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