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Internal Parasite Management in Pasture-Based Sheep

Kathy Bielek kathy.bielek@gmail.com

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Acknowledgements

• Dr. William Shulaw (OSU Extension Veterinarian)

• Rory Lewandowski (OSU Extension, Wayne County)

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Cost of Parasites

• Reduced milk production in ewes• Slower lamb growth• Appetite suppression• Reduced wool production and quality• Reduced fertility• Less immunity to other diseases• Lamb deaths

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The “costs” of parasitism

• “…thus acquisition of immunity in the young lamb has a higher priority than growth, but in the adult, expression of immunity will have lower priority than reproductive effort…”

Sykes and Coop New Zealand Veterinary Journal 2001;49:222-226.

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How do we “manage” internal parasites in sheep and goats?

Approaches

Conquer or Eliminate Co-exist Avoid

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Conquer by Chemicals

• Requires regular, by the calendar, drenching with a chemical dewormer.

• Requires an effective chemical dewormer

• Requires development of new chemical brought to market about every 5 years

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Drug resistance: How Does It Develop?• Drug resistance develops as a genetic trait.•Once resistance is present, it is likely to be permanent.• Resistance develops when worms have frequent exposure

to a drug.• A major cause of drug resistance is under dosing.• underestimating weight• incorrect dose calculation• incorrect dilution of products• improperly calibrated equipment• Treatment of ALL animals and movement to a “safe” or

“clean” pasture

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TREATMENT

RESISTANCE SELECTION IN

ADULT WORMS

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100% - and survivors of TX

no refugia of unselected

worms

On the new pasture

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5%

95%

Refugia: parasites not exposed to chemicals and selection pressure

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Log of conc. ng/ml

0 10 20 30 40 50 60 70

from: Shoop et al. 1997. J Vet Pharmacol Therap. 20(Suppl. 1), 12-14

1.5

1.0

0.5

0

-0.5

-1.0

-1.5

moxidectin

ivermectin

200 ug/kg oral dose

35 days of selection for resistance in larvae acquired from pasture

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You may not think you have a problem

• Resistance is relative– Not all worms on farm

are resistant

• Killing some worms may relieve disease symptoms– Clinically it appears

that the treatment was effective

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Drug Resistance

All control programs that rely strictly on the use of chemical dewormers will eventually fail as a result of development of resistance.

The question is how soon it will happen on YOUR farm, or how well can you develop strategies that minimize drug use.

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Avoid Parasites if Possible• Especially useful when pasture options or

acreage are limited• Fall lambing• Early wean, raise lambs in barn or feedlot• France: lactating ewes to pasture during the day,

back to barn at night. Lambs remain in the barn. (Also Wooster bulletin from April, 1900)

• Goats: Consider the use of browse and brush to avoid contact with the parasite.

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Early weaning and dry lot

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Management Concepts for co-existing• Nature bats last, worms will adapt.• Must co-exist with the parasites, they are not going

away.• Lambs/kids are the weak link, most susceptible to

parasite infections. In a pasture system, lamb and kid management is labor intensive.

• Dry ewes/does have good level of resistance to parasite infections and require low level of management.

• Option: minimize lamb/kid time on the farm or on pasture.

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Hemonchus

Telodorsagia (Ostertagia)

Trichostrongylus

Cooperia

Nematodirus

About one-half inch

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Referred to as “L3”

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egg to L3 >3.5 days L3 to eggs in feces – 19 to 21 dayscomplete cycle – 24 to 25 daysL3s tolerate cold well

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Haemonchus contortus will survive

• Adult female can produce 5000 eggs per day

• If each animal has 500 female worms• 50 animals can contaminate your pastures

with approximately 1 billion eggs per week!

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On Farm Research:Lessons Learned• Lambs/kids are very susceptible to parasite

infections• Overwintered larvae must be considered• Making more than one grazing pass across

grass/legume paddocks with lambs/kids has the potential to significantly increase the worm load

• Lambs/kids need some “safe” pastures

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• Farm #1 – All dewormed 7/20/06– Rotated across previously

grazed pastures

Farm #2 All dewormed 7/16/06 Moved to clean pasture every

week

Factors influencing FEC counts: Pasture Management Matters

Lamb ID Sire ID FAMACHA FEC Lamb ID Sire ID FAMACHA FEC603 A 3 300 11 B 2 0612 A 3 0 14 B 2 0613 A 1 250 46 B 1 0616 A 3 1100 5 B 1 50638 A 2 300 10 B 1 0639 A 3 500 49 B 1 0640 A 3 3450 6 B 3 50641 A 3 1800 24 B 2 0645 A 3 250 29 B 2 150646 A 3 3150 3 B 2 0

Sire A Average 3 1110 Sire B Average 2 25

Farm #2 - 8/19/06Farm #1 - 8/16/06

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What is safe pasture for lambs?• Young lambs/kids do not have a developed immune

system, any infective L3 larvae they ingest will get multiplied!

• One where L3 larva concentration is low: managed so that minimal levels of L3 are ingested.

• One where no L3 larvae have survived: a long enough time period has passed that L3 larvae have died. How long? Over-wintered larvae?

• One that limits grazing height/How does grazing height influence parasite infection?

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Based on farm research results:

• Over wintered larvae are a concern. Spring grazing (April/May) of pastures that were used the previous fall (Sept./October) increases the risk of parasite infection.

• Lamb/kid nutrition on pasture is a challenge. Nutrition is an important component of parasite management.

• There needs to be an effective chemical de-wormer that can be used selectively and as a rescue treatment.

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Possible alternatives to preserve a refugia

• treat selectively with FAMACHA, or body condition score; then move

• leave heaviest 10-15% untreated; then move

• treat all animals with a non-persistent dewormer and leave on contaminated pastures 3-5 days

• move, wait a few days, then treat

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Concept Behind Selective Treatment

• Every animal in the flock does not have the same parasite numbers/level of infection

• 20-30 % of animals harbor most of worms, responsible for most of egg output

• Selective treatment targets these animals only• Tools:

– FAMACHA– Fecal Egg Counts?

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XXX Farm Daily Egg Output

02000000400000060000008000000

1000000012000000140000001600000018000000

1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46

all sheep

num

ber o

f egg

s

103,546,200 eggs per day for just 46 sheep

Just 10 (21%) of the lambs excreted 77% of the eggs !!

Fall 2000

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600 epg

50 epg

1150 epg

3150 epg

100 epg

1150 epg

0 epg

1050 epg5550 epg

0 epg

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The FAMACHA© System

• Eye color is correlated with the level of anemia, and to a lesser degree, fecal egg shedding levels

• Eye color is an indirect measure of the worm burden – applies to Hemonchus contortus ONLY

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The FAMACHA© System

• By selecting only the most heavily infected animals for treatment, we can significantly reduce the number of treated animals while still reducing pasture contamination and providing treatment to the animals that need it most.

XXX Farm Daily Egg Output

02000000400000060000008000000

1000000012000000140000001600000018000000

1 4 7 10 13 16 19 22 25 28 31 34 37 40 43 46

all sheep

num

ber o

f egg

sThis approach should slow the development of resistance to dewormers.

Refugia

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The FAMACHA© System

• current recommendations are to treat:– non-lactating ewes in categories 4 and 5 – lactating ewes and lambs in category 3, 4, or

5 should be treated– goats in categories 3, 4 and 5– all animals with “bottle jaw”

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FAMACHA• In Ohio, the parasite life cycle begins to ramp up

in May.• Animals should be scored beginning in May.• If FAMACHA is the only strategy employed, it

must be done at least every 14 days, or more frequently, by mid-June.

• It can be used in large flocks, by examining subsets of animals.

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TECHNIQUE

UrbanShepherds.orgHow not to do it !!!

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Always use the card !!!

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score 5/5/08 6/5/08 6/23/08 7/8/081 0.77 0.36 0.29 0.092 0.23 0.64 0.65 0.423 0.00 0.00 0.05 0.424 0.00 0.00 0.02 0.055 0.00 0.00 0.00 0.02

FAMACHA percentages over time

FAMACHA scores by group and over time - 2008

early weaned

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FAMACHA correlation with FEC is good but not perfect

FAMACHA average median range in

number Score FEC FEC FEC

10 2 6,930 6,000 1,100 to 15,000

30 3 9,998 7,925 2,000 to 26,000

19 4 20,120 19,100 6,000 to 35,000

59 lambs scored and sampled July 4, 2011

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FAMACHA Limitations• Requires some type of handling

system• Labor intensive• Can disrupt grazing rotations• Needs a record keeping system

that can track trends• Extends effectiveness of

chemicals but does not eliminate resistance already present

• Limited to Haemonchus contortus detection

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But wait, I heard that Garlic works as a dewormer…..• Where is the information coming from?• How was it evaluated? Cause and effect are not

so easy, there can be confounding factors. Nutrition is one.

• To have confidence, should be the result of scientifically designed and replicated studies. This includes control groups and statistical analysis.

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literature review/results of designed studies• Diatomaceous earth (DE): No scientific evidence• Copper Oxide Wire Particles (COWP):yes, some trials

indicate effectiveness. Should be used under veterinarian supervision. However: potential toxicity, this is extra label use, and effectiveness may be limited.

• Garlic: No• Sericea lespedeza pellets: Some trials indicate effectiveness,

but possible nutrition effect?• Papaya seeds: No• Wormwood species: Artemisia absinthium in some trials

showed some positive effects• Others???

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Resources• OSE Veterinary Extension – Decision making

support tool– http://vet.osu.edu/extension/decision-tree

• OSU Veterinary Extension Fact Sheets– http://vet.osu.edu/extension/beef-sheep-resources

• OSUE - Small Ruminant Pastures, Parasites, and Profits: Putting it all together – three 90 minute programs

•http://vet.osu.edu/extension/sare/parasite_control Scroll down to mid page

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Additional Resources

– University of Maryland Extension:http://www.sheepandgoat.com/ click on parasites heading

• American Consortium for small Ruminant Parasite Control

• http://www.wormx.info/index.html

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Animal Health Regulations• USDA-National Organic Programhttp://www.ams.usda.gov/AMSv1.0/nophttp://www.ams.usda.gov/AMSv1.0/nopgeninfo

• Food Animal Residue Avoidance Databasehttp://www.farad.org/

• U.S. Food and Drug Administrationhttp://www.fda.gov/http://www.fda.gov/AnimalVeterinary/default.htm

• FDA Requirements: – Use of unlicensed drug is prohibited – Veterinary Client - Patient Relationship– Producer must not administer drugs in violation of FDA guidelines

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Conclusion• Currently there is not an easy answer to internal parasite

control.• Each farm must use various “tools” to put together a

integrated parasite control strategy + monitoring program• The management strategy on your farm depends upon your

goals, your market and the size of your flock• Recognize economic factors. Pasture is the cheapest feed.

Grains are expensive. Indoor facilities are costly, require more labor and a manure management plan.

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Questions?