Internal parasites pose a significant health problem for sheep farms. Common internal parasites include various nematodes (roundworms) and flukes. The barber pole worm causes major losses worldwide. Widespread anthelmintic (dewormer) resistance has developed due to overreliance on and misuse of dewormers. Studies show resistance to common dewormers on many Alberta farms. Integrated parasite management is needed to control parasites in a sustainable manner while reducing selection pressure for resistance.

1. THE IMPACT OF INTERNAL PARASITES
ON FLOCK HEALTH AND PRODUCTIVITY
SUSAN SCHOENIAN
Sheep and Goat Specialist
University of Maryland Extension
sschoen@umd.edu – www.sheepandgoat

2. INTERNAL PARASITES
GASTRO-INTESTINAL PARASITES, NEMATODES, WORMS
 Internal parasites are the primary
health problem of sheep raised in
warm, moist climates or during
periods of warm, wet weather.
 Parasite risk varies by geographic
area, year, season, and production
practices.
 Internal parasitism is exacerbated by
the widespread development of
anthelmintic-resistant worms (caused
by over-reliance on and misuse of anti-
parasitic drugs).

3. MANY INTERNAL PARASITES CAN AFFECT SHEEP.
1. Nematodes (roundworms)
 Haemonchus contortus (barber pole)
 Trichostrongylus
 Teladorsagia (Ostertagia)
 Nematodirus
 Meningeal worm
 Lungworms
2. Trematodes (flatworms)
 Tapeworms - Moniezia expanza
 Flukes - Fasciola hepatica
3. Protozoa
 Coccidia - Eimeria spp.

4. THE BARBER POLE WORM
HAEMONCHUS CONTORTUS
 Originally thought of as a tropical
parasite, the range of the barber pole
worm is expanding, as the parasite is
adapting to more northern climates
(because of climate change ?).
 The blood-sucking barber pole worm is
deadly. It is usually the most
pathogenic parasite affecting small
ruminants.
 The barber pole worm probably causes
more death losses (in small ruminants)
than any other parasite worldwide.

5. ANTHELMINTIC RESISTANCE
ABILITY OF WORMS IN A POPULATION TO SURVIVE DRUGTREATMENTS THAT ARE GENERALLY EFFECTIVE
AGAINSTTHE SAME SPECIES AND STAGE OF INFECTION ATTHE SAME DOSE RATE.
 Anthelmintic resistance has been
reported in all sheep-raising countries
of the world.
 Worms have developed resistance to
all dewormers and dewormer classes.
 There is cross-resistant among drugs
in the same class; worms develop
resistance to mode of action, not
specific drug.
 Some farms are experiencing total
anthelmintic failure.
 Less is know about anthelmintic
resistance in Canada and Alberta.
< 95% reduction in FEC = suspected resistance
< 90% reduction in FEC = resistance

6. ANTHELMINTIC RESISTANCE IN USA

7. PILOT STUDY IN ALBERTA (SUMMER 2014)
Farm # Mean FEC
1 162
3 2753
4 458
5 837
7 562
11 392
12 983
13 271
15 700
16 322
18 8
19 8
20 2520
21 1091
22 1604
23 1520
24 4507
25 271
Fenbendazole Ivermectin
Farm % reduction 95% CI % reduction 95% CI
7 16 0-81 77 10-94
15 70 13-91 41 0-79
20 38 0-71 78 33-93
24 -94 0-20 -34 0-47
Source: N’ewesletter, January 2015, Alberta Lamb Producers

8. CONCLUSIONS OF PILOT STUDY
 As evidenced by high egg counts in ewes,
manyAlberta sheep flocks have high
parasite burdens.
 ManyAlberta farms have resistance to
fenbendazole (benzimidazole) and
ivermectin (macrocylic lactone -
avermectin).
 The high egg counts could be indicative of
a heavy burden of Haemonchus contortus
(barber pole worm) on some farms.
 A larger study is planned to confirm
preliminary findings and provide a detailed
picture of the prevalence, distribution, and
anthelmintic sensitivity of GI parasites in
Alberta sheep.

9. TWO PRIMARYTESTSTO DETERMINE
ANTHELMINTIC RESISTANCE (AR)
1. In vivo
Fecal egg count reduction test
 Compare before and after treatment fecal egg
counts of treated and untreated (control)
animals for each drug.
2. In vitro
Larval development assay (LDA)
DrenchRite® test
 Lab test that uses a pooled fecal sample to
detect anthelmintic resistance to four different
anthelmintic groupings.

10. FECAL EGG COUNT REDUCTIONTEST (FECRT)
 Compare before and after fecal egg counts (10-14 d):
Calculate percent reduction in FEC
<90% = resistance present <95% = resistance suspected
 High variability after 95%.
Most accurate when results are between >97 and <60%.
 Few animals and lower egg counts increase variability (and
bias) of results.
 Need groups of 15 animals (lambs=best, >200 epg) not
dewormed for previous 8-12 weeks .
 Evaluates one drug, one dose
 Local vet or diagnostic lab can do; producer can learn to do.

11. DRENCHRITE® ASSAY
LARVAL DEVELOPMENT ASSAY (LDA)
 Labor-intensive lab test
a. Utilizes eggs isolated from feces from infected animals.
b. Eggs are placed in well assay plate.
c. The plates have doubling concentrations of different
drugs in them, along with “no drug” controls.
d. Eggs are hatched to 3rd stage larvae.
e. At end of incubation period, the plate is examined .
 Samples (from about 10 animals, >200 epg) need to be
properly collected and shipped.
 Determines resistance or suspected resistance for four drench groups.
 Identifies parasite species from larvae, e.g. % Haemonchus
 Test is done by Dr. Ray Kaplan’s lab at the University of GeorgiaVet School.

12. COMPARISON OFTESTS
FECRT
 Tests one drug, one dosage
 Egg count is for all strongyle-type worms
 Need more animals to sample
 More practical, but requires considerable
on-farm work
 Veterinarian or diagnostic lab can
do fecal egg counting.
 Producer can learn to do
 Cost varies; more expensive than LDA if
you pay to have fecal egg counts done
(US$3-20 per sample).
DRENCHRITE® - LDA
 Tests all drug groups simultaneously
- Resistance to moxidectin is estimated
 Identifies worm species by %
 Requires fewer animals, ~10
 Expensive (?) - $450
 University of Georgia is only lab in US that
does DrenchRite test.
 Alberta (x), elsewhere in Canada (?)

13. THE PRIMARY COST(S) OF INTERNAL
PARASITISM MAY BE SUB-CLINICAL
 Reduced milk production
 Reduced growth rates
 Reduced feed and grazing efficiency
 Gut motility (tapeworms)
 Increased days to market
 Reduced wool growth
 Lower body condition
 Increased dag scores/higher breech scores
 Reduced feed intake
 Reduced immunity to other disease
conditions.

14. MODELING EFFECTS OF INTERNAL PARASITISM
 For a project in Mexico, Dr. Dave
Notter (VATech, retired) modeled
the effects of internal parasitism on
grazing lambs.
 In Mexico, there are large regional
differences in parasite challenge, drug
resistance is prevalent, making
intensive use of chemical dewormers
ineffective, and there are both highly
susceptible and resistant breeds in
the sheep population.
 He presented this series of graphs at
the 2014 SouthwestVirginia Sheep
Field Day & Ram Sale.

15. MODELINGTHE EFFECTS OF INTERNAL PARASITISM

16. MODELINGTHE EFFECTS OF INTERNAL PARASITISM

17. MODELINGTHE EFFECTS OF INTERNAL PARASITISM

18. MODELINGTHE COSTS OF INTERNAL PARASITISM

19. MODELINGTHE COSTS OF INTERNAL PARASITISM

20. MODELINGTHE COSTS OF INTERNAL PARASITISM

21. MODELINGTHE COSTS OF INTERNAL PARASITISM

22. MODELINGTHE COSTS OF INTERNAL PARASITISM

23. PRODUCTION COST OF ANTHELMINTIC
RESISTANCE (New Zealand, 2012)
 Ten farmlets, each stocked with 30
lambs, were used to determine
economic impact of anthelmintic
resistance.
 Lambs were grazed for five months
and dewormed monthly with either
albendazole, to which resistance
existed, or a new combination
product (derquantel + abamectin) to
which there was no resistance.
 Productivity measures were
determined on five farms.
 Anthelmintic efficiency was measured
at last two dates.
Drug
Trichostrongylus
spp.
Teladorsagia
circumcincta
Albendazole 48.4% 40.9%
Combination >99% >99%

24. PRODUCTION COST OF ANTHELMINTIC
RESISTANCE (New Zealand, 2012)
(---) Highly-effective drench (combination: derquantel + abamectin)
(__) Ineffective drench (albendazole)
Parasite species: trichostrongylus, teladorsagia, and nematodirus

25. PRODUCTION COST OF ANTHELMINTIC
RESISTANCE (New Zealand, 2012)
Improved performance of lambs
treated with effective dewormer
 + 9 kg (4.1 lb.) live weight gain
 + 4.7 kg (2.1 lb.) carcass weight
 + 10.4% increase in carcass value
 Time required for 50% of lambs to reach
target weight (38 kg/83.6 lbs.) was
significantly shorter (17 days) in animals
treated with effective dewormer.
 Significant differences in body condition
scores, breech scores, and fleece weights
were also recorded -- all in-favor of lambs
treated with effective dewormer.

26. COST-BENEFIT OF ANTHELMINTIC PROTOCOLS
Group Anthelmintic protocol
Group A
(n=10)
Without drug rotation
Levamisole every 60 d
Group B
(n=10)
With drug rotation
Levamisole at months 2, 4, 8, and 12;
albendazole at month 6
Group C
(n=10)
Targeted SelectiveTreatment (TST)
Treated according to FAMACHA© (4,5)
or FAMACHA© + body condition score (3)
One year study at a farm in Southern Brazil
Primary species: Haemonchus contortus, Trichostrongylus ,Teladorsagia (Ostertagia)
Source:Acta ScientiaeVeterinariae, 2014

27. COST-BENEFIT OF ANTHELMINTIC PROTOCOLS
Group A
Bi-monthly, no rotation
Group B
Bi-monthly, rotation
Group C
FAMACHA© (selective)
Unnecessary cost of 66.6%
Increased selection for
resistant worms (LEV)
7.4% lower cost than A
Unnecessary cost of 63.3%
Increase selection for resistant
worms (LEV, ALB)
Lower fecal egg counts
49.6% lower cost than A
Reduce use of anthelmintics
Less treatment costs
Reduced selection for resistant parasites
Reduced chance of drug residues
Best cost-benefit ratio
**Constant management**
Source: Acta ScientiaeVeterinariae, 2014

28. EFFECTS OF INTERNAL PARASITISM ON
NUTRITION
 Nutritional requirements (NRC)
are generally for confined
animals, e.g. low parasite
burden.
 Internal parasitism affects both
energy and protein (and amino
acid) requirements of sheep.
 There is need for more
information on the consequence
of internal parasitism on
nutritional requirements.

29. EFFECTS OF INTERNAL PARASITISM ON
NUTRITION (ENERGY)
 Effects of parasitism on MEm have not been well
quantified, but is thought to involve a decrease in Km as a
result of increased turnover of GI tract protein, apart from
frequent occurrences of reduced feed intake.
 Immune response to parasites could have nutritional costs
as high as 15% of maintenance needs, which is supported
by decreased wool growth by sheep selected for resistance
to internal parasitism.
 An example cost of 5% has been calculated.
 Nutrient partitioning during pregnancy and lactation
compromises ewe’s ability to resist parasite infection.
K = efficiency

30. EFFECTS OF INTERNAL PARASITISM ON
NUTRITION (PROTEIN)
 Decreased feed intake in response to internal parasite
would entail an increase metabolizable protein requirement
both on an absolute and dietary concentration basis.
 Numerous studies now support the view that providing
supplemental metabolizable protein to sheep with
subclinical infections of GI parasites improves their
resistance and resilience to parasites.
 The response to supplementation is greater when the
protein source is not extensively degraded, i.e. by-pass
protein, e.g. fish meal.
 Requirement for sulfur-amino acids will be greater (benefit
of methionine supplementation demonstrated).

31. WHAT WE DON’T WANTTO HEAR
 Anthelmintic resistance is real.
 Anthelmintic resistance is widespread.
 Anthelmintic resistance is increasing
 Anthelmintic resistance is permanent.
 There is multiple drug resistance.
 Anthelmintic resistance is inevitable; all we can
do is affect the rate at which it occurs.
 Sequential deworming and combination
dewormers are only a short-term “fix.”
 Anthelmintics (dewormers), including new ones
(Zolvix®/monepantel) are not the answer to
controlling parasites.

32. THANKYOU FORYOUR ATTENTION.
QUESTIONS? COMMENTS?
SUSAN SCHOENIAN
Sheep & Goat Specialist
University of Maryland Extension
sschoen@umd.edu
www.sheepandgoat.com
www.wormx.info