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This article was published in 1999
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INSTITUTE OF INSPECTORS OF STOCK OF N.S.W. YEAR BOOK.
CONTROL OF HAEMONCHUS CONTORTUS IN THE FACE OF CLOSANTEL RESISTANCE
JA Macfarlane, Rural Lands Protection Board, Armidale
Abstract
Recent reports of closantel and macrocyclic lactone anthelmintic resistance to H. contortus in an area west of the New England Tablelands galvanised a local farm management group, perceiving that long-term sustainability of sheep farming in this area to be threatened, to apply for funds to look at alternative methods of H. contortus control. The group obtained funds to try three alternative approaches; namely the use of copper oxide wire particle (COWP) pellets in weaners, vaccination using a radiation attenuated vaccine and by-pass protein supplements to ewes prior to lambing. Only one of two years trial results are available to date. The COWP pellets gave good protection for 4 weeks under severe challenge when used with an effective anthelmintic, the vaccination trials were inconclusive due to the low numbers of H. contortus in all sheep, and the nutrition trials were essentially negated due to an uncharacteristic mild winter. All trials are in the process of being repeated.
Introduction
Following the confirmation of widespread resistance of Haemonchus contortus to closantel in an area west of the New England Tablelands (1), and the discovery of macrocyclic lactone resistance in the same species (2), a local farm management group applied for funds to investigate alternate methods of Haemonchus control. The group was successful in its application for a Woolmark Producer Initiated Research Development (PIRD) grant and this is a report on results of trials to date.
The group sought guidance from international parasitological consultant, I Barger, and subsequent practical advice and assistance from M Knox and L Le Jambre, CSIRO, Armidale. Following discussions on the epidemiology of H. contortus in the area, the group decided to concentrate on the two situations when most problems occur and/or are created. These are when sheep are least resistant to parasites,i.e., the post-weaning period and the periparturient period in ewes. Three specific trials for control at those crucial times were put into place on member's farms; these being:
1. Copper Oxide Wire Particle (COWP) Pellets
Previous experiments have suggested that COWP pellets give good reduction of adult and larval stages of H. contortus (3) and gives at least 3 weeks protection (4). Local trials have suggested the pellets can be used safely in the New England region (5).
An initial trial on-farm was performed to give a guide to see if this method was worth pursuing further. This was followed by 3 on-farm trials.
2. Vaccination Trials
The potential for radiation-attenuated vaccines has long been recognised (6), however, research into their use against gastro-intestinal parasites in sheep was abandoned on the basis that response was not equivalent to commercial lungworm vaccine in cattle, and younger sheep were even less responsive (7). However, the emergence of multiple drench resistance and the failure of more "modern" vaccines has prompted a re-evaluation of this overlooked vaccine. Three on-farm trials were conducted.
3. Nutrition Trials
Nutrition has long been considered an important component of the epidemiology of H. contortus (8). Recent work has suggested that the periparturient breakdown in resistance to internal parasites and the subsequent pasture contamination can be modified by nutrition (9). It is logical that in the New England Tablelands when pasture growth during this period is negligible (10) and the demand during the late periparturient period is high that protein supplementation may at least partially overcome this nutrition deficiency. Three on-farm trials were initiated to test this.
Materials and Methods
1. COWP Pellet Trials
An initial trial was carried out on one property, where 50 weaners in a mob of 400 were each treated with COWP pellets (Permatrace Copper Capsules for adult sheep and goats, Reg(TM) Coopers Animal Health). Weaners were grazed as one mob in a paddock thought to be heavily contaminated with H. contortus larvae as judged by FECs in sheep previously grazing the paddock.
Ten treated and ten non-treated weaners were randomly selected and FECs carried out every two weeks following treatment. Copper blood levels were monitored in the same sheep.
No tests were carried out to establish if COWP pellets remained in the sheep.
Subsequently, trials were carried out on 2 properties, in which a mob of 50 weaners was run as one group, and half treated with COWP pellets. These properties have a history and pre-trial monitoring indicating H. contortus was a major problem.
All sheep were tested for FECs, faecal copper, blood PVCs and LDHs, and weighed on a regular basis. Hopefully, fleece weights will also be available.
On a third farm, a mob of 400 weaners was treated with COWP pellets, leaving 25 untreated controls. Pre-treatment monitoring indicated high levels of H. contortus. Tests were conducted as above.
2. Vaccination Trials
On four properties, approximately half (ranging from 50-150) the ewes in a mob were selected at random, and treated twice using a vaccine consisting of 10000 larvae (L3) of H. contortus attenuated by radiation (McMaster Strain as supplied by CSIRO) (12). Ewes were initially drenched with levamisole 7 days prior to first vaccination. A first vaccination was given at 6-8 weeks and the second vaccination was at 4 weeks prior to commencement of lambing.
FECs were conducted on 25 sheep in each group selected at random at the first and second vaccination, immediately prior to lambing, at lamb marking and approximately 6 weeks later (depending upon farm management practices).
3. Nutrition Trials
On three properties, two mobs of similar ewes were selected 8 weeks prior to lambing and run on similar pastures with respect to pasture and previous grazing history.
One mob was supplementary fed three times a week with high by-pass protein sheep nuts (Millmaster 27% rumen by-pass pellets) at the equivalent rate of 200 grams per sheep per day. (On most properties, sheep were fed 500 grams 3 times a week as a matter of convenience.) Feeding commenced six weeks prior to lambing (with some pre-trial training where necessary) until immediately prior to lambing.
Twenty-five sheep were selected at random for FECs from each mob prior to feeding, at the commencement of lambing and 6 weeks later (around lamb marking).
Results
1. COWP Pellet Trials
Table 1: Farm 1
| Treated | Control | |||||
| Date | FEC (epg) | Haem (epg) | Plasma Cu (µmol/L) | FEC (epg) | Haem (epg) | Plasma Cu (µmol/L) |
| 30/10/97 | 616 | 228 | 17.2 | 616 | 228 | 20.2 |
| 10/11/97 | 408 | 175 | 16.0 | 1280 | 1126 | 14.7 |
| 28/11/97 | 360 | 154 | 13.8 | 2056 | 1809 | 12.52 |
| 9/12/97 | 3016 | 2081 | No test | 6660 | 5860 | No test |
LV treatment 15/10/97.
COWP pellet administered on 30/10/97.
Table 2: Farm 2
| Treated | Control | |||
| Date | FEC (epg) | Haem (epg) | FEC (epg) | Haem (epg) |
| 9/2/99 | 38 | 4 | 42 | 27 |
| 2/3/99 | 125 | 93 | 341 | 285 |
| 11/3/99 | 178 | 124 | 909 | 890 |
| 25/3/99 | 503 | 447 | 1362 | 1253 |
| 6/4/99 | 2137 | 1923 | 2673 | 2058 |
Pre-trial monitor 14/1/99. FEC 1164, Haem 756.
Drenched IVOMEC (Reg TM) 2/2/99.
COWP administered 9/2/99.
Table 3: Farm 3
| Treated | Control | |||
| Date | FEC (epg) | Haem (epg) | FEC (epg) | Haem (epg) |
| 11/2/99 | 54 | 16 | 98 | 95 |
| 2/3/99 | 143 | 128 | 184 | 158 |
| 9/3/99 | 10 | 2 | 229 | 213 |
| 23/3/99 | 9 | 8 | 277 | 257 |
| 6/4/99 | 97 | 82 | 491 | 486 |
| 19/4/99 | 1287 | 1274 | 2978 | 2978 |
| 4/5/99 | 3597 | 3561 | 22 | 0 |
Pre-trial monitor 18/1/99. FEC 544, Haem 531.
Pre-trial drench and Ivomectin (Reg TM) 3/2/99.
COWP administered 18/2/99.
Table 4: Farm 4
| Treated | Control | |||
| Date | FEC (epg) | Haem (epg) | FEC (epg) | Haem (epg) |
| 15/4/99 | 2927 | 2868 | 2594 | 2594 |
| 21/4/99 | 1250 | 1237 | 2794 | 2766 |
| 4/5/99 | 670 | 462 | 16 | 6 |
| 19/5/99 | 1045 | 909 | 91 | 73 |
| 3/6/99 | 867 | 841 | 272 | 239 |
COWP administered 5/4/99.
White LV treatment 23/4/99.
Graph 1. H. contortus egg counts (epg) after COWP administration on Farm 1. These sheep were drenched 2 weeks prior COWP administration.
Graph 2. H. contortus egg counts (epg) after COWP administration on Farm 2. These sheep were drenched 2 weeks prior COWP administration.
Graph 3. H. contortus egg counts (epg) after COWP administration on Farm 3. These sheep were placed on clean pasture after drenching 2 weeks prior COWP administration, giving a longer protection period.
Graph 4. H. contortus egg counts (epg) after COWP administration on Farm 4. These sheep had not been drenched. Control sheep were drenched after the first week.
2. Vaccination Trials
Table 5: Farm 5
| Vaccinated | Non-Vaccinated | Activity | |||
| Date | FEC (epg) | Haem (epg) | FEC (epg) | Haem (epg) | |
| 3/8/98 | 1324 | 636 | 1324 | 636 | Pre-vaccination monitor |
| 13/8/98 | 708 | 0 | 708 | 0 | First vaccination |
| 17/9/98 | 559 | 78 | 445 | 36 | Second vaccination |
| 30/11/99 | 868 | 43 | 812 | 8 | Lamb marking |
Lambing dates: 10/10/98 - 31/10/98
Table 6: Farm 6
| Vaccinated | Non-Vaccinated | Activity | |||
| Date | FEC (epg) | Haem (epg) | FEC (epg) | Haem (epg) | |
| 24/7/98 | 252 | 149 | 252 | 149 | Pre-vaccination monitor |
| 7/9/98 | 220 | 13 | 99 | 19 | First vaccination |
| 18/9/98 | 134 | 9 | 48 | 1 | Second vaccination |
| 5/11/98 | 323 | 158 | 627 | 301 | Lamb marking |
| 10/12/98 | 1065 | 703 | 1078 | 658 | |
Lambing dates: 19/9/98 - 27/10/98.
Table 7: Farm 7
| Non-vacc Non-preg | Vacc Non-Preg | Vacc Preg Ewes | Non-Vacc Preg Ewes | Activity | |||||
| Date | FEC | Haem | FEC | Haem | FEC | Haem | FEC | Haem | |
| 15/7/98 | 213 | 0 | 425 | 0 | 260 | 0 | 260 | 0 | First vaccination |
| 19/8/98 | 108 | 12 | 550 | 5 | 386 | 0 | 548 | 0 | Second vaccination |
| 21/10/98 | 0 | 0 | 12 | 2 | 483 | 0 | 595 | 12 | Lamb marking |
| 21/12/98 | 267 | 174 | 160 | 77 | 1046 | 73 | 530 | 48 | Weaning |
Lambing dates: 1/9/98 - 6/10/98.
3. Nutrition Trials
Table 8: Farm 8
| Treated (Fed) | Control (Non-Fed) | |||
| Date | FEC (epg) | Haem (epg) | FEC (epg) | Haem (epg) |
| 7/8/98 | 0 | 0 | 0 | 0 |
| 11/11/98 | 427 | 205 | 304 | 243 |
| 17/12/98 | 901 | 881 | 627 | 621 |
Table 9: Farm 9
| Treated (Fed) | Control (Non-Fed) | |||
| Date | FEC (epg) | Haem (epg) | FEC (epg) | Haem (epg) |
| 15/7/98 | 518 | 0 | 345 | 0 |
| 19/8/98 | 710 | 92 | 910 | 0 |
| 21/10/98 | 163 | 51 | 50 | 5 |
| 21/12/98 | 682 | 300 | 742 | 267 |
Table 10: Farm 10
| Treated (Fed) | Control (Non-Fed) | |||
| Date | FEC (epg) | Haem (epg) | FEC (epg) | Haem (epg) |
| 7/7/98 | 1110 | 1077 | 1784 | 1784 |
| 20/7/98 | 0 | 0 | 0 | 0 |
| 28/8/98 | 260 | 242 | 120 | 110 |
| 17/9/98 | 59 | 2 | 173 | 145 |
Discussion
1. COWP Pellet Trials
COWP Pellets
COWP pellets are small particles of oxidised copper wire, approximately 1 mm in diameter and about 5 mm long. They contain 80% of their weight as copper. They are delivered orally in a gelatin capsule, which dissolves in the rumen. The released copper oxide needles, due to their high specific gravity and low mass, are readily transferred from the rumen to the abomasum, where they remain in the folds of the abomasal mucosa. In the acid medium of the abomasum, the copper oxide is slowly dissolved and absorbed from the intestinal tract and stored in the liver.
Copper oxide is used as elemental copper is not available to the animal (13).
The use of COWP pellets for H. contortus depends on its copper ions being released into the abomasum. This is in contrast to its action to control copper deficiency, where the accumulation and storage of copper in the liver is the limiting factor.
Work has indicated that the dwell time for COWP in the abomasum is 6-7 weeks, although this is variable. For example, 30% of COWP was found in the abomasum 4 weeks after administration, with a range of 9-83% in one trial (14).
In the initial trial, the COWP pellet (2.5 g Cu) gave significant control of H. contortus when compared with controls for 4 weeks. There was a significant difference at 6 weeks, but in the COWP pellet group, an unacceptably high count had developed. There was no significant difference in plasma copper levels.
Previous trials showed 2.5 g COWP pellets gave a 97% reduction against incoming third-stage H. contortus larvae (3) and a 96% reduction was found using 5 g COWP, 3 weeks after giving H. contortus larvae (4).
In the initial trial (Farm 1), weaners were run on a contaminated paddock, and in the mob of 400, only 50 were treated. This effectively negated any chance of the COWP reducing the environmental contamination and may explain the high count in treated animals at 6 weeks. As this result was encouraging, 3 on-farm trials were completed for the 98-99 summer. Further, local trials at CSIRO are reported to be giving very encouraging results (11).
In trials (Farms 2 and 3), 50 Merino weaners, half treated and half not, run together, COWP pellets gave a protection for 6 weeks when sheep were run on contaminated paddocks, and eight weeks when run on paddocks reasonably thought to be H. contortus free.
In the third trial (Farm 4), where the sheep were not treated prior to COWP pellet administration, and the majority of the sheep were treated, demonstrated that a degree of control was afforded by the COWP pellets.
However, the high level of contamination was such that, while levels were reduced, this was not at a level comparable with effective anthelmintics. In this trial, the control group had to be treated, and this group only slowly developed adult worms over 6 weeks.
Although COWP pellets removed adults, it was not comparable to efficient anthelmintics.
Besides the issue of anthelmintic effectiveness, studies are needed to determine the toxicity and food safety issues, clarifying the payout rates of the pellet. Finally, on the New England Tablelands, the effect of the recommendation of high Molybdenum content fertilisers will need to be considered (5).
2. Vaccination Trials
Despite what one would consider reasonable pre-trial H. contortus burdens, what is immediately evident is the lack of H. contortus present during the trials.
Effectively, as a result of weather conditions, winter and spring were cool and damp throughout, the expected H. contortus spring challenge did not occur. In a normal year, enough H. contortus larvae remain on pasture to infect ewes in spring, however, in this season it appears numbers were negligible by spring.
Following advice that current pen trials are giving encouraging results (12) and the fact that some farms developed significant T. colubriformis burdens, the group has decided to consider a combined H. contortus and T. colubriformis attenuated vaccine for 1999.
3. Nutrition Trials
Once again, the season was not ideal - the mild and damp autumn and winter produced unusually good winter feed; as well as making the feeding of sheep extremely difficult, both because sheep were not keen to eat and because feeding nuts in the field under wet conditions presents problems not usually encountered in this district.
The group has decided to repeat the trials in 1999, as local CSIRO field trials gave very encouraging results (11).
General Discussion
Copper Sulphate
Copper sulphate is a time-honoured drench for H. contortus (15), the dose rates in metric equivalents extrapolated from old data (16) are 1 ml of 2% solution per kg BW.
Copper sulphate is reasonably effective against adult Haemonchus contortus, but relatively ineffective against immature forms (16).
Copper sulphate was used in combinations of drugs now no longer considered acceptable, but is being trialed with the newer drugs. "Bundarra Blue" is commonly used in areas where Haemonchus has again become common due to closantel resistance. It is a combination of Levamisole and copper sulphate.
One on-farm drench trial gave the following results:
| Drench | % Reduction |
|---|---|
| LV | 100% |
| Cu SO4 | 88% (range 95-68%) |
| Combination | 100% |
In theory, the combination should prolong the useful life of LV;i.e., by delaying the development of resistance, and as it is cheap, it seems a logical combination to use.
Alternative Methods
In considering the alternatives, the group was also keen to use biological control methods, especially the nematophagous fungi (17), however, at this stage, there are problems of availability under commercialisation (18).
The group looked at grazing management and the use of cattle, as unquestionably, there is much scope for adaption of these techniques (19). However, the Worn kill program provides for safe pastures for sheep in this environment and it is not an area where cattle are run in any number. Hence, it was decided that this avenue offered no scope for major improvement.
The nutritional approach appears to offer a partial long-term solution, especially if used in association with worm resistance selection techniques (7), and its use has been demonstrated elsewhere (20). Its use has also been demonstrated in younger sheep (21).
Under the current wool prices, the lack of any demonstrated short-term economic benefit makes it difficult to progress this option, although the recent adoption of Prograze techniques for quantative pasture assessment may overcome this.
Acknowledgment
The Bundarra-Kingstown Farm Management group gratefully acknowledge the financial assistance of the Woolmark PIRD scheme and the full guidance of Ian Barger, offered free of charge, and other encumbrances.
These trials have been carried out with the advice and cooperation of M Knox and L Le Jambre, CSIRO "Chiswick", and it is intended future trials be on this cooperative basis.
Reference List
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