DrenchRite® LDA ▪Developed in Australia in the 1990’s

▪ Tests all 3 drug classes (moxidectin validated later)

▪ Effective for detecting resistance to H. contortus and T. colubriformis

Rows A,B,C Benzimidazole

Rows D,E Levamisole

Rows F,G,H Ivermectin

Internal parasite resistance to anthelmintics in Montana and Wyoming

(Year 2 Preliminary Summary)

Whit C. Stewart1, Tom W. Murphy2, Dave Scott3, Sue Howell41University of Wyoming, Department of Animal Science

2Montana State University, Department of Animal and Range Science3National Center for Appropriate Technology, Livestock Specialist/Sheep Producer

4University of Georgia, College of Veterinary Medicine, Kaplan Lab

Nebraska StatisticsUSDA NASS 2017 Census of Agriculture

71,771

63,043

58,000

60,000

62,000

64,000

66,000

68,000

70,000

72,000

74,000

Total Sheep and Lambs

Sheep and Lamb Inventory 2012 and 2017

2012 2017

Meat Goats: 2012- 21,321 hd; 2017- 24, 279 hd

1464

1153

0

200

400

600

800

1000

1200

1400

1600

Sheep Operations

Sheep Operations 2012 and 2017

2012 2017

Nebraska StatisticsUSDA NASS 2017 Census of Agriculture

County Sheep and Lambs 2012

Sheep and Lambs 2017

Clay 3,967 3,770

Knox 1,512 3,421

Webster 3,645 3,360

Dawes 849 2525

Pierce 3,656 2,002

Meat Goats: 2012- 21,321 hd; 2017- 24, 279 hd

DrenchRite® LDA ▪Developed in Australia in the 1990’s

▪ Tests all 3 drug classes (moxidectin validated later)

▪ Effective for detecting resistance to H. contortus and T. colubriformis

Rows A,B,C Benzimidazole

Rows D,E Levamisole

Rows F,G,H Ivermectin

Internal parasite resistance to anthelmintics in Montana and Wyoming

(Year 2 Preliminary Summary)

Whit C. Stewart1, Tom W. Murphy2, Dave Scott3, Sue Howell41University of Wyoming, Department of Animal Science

2Montana State University, Department of Animal and Range Science3National Center for Appropriate Technology, Livestock Specialist/Sheep Producer

4University of Georgia, College of Veterinary Medicine, Kaplan Lab

PROJECT OBJECTIVES

• Determine extent of H Contortus barber Pole worm resistance to common dewormers in Montana and Wyoming flocks

• Characterize risk factors associated with internal parasite challenges

– Current de-worming protocol

– Identifying operational risk factors (irrigated/sub-irrigated)

• Develop region specific resources (Intermountain West)

Benzimidazoles: (Panacur, Safeguard, Valbazen)

Ivermectin: (Ivomec,

Eprinex, Dectomax)

Levamisoles: (Prohibit, LevaMed) Moxidectin: (Cydectin)

Available Dewormers:Do they still work on my ranch?

Category Wyoming Nebraska

Geography 97,814 sq. mi. 77,358 sq. mi.

Sheep Inventory (rank) 367,702 (4th) 71,771 (18th)

1Sheep Operations 859 1153

1 to 99 hd (%) 70% 87%

100 to 299 hd (%) 11% 10%

300 to 999 hd (%) 8% 2%

1000 to 10,000 hd (%) 11% 0.4%

1USDA-NASS, 2012; 2USDA-NASS, 2017

Continuously Grazed- Irrigated Operations

Many sheep spend some time on irrigated or sub-irrigated acreage in the Intermountain West.

• Most important gastrointestinal parasite affecting sheep on pasture

• Damages functionality of abomasum and basic physiological proccesses

• Result is anemia or below normal numbers of red blood cells• 1 adult worm 0.05 mL/day, • 5000 worms 250 mL= 1 cup/day

• Decreased production (milk, weight gain)

Haemonchus Contortus(Barber Pole Worm)

H. Contortus Biology

• Hatching of an H. Contortus egg is followed by a few larval stages.

• During early stages, the larva feed on bacteria present in sheep feces.

• The infective larval stage is referred to as L3.

• L3 larva can’t eat, they need to be ingested by a host or will eventually die!

• L3 larva don’t “inch” like a typical worm, they move up and down leaves in dew.

H. Contortus Life Cycle• ~7 d from egg to L3

• Once ingested, ~3 wkfrom L3 to adult

• Adults can live for months inside the abomasum.

• 200 female adults can produce 1 million eggs per day!

• Eggs are shed in the feces and deposited in the environment.

H. Contortus Overwintering• H. Contortus eggs and L3 larvae do not do well during hard

winters.

• Several freezing/thawing events will kill a large population on H. Contortus eggs and L3 larvae on pasture – some always survive

• After ingestion in the fall, a lot of L3 larvae will overwinter in a dormant state inside the abomasal wall – hypobiosis.

• Do not become adults (and produce eggs) until spring/lambing time

Physiological Changes

Hoste et al., 2016

Nutritionally Disadvantaged

Coop and Kyriazakis, 1999; Coop and Kyriazakis, 2001; Hoste et al., 2016

Anthelmintic Efficiency in Australia

Anthelmintic Resistance Regions(Published Research)

Anthelmintic Class Prevalence of resistance

Mid Atlantic U.S., (Crook et al 2016)

• Benzimidazoles (Safeguard, Valbazen)• Ivermectin (Eprinex, Dectomax)• Moxidectin (Cydectin)• Levamisole (Panacur, Prohibit, Safeguard)

100%82%47%24%

Southeastern U.S.(Howell et al., 2008)

• Benzimidazoles (Safeguard, Valbazen)• Ivermectin (Eprinex, Dectomax)• Moxidectin (Cydectin)• Levamisole (Panacur, Prohibit, Safeguard)

93%76%24%54%

Ontario,Canada(Falzon et al., 2012)

• Benzimidazoles (Safeguard, Valbazen)• Ivermectin (Eprinex, Dectomax)• Moxidectin (Cydectin)• Levamisole (Panacur, Prohibit, Safeguard)

95%97%---6%

Drug Resistance= treatment fails to reduce fecal egg counts by more than 95%

Methods

• Fecal Sample Collection (June to August, 2017-2018)

• Irrigated and Sub-Irrigated Ranches• 8 Montana Ranches

• 4 Wyoming Ranches

• Larval Development Assay (DrenchRite™)

• Coproculture (Speciation of Parasites)

DrenchRite® LDA

▪ Developed in Australia in the 1990’s

▪ Tests all 3 drug classes (moxidectin validated later)

▪ Effective for detecting resistance to H. contortus and T. colubriformis

Rows A,B,C Benzimidazole

Rows D,E Levamisole

Rows F,G,H Ivermectin

Preliminary Results• Ranches (n=12)

• Sub-Irrigated = 3 ranches

• Irrigated (flood, sprinkler) = 9 ranches

• Average Fecal Egg Count (FEC): = 3800 eggs per gram (EPG)• Sub-Irrigated FEC = 683 EPG

• Irrigated FEC = 4,435 EPG

• Nematode Species:• Haemonchus Contortus (Barber Pole) ∼ 80%

• Teladorsagia ∼ 12%

• Trichostrongylus∼ 8%

Benzimidazoles: (Panacur, Safeguard, Valbazen)

Ivermectin: (Ivomec,

Eprinex, Dectomax)

Levamisoles: (Prohibit, LevaMed) Moxidectin: (Cydectin)

Available Dewormers:Do they still work on my ranch?

Results: Benzimidazole

83%

8% 8%

0%

20%

40%

60%

80%

100%

HighResistance

(~0 %)

ModerateResistance(~50-80%)

LowResistance(~80-90%)

Susceptible (≥ 95%)

% o

f O

pe

rati

on

s

Anthelmintic Efficacy (%Efficacy)

Results: Levamisole(Year 1, n= 6 ranches)

Anthelmintic Efficacy (%Efficacy)

16%

66%

16%

0%

20%

40%

60%

80%

HighResistance

(~0 %)

ModerateResistance(~50-80%)

LowResistance(~80-90%)

Susceptible (≥ 95%)

% o

f O

pe

rati

on

s

Results: Ivermectin

Anthelmintic Efficacy (%Efficacy)

16%25%

58%

0%

20%

40%

60%

80%

HighResistance

(~0 %)

ModerateResistance(~50-80%)

LowResistance(~80-90%)

Susceptible (≥ 95%)

% o

f O

pe

rati

on

s

Results: Moxidectin

Anthelmintic Efficacy (%Efficacy)

16%

84%

0

0.2

0.4

0.6

0.8

1

HighResistance

(~0 %)

ModerateResistance(~50-80%)

LowResistance(~80-90%)

Susceptible (≥ 95%)

% o

f O

pe

rati

on

s

De-wormer Costs

Product Dosage $/mL $/ 100 lb. $/ 160 lb.ewe

$/ 200 ewes

Valbazen 3 mL/ 100 lb. $0.07 $0.21 $0.34 $68

Safeguard 2.3 mL/ 100 lb.

$0.12 $0.28 $0.45 $90

Ivermectin 3 mL/ 100 lb. $0.07 $0.21 $0.34 $68

Prohibit (Levamisole)

30 mL/ 100 lb. $0.01 $0.30 $0.48 $96

Cydectin(Moxidectin)

1 mL/ 11 lb. $0.07 $0.63 $1.00 $200

What is FAMACHA(FAffa MAlan Chart)

• Selective deworming tool for sheep and worms susceptible to barber pole worm (H. contortus

• Treating sick animals not eradicating the presence of parasites

• 20% of the sheep harbor 80% of the parasite load

Van Wyk et al. 2002; Burke et al. 2007;

Cover, Push, Pull, Pop

Other Clinical Signs of Parasitism

• Diarrhea

• Bottle Jaw

• Poor body condition

• Abnormal fleece or hair coat

• Intolerant to heat and exercise

• Overwintering of barber pole worm was due to resistant tissue dwelling L4 larvae• Doramectin “Dectomax”- 69% efficacy• Albendazole “Valbazen”- 90% efficacy• Moxidectin- “Cydectin” – 100% efficacy

Know what dewormer works on your operation!

Management Considerations

Don’t purchase resistant worms! Treat purchased replacement animals at beginning of quarantine period!

• Stocking density• Without good pasture rotation, higher stocking density results in higher pasture

contamination

• Effectiveness of deworming program• If some portion of a worm population has developed resistance to an

anthelmintic, pasture contamination will be higher

• Climate• Pasture contamination will be highest during periods of warm, wet and/or

humid weather

• Optimal Temperatures for hatching, larval development, L3 Survival• Teladorsagia circumcinta- 60.8˚ F to 86˚F• Trichostrongylus colubriformis- 71.6˚ F to 91.4˚F• Haemonchus contortus- 77˚ F to 98.6˚F

• More than ¼ to ½ inch of precipitation during 70˚ to 90˚ temps can increase incidence

Management Considerations

• Ewes had greatest fecal egg counts 28 days post-lambing• Yearling ewes had higher fecal egg counts than adult ewes• Lambs greatest risk from 60 to 120 days• Lambs from yearlings, and lambs reared as multiples

greatest risks

Management Considerations

• Range operation vs. irrigated/ sub-irrigated?• Irrigated = higher risk of internal parasites• Range = lower risk of internal parasites

• Utilizing diagnostic testing prior to major sheep working events to determine whether to worm.• Fecal egg count- WY $15.00 to $25.00• Deworming 200 hd flock = $90

• Fasting ewes 24 h prior to administration of Benzimadazoles will increase drug efficacy (Lifshitz, 1997, Singh, 1999)

Management Considerations

De-wormer Costs

Product Dosage $/mL $/ 100 lb. $/ 160 lb.ewe

$/ 200 ewes

Valbazen 3 mL/ 100 lb. $0.07 $0.21 $0.34 $68

Safeguard 2.3 mL/ 100 lb.

$0.12 $0.28 $0.45 $90

Ivermectin 3 mL/ 100 lb. $0.07 $0.21 $0.34 $68

Prohibit (Levamisole)

30 mL/ 100 lb. $0.01 $0.30 $0.48 $96

Cydectin(Moxidectin)

1 mL/ 11 lb. $0.07 $0.63 $1.00 $200

Example: 10,000 ewes wormed at weaning (fall) and docking (spring). Resulted in 20,000 de-worming doses annually @ $9,000 per year ($.45 per hd).

Woody Plants as Anthelmintic

• Feeding juniper improved ivermectin efficiency on barber pole worm

• Feeding ground juniper inhibited parasite larval migration

• Sericea Lezpedeza proven to reduce parasite burden

Forages with Condensed Tannins

Birds foot Trefoil Sanfoin

Anthelmintic bioactivity?

Paolini et al., 2004; Inhibitory on L3Paolini et al., 2005; reduce pasture contamination and host resilienceBrunet et al., 2007; exsheathmentsignificantly disturbed

Marley et al., 2003; Lowered FECHeckendorn et al., 2007; Lowered FECBernes et al., 2000; No effect on FEC

Acknowledgements

• Funding Agency- Western-Sustainable Agriculture Research and Education Grant• Dr. Whit Stewart (Co-PI) University of Wyoming• Dave Scott (Co-PI) National Center for Appropriate Technology/Montana Highland Lamb• Dr. Tom Murphy (Co-PI) Montana State University• Sue Howell and Dr. Ray Kaplan (Collaborator) Univ. Georgia , College of Vet Med• American Consortium for Small Ruminant Parasite Control

• Cooperating ranches in Montana and Wyoming

Questions