1. Dealing with anthelmintic
resistance in small ruminants
SUSAN SCHOENIAN
SHEEP & GOAT SPECIALIST
UNIVERSITY OF MARYLAND EXTENSION (UME)
WESTERN MARYLAND RESEARCH & EDUCATION CENTER (WMREC)
SSCHOEN@UMD.EDU - WWW.WORMX.INFO - WWW.SHEEPANDGOAT.COM

2. Gastro-intestinal parasites (worms) are the
primary health problem affecting small ruminants.

3. The barber pole worm (Haemonchus
contortus) is the primary parasite affecting
small ruminants in warm, moist climates.
Bottle jaw
Anemia

4. The barber pole worm has developed resistance
to all anthelmintics and all anthelmintic classes.
Anthelmintic resistance
When an anthelmintic
treatment fails to
reduce fecal egg
counts by 95% or more.

5. Anthelmintic resistance was (is) inevitable.
No treatment will kill 100% of worms.

6. Numerous on-farm practices have accelerated the
development of resistant worms in small ruminants.
 Frequent deworming, especially without regard to clinical need.
 Underdosing drugs (failure to dose based on accurate weights).
 Injecting an anthelmintic instead of using a drench.
 Pouring an anthelmintic on the back instead of using a drench.
 Improper administration of drenches, e.g. depositing drug in mouth
 Use of persistent-activity dewormers (e.g. moxidectin).
 Treating all animals in flock/herd, leaving no refugia.
 Putting treated animals onto a clean pasture: no refugia.
 Treating animals when pasture contamination is low.
 Giving more than one dewormer at a time.
 Introduction of resistant worms to a farm via new animals; failure to
quarantine drench.

7. Anthelmintic resistance
 Is not fully appreciated by some producers
and veterinarians.
 Varies by geographic region and farm.
 Is result of past deworming practices.
 On most farms, resistance is probably still
at a level where there is still time to slow it
down and enable the continued use of
(some) anthelmintics.
 Most small ruminant producers do not
know which dewormers work on their farm.
? ?
??

8. Dealing with anthelmintic resistance
on the farm.
 The first thing you need to do is
determine which dewormer(s) still
work on your farm.
 All producers need to devise
production/ management systems
that minimize the need for
deworming.

9. There are two methods to determine
anthelmintic (dewormer) resistance.
Fecal egg count
reduction test (FECRT)
 Comparison of pre- and post-
treatment fecal egg counts.
 Must compare egg counts for
each individual anthelmintic.
DrenchRite® larval
development assay (LDA)
 In vitro test for anthelmintic
resistance (for all drugs).

10. Fecal egg count reduction test (FECRT)
 Collect samples at the time of
treatment (deworming).
 Collect post-treatment samples
 8-10 days, benzimidazoles
 14-17 days, macrocylic lactones
 5-7 days, levamisole
 10-14 days, all dewormers
 Need FECs > 250 epg
 Favor animals with higher FAMACHA©
scores and positive dag scores.
 Should include a control group
for comparison.
DrenchRite® larval
development assay (LDA)
 Collect pooled fecal sample
from at least 10 animals.
 Need FECs > 350-500 epg
 Favor animals with higher
FAMACHA© scores and
positive dag scores.

11. Fecal egg count reduction test (FECRT)
 Takes 7-14 days (or more) to get results,
longer if done by someone else.
 Cost of testing varies
(15 samples x 4 anthelmintics + control group)
75 x free labor = no cost
75 x $5/sample = $350
75 x $10/sample = $750
 Requires a lot more animals (ideally,
12-15 per treatment group); many
producers don’t have enough
animals for accurate testing.
 Results
% reduction (whole flock/herd)
Results from individual animals can be quite
variable.
DrenchRite® larval
development assay (LDA)
 Takes 3-4 weeks to get results
 Only one lab in US that does test:
Dr. Ray Kaplan’s lab at the University
of Georgia College of Veterinary
Medicine.
 $450 per sample
 Results
Resistant (R)
Susceptible (S)
Suspected resistance (SR)

12. There are many things a producer can do to
potentially reduce the number of animals that require
deworming and/or the frequency of deworming.
 Pasture and grazing management
 General management
 Animal management
 Nutritional management
 Genetic selection
 Targeted selective treatment (TST)
 “Natural” things

13. The foundation of parasite control is good
pasture and grazing management.
 Evasive grazing: pasture rest and rotation
 Maintaining minimum grazing heights (> 3 in.)
 Browsing
 Mixed swards
 Clean pastures
 Annual pastures
 Tannin-rich forages
 Mowing, haying, cropping
 Mixed species grazing w/alpacas, llamas
 Low/reduced stocking rates ****

14. Certain management practices may
reduce the need for deworming.
Management
 Winter or fall lambing/kidding
 Early marketing
 “Early” weaning
 Night penning
 Zero grazing
 Delay grazing until after dew lifts
 Put treated animals in dry lot for 48
hours after deworming
 Good sanitation/hygiene
Nutrition
 Manage pastures so that plants are in a vegetative
stage for grazing.
 Plant annuals, legumes, and warm season plants to
improve nutrition of pasture.
 Provide supplemental nutrition when pasture
quantity or quality is low/poor and/or to susceptible
animals.
 Soy hulls
 Distiller’s grains (DDSG)
 By-pass protein (?)
 Increase protein in late gestation ration to counter
periparturient egg rise.
 Maintain animals in good body condition (BCS > 2.5)

15. Genetic selection can reduce the
number of animals that require deworming.
Between species/breed
 Goats are usually more susceptible
to parasites than sheep.
 Some sheep breeds are more
resistant to parasites.
 Hair sheep of tropical origin:
St. Croix, Barbado, Katahdin
 Native breeds of the Southeast:
Natives, Crackers
 Other breeds: Texel (?)
 Some goat breeds seem to be
more resistant to parasites than
others: Kiko, Spanish, Myotonic.
Within breed
 80:20 (or 70:30) rule
20-30 percent of flock/herd is responsible
for 70-80% of pasture contamination
(egg shedding).
 Can select any breed for improved
resistance to parasites
 Select individuals with lower FECs.
 Use EBVs (estimated breeding values) to
choose resistant males for breeding.
 Parasite resistance (fecal egg counts) is
a moderately heritable trait (20-40%):
heritability of prolificacy is only 10%.
 Resilience is less heritable.

16. Targeted Selective Treatment (TST)
Only treating animals that require treatment or would benefit from treatment; increases refugia.
FAMACHA© SYSTEM
 Uses color eye chart to estimate
level of anemia (packed cell
volume/PCV); thus, need
for deworming.
 Only useful for blood-feeding
parasites, such as barber pole worm.
Category Color PCV Tx?
1 Red > 28 No
2 Red-Pink 23-27 No
3 Pink 18-22 ?
4 Pink-White 13-17 Yes
5 White < 12 Yes
Refugia – worms
not exposed to
anthelmintic(s).

17. Targeted Selective Treatment (TST)
Only treating animals that require treatment or would benefit from treatment; increases refugia.
FIVE POINT CHECK© - 5.
 Extension of FAMACHA© system: decision-
making tool for all parasites that commonly
affect small ruminants.
 Involves 5 check points on animal’s body
1. Eye
FAMACHA© score (anemia) (1-5)
2. Jaw
Submandibular edema (bottle jaw)
3. Back
Body condition score (1-5)
4. Tail
Dag score, fecal soiling (scouring) (0-5)
5. Nose
Sheep: nasal discharge (bot flies)
Goats: coat condition

18. The FAMACHA© system is a perfect example of
the land grant mission: to get producers to apply
research-based knowledge to solve a problem.
 Producers must take an
approved training in
order to receive a
FAMACHA© card.
 Since 2003, over 29,000
FAMACHA© cards have
been sold to over 40
states and various
Caribbean and Latin
American countries.
 Two formal evaluations of
FAMACHA© workshops
have been conducted.
91%
78% 76%
95%
74% 75%
0
10
20
30
40
50
60
70
80
90
100
Using FAMACHA Deworming less Saving money
2004 2009

19. What are limitations to producers adopting
the FAMACHA© system/Five Point Check©?
 Conflicting information
Many veterinarians give out-dated advice.
 Tradition
Many producers still think of deworming as a
preventative and best management practice.
 Availability of training
Workshops are not always available at
convenient locations or times.
 New anthelmintic
There is a new anthelmintic in the pipeline
(Zolvix®); the urgency of anthelmintic
resistance may be abandoned (?).
 The FAMACHA© system was
developed for “small” farms;
FAMACHA© scoring is labor-
intensive.
 It is easier to deworm all
members of the flock/herd
than to check their
FAMACHA© and other scores.
 Sub-clinical parasitism is not
treated; it is a cost of Targeted
Selective Treatment.

20. “Natural” dewormers
SOME: (GENERALLY) EFFECTIVE
 Kill parasites
 Copper oxide wire particles (COWP)
 Copper sulfate ()
 Tobacco and nicotine sulfate ()
 Reduce treatment #’s
 Condensed tannins
Sericea lespedeza
 Duddingtonia flagrans
nematode-trapping fungus
***not commercially available yet**
MOST: INEFFECTIVE AND/OR UNPROVEN
 Diatomaceous earth (DE)
 Garlic
 Papaya
 Paprika
 Pine bark
 Pumpkin seeds
 Commercial herbal dewormers
(e.g. Hoegger’s herbal dewormer)
 Many, many more…

21. Copper oxide wire particles (COWP)
 Copper oxide wire particles have been shown to
reduce parasite burdens (H. contortus) in lambs
and kids.
 Less effective in mature animals.
 Copper oxide wire particles are a slow-release form
of copper
 Less potential for toxicity in sheep; sheep are sensitive
to excess copper in the diet.
 Copasure® is a copper supplement (12.5 and 20 g) for
cattle that can be repackaged into smaller doses for
sheep and goats (0.5 to 4 g).
 Copasure® capsules are now available in 2 g and 4 g
dosages for sheep and goats (as Cu supplement).
 Selective treatment with COWP advised.
 FAMACHA© scores of 3, 4, 5 only.

22. Effect of copper oxide wire particles on the parasite status of
bucks in the 2014 Western Maryland Pasture-Based Meat Goat
Performance Test (0.5 g COWP administered on d-42)
0
500
1000
1500
2000
2500
3000
3500
4000
4500
5000
d (-6) d-0 d-14 d-28 d-42 d-56 d-70 d-84
Test - COWP
Study - no COWP

23. Condensed tannins
 Tannins are plant compounds that bind to proteins
and other molecules.
 Effects of tannins vary depending upon type,
concentration, and the animal consuming the tannin.
 Tannins can have both negative or positive effects.
 Sericea lespedeza (AU Grazer™) is a high-tannin
forage (warm season legume) that has been
scientifically-proven to reduce parasite burdens in
sheep and goats.
 Fresh forage
 Hay
 Leaf meal (pellets) [simsbrothers.com]
Sericea cuneata

24. “Natural” dewormers (IMO)
 Most likely effect of “natural” dewormers will be to reduce the
number of animals that require deworming by . . .
 Disrupting the free-living stage of the parasite (e.g. egg hatching, larval development)
 Improving the immune function of the host.

25. THANK YOU. QUESTIONS? COMMENTS.
American Consortium for Small Ruminant Parasite Control - www.wormx.info