WRML.2015-03-20.WormFax. Resistance-Parascaris-AU.Other

To WormMail mailing list (recip. undisclosed).

In this issue:



New South Wales Wool Industry & Future Opportunities Review

Australia – where birdsong and intelligence began

Kidney recipient gets horse worm



The latest edition has been published to the website.


This summary of sheep WormTest results is from NSW DPI’s lab at Camden/Menangle and Veterinary Health Research at Armidale.

Each WormTest usually is 10 samples, generally from individual animals in a mob, but sometimes are bulked samples.

Some ‘high’lights from around NSW (mean worm egg count, and sometimes the range of individual WECs in brackets):

Armidale: Weaners. 5220 epg

Northern New England: Ewes. 21,364 (240-41,200). No culture. Another WormTest: Ewes. ~ 28,000 (4200-57,200). 99% Haem.   (Well done, Andrew).

Cooma: Ewes. 1272. Larval differentiation:100% Haemonchus

Tamworth. Weaners. 4564. 100% Haem.

Coonabarabran: Ewes. 4024. 89% Haem.

Central North: Rams?. 11,020 (4000-29000). 100% Haem.

Tablelands. Weaners. 3324. 99% Haem.

Molong. Weaners. 2316. 78% Haem., 20% Trichostrongylus.

Mudgee. Weaners. 3276. 100% Haem.

Lachlan. Weaners. 3180. 100% Haem.

Yass. Weaners. 7864 (0-24120). 85% Haem., 14% Trich. ( A NSW Northern Tablelands-style result).

South Coast. Weaners. 4812. 96% Haem.

Mid Coast. Weaner ewes. 3520.

These reflect above average rain in many areas (certainly in the north-eastern quadrant of NSW) in December and January. However, it has dried off considerably since then.

For expert local advice on what is happening in your patch, subscribe to ParaBoss News, which incorporates WormBoss News.

Resistance – Parascaris

See: Armstrong S, Woodgate RG, Gough S, Heller J, Sangster NC, K.J. Hu, 2014. The efficacy of ivermectin, pyrantel and fenbendazole against Parascaris equorum infection in foals on farms in Australia Veterinary Parasitology, Volume 205, Issues 3–4, 15 October 2014, Pages 575–580.


‘We examine the efficacy of anthelmintics against Parascaris equorum in Australia.

Ivermectin resistance was found most commonly.

Evidence of resistance to fenbendazole was found on two farms.

Multiple drug resistance in Parascaris equorum may occur on individual farms’.

See also: https://wormmailinthecloud.wordpress.com/2015/03/12/wrml-2015-03-12-get-up-to-date-on-horse-worms-other/

New South Wales Wool Industry & Future Opportunities Review


From the review: “NSW is the largest wool producing state. If it were a country, it would be the world’s fourth largest supplier”.

Australia – where birdsong and intelligence began


Kidney recipient gets horse worm



‘Sorry mate I didn’t see you’. The most common thing car drivers say when they hit a bicycle or motorcycle.

Here is a SMIDSY moment, with a remarkable outcome.   As to the car drivers: were they tailgating? ‘paying attention?

http://www.news.com.au/video/id-5sNDdyczoqKaVM2KS45rld1rNK3NW7OQ/Motorcyclists-miracle-escape   (Accessed 2015-03-20).



SL, 2015-03-20, Armidale.










WRML.2015-03-12 Get up-to-date on horse worms + other

In this issue of WormMail (WRML):


  • Resistance of Oxyuris equi?
  • Off-label use of anthelmintics in horses – a NZ case study
  • Real men don’t need instructions


  • Pinworm and Kemo Sabe
  • Using sheep as wi-fi hotspots
  • Bulverism

Get up-to-date on horse worm control 

On Melbourne Cup Day in 2013, I cobbled together a relatively non-expert post on resistance of horse worms to anthelmintics.

Here it is: https://wormmailinthecloud.wordpress.com/2013/11/05/wrml-resistance-of-important-horse-worms-to-anthelmintics-closantel-tox-in-human-britney-repels-pirates-etc/

I have recently updated that post, suggesting that those interested in horse worm control could do worse than consulting more expert and, in some cases, more recent overviews. I suggest you look at these:

  • AAEP Parasite Control Guidelines – http://www.aaep.org/custdocs/ParasiteControlGuidelinesFinal.pdf – by various including R M Kaplan and MK Nielsen.   Undated as far as I can see, but probably ~ 2012 – 2013 (SL).  AAEP = American Association of Equine Practitioners.
  • Kaplan RM and Nielsen MK, 2010. An evidence-based approach to equine parasite control: It ain’t the 60s anymore. Equine vet. Educ. (2010) 22 (6) 306-316. http://onlinelibrary.wiley.com/doi/10.1111/j.2042-3292.2010.00084.x/abstract
  • Nielsen MK et al, 2014. Anthelmintic resistance in equine parasites – Current evidence and knowledge gaps. Vet. Parasitol. (2014), http://dx.doi.org/10.1016/j.vetpar.2013.11.030

Some notes from the AAEP guidelines

Here are some notes I made, an interpretive summary. (My comments are italicised). However, read the original documents (above) for yourself. These notes are just a starter. The guidelines may have wide application but keep in mind regional variations (climate, management practices, available anthelmintics etc.)

Horse worm control practices are commonly based on knowledge that is more than 40 years old.

These points underpin the recommendations in the guidelines:

  1. Strongylus vulgaris and other large strongyles are now rare (in managed horses in the USA and perhaps most countries). Cyathostomins (‘small strongyles’) are now most important in adults. Parascaris equorum remains the most important parasite in foals and weanlings.
  2. Anthelmintic resistance of cyathostomins and P equorum is very common.
  3. Innate susceptibility of adults to infection with cyathostomins – and strongyle egg shedding as a result – is highly variable. Individualized management is required.
  4. Horses less than about 3 years old are more susceptible and require special attention.

The old approach to horse worm control was to kill S. vulgaris worms before they could produce eggs and contaminate pasture. This required treatment every two months (it took ~ 2 months for eggs to reappear after treatment). The importance of the ‘small strongyles’ (‘small redworms’) was overshadowed by the ‘large strongyles’ (‘large redworms’) which were considered to be more pathogenic.

(Aside: Most “small strongyles” are appreciably smaller than the “large strongyles,” but Triodontophorus spp (sometimes classified as nonmigratory large strongyles) are almost as long as Strongylus vulgaris. Source: http://www.merckmanuals.com/vet/digestive_system/gastrointestinal_parasites_of_horses/small_strongyles_in_horses.html#v3264928)

The tapeworm  Anoplocephala perfoliata has been recognised as a potential cause of colic.

The epidemiology of cyathostomins, P equorum and A perfoliata differs from that of S vulgaris and thus they require different control strategies.

Cyathostomins are ubiquitous, infecting all grazing horses. But they are relatively mild pathogens, causing disease only with heavy burdens.

After decades of frequent anthelmintic (‘drench’) use, drench resistance – an inherited trait – is common (ranging from ‘early indications’ to ‘common’ to ‘widespread’, depending on drench class/group) in cyathostomins and P equorum.

Table 1, page 3 summarizes the situation in south eastern USA (benzimidazoles (BZs)), pyrimidines (notably, pyrantel salts), and macrocyclic lactones (MLs) vs cyathostomins, large strongyles (apparently no resistance) and P equorum.

Table 1 (modified). (SE USA)

Cyathostomins (‘small’ strongyles) Large strongyles P equorum
BZs Widespread None Early indications
Pyrimidines. e.g. pyrantel Common None Early indications
MLs Early indications None Widespread

(As of December 2012, resistance of strongyles to IVM or MOX had not been diagnosed in the US –although (page 18) signs of emerging resistance reported (~ 2012) from Central Kentucky)).

Parasite ‘refugia’ is discussed (page 3.) Eggs and larvae on pasture are in refugia, as are stages in the horse against which a drench has no efficacy, e.g. pyrantel has no effect on worms outside the gut lumen, and ivermectin (IVM) has no documented efficacy against encysted cyathostomin larvae.

Minimise treatments when pasture refugia is low. The old practice of ‘drench and move’ (to a ‘clean’ paddock) selects more strongly for resistance.   Leaving some horses untreated utilises refugia. Identify moderate and high egg shedders by faecal worm egg count (WEC).  In one study (Kaplan and Nielsen, 2011): just treating horses with WEC>200 worm eggs per gram of faeces(epg), resulted in 50% of horses being treated but reduced egg shedding by ~ 95%.

Faecal or worm egg count reduction test (WECRT or FECRT) – described, page 4ff.

Table 2, page 5.  Suggested cut-off values (mean reduction in strongyle WEC) for the categories ‘susceptible’, ‘suspected resistant’ or ‘resistant’, for BZs, pyrantel and MLs.

Practical pointers include: at least 6 horses in a WECRT on a farm; aim for highest possible pre-treatment WEC; use egg counting technique with limit of detection of 25 epg or less; no prior drench within 8 weeks or more (12 weeks if moxidectin (MOX) used). Interpret results with care.

ERP – egg reappearance period (page 5) – a simple definition: the time from the last effective treatment until significant strongyle egg shedding resumes.  Another definition: the week post-treatment when the reduction in WEC falls below 80% (BZs, pyrantel) or 90% (IVM, MOX). This requires weekly WECs until eggs reappear. A shortening ERP may indicate emerging resistance.

Table 3, page 6. Cyathostomin ERPs for different horse drenches.

Strongyle shedding / pasture contamination (page 6). ‘Over-dispersion’ is common in all species including horses. i.e., for horses, about 20-30% of adult horses (i.e. >3 yo) shed about 80% of the eggs. (Yet another example / corollary of the Pareto or 80/20 principle). Healthy low or high shedding horses on pasture tend to remain low or high shedders. Test shedding status of adult horses using WEC at least 4 weeks after the ERP for the last drench used.

Table 4, page 7. Currently suggested guidelines/ best guesstimates for categorising shedders (of strongyle eggs)/contaminators, preferably based on more than one test (because some horses – not usually the ‘high shedders’ – switch categories):

Low shedders: 0-200 epg (50-70% of adult horses); medium: 200-500 epg (10-20%); high:  >500 epg (20-30% of adult horses).

(No exact guidelines have been published re acceptable numbers of P equorum eggs in young horses).

Parasites (apparently horse ones at least?) shed less eggs when conditions are less favourable for free-living stages (on pasture), so WECs may be less reliable in cold winter months (northern USA) or hot dry summers (southern USA).

Goals of parasite control, page 7ff.

Eradication is impossible and attempts to do so result in accelerated drench resistance. Also strongyles, small and large, cause most damage during the larval stages, against which most drenches are ineffective. But, killing adult worms, although of limited direct benefit to the horse, is of indirect benefit because of reduced pasture contamination.

Goals of worm control:

  1. minimise risk of disease
  2. control egg shedding
  3. maintain drench efficacy as much as possible

Achieve this by knowing who the high shedders are (this requires periodic worm egg counting) and treating them with the right drench (effective) and at the right time (i.e. before they start shedding large numbers of eggs; and not when conditions are adverse for free-living stages (few worms in refugia), unless clinical signs indicate a horse is parasitized and needs de-worming).

Reasons to WEC

  1. to test drench efficacy (by WECRT)
  2. to monitor the ERP after drenching
  3. to ascertain shedding status of a horse
  4. to see if foals / weanlings have P equorum and / or strongyles

Limitations of WEC

  1. not an accurate indicator of size of burden of adult P equorum or strongyles
  2. does not detect immature / larval incl migrating larval stages of large strongyles or ascarids, and / or encysted cyathostomins.
  3. tapeworm infections can be missed or underestimated, because of intermittent egg shedding
  4. pinworm infections often missed: egg packets are glued to the perianal skin

Faecal sampling, storage, worm egg counting, microscope maintenance – page 9

Interpreting WECs, page 9ff. Ninety nine percent of strongyle eggs in managed horses are from cyathostomins; this is 90-95% in feral and severely neglected horses (the rest being from large strongyle species) (USA-centric information? but seemingly applies similarly elsewhere). Differentiating large from small strongyles requires larval culture and ID (not apparently offered in commercial labs in the USA (I was surprised by that), but it is in Australia – but, some Australian labs may not routinely offer larval culture of strongyle dominated WECs because they are usually almost all cyathostomins). A PCR for S vulgaris eggs in faeces has been developed – currently (~ 2012 – 2013?) only for research purposes.

Other gastrointestinal parasites – pages 10 – 12.

  • Anoplocephala perfoliata (tapeworm). Common in many areas. Intermediate host: oribatid (pasture) mites (as with Moniezia spp in sheep). Possibly higher numbers of mites under moist conditions. So, less tapeworms in arid areas. Evidence for tapeworms as an important cause of colic is still scant.  They cause small mucosal erosions at attachment points and when present in high numbers have been associated with ileocaecal impaction and spasmodic colic. Most horses have relatively few tapeworms – unlikely to cause significant pathology.  Seeing eggs in standard egg counts is a chance event, unless burdens are heavy – eggs are shed intermittently. Therefore report result as positive or negative; eggs are clustered in faeces.  Other test methods can improve test sensitivity. Also greatly improved sensitivity if egg counting 24 hours after treatment with a cestocide (praziquantel (PRAZ), or cestocidal dose (2x the nematode dose) of pyrantel (PYR)). Validated serological test (Proudman – Univ Liverpool) is commercially available. (A perfoliata specific antibodies; titres correlate with burden). Annual treatment (PRAZ or PYR, as above) when transmission ends (cold weather) is suggested. More frequent treatment of dubious value. Treatment may be unnecessary in dry areas.
  • Parascaris equorum (roundworm; ascarid), page 11 ff. Most important in foals, causing ill-thrift. Airway inflammation, cough, nasal discharge (migrating larvae); higher risk of intestinal impaction. A possible link, evidence suggests: after treating with effective drugs with paralysis as mode of action (unlike BZs), sometimes complicated further by intestinal rupture. P equorum is very common in breeding operations; eggs can be viable / infectious for several years if organic material in soil. Adult horses occasionally infected (possibly becoming more common – usually on farms with foals), but rarely with clinical disease.  Resistance: high levels world-wide to IVM and MOX (fenbendazole at 10 mg/kg daily for 5 days may on some of these farms be the only larvacidal option); early indications of PYR resistance; no confirmed cases (~ 2013) of BZ resistance.
  • Oxyuris equi (pinworms). Previously mainly caused clinical signs in young horses; now becoming more common in adults. Infections often sporadic; usually just a few horses affected – perianal itching (due to material secreted by female when depositing eggs). Eggs are hardy and rubbing spreads eggs through the horse’s environment. Resistance: anecdotal reports of resistance to MLs; none yet documented (2012). (But, see below…). BZ or PYR are alternatives. Use good hygiene when clearing rear end of affected horses (eggs are hardy).
  • Bots (Gasterophilus spp.) Unsightly, but rarely associated with measurable disease. Boticide annually at onset of cold weather often recommended.  IVM and MOX currently the only effective drugs available.

Methods of parasite control. p 12ff

  • Environment-based approaches.  Removal of faeces from pasture. One study: twice weekly vacuuming controlled pasture infectivity better than regular de-worming, but very expensive and only worked well on level fairly dry pasture.
  • Environmental control. p.14ff. Table 5, page 14: Effects of temp. on development and survival of free-living stages of strongyles. (Broadly similar to important nematodes of sheep – see WormBoss.com au here and here). Composting (manure, soiled bedding) – a good practice; can kill even ascarids. Most strongyle larvae in manure die after 2+ weeks at >40 degrees C. Never spread non-composted horse manure onto pasture. Spelling pasture. Depends on temp:  L3s may only survive a few weeks in hot weather but can last 6-9 months in colder weather. Drench at right time: focus on treating when conditions optimal for larval development. Avoid treatments in times of low refugia – very cold winters or very hot summers.  Other:  haymaking; cross-grazing with ruminants, camelids; nematophagous fungi (not yet available commercially (~ 2013)).

(My understanding is that, in Australia, a nematophagous fungi-based product is still proceeding towards commercialisation – and for a number of livestock species. SL, 2015-03-11).

Table 5 (somewhat abbreviated; see paper). Effects of temperature (degrees C) on free-living horse strongyles (eggs, larvae (L1-L3)). (Nielsen et al., 2007).

Development Temp. range Survival
No development above this >40 Free-living stages outside faecal balls die rapidly
Optimal for devel. of eggs, larvae, getting to L3 in as little as 4 days 25-33 Larvae survive a few weeks; too warm for long survival
No hatch, no devel. <6 Eggs, L3 survive many weeks, even months just above zero (but repeated freeze-thaw is detrimental)
  • Alternative remedies. p.14ff. Efficacy has never been demonstrated in formal, controlled evaluations.
  • Anthelmintics available. p.15ff. Benzimidazoles (BZs): Affect energy metabolism; prevents creation of mictrotubules. Tetrahydropyrimidines pyrantel (PYR). Affects intra-luminal adults only. Sometimes used as a preventative – regular admin. in feed. Heterocyclic compounds: piperazine; depolarizes muscle membranes, causing resistance to acetylcholine. -> rigid, irreversible paralysis. Adulticide only. Infrequently used now. (In the olden days, we used to give it by stomach tube: e.g. piperazine, thiabendazole, trichlorfon. I never got a nose-bleed – neither did the horses).  Macrocyclic lactones.  Act on glutamate-gated chloride channels in nematode nerve, muscle cells -> flaccid paralysis. Also kill ectoparasites, and cutaneous larvae of Onchocerca, Habronema, and Draschia. Isoquinoline-pyrozines: praziquantel – tapewormer. No effect on nematodes.
  • Parasite control programs- points to ponder. p.15ff

Mature horses. Focus on cyathostomins (small strongyles). Test drench efficacy (FECRT) at least every 3 years. Basic program for all horses: 1-2 treatments per year for large strongyles, tapeworms, bots, and spirurid nematodes (Habronema, Draschia) causing summer sores. Extra treatments are for high shedders. Focus treatments during peak transmission periods – usually spring/autumn when pasture refugia highest.

Foals, weanlings, yearlings. Don’t do targeted (selective) treatments, i.e. based on FECs, in this group. First year of life: at least 4 drenches, first at 2-3 months old, with BZ (for efficacy against ascarids); second just before weaning (~ 6 months old); maybe an extra before weaning if the time between treatments is > 3 months. WEC (FEC) at weaning to see if mainly strongyles or ascarids (to ensure right drug choice). Third and fourth at 9 and 12 months, mainly targeting strongyles. Tapewormer also at 9 or 12 months. Annually test (WECRT) drug efficacy against ascarids, strongyles. Strongyloides westeri: rare cause of diarrhoea in young foals since advent of BZs, MLs. MLs often used on mares pre-foaling to prevent lactogenic spread of S westeri, but not justified if recently (same spring) treated with an ML. Move recently weaned foals to ‘cleanest’ pastures. Treat yearlings and 2 year olds as high shedders: 3-4 effective drenches p.a.

General considerations. Correct dose – use weight tapes or scale. Sources of infection: cyathostomins, large strongyles, tapeworms – from pasture; ascarids, pinworms – in confinement as well as on pasture. Consider using tapeworm serology (ELISA). Do most of the drenching when conditions favour worm transmission. Drench less when conditions are adverse (very hot, or freezing). Fine-tune worm control program for each farm – consider stocking density, time spent on pasture, age of horses, open or closed herd? – new arrivals: WEC and larvacidal deworming before release; non-chemical options – manure removal / composting, pasture rotation, cross-grazing with other species.

Other (included in summary): individual horses, with overt endoparasitism, may need treating at any time, with MOX being best for strongyles (e.g. efficacy against encysted mucosal larvae), or, if WECRT shows high efficacy, ‘can use fenbendazole larvacidal regimen – 10mg/kg for 5 consecutive days.

Oxyuris equi – drug resistance? and/or innate lack of efficacy?

There have been a few recent papers which suggest at least apparent lack of drench efficacy against pinworm in horses. Some examples:

Reinemeyer CR, 2012.Anthelmintic resistance in non-strongylid parasites of horses.Vet. Parasitol. 2012 Apr 19;185(1):9-15. “.. Some specimens of Oxyuris equi regularly survive treatment with macrocyclic lactones, but it is uncertain whether this constitutes resistance or merely confirms the incomplete oxyuricidal efficacy of virtually all broad spectrum equine anthelmintics”.

Schankova et al.,2013. Research Note: Treatment failure of ivermectin for Oxyuris equi in naturally infected ponies in Czech Republic. HELMINTHOLOGIA, 50, 3: 232 – 234, “Case report and overview of anthelmintic resistance of horse worms. “This is the first European study to demonstrate anthelmintic resistance in Oxyuris equi to macrocyclic lactones in naturally infected ponies.”

Wolf D, Hermosilla C and Taubert A, 2014. Short Communication. Oxyuris equi: Lack of efficacy in treatment with macrocyclic lactones. Veterinary Parasitology http://www.elsevier.com/locate/vetpar Short Communication. “This is the first report in Europe showing inefficacy of commercial ivermectin compounds and furthermore the first report at all documenting ineffectiveness of moxidectin compounds in the treatment of O. equi infections in horses indicating a possible development of resistance or confirming an existing incomplete oxyuricidal efficacy.”

(So, two ‘first reports’ from Europe…?).

Rock, C., Pomroy, W., Gee, E., Scott, I., 2013. Macrocyclic lactone resistant Oxyuris equi in New Zealand. In: Proc. 24th. Int. Conf. of the WAAVP, 25–29 August, p. 520. “The studies on these two horses provide some evidence to support the anecdotal reports of ML resistance in Oxyuris equi in New Zealand.”

Off-label use of anthelmintics in horses – a NZ case study

Scott and others in 2014 discussed a case of off-label use – which is frequently done – of a ‘drench’ (anthelmintic) in horses.

In this case it was injectable moxidectin for sheep given orally to horses. Three weeks after dosing a group of horses with this product at 400 µg/kg, worm egg counts (WECs) had gone done by only 72%. To determine whether sub-optimal pharmacokinetics and / or drench resistance was involved, the horses were later treated with an ivermectin paste formulation registered for horses, at 200 µg/kg, and sampled 7 and 22 days later. The WEC reduction was 100% and 99.5 % respectively.

Conclusion: inappropriate use of drenches may result in reduced efficacy and possibly higher selection for drench resistance.

Scott I, Pomroy W, Gee E, Toombs-Ruane L, Adlington B, Moss A, Reilly M, and Sparrow G, 2014. Off-label use of anthelmintics in equines – a case study. New Zealand Society for Parasitology – 42nd Annual Conference, 19-212 October, 2014.

Real ‘men’ don’t need instructions

I recently got a call from a producer (NSW South Coast, cattle producer) who bought a couple of goats from someone.

The original owner  used the oral sheep drench, ‘Q-Drench®’.   Method of application: mix some of it with water and spray it onto the goats….


Pin worm and Kemosabe

Allegedly The Lone Ranger in retirement discovered Kemo Sabe means ‘rear end of a horse’. If so, hopefully that related to a horse without pin worm.

But Tonto was the butt (sic) of someone’s joke as well: Tonto is Spanish for ‘fool’.


Using sheep as wifi hotspots



“Bulverism is a logical fallacy in which, rather than proving that an argument in favour of an opinion is wrong, a person instead assumes that the opinion is wrong, and then goes on to explain why the other person held it. It is essentially a circumstantial ad hominem argument. The term “Bulverism” was coined by C. S. Lewis.”

“Lewis wrote about this in a 1941 essay which was later expanded and published in The Socratic Digest under the title “Bulverism”. This was reprinted both in Undeceptions and the more recent anthology God in the Dock. He explains the origin of this term:

“You must show that a man is wrong before you start explaining why he is wrong. The modern method is to assume without discussion that he is wrong and then distract his attention from this (the only real issue) by busily explaining how he became so silly.

In the course of the last fifteen years I have found this vice so common that I have had to invent a name for it. I call it “Bulverism”. Some day I am going to write the biography of its imaginary inventor, Ezekiel Bulver, whose destiny was determined at the age of five when he heard his mother say to his father — who had been maintaining that two sides of a triangle were together greater than a third — “Oh you say that because you are a man.” “At that moment”, E. Bulver assures us, “there flashed across my opening mind the great truth that refutation is no necessary part of argument. Assume that your opponent is wrong, and explain his error, and the world will be at your feet. Attempt to prove that he is wrong or (worse still) try to find out whether he is wrong or right, and the national dynamism of our age will thrust you to the wall.” That is how Bulver became one of the makers of the Twentieth Century.”

Source: https://en.wikipedia.org/wiki/Bulverism


WRML.2015-03-05.Sheep worm resistance in Australia – an update

Sheep worm resistance in Australia – an update

Stephen Love, Veterinarian / Parasitologist, NSW DPI, Armidale NSW

Worms are the number one health problem of sheep in Australia, and resistance of worms to drenches is one of the big issues. But, drench resistance is more or less invisible, much like the worms themselves, and the production losses caused by worms.

Playford and others recently published the results of a study of drench resistance in Australia.

Here, in the graph below, is a partial summary.

Love S. sheep farms with drench resistance from Playford et al JPEG of graph

Notes: BZ=benzimidazole, ‘white’. LEV=levamisole, ‘clear.’ MPL=monepantel (‘Zolvix’, an ‘AAD’. No resistance detected).The macrocyclic lactone (ML, ‘mectin’) drenches are: IVM=ivermectin, ABA=abamectin, MOX=moxidectin. BZ/LEV etc. are combination drenches. CLOS=closantel. *Less than 50 usable drench tests for this drench. ‘Resistance’ here means the worm egg count reduction after treatment was <95% for one or more of Haemonchus, Trichostrongylus or Teladorsagia species.

Probably no more than 5-10% of sheep producers regularly check their drenches, either by DrenchTest, or DrenchCheckDay10, which is a WormTest (worm egg count) done after drenching. It’s likely then that most producers are unwittingly using drenches that are not highly effective. This translates into production losses and reduced income, and sometimes sheep health issues.

Don’t guess, WormTest.

References /more information:

Playford MC, Smith AN, Love S, Besier RB, Kulver P and Bailey JN, 2014. Prevalence and severity of anthelmintic resistance in ovine gastrointestinal nematodes in Australia (2009-2012). Australian Veterinary Journal, December 2014.

See WormBoss.com.au for more information on WormTest, DrenchTest, DrenchCheck and other.

WormMail.2015-03-04. RESO calculator for managing results of worm egg count reduction tests

Many labs and individuals use some version of the Microsoft Excel-based RESO calculator.

I recently asked Robert Dobson (Murdoch University, formerly of CSIRO) what ‘RESO’ stands for. He gave me this answer, which includes some history:

“The original RESO was pre-Excel in something called Lotus-123.  It came out of (CSIRO) Melbourne involving Paul Martin and Norm Anderson. This does not help with the acronym.

It moved with the times and was converted to Excel, driven by Nick Sangster who utilised the skills of Angus Cameron.

In my mind there were a few minor issue with some calculation which I amended, so I added Loot to make “resolute” because (a) that’s the way my mind works and (b) I cannot spell.  

In 2013 I made the “resoLootNew” version which provided a CL (Confidence Limit) when efficacy is 100% (this is incorrectly reported as CL = 100% – 100% in early versions).  It also reported a new category “Low Count” i.e. “Low Count” is flagged when the observed efficacy is 100% and the lower confidence limit for that result is less than 90% efficacy. I also updated some of the common drug names (somewhat cosmetic). 

I think I sent this version to you but can send again if interested.

Paul Martin is the best bet on the meaning of reso.


PS my wild guess Resistant Eggs Spreadsheet Observations “

Paul Martin gave me a bit more information:

“RES is an abbreviation for Resistance and just as we affectionately put an O on words like Dobo, so too on RESO. At least that is the case as best I remember. ‘Good to know it still has relevance”.

 This information from the front piece (Instructions tab/worksheet) of the Excel-based RESO:

 “This spreadsheet was created by Angus Cameron, AusVet Animal Health Services for the University of Sydney. Its calculations are based on those of the ‘Reso’ FECRT analysis program (Version 2.0   Revised 17-07-90) by Leo Wursthorn and Paul Martin of CSIRO, Animal Health Research Laboratory, PARKVILLE, 3052. The calculations are based on those published in ‘Anthelmintic Resistance’: Report of the Working Party for the Animal Health Committee of the SCA. CSIRO, 1989.”  

 (SCA= Standing Committee on Agriculture. Then there is SCAHLS – Sub-Committee on Animal Health Laboratory Standards, which publishes ‘standard diagnostic procedures’, including one on nematodes of ruminants).

Here are some extra notes that go with – and are built into (in the Instructions tab/sheet and elsewhere) – Robert Dobson’s 2013 modification of the RESO calculator:

“Modified by Robert J Dobson to change common drug names and in some cases use confidence limit estimations based on the number of eggs observed in the controls (Jeffreys interval). If efficacy for a drug is 100% then the LCL is determined by the Jeffreys interval as described by Dobson et al 2012.

 Additional information required to estimate LCL: When 1 egg was seen in 1 counting chamber what is the EPG for the single egg?  This is the detection/dilution level for the technique.      

How many chambers were counted per animal?    This is the number of replicate counts per animal.

 Drench Effectiveness: When the result is shown as “Low Count” this indicates insufficient eggs were seen for that species to accurately determine if the efficacy was greater than 90%.  “Low Count” is flagged when the observed efficacy is 100% and the lower confidence limit for that result is less than 90% efficacy.”

Cast (alphabetical order) in the unfolding RESO story:

Angus Cameron. Aus Vet Animal Health Services. (Current situation unknown to me).

Robert Dobson. Murdoch University, WA; formerly of CSIRO.

Richard Jarrett (formerly of CSIRO) built the statistical model.

Paul Martin. Formerly of Virbac, before that, CSIRO. Currently: PJM Scientific Pty www.pjmscientific.com.au

Nick Sangster. Formerly of University of Sydney, currently of Charles Sturt University, Wagga Wagga, NSW

Leo Wursthorn. Formerly of CSIRO. Leo Wursthorn also wrote a standalone version, RESO.EXE.

Sources : RJ Dobson, PJ Martin. Information used with permission.

SL, NSW DPI Armidale. 2015-03-04