Combination anthelmintics (dewormers):

High Time to Implement

SUSAN SCHOENIANSheep & Goat SpecialistUniversity of Maryland Extension

sschoen@umd.edu www.sheepandgoat.comwww.sheep101.infowww.wormx.info

www.slideshare.net/schoenian/ or go to www.sheepandgoat.com and choose SlideShare from the social media drop-down menu

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 (Haemonchuscontortus) 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.

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).

Anthelmintics 101

An anthelmintic or “dewormer” kills or expels worms.

There are three “chemical” classes of

dewormers for small ruminants (in US).

GROUP 1Benzimidazoles

(BZ)

GROUP 2Macrocylic lactones (ML)

GROUP 3Nicotinic agonists

Avermectins MilbemycinsImidazo-thiazoles

Tetrahydro-pyrimidines

FenbendazoleSafeGuard®

Panacur®

IvermectinIvomec®

MoxidectinCydectin®

Quest®

LevamisoleProhibit®

Leva-Med®Tramisol®Levasol®

Morantel tartrateRumatel®

AlbendazoleValbazen®

DoramectinDectomax®

PyrantelStrongid®Eprinomectin

Eprinex®OxfendazoleSynanthic®

Anthelmintics FDA-approved for sheep1

BenzimidazolesValbazen®

sheep drench

2aAvermectins

Ivomec®sheep drench

2bMilbimycinsCydectin®

sheep drench

3LevamisoleProhibit®

Leva-Med®

Adult worms

Larvae (L4) Limited

Hypobiotic larvae Limited

Lungworms

Tapeworms

Liver flukes Adult stage

Coccidia

External parasitesSome

labeled for bot control

SomeNot labeled

Persistent activity

Safety10x

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

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).

Levels of resistance to benzimidazoles

Number of farms (n=26)

0

5

10

15

20

25

30

Susceptible Suspectedresistance

Low tomoderateresistance

Moderate tohigh 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).

Levels of resistance to ivermectin

Number of farms (n=26)

0

2

4

6

8

10

12

Susceptible SuspectedResistance

Low resistance Moderate to highresistance

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).

Levels of resistance to moxidectin

Number of farms (n=26)

0

2

4

6

8

10

12

14

16

Susceptible Suspectedresistance

Low to moderateresistance

Moderate to highresistance

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).

Levels of resistance to Levamisole

Number of farms (n=26)

0

2

4

6

8

10

12

14

16

Susceptible Suspectedresistance

Lowresistance

Moderateresistance

Highresistance

Georgia

Virginia

Maryland

Two ways to test for dewormer resistance.

FECAL EGG COUNT REDUCTION TEST (FECRT)

DRENCHRITE® LARVAL DEVELOPMENT ASSAY

1. Old protocolCompare fecal egg counts of treated and untreated (control) animals.

2. Newer protocolCompare 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

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)

“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

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.

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

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

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%

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™.

Recommendations for using

dewormers in combination

Valbazen® Cydectin® Prohibit®

DosageWithdrawal

3 ml/100 lbs.7 days

1 ml/11 lbs.7 days

Depends on dilution3 days

Using copper oxide wire particles

to improve dewormer efficacy

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

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

American Consortium for Small

Ruminant Parasite Control (ACSRPC)

www.acsrpc.orgwww.wormx.info

The ‘go-to” place for information about

controlling internal parasites in small

ruminants.

SUSAN SCHOENIANSheep & Goat SpecialistUniversity of Maryland Extension

sschoen@umd.eduwww.sheepandgoat.comwww.sheep101.infowww.wormx.info

Thank you for your attention. Questions? Comments?

Purchased at 2015 KHSI Expo“Carly” (named after Carl Ginapp)