could a fungus be the big breakthrough in the fight against parasites?
can save your animals from worms
It’s almost 30 years since Australian scientists first identified a fungus that had the potential to fight parasites in livestock.
It’s taken all that time for Sydney company International Animal Health Products (IAHP) to research, create, patent and trademark a successful product. It’s now at the final stage, awaiting approval from the Australian Pesticides and Veterinary Medicines Authority.
Their product – its name will be announced when it gains approval – uses Duddingtonia flagrans to fight parasites. It is a naturally-occurring fungus found all over the world.
Spores are fed to livestock in feed supplements and these are passed in manure onto pasture. They don’t affect a parasite burden already living in the animal’s gut. The fungus then trap and eat the larvae of the worst parasites to affect sheep, cattle, horses and goats, including: • barber’s pole • roundworm • Ostertagia (brown stomach worm) • stomach hair worm • Cooperia • Nematodirus (thin/thread necked worm)
Chris Lawlor of IAHP says animals should be drenched. They can then be moved onto ‘clean’ pasture (ungrazed by the same species for at least six weeks), and fed the spores in a daily ration to help reduce larvae. In time, if used properly, it can reduce drenching frequency and slow resistance to drench products.
The fungus will be available as a concentrate for feed mills and vets, and as an over-the-counter product. It will be sold in NZ but details won’t be available until final approval is granted.
One of the biggest problems facing farms of all sizes is drench resistance, and one of the answers is to stop drenching.
Warm, wet summer weather can be the best and worst of times if you have bouncing lambs, kids and calves running around your block.
The conditions that bring lots of grass also create the ideal conditions for killer parasite burdens.
We all like quick, simple fixes. For the past 40 years or so, that has meant picking up a bottle of drench and chemically killing the problem.
But the result is that most farms in NZ now have parasites that are resistant to all the drench products. The chemicals in drench have gotten stronger and more sophisticated over time, but there is still an increasing population of parasites that survive.
Science is almost at the end of its abilities to supply new chemicals. That has meant farmers have had to find new strategies.
One is to make livestock more resilient by breeding animals that can thrive when they have a worm burden.
Another is to offer refuge to the very worms you've spent decades trying to kill off.
'Refugia' is a worm population not exposed to drenching. It means you deliberately keep a core population or refugia of genetically susceptible-to-drench worms on your block. The three common ways to do it are: leave all or part of a flock or herd undrenched at certain times;
follow drenched younger livestock (which have lower immunity to worms) with undrenched, higher immunity adults – the susceptible worms shed by the adults ‘dilute' the population of resistant parasites left behind by younger livestock by contributing to the next worm population;
leave a proportion of younger livestock undrenched, at each drenching.
Another option is to drench a herd or flock and return them to the same infected pasture they previously grazed, for a week or so. This ensures that susceptible worms in that pasture mate with any worms that survive drenching, so the number of resistant worms in that pasture falls. After a week, the animals can then be moved to ‘clean' pasture. Clean pasture is where another type of livestock have been grazing, for example, sheep are put
If we aren't strategic in how we drench, we kill all the non-drench-resistant worms and leave behind those that are resistant to drench.
in a paddock previously grazed by cattle. The cattle will have ingested any sheep parasite eggs in the pasture. Sheep parasites can't complete their lifecycle in cattle and die off instead of reproducing, leaving the pasture ‘clean'.
How offering refuge helps you
Refugia means there are always some susceptible worms left behind to reproduce. When non-resistant (susceptible to drench) worms still remain in the population base, the gene frequency for resistance will be diluted.
The research to follow was conducted on sheep, but the principles are relevant for all livestock.
What happens when you don’t drench all your livestock
A field trial funded by Beef + Lamb New Zealand showed that using refugia as a management tool can dilute resistant worms on pasture. Leaving 10 per cent or 20 per cent of lambs undrenched results in a significantly lower level of drench resistance in the worms on that pasture, compared to when all animals were drenched.
Dr Dave Leathwick of Agresearch compared the resistance status of worms shed by nine different mobs of Romney lambs. All nine mobs of lambs (20 lambs per mob) were uniformly infected with a mixture of albendazole-resistant and susceptible parasites.
Different proportions of the mob were left undrenched (either 0 per cent, 10 per cent or 20 per cent). After grazing a 'clean' paddock for seven weeks, the lambs were again drenched and moved to a second set of ‘clean' paddocks, again for seven weeks.
The worm populations created by the different treatments were measured by putting fresh ‘parasite-free' lambs on the blocks three weeks later to sample the worm populations. Drench resistance was measured using larval development and egg hatch tests.
The results are in the graph below.
What they found
Drenching all lambs increased resistance four-fold from original levels.
When 20 per cent of lambs were left undrenched, resistant worms on pasture were diluted 10 times compared to when all lambs in the mob were drenched.
The biggest negative from leaving some stock undrenched was that the level of larvae on the pasture increased in the trial. However, some increase has to happen for refugia to work. The essence is to allow enough worms through to dilute the resistant ones without significantly compromising productivity.
How to get started
You need to develop a plan with help from your veterinarian. Things you need to know include:
The drench resistance status of the worms on the farm. It has been calculated that the proportion of animals required to be left undrenched goes up dramatically as drench efficacy goes down. If a drench is 99.9 per cent effective then 1 per cent left untreated is probably enough. If the drench used is only 95 per cent effective then closer to 30 per cent untreated is required to give the same dilution of resistant worms. Sheep/cattle ratio and your stocking rate. Key risk periods to stock from parasitism so you can work out the best time of year for some stock to go undrenched.
Current ewe management/drenching policy (ie, will you have undrenched adult ewes that can follow newly-drenched lambs).
Feed quantity and quality.
7 general principles to follow
Where possible, find a solution that
When non-resistant worms remain, the gene frequency for resistance will be diluted.