* Dan Salmon, District Vet, Deniliquin, NSW :
In the western Riverina Nematodirus causes an occasional train crash.
Especially in tough years we can get very significant burdens, particularly in young sheep. The worms form a visible mass along significant lengths of the small intestine: more like pig ascarids than sheep worms.
The episodes can occur in the absence of what we could consider suitable environmental conditions: warm dry autumns after hot dry summers.
The embryonated eggs are extremely hardy, one year we had tracer lambs picking up 15,000 Nematodirus per week in September on a paddock which had been de-stocked since May.
The very little histopathology that I have had done on clinical cases has hinted that the damage may be due to the immune response rather than the damage caused by the parasites.
It may be that we are starved of true parasites: Teladorsagia is our dominant parasite with Trichostronglyus being an issue about one year in ten and Haemonchus about one year in 25.
* Justin Bailey, Technical Services Veterinarian, Novartis Animal Health Australasia:
HI Steve, I had better comment since I am quoted below. In NZ, Nem spathiger would generally be considered a second order parasite that can contribute to clinical disease on occasion. It was a significant issue in the 80s when BZ resistance was first becoming an issue as BZ resistance in Nem spathiger was the most common cause of drench resistance we saw at that time. There were a large number of cases of clinical disease on farms who didn’t realise they had an issue with resistance and lambs would die of large burdens of this particular species – presentation pretty similar to a heavy burden of Trichostronglyus(black scour worm). This did illustrate that if not controlled N spathigercan be a very significant parasite throughout the country. Nem filicollis is considered to be an occasional problem in the cooler southern areas where numbers of larvae build up and are available to young lambs soon after birth with resultant clinical problems even before weaning. It is generally considered a species that needs a period of chilling for the larvae to develop. There are less issues with this clinical presentation now than reports would suggest for 30 years ago. We didn’t see the same issues with BZ resistance in this species as with Nem spathiger. Overall though we are actually somewhat deficient in our understanding of the epidemiology of both Nem spathiger and Nem filicollis, especially the picture in recent years. There can be an issue where egg counts are low but burdens are very high, especially in lambs in the 3-9 months of age bracket presumably with some level of immunity but not enough. Nem. helvetianus in cattle is a very occasional parasite of young cattle and I can’t recall ever seeing a significant burden.
Trichostrongylus axe(stomach hair worm) in sheep would be more likely to be seen in older sheep than young lambs unless you get the exceptional situation of lambs grazing pasture heavily contaminated by young wormy cattle. Remember in NZ we are referring here to Romney-type breeds where the mixed age ewes can largely control nematodes on their own without assistance, but from time to time we see subclinical/clinical burdens that require intervention. However, you do see them as part of mixed burdens even in young sheep but usually in smaller numbers compared to intestinal species. We have yet to see significant issues with resistance in this species which could change that picture.
* Dave Gardiner, District Veterinarian, LHPA, Mudgee NSW :
I read Paul’s column with interest as I too have recognised Nematodirus as a serious problem in Merino weaners around here, mostly Merryville bloodlines and guess Pauls are Saxons. I have set a level of 200 or above epg as being associated with ill thrift and mortality so maybe 150 will become my new trigger level for a drench. It is funny how these disappear in adults and I suspect it is a combination of immunity in the older sheep and management as weaner paddocks I suspect are flogged year after year there usually not being much choice when it comes to finding a paddock with good feed and good fencing in wool growing country. I have also associated Nematodirus and other worm burdens in weaners as being associated with Se & Co deficiency and suspected Cu deficiency in the Gulgong/ Dunedoo area so immune suppression may play a role.* Paul Mason, Consultant Parasitologist, New Zealand (South island) Hi Steve Here is something I sent to you in 2005, with a few additions: Nematodirus is a common parasite of lambs in the South Island of New Zealand. The emphasis in the previous sentence is on lambs, because the involvement of ewes in the life cycle of
Nematodirus is minimal. [When I worked in the MAF diagnostic lab, finding Nematodirus eggs in ewe faeces was a good indicator for Johnes.] On many farms lambs can become heavily infected with Nematodirus about a month prior to weaning, and many of the pathogenic effects can occur before the worms have started laying. This would suggest that these Nematodirus require a period of cold during their free-living time (as occurs with Nematodirus species in the UK) and that a synchronised hatch has occurred in the spring. If such an outbreak is unexpected, the cause is not detected until the lambs are passing eggs, so considerable pasture contamination with Nematodirus eggs has occurred by the time of diagnosis and treatment. When this happens we know that there is the potential for the same condition to develop next season to lambs on the same pasture. So, we have Nematodirus with a one year life cycle that is essentially restricted to cycling through lambs. On farms where Nematodirus is expected pre-weaning farmers routinely drench lambs
3 to 4 weeks before weaning, usually early November. In support of this diapause is the observation that Nematodirus is erratic to grow in larval culture. I achieved much better yields in culture when I incubated for 10 days, put the culture in the fridge for 14 days, then incubated for a further 10 days. Many years ago I read somewhere in the literature that age resistance to Nematodirus is a threshold effect and occurs after exposure of the lamb to a particular number of worms, which may explain why it occurs somewhat erratically through a mob of lambs. But we used to find that there was little point in running a FECRT (faecal egg count reduction test) for Nematodirus after about mid-January. The first effect of age resistance was a suppression of egg laying by the Nematodirus worms, so it was common at this time to cut open a lamb and find a Nematodirus burden, even though there were no Nematodirus eggs to be seen in the faeces. The most abundant Nematodirus species in sheep in NZ is now N.spathiger. It was not always so. This probably happened because N.spathiger was an early adopter of resistance to BZ drenches. * Dr Peter Rolfe, Head, Safety and Clinical Development, Novartis Animal Health Australasia Hi Steve,
A few thoughts from the bunker. Nematodirus in lambs is a significant issue on the southern tablelands of NSW and in conditions mentioned in (your) text below -especially first summer lambs after storm rains or under irrigation. FEcs (faecal (worm) egg counts) tend to be quite low/variable and not reflect the clinical /subclinical disease that has been caused but are still diagnostic once patency is reached. You have also captured other risk factors. I am not sure it is second order in the south especially if they are dying….which was quite common this last summer. They are always present in some numbers and should be closely considered especially when the conditions do not seem to be favorable for parasitism, for example in hotter dry conditions with sporadic downpours. Add to the mix * Elizabeth Braddon, Senior District Veterinarian, Young Office, Lachlan Livestock Health and Pest Authority. NSW
We certainly see Nematodirus in Young district as pathogenic in weaners <11-12 mos of age. As mentioned counts can be a bit misleading particularly if just had rain after dry … get mass hatchings and lots of immature so our trigger is 100-150 epg (or higher counts in ewes / older wether mobs as an indicator of contamination for lambs).
We have had deaths – without scouring – just illthrift, poor performance compared to feed available and then find dead or moribund then dead! PMs show very large numbers of Nematodirus (immature and mature).
I would agree with all the comments below.
Eliz# WormMail 201005131100 Following is the start of a conversation regarding Nematodirus (thin-necked intestinal worm; ‘Nem’) with Graham Lean following on Paul Nilon article on Parasites in Sheep in Tasmania( Turning the Worm newsletter Issue 26, May 2010; also here). Graham has given permission to put this in a WormMail i.e. essentially public). If you would like to comment – and agree to have you comments added to a final compilation to be published in WormMail i.e. public)- then feel free to reply to this email. Here is the conversation:
[GL]: Hi Steve, [GL]: I enjoyed Paul’s article. I thought it was very good. [SL]: I agree. Interesting stuff and nice writing style. It was the second in a series…the first (some time go) being one on sheep worms in the Falklands…. (Derek Clelland, TTW Issue 5, July 1999) [GL]: I also thought that his observation of Nematodirus was similar to mine in SW WA when I was there and also here in western Victoria. Some parasitologists agree with our view, others dismiss it. [SL}: Here is what Paul Nilon said in his TTW article Nematodirus spp  (don’t ask which species) predominates in dry summers and autumns. While it is regarded as relatively benign in other parts, in Tasmania it can cause significant parasitism, particularly in weaners. Moreover, because of sporadic egg output FEC Faecal worm egg count. triggers for treatment are low (150 epg). [SL]: My view…. It is a second order parasite (in NSW at least) compared to Haemonchus-Ostertagia-Trichostrongylus in sheep – but under certain circumstances can be quite important… [SL]: eg. * young sheep – more vulnerable.
* certain seasonal conditions … eg rain after prolonged dry spell…through which the tough Nem eggs can survive for extended periods
* certain management conditions…e.g paddocks set-stocked with young sheep or regularly used by young sheep…resulting in higher numbers of Nem eggs
* other stressors contributing…. nutrition, weather, other parasites
* drench resistance [SL]: And… there may be clinical disease before Nem egg counts rise much at all…due to large numbers of immatures [GL]: Agree with all that. Nicely put. [SL]: Nem (N filicollis at least?) is a big deal in NZ…but it was not always so. I seem to recall it become a 1st order parasite only since the 1960s? (Love and Hutchinson 2003) …. not sure why….Changes in farming practices?? (Our NZ colleagues may help out here) [SL] [Postscript] Regarding Nematodirus species in sheep in NZ, Pomroy lists N. filicollis of major importance, and various other species (spathiger, helvetianus, and abnormalis) of minor importance.(Interestingly Pomroy also lists Trichonstronglyus axei – stomach hair worm- as of major importance, which is generally not the case in Australia). [SL]: Maybe we can run Paul’s comments (in the Tassie article), your comments, and my comments above…. through WormMail…and invite comments… then compile all the comments into a follow-up?? [GL]: More than happy to see that occur. [GL]: Hate to open up a can of worms (yes, I couldn’t resist the pun), but this might be worth looking in more detail at some stage in turning the worm, or worm mail? What do you think? Cheers, GL [GL]: = Graham R. Lean BVSc, MAAAC, authorised rep AFS License No. 316516 (futures) PO Box 105 Hamilton VIC 3300 Australia Principal Consultant Graham Lean and Associates Farm Business Advisers [SL]: = Stephen Love References ( from SL) Pomroy WE (1997).Internal helminth parasites of ruminants in New Zealand. In, Sustainable control of internal parasites in ruminants, Animal Industries Workshop, June 1997, Lincoln University, NZ. Ed: GK Barrell Nematodirus at WormBoss: http://www.wool.com/Grow_WormBoss_Know-your-worms_Thin-necked-intestinal-worm.htm Love and Hutchinson (2003): "Nematodirus spathiger is a very common parasite of young Australian sheep, and usually relatively non-pathogenic unlike the situation in New Zealand where this parasite inexplicably become more
important from the 1960s. Heavy infections, scouring and ill thrift with mortalities can be seen in young sheep under or soon after drought conditions in Australia (south western NSW, for example)
presumably become Nematodirus eggs are relatively desiccation–tolerant. Clinical nematodirosis is also not uncommon in young lambs in irrigation areas such as the Riverina area of southern New
South Wales." (Love and Hutchinson 2003) or Love SCJ, Hutchinson GW (2003). Pathology and diagnosis of internal parasites in ruminants. In Gross Pathology of Ruminants, Proceedings 350, Post Graduate Foundation in Veterinary Science,
University of Sydney, Sydney;Chapter 16:309-338. For more information on service providers such as Paul Nilon and Graham Lean go to: http://www.wool.com/Grow_WormBoss_Professional-service-providers.htm Nematodirus – a conversation Turning the Worm – Issue 19 – 5 December 2005 Nematodirus (‘Thin-necked intestinal worm’) is usually not a big problem in sheep but under certain conditions it can be! This parasite’s little speciality is its hardy egg. It can survive a long time on pasture under tough, droughty conditions and then – with a break in the season (good rain) – young sheep in particular can pick up sizeable burdens of Nematodirus in a short time. The result may be scours and ill-thrift, sometimes with low or even zero Nematodirus faecal egg counts. Dr John Evers – District Vet at the RLPB at Young – tells me they have had Nematodirus problems two years running in autumn drop lambs in his district. In one case lambs were drenched with a known effective drench at marking, and three weeks later had a clinical problem with Nematodirus.
The reasons for this may be the weather pattern in Young and other districts for the last two years: a very dry autumn, and a season break occurring a month or so later (~ May/June) than usual. Nutritionally stressed late-pregnant and lactating ewes perhaps were passing more Nematodirus (and other worm) eggs in the faeces than usual, and this contributed to lambing paddocks being more heavily contaminated than in normal years. Young lambs, with minimal ability to handle worms, picked up significant burdens in a short time.
You might wonder about management factors, but John says that set-stocked as well as rotationally grazed farms have been affected.
The solution? Regular WormTesting (worm egg count monitoring) is one of the pillars of good worm control, but in unusual seasons, this may sometimes pick up Nematodirus problems after ‘the horse has bolted’. This is one obvious situation where local, expert knowledge (vets like John Evers for example) is invaluable. Other comments on Nematodirus: Dr Justin Bailey (Veterinarian and PhD student at the University of New England). Hi Steve – ‘Just a brief comment with regards to Nematodirus. Results from worm monitoring at Veterinary Health Research, Armidale certainly bear out the value of using levamisole
against Nematodirus – in fact it is the only drench consistently found to be fully effective against this parasite. (Another vet replied with information on the value of a particular product against Nematodirus but, as this was not a registered claim, it cannot be reproduced here. –Ed).
However, a case of scours and ill-thrift in a weaner mob in the New England last year provides a cautionary tale and underlines the potential significance of Nematodirus. The weaners in question displayed scours and ill-thrift in >20% of the mob with a mean FEC of not much more than 100epg for Nematodirus and minimal other roundworm infection. Treatment with levamisole did not alleviate the clinical signs, although a further monitor indicated that the treatment had been fully effective. An autopsy on one of the more severely affected animals showed little in the way of gross pathology. However, subsequent histopathology clearly demonstrated the effects of the prior Nematodirus infection on the gut lining. This resulted in continued scours and ill-thrift for a considerable period of time after the successful resolution of the infection. The cost in terms of lost animal production would have been significant. (UNE Armidale 22 Aug 05). Dr Dan Salmon (District Veterinarian, Riverina RLPB, NSW) (Regarding the efficacy of various drenches…) That pretty well agrees with the results Harry Suddes and I got in our survey last year.
We found that
o on14 ex17 farms, levamisole had 100% efficacy (faecal egg count reduction) against Nematodirus, on 1 ex17 the efficacy was 99%; and on 2 ex17, the efficacy 89%. o For albendazole we found 1005 efficacy on 5 ex17 farms, 95-99% on 4 ex 17; 85-94% on 3 ex 17, and <85% on 6 ex 17 farms. Of interest we are seeing more worms than for 15 years, mostly Ostertagia and Nematodirus, some almost pure growths of Nematodirus with significant clinical problems.
(Comment: because Nematodirus faecal egg counts (FECs) are usually low and variable, efficacy based on FEC reduction post-treatment needs to be interpreted with caution. – Ed). Dr Brown Besier (Senior Vet Parasitologist, Albany WA): Hello Steve – One point possibly of relevance – in WA, at least, is that we find that levamisole is still usually effective against Nematodirus. Where we see almost all Nematodirus eggs in a count, and virtually no strongyles, it is an opportunity to use a drench of otherwise little use (in situations where there is no Haemonchus).
(The same applies in NSW: few if any Nematodirus eggs are seen in a count following a levamisole drench, whereas some Nem eggs are commonly seen post-BZ drenches.
So, this is the situation with levamisole:
o resistance in small brown stomach worm (Ostertagia/Teladorsagia) and black scour worm(Trichostrongylus) is very common o barber’s pole worm is still susceptible to levamisole on most farms, but this is now changing. (It would be wise to consider routinely using levamisole in combination with other drenches, eg naphthalophos). o Levamisole still seems to be effective against Nematodirus. – Ed) Dr Paul Mason (Consultant Parasitologist, Dunedin, New Zealand) Nematodirus is a common parasite of lambs in the South Island of New Zealand. The emphasis in the previous sentence is on lambs, because the involvement of ewes in the life cycle on Nematodirus is minimal.[When I worked in the MAF diagnostic lab, finding Nematodirus eggs in ewe faeces was a good indicator for Johne’s.]
On many farms lambs can become heavily infected with Nematodirus about a month prior to weaning, and many of the pathogenic effects can occur before the worms have started laying. This would suggest that these Nematodirus require a period of cold during their free-living time (as occurs with Nematodirus species in the UK) and that a synchronised hatch has occurred in the spring. If such an outbreak is unexpected, the cause is not detected until the lambs are passing eggs, so considerable pasture contamination with Nematodirus eggs has occurred by the time of diagnosis and treatment. When this happens we know that there is the potential for the same condition to develop next season to lambs on the same pasture. So, we have Nematodirus with a one year life cycle that is essentially restricted to cycling through lambs.
On farms where Nematodirus is expected pre-weaning farmers routinely drench lambs 3 to 4 weeks before weaning, usually early November.
In support of this diapause is the observation that Nematodirus is erratic to grow in larval culture. I achieved much better yields in culture when I incubated for 10 days, put the culture in the fridge for 14 days, then incubated for a further 10 days.
Many years ago I read somewhere in the literature that age resistance to Nematodirus is a threshold effect and occurs after exposure of the lamb to a particular number of worms, which may explain why it occurs somewhat erratically through a mob of lambs. But we used to find that there was little point in running a FECRT for Nematodirus after about mid-January. The first effect of age resistance was a suppression of egg laying by the Nematodirus worms, so it was common at this time to cut open a lamb and find a Nematodirus burden, even though there were no Nematodirus eggs to be seen in the faeces. (NZ 19 Aug 05). Good times create pregnancy problems for ewes Media release: http://www.dpi.nsw.gov.au/aboutus/news/recent-news/agriculture-news-releases/good-times-create-pregnancy-problems-for-ewes 14 Jul 2010
The best seasonal conditions in NSW for many years look set to create some unique challenges for NSW sheep producers this lambing season.
Industry & Investment NSW livestock officer Chris Shands said the abundance of quality feed will present challenges producers had not encountered in recent, leaner years.
"The main risks to lamb survival are starvation and mismothering, mainly caused by poor nutrition in late pregnancy," said Mr Shands from the Glen Innes Agricultural Research Station.
"Abundant feed supply this year should help reduce losses from this problem, but it is likely that single bearing ewes on high quality feed will be over-nourishing their lamb.
"This will lead to a single lamb growing too quickly in the last two to three weeks before lambing and there is potential for this fatter than normal ewe to have difficulty lambing."
Mr Shands said producers who have scanned their ewes for pregnancy status will have a much better chance of optimising lamb survival.
"Lambs with birth weights at six kilograms or heavier have a greater chance of getting stuck during the lambing process,"
Mr Shands said.
"To try to avoid single bearing ewes experiencing lambing difficulties, it is imperative to restrict the intake of ewes that are grazed on high quality pastures or fodder crops in the last month before lambing.
"Producers will need to significantly increase the stocking rate of single bearing ewe groups to restrict intake," he said.
Mr Shands said pasture targets for these single bearing ewes should be no more than 800 kilograms of green pasture or fodder crop, equivalent to no more than two centimetres of pasture height.
"Under current pasture conditions this grazing management regime will be difficult to achieve, but it’s a better option than losing both the ewe and the lamb through dystocia," he said.
Mr Shands said pregnancy scanning contractors have reported some flocks with over half the ewes carrying twins this year.
"In pasture terms, twin bearing ewes need a minimum of 1200kg of green dry matter per hectare (three to four centimetres pasture height) in the last four weeks before lambing," Mr Shands said.
Mr Shands said twin bearing ewes were highly susceptible to pregnancy toxaemia in the last three weeks before lambing, so a balanced and concentrated diet is imperative.
"Any management activities like drenching and vaccinating should take place at least four weeks prior to the start of lambing to avoid pregnancy toxaemia," he said. (Emphasis mine – SL)
Industry & Investment NSW – Primary Industries
University of New England – Armidale NSW 2351 W: http://www.dpi.nsw.gov.au/agriculture/livestock/health W: http://www.wool.com/WormBoss W: https://wormmailinthecloud.wordpress.com/
Lists of registered drenches – cattle-sheep-goats-horses etc – InfoPest March 2010WormMail 201005181530 WormMail mailing list (recip. undisclosed) Beef LOs etc In the attached Excel workbook are lists of drenches for various species extracted (hopefully accurately) from the March edition of InfoPest. For the most up-to-date lists, search ‘PUBCRIS’ at the APVMA website: www.apvma.gov.au