'Wormwise' - Time to move on

By Dr Clive Dalton

Launch
'Wormwise' was formed to come up with a 'National Strategy' to combat the rising resistance of internal parasites in sheep and cattle to the chemicals used in drenches to kill them. It's launch in 2006 was sponsored by Meat & Wool NZ, the NZ Veterinary Association, the Ministry of Agriculture and Forestry and Agcarm. It is still in business with the same objectives, but its work and promotion seems to have gone quiet.

Getting the message out


The Wormwise message was spread by farmer meetings, field days and a seasonal newsletter with Number 1 in May 2006, and the last one I have is Number 9 in September 2009. Wormwise also appointed a national manager (a veterinarian) to keep up the momentum and motivate farmers into action. There have now been two of these.

What's gone wrong?
There's now big concern that the 'national worm management strategy' may have run out of gas, while the problem certainly has not gone away. I believe the programme has done well to last this long, and the organisers should not be surprised at its current status if they looked at what happened to the many other national farming campaigns.

Campaign stages
In my MAF days I worked on many campaigns that went for a while then tailed off, no matter how much money or resources were thrown at them. There were always these well-recognised stages, listed in rough order of priority:

• Identify a problem. Report and publicise it as a 'crisis'.
  
• Brief the Minister to get political traction, and make sure he gets political kudos from it.
• Get boffins to push the campaign stressing that ‘this has got to be good for farmers’.
• Use panic to get the attention of farmers via the media who are always hungry for 'news', especially if it's new and generally bad.
  
• Keep the panic going to extract a budget from the bean counters, and keep complaining (through the media) that it’s never enough, and if you don't get more, an even greater disaster will hit the industry.
• Prepare an information ‘package’ and a ‘campaign’. Hire costly PR help, or build your own communications team with a ‘champion’ for the programme.
• Organise 'delivery of the programme' with publications, press releases, newsletters, videos, print and TV adverts, field days and seminars.
• Have media-trained 'experts' in your team available for interview at all times.
• Always have a press package available.
• Nowadays, set up a website - and forget to keep updating it or run out of ideas over what to put on it. Keep repeating the same old message.
  
• Keep informing the knowledgeable, and preaching to the converted.
  

Initial flush of success
Things go well for the first 18–24 months, and then they start to go flat. It’s like a slow puncture, which you try to ignore hoping it will stabilise, and you won’t have to buy a new tube or worse still a tyre.

Failing the basic marketing test
We boffins regularly failed the basic test of marketing - ‘to wear your clients’ boots’ and we forgot that farmers had a million other things to worry about as well as what we were pushing at them.
We remembered the boot's advice at the beginning, but forget to keep running the check as things tailed off to see what was changing. We failed to see things were changing all the time.

Blame the innocent
We also operated the great ‘Yes Minister’ advice from Sir Humphrey, of never taking the blame for failure, and always blame the electorate. In our case it was farmers who didn’t take up our brilliant ideas, didn’t come to field days and didn’t read our literature. They couldn't see what was good for them! It was their entire fault and never ours.

Looking back now, I’m not proud of the opportunities we botched through running around like headless chooks, and missing the obvious signs of where the wheels were getting loose.

Why Wormwise has done its time and should RIP:
Here's my thoughts:

• Killing the wool levy and the new drenches on the market are not the main reasons.
• The campaign always had too much veterinary input, and not enough farmer psychology.
  
• Farm owners (average age around 60) quickly got weary of being earbashed about the impending disaster, and their failure to act. Humans get sick of this after a while, especially when disaster doesn't arrive.
  
• The main Wormwise message to find out where your sheep were in terms of drench resistance seemed great, but unless farmers had big death rates, it was one of those things that could be left ‘till the first wet day’.
• Most farmers genuinely believed that they didn’t have a drench resistance problem - again as death rates were not high, and worms were not an obvious problem.
  
• When asked about the drenches used, most farmers said that their current drenches ‘seemed to be working OK’.
• Farmers accepted dagging and drenching, and then more dagging and drenching as normal routine. Things had to get very bad to get some veterinary involvement.
  
• Farmers realised that a full Faecal Egg Count Reduction Test (FECRT) took a lot of work, and cost a lot more than expected. Vets didn’t feature this - obviously.
• Many farmers simply didn’t want to know. It was like being told to have a health check. Farmers in the last 10 years have had other things to worry about like finding ways to stay viable and reduce work as staff became harder to find.
• Farmers can be easily convinced that their stock need a drench, and few base this on a FEC. If in doubt they drench, and at least they feel better afterwards and the dogs have enjoyed their run!
  
• Farmers are starting to understand the ‘Refugia’ concept of not drenching big healthy-looking individuals in a mob. They like it as it saves drench!
• The advertising for the new drenches reassured farmers that if they did have major problems with resistance, these products (which were expensive) would save them quickly.
• Repeating a known message soon gets boring as farmers know what it is, so ignore the repeats and switch off.
  

The future for worm resistance
Drenching based on ‘chemotherapy’ was never sustainable in the past, although we thought it was. It cannot be part of a future New Zealand which is clean and green, and a low-chemical animal protein export business. Evolution being what it is, the more drugs we hit parasites with, the more they will use genetics to get around their problem. We must use the same weapons.

Sadly the large international pharmaceutical companies who manufacture anthelmintic drenches don't see it this way in marketing their products. So large animal vets are in a quandary as they depend on drench sales for a large part of their income, while on the other hand trying to carry out the Wormwise principle of reducing the overall rate of anthelmintics.

The drench business is very competitive with few products being sold as 'vet only'. So this results in a massive adverting push in all the media, especially on TV during rugby events. The list of promotional giveaways used to be limited to domestic products and clothing, but now it has moved to electronic equipment.

Reduce chemotherapy


More and more chemotherapy is not the answer - genetics is, but this message has problems as it is mentioned, almost as a last resort in the Wormwise programme. New Zealand trained veterinarians are not strong on genetics, and in any case, using genetics doesn't earn them much money, other than from Faecal Egg Counts which farmers can do themselves now.

Plenty of evidence that genetics is working
We now know that sheep can be bred that can handle worms, to cut the costs of dagging and drenching (in that order). It’s simply a repeat of how sheep breeders fixed Facial Eczema using the survival of the fittest, and with modern technology, progress could be very much quicker.

There are now plenty of breeders who have been working away unrecognised for years, and now have a genetic solution. This is measured in many ways but the simplest one is how few drenches they need to give to their lambs and hoggets. Their mature ewes have never been drenched for years.

Change when profits decline more
Sadly genetics won’t get traction unless sheep profits decline further, and farmers realise how much they are spending on animal health (mainly drench). Also that farm labour dries up as young folk realise there's an easier way to make a living than hauling around today's 80-100kg ewes to take dung off their rear ends.

It's not worth Wormwise getting upset at farmers' complacency over the national strategy. Somebody needs to talk to farmers and get their views about how they want to manage internal parasites, and not fall into the age old trap of boffins preaching that 'this has got to be good for them'.

And it would be a good idea to get more lectures on animal breeding and genetics into vet training.

Drench resistant worms in sheep – current myths & half truths

Sheep, farming, husbandry, health, worms, internal parasites, current practices, myths, half truths.

By Dr Clive Dalton

Myths & half truths won't clean up these backsides!
Dagging has been an accepted part of sheep farming since
the start of farming, but we can't afford the time, cost & physical pain
of dagging sheep any more.

Because of the way internal parasites operate in sheep, and the methods we have used in the past to control them, a lot of myths and half truths have become interwoven with good solid facts.

Myths are defined as ‘traditional narrative embodying popular ideas’ so some bits are true or half true, but others are certainly not. Myths are things we want to be true!

Examples:

1. The more you drench, the quicker you’ll have worm-free stock.

Not true. You will never create worm-free stock and you would not want to either. Sheep need worms to challenge their immunity. But the more you drench the greater the chance of multiplying resistant worms.

2 You cannot farm without drench.

Not true. Some farmers are already doing this. They had no choice as they have already ‘hit the wall’ and used up all their drench options.

3. Drenching stock will eliminate worms from pastures.

It won’t. It will reduce larval numbers but to what extent will depend on a long list of factors.

4. If you don’t graze pastures for 3-6 weeks, all or most of the worm larvae will have died.

Not true. We now know that larvae can remain viable for up to 6 months, never mind 6 weeks.

5. Drenching hoggets at monthly intervals from weaning through autumn and winter with 5 to 7 drenches will make doubly-sure that they are worm-free as two-tooths.

Not true. Hoggets and two-tooths still produce worms long after the drenching stops.

6. If one drenching interval is not working, then shortening it will.

Not true. Drenching more often can easily build up drench resistance as resistant worms have a reproductive advantage.

7. Using long-acting drenches in sheep will delay the onset of drench resistance in worms.

Not true. Good evidence is building up that this will hasten the development of drench resistance.

8. Drenching ewes, especially with long-acting drenches, at pre-lambing and docking will prevent them infecting their lambs.

Not true. This will build up drench resistance in the flock even faster because the resistant larvae passed out by the ewes and recycled by the lambs will have a reproductive advantage.

9. Tapeworms have serious effects on the health of lambs.

Not true. Masses of research prove that tapeworms are not a serious problem. They look much worse than they really are.

10. Newly-drenched lambs should be immediately put on to clean pasture or special lamb blocks.

Not true. The chances are very high that the clean pastures will be contaminated with drench-resistant worms as all the susceptible worms will have been killed by the drench. They should be held for at least 4-5 days (some vets say 2 weeks) on old contaminated pasture before shifting them on to the lamb block.

11. Breeding is far too slow a way to fix the worm problem.

Not true. If you use an accurate way to identify worm resistance in both males and females and select flat out for this trait, you’ll be surprised at how fast things can change

12. New worm resistant genes, and developing new drenches and vaccines are just around the corner.

Pigs will fly! The current generation of farmers with average age 50+ should not hold their breath.

Disclaimer This material is provided in good faith for information purposes only, and the author does not accept any liability to any person for actions taken as a result of the information or advice (or the use of such information or advice) provided in these pages.

Drench resistant worms in sheep – a worm's life

Sheep, farming, husbandry, worms, internal parasites, health, definitions, genus & species, life cycles, signs of wormy sheep, effects of worms on sheep

By Dr Clive Dalton

What are ‘worms’?
‘Worms’ is a general term used for internal parasites that affect sheep. Plenty of other terms are used such as:

• Roundworms (the main species that are round in cross section)
• Nematodes (a general name for roundworms)
• Cestodes (a general name for tapeworms)
• Helminths (includes round worms, flukes and tape worms.
• Internal parasites (live inside the animal which is their host).
• Gastrointestinal worms (inhabit the sheep’s four stomachs and intestines
  

Worms in New Zealand

• Apparently twenty nine species of internal parasites got a free ride to New Zealand with livestock but the most important ones in sheep ended up being the round worms - Haemonchus, Ostertagia, Trichostrongylus and Nematodirus.
• All the roundworms are found throughout New Zealand but their relative abundance varies between districts, and with the age of the sheep and time of year.
• Only sheep and goats share the same species of worms. Some sheep and goat worms may survive going through other species, e.g. cattle, but they are not viable after their journey.
• All worms are classified by the Latin name of their genus and species. A few have common names but some of these are as ugly as the Latin names so they are not in common use.
• The table below gives some examples. Within each genus there are many species only some of which cause problems. The subject can be complex when discussing any problems they cause. Often the genus is only used to describe the species adding to the confusion.
  

• The abomasum is the 4th stomach where final gastric digestion takes place. In the previous three stomachs (rumen, reticulum and omasum) fermentation by bacteria and micro-organisms takes place.
  
• When using the species name the first letter of the genus is used to save writing it out in full.
• Key point: In the past, farmers didn’t need to worry about these names but things have changed, so use this table as a quick reference when talking to your vet or consultant. Hopefully you won’t ever have to write them down!
  

Can you see them?

Barber's Pole (Haemonchus) can be seen by eye once concentrated in a jar

• You can’t see round worms with the naked eye when mixed in among stomach and gut contents.
• Once the gut contents have been washed through a fine sieve and the worms collected and suspended in alcohol, then you can see them en masse. Some are so fine you can only see them when the specimen jar is shaken.
  
• Haemonchus are easy to see in a specimen jar.
• Tape worms sections are easy to see when passed out in the dung. These regularly panic farmers into drenching lambs.
• Tapeworms are a very minor issue in stock health and plenty of research shows they can be ignored.
  
• However, some farmers believe they are associated with other health problems in lambs such as pulpy kidney, flystrike and trace element deficiencies and so drench lambs as a protection.
  

The sections of tape worms are easy to see in faeces

Worm life cycles
Round worms:

• Both sexes of the mature worms live inside the sheep (the host) where they mate and produce eggs.
  
• These then pass out on to the pasture in the dung which protects them, and where they feed off bacteria.
• The eggs hatch inside the faeces and start to develop into larvae. They go from the L1 to L2 stages, and then to the L3 stage which is the critical one, as it’s eaten by another sheep to start the cycle all over again.
• The ecology of these larvae is not fully understood, but it’s known that L3 larvae can spend a long time in the ground. They can go 10-20cm down and move back to the surface when sufficient moisture is present. They are aquatic creatures.
• Warm moist conditions encourage the L3 larvae to migrate up plant leaves in a film of moisture to be eaten by the new host.
• Larvae need a minimum of 2-6 weeks of warm moist conditions to develop successfully.
• It takes about 21 days for ingested larvae to develop into adults capable of laying eggs.
• When developed, larvae survive longest in moist and cool (even frosty) conditions. Larval peaks occur in autumn (the autumn rise), with a more variable peak in spring (the spring rise).
• Some larvae can live for 6-8 months in cooler temperatures (sometimes even longer) and in warmer conditions they will die after 2-3 months.
  
• These facts have come as a shock to most of us who were taught that a 3-6 weeks grazing rotation would kill most of them. It won’t.
• Key point: In New Zealand, 85-95% of the worm population is found as larvae on pasture, so only a small proportion is inside the animal at any one time.
  
• Lambs are the real culprits by ingesting larvae and putting out large numbers of eggs, and this continues through to the hogget and early two-tooth stage.
  
• Worms love lambs and the earlier they can infect them the better.
  

Liver flukes:

• After ingestion the fluke larvae bore their way through the liver tissue causing damage which then affects liver function.
• Mature flukes are hermaphrodites (having both male and female sex organs) and live in the bile ducts from where their eggs pass out.
  
• These eggs need to go through a fresh water snail to hatch into larvae which are eaten by the sheep again.
  

Lungworms:

• They reach maturity in the lungs where they mate and lay eggs.
• These hatch and L1 larvae move up in the mucus and are swallowed to pass out in faeces.
• On the pasture they moult until the L3 infective stage and are eaten by the sheep off the pastures to complete the cycle.
  

Tapeworms:

• Their heads attach by hooks to the small intestine wall, and with no mouth they absorb nutrients through their skin. The egg-rich (gravid) rectangular sections pass out in the faeces where the eggs after hatching (either inside or outside the sheep) are eaten by a pasture mite.
• After 15-30 weeks they develop into larvae and are eaten again by a sheep. Lambs are most prone to tapeworms but seem to self-cure themselves by 8 months of age.
• A large evacuation of tape worm sections in the faeces of lambs is certainly impressive. It’s easy to panic when seeing them, assuming they block the gut so must have a terrible effect on lamb growth.
• The experience of some farmers shows that the very distinctive smell of lambs with tapeworms and their scour attracts blowfly and drenching avoids all this extra work.
  

What do worms feed on?

• Roundworms live off the proteins in the mucus lining the gut wall.
• Lungworms feed off similar mucus in the lungs.
• Blood suckers (Haemonchus only) attach themselves to the gut wall with savage-looking mouth parts and feed on blood.
  

What do worms do?
They cause a range of problems, either singly or in combinations. Here’s a selection:

• Key point. Partial or complete loss of appetite.
• Damage to the gut lining causing inflammation.
• Interference with the production and absorption of digestive juices.
• Leakage of fluid from the gut and an increase in mucus production.
• Dehydration through scouring.
• Blood loss from the gut wall (Haemonchus only).
  

Have worms any benefits?

• All animals have worms so it’s important that their immune systems can respond to deal with them.
  
• So they actually need a worm burden to stimulate the very complex immune system to respond to the challenge.
  
• This takes time, and when a worm burden swamps the immune system problems will arise.

What are the signs of ‘wormy’ sheep?
There are plenty of signs and you may see some or all of the following:

• General unthrift and looking tucked up and lethargic.
• They are easy to catch as they generally fall over!
• They can show a massive weight loss.
• Pot belly and low body condition. They are very skinny and their backbones will be visible from a distance despite their wool covering.
• Diarrhoea (scouring) instead of well-formed faecal pellets or ‘marbles’.
• Mucus in the faeces. Note this does not always mean worms.
• Anaemia. The mucous membranes of the eyes and gums are very pale. There is no skin pigment anywhere.
• White rectangular sections in the faeces (tapeworms).
• A ‘bottle jaw’ – skin pouch hanging down from lower jaw (liver fluke).
• Lack of ‘bloom’ in the wool. Wool with good bloom has high grease content.
  

In the past, when you saw scouring (diarrhoea), you automatically suspected worms and grabbed the drench gun. Not any more! There are many reasons for scouring, so get a veterinary diagnosis before drenching.

Disclaimer This material is provided in good faith for information purposes only, and the author does not accept any liability to any person for actions taken as a result of the information or advice (or the use of such information or advice) provided in these pages.

Drench resistant worms in sheep – drenching to control worms

Sheep, farming, husbandry, animal health, worms, internal parasites, drenches, anthelmintics.

By Dr Clive Dalton

Well, which one are you going to buy? Will the store assistant know enough to help you?
Beware of being told that 'this one's a good seller at the moment'! Or this one has the free jerkin'.

Drenches on the market
It is mind boggling to see the enormous range of products (anthelmintics) on the market to treat internal parasites in sheep.

Anthelmintics are any products that kill internal parasites, and past annual surveys in farming press show the following:

• There were around 40 different brands on the market.
• These were made by 5 companies.
• 15 were sold by vets only, and 16 were available from all outlets.
• Concentration of the chemicals ranged from 1g/Litre to 40g/Litre.
• Ingredient dose rate ranged from 0.2mg/kg LW to 10mg/kg LW.
• Formulated dose rate ranged from 1ml/5kg LW to 1ml/20kg LW.
• Withholding periods for meat ranged from 3 to 91 days.
• Safety margins ranged from 3x the dose to 100x.
• 15 of the products were ovicidal (killed worm eggs) and 16 did not.
• All of them killed both mature and immature parasites.
• 17 products included minerals, 1 had vitamins and 2 included vaccines
  

Ways to deliver

• Products can be given as an oral drench, as an oral bolus or capsule that stays in the rumen, or they can be injected.
• Check the label about the injection method (it’s usually subcutaneous) and for the best site (in the neck).
• There are no straight pouron ‘anthelmintics’ for sheep.
• Other products are called ‘endectocides’ as they kill both internal and external parasites and can be administered by mouth or injection in sheep. Pouron endectocides are not used in sheep.
• Some products are ‘ovicidal’ which means they also kill worm eggs in the sheep, as well as the worms.
• When checking the survey table of drench brands on the market, remember the ‘active ingredient’ column is much more important than the brand.
• And when you buy, don’t let the promotional ‘giveaways’ bias your decision.
  

Key questions:

• Is it any wonder that we get confused when buying drench? Have sympathy for the shop assistant too having to give advice and make recommendations when customers have no knowledge of the subject.
  
• Is it any wonder the customer buys a product with the lowest price and the best promotional give-away?

The drench chemical families

• Only a few years ago we didn’t need to know much about the chemicals used in drenches, but things have now changed.
• The key issue is that all the different products on the market are based on only three chemical ‘action families’ or ‘actives’. Active ingredients have long names that are hard to remember.
• We’ve got to get over this as it’s now very important to be able to ‘talk chemicals’ to your veterinarian or consultant.
• Calling them ‘white’ and ‘clear’ drench families was once helpful, but now not all white drenches are white and not all clear drenches are clear!
• Labeling does not always tell you clearly which family the product belongs to. You have to know your chemicals to find this out with far too many products.
• The printing on the labels is very small to fit in all that legally has to be presented. So it’s hard to read and no company has provided a small cheap lens to help the ‘average’ farmer who at over 50 years old needs some visual assistance!
• Current knowledge is that each chemical family kills worms the same way – thank goodness for that! So if a worm is not killed by one type of white drench then it won’t be killed by any other chemical in the white drench family.
• The unfortunate result of all this is that farmers now need to be more aware of the active ingredients in the specific brands of drench within each chemical family.
• This is now especially important when buying a branded product. You’ll have to recognise which chemical family the drench belongs to and know what species of worms it is expected to kill.
• Use the Table below as a check list to show which active ingredient is in which chemical drench family. You’ll need to check this when buying branded products. The table doesn’t list the chemicals used in double- or triple-combination products – so check the label. Don’t buy the product if you are not sure what’s in it and you cannot find out.
  

Key point:
Once your sheep have drench resistance to some or all three families of actives, flock management and your life will be a lot more complicated.


How anthelmintics work

• After drenching, the active ingredient is absorbed from the gut and circulates through the blood stream throughout the body, and is then resecreted back into the gut to do its work.
• Some active ingredients can also kill worms through direct contact with the parasite in the gut.
• When blood levels of the chemical drop below an ‘active’ level, then the drench loses its power.
• The length of activity of a drench depends on a range of factors related to the formulation and the worm species in the host.
• ‘Persistence’ is the term used to describe how long after administration a chemical in the drench will still work. For example the chemical in control-release capsules lasts a long time so is very persistent.
  

The gut trigger

• This is a clever bit of engineering in ruminants called the ‘oesophageal groove’.
• It is nature’s way of making sure milk when swallowed by the young lamb goes straight into the 4th stomach or abomasum for gastric digestion where it can clot.
• You don’t want milk going into the other three fore-stomachs (rumen, reticulum and omasum) where bacteria and other micro-organisms are developing to digest fibre.
• In the adult animal certain minerals and chemicals can close the groove so the drench will bypass the rumen where you want it to go.
• Large volume drenches are more likely to trigger the groove than low-volume drenches – so low volume products are a feature you should also look for and check with your veterinarian.
  

Disclaimer This material is provided in good faith for information purposes only, and the author does not accept any liability to any person for actions taken as a result of the information or advice (or the use of such information or advice) provided in these pages.