Prepared for 2017 KHSI Expo in Indiana

1. Combination anthelmintics (dewormers):
High Time to Implement
SUSAN SCHOENIAN
Sheep & Goat Specialist
University of Maryland Extension
sschoen@umd.edu
www.sheepandgoat.com
www.sheep101.info
www.wormx.info
www.slideshare.net/schoenian/ or go to www.sheepandgoat.com
and choose SlideShare from the social media drop-down menu

2. Gastro-intestinal parasites (worms)
• Gastro-intestinal parasites (worms) are
the primary health problem affecting
sheep grazing in warm, moist climates,
especially during periods of summer
rainfall.
• The barber pole worm (Haemonchus
contortus) is the most pathogenic worm
species, causing significant morbidity
and mortality on many farms.
• Katahdins are more resistant to
internal parasites than wooled breeds,
but they (especially lambs) are not
completely immune to the effects of
internal parasitism.

3. Integrated Parasite Management (IPM)
MANAGEMENT ANTHELMINTIC USE
• Pasture and grazing
• Lambing and weaning
• Growing and finishing
• Nutrition
• Genetics
• Targeted selective treatment (TST)
1) FAMACHA© system
2)Five Point Check©
3) The Happy Factor™
 Proper anthelmintic use
Effective internal parasite control requires an integrated or holistic
approach that relies on management (mostly) and anthelmintics (targeted).

4. Anthelmintics 101
An anthelmintic or “dewormer” kills or expels worms.

5. There are three “chemical” classes of
dewormers for small ruminants (in US).
GROUP 1
Benzimidazoles
(BZ)
GROUP 2
Macrocylic lactones (ML)
GROUP 3
Nicotinic agonists
Avermectins Milbemycins
Imidazo-
thiazoles
Tetrahydro-
pyrimidines
Fenbendazole
SafeGuard®
Panacur®
Ivermectin
Ivomec®
Moxidectin
Cydectin®
Quest®
Levamisole
Prohibit®
Leva-Med®
Tramisol®
Levasol®
Morantel tartrate
Rumatel®
Albendazole
Valbazen®
Doramectin
Dectomax®
Pyrantel
Strongid®Eprinomectin
Eprinex®
Oxfendazole
Synanthic®

6. Anthelmintics FDA-approved for sheep
1
Benzimidazoles
Valbazen®
sheep drench
2a
Avermectins
Ivomec®
sheep drench
2b
Milbimycins
Cydectin®
sheep drench
3
Levamisole
Prohibit®
Leva-Med®
Adult worms    
Larvae (L4)    Limited
Hypobiotic larvae    Limited
Lungworms    
Tapeworms 
Liver flukes Adult stage
Coccidia
External parasites
Some
labeled for bot control
Some
Not labeled
Persistent activity  
Safety
10x
pregnancy restriction
(first 30 days)
20x 5x 3x
Labeled Dosage 3 ml/100 lbs. 3 ml/26 lbs. 1 ml/11 lbs.
Depends on dilution
2 ml/50 lbs
(concentrated drench)
Meat withdrawal 7 days 11 days 7 days 3 days

7. Worms have developed varying degrees of
resistance to all dewormers and classes.
0
10
20
30
40
50
60
70
80
90
100
Benzimidazoles Ivermectin Levamisole Moxidectin
Maryland Virginia Georgia
42.3%100% 92.3% 84.6%
Source: Determining anthelmintic resistance on sheep farms in the
southeastern US (2016). This study was made possible by funding from the
Let’s Grow committee of the American Sheep Industry Association (ASI).

8. Levels of resistance to benzimidazoles
Number of farms (n=26)
0
5
10
15
20
25
30
Susceptible Suspected
resistance
Low to
moderate
resistance
Moderate to
high resistance
Full resistance
Georgia
Virginia
Maryland
Source: Determining anthelmintic resistance on sheep farms in the
southeastern US (2016). This study was made possible by funding from the
Let’s Grow committee of the American Sheep Industry Association (ASI).

9. Levels of resistance to ivermectin
Number of farms (n=26)
0
2
4
6
8
10
12
Susceptible Suspected
Resistance
Low resistance Moderate to high
resistance
Full resistance
Georgia
Virginia
Maryland
Source: Determining anthelmintic resistance on sheep farms in the
southeastern US (2016). This study was made possible by funding from the
Let’s Grow committee of the American Sheep Industry Association (ASI).

10. Levels of resistance to moxidectin
Number of farms (n=26)
0
2
4
6
8
10
12
14
16
Susceptible Suspected
resistance
Low to moderate
resistance
Moderate to high
resistance
Georgia
Virginia
Maryland
Source: Determining anthelmintic resistance on sheep farms in the
southeastern US (2016). This study was made possible by funding from the
Let’s Grow committee of the American Sheep Industry Association (ASI).

11. Levels of resistance to Levamisole
Number of farms (n=26)
0
2
4
6
8
10
12
14
16
Susceptible Suspected
resistance
Low
resistance
Moderate
resistance
High
resistance
Georgia
Virginia
Maryland

12. Two ways to test for dewormer resistance.
FECAL EGG COUNT
REDUCTION TEST (FECRT)
DRENCHRITE® LARVAL
DEVELOPMENT ASSAY
1. Old protocol
Compare fecal egg counts of treated
and untreated (control) animals.
2. Newer protocol
Compare before and after (treatment)
fecal egg counts.
• 15 animals per test group.
• Minimum FEC of 250 epg
(preferably higher).
• Individual and composite samples yield
similar results.
• Labor intensive and costly, but you can learn
to do your own FECs.
• Labor-intensive lab test that
determines resistance to all
dewormer classes simultaneously
from a single, pooled fecal sample.
• Also identifies larvae (% HC)
• Need samples from 10-15 animals.
• Minimum FEC of 500 epg
• Dr. Ray Kaplan’s lab at University of
Georgia is only place that does test.
• $450 per sample

13. Animal Before After % FECR
1 1000 100 90%
2 500 25 95%
3 6000 150 98%
4 4350 250 94%
5 3000 1000 67%
6 1200 400 67%
7 1500 200 87%
8 750 50 93%
9 1100 100 91%
10 3100 200 94%
11 2900 200 93%
12 475 200 58%
13 900 100 89%
14 1100 50 95%
15 300 0 100%
1878 145 87%
Fecal egg count reduction test (FECRT)

14. “There now is very strong evidence that
using combination treatment is the best
method for using dewormers and should
be instituted on all farms immediately.”
Dr. Ray Kaplan, University of Georgia
http://www.wormx.info/combinations

15. Rationale for combination Tx
• Most farms have resistance to at
least two of the three major
groups of dewormers; some
have resistance to all.
▫ At first introduction, drug efficacy
is over 99%.
▫ Once efficacy falls below 95%, drug
resistance is present, though drug
is still useful for treatment.
▫ As effectiveness of dewormer
decreases (<95%), as it is used
more, it provides less and less
benefit to animals.
▫ Below 50%, it is no longer effective
as sole treatment. There is already resistance to Zolvix® in
other countries. Zolvix® is not sold in US.

16. Why give combination treatments?
• Contrary to popular belief,
rotating between dewormers will
not prevent resistance from
worsening; in fact, it is no longer a
recommended practice.
• Research done in New Zealand
has convincingly shown that the
best approach is to use several
different dewormers at one time
as a combination treatment. Sold in Australia and New Zealand

17. Why give combination treatments?
• When combined with “best
management practices” (that help to
maintain refugia), combination
treatments may improve drug efficacy
and result in a reversion back toward
susceptibility.
• Most dewormers sold in New Zealand
and Australia are combination
products (multiple drug actives in
same product); combination products
are not available in US.
Sold in Australia and New Zealand

18. Why do combinations work?
• Unlike rotating drugs, you get
an additive effect with each
drug used in a combination
treatment.
• By achieving a higher efficacy,
there are fewer resistant
worms that survive treatment.
• The sooner you start using
combination treatments the
better, as you achieve the
greatest difference in the
percentage of resistant
survivors when efficacy of
dewormers is high.
Drug 1 Drug 2 Drug 3 Combo12 Combo123
80% 80% 80% 96.00% 99.20%
90% 90% 90% 99.00% 99.90%
60% 95% 98.00% 98.00%
60% 60% 95% 84.00% 99.20%
99% 99% 99.99% 99.99%
60% 60% 60% 84.00% 93.60%
50% 50% 50% 75.00% 87.50%
40% 40% 40% 64.00% 78.40%
95% 80% 20% 99.00% 99.20%

19. Recommendations for using
dewormers in combination
 Do not mix the dewormers.
 They are not chemically-compatible.
 Only veterinarians are allowed to compound
medications.
• Purchase and administer each dewormer
separately in a different syringe.
• Administer each dewormer at full dose.
• Can give one drug immediately after the other.
• Observe the withdrawal period of the dewormer
with the longest withdrawal period.
• Maintain refugia: use selective treatment
approach based on FAMACHA©, Five Point
Check©, and/or The Happy Factor™.

20. Recommendations for using
dewormers in combination
Valbazen® Cydectin® Prohibit®
Dosage
Withdrawal
3 ml/100 lbs.
7 days
1 ml/11 lbs.
7 days
Depends on dilution
3 days

21. Using copper oxide wire particles
to improve dewormer efficacy

22. What are copper oxide wire particles?
• Tiny metal rods of copper oxide.
• Slow release form of copper.
• Poorly absorbed form of copper,
as compared to copper sulfate,
which risks copper toxicity in sheep.
• COWPs have been shown to reduce
barber pole worm infections in sheep
(and goats).
• COWPs are sold as a copper supplement for cattle (12.5 g boluses)
and goats (2 & 4 g boluses).
• You should repackage cattle boluses into smaller doses for sheep.
• Goat boluses contain more copper (per dose) than is generally
recommended for sheep (0.5-1 g for lambs; 1-2 g for ewes).
http://www.wormx.info/copper-oxide-wire-particles

23. Using copper oxide wire particles
(COWPs) to improve dewormer efficacy
COWP + albendzole (Valbazen®)
Treatment
(10-23 lambs per Tx group)
Efficacy
(%FECR)
No treatment (control) Increase
Valbazen® (3 ml/50 lbs.) 20%
COWP (2 g, Ultracruz™) 58%
COWP (2 g, Copasure®) 12%
Valbazen® + COWP 99%
Similar results could be expected if
COWPs were combined with other
dewormers (e.g. Prohibit®).
http://www.wormx.info/cowpcombo

24. American Consortium for Small
Ruminant Parasite Control (ACSRPC)
www.acsrpc.org
www.wormx.info
The ‘go-to” place for
information about
controlling internal
parasites in small
ruminants.

25. SUSAN SCHOENIAN
Sheep & Goat Specialist
University of Maryland Extension
sschoen@umd.edu
www.sheepandgoat.com
www.sheep101.info
www.wormx.info
Thank you for your attention. Questions? Comments?
Purchased at 2015 KHSI Expo
“Carly” (named after Carl Ginapp)