Dealing with anthelmintic resistance in small ruminants

SUSAN SCHOENIANSHEEP & GOAT SPECIALISTUNIVERSITY OF MARYLAND EXTENSION (UME)WESTERN MARYLAND RESEARCH & EDUCATION CENTER (WMREC)SSCHOEN@UMD.EDU - WWW.ACSRPC.ORG - WWW.SHEEPANDGOAT.COM

Gastro-intestinal parasites (worms) are the primary health problem affecting small ruminants.

The barber pole worm (Haemonchus contortus) is the primary parasite affecting small ruminants in warm, moist climates.

Bottle jaw Anemia

The barber pole worm has developed resistance to all anthelmintics and all anthelmintic classes.

Anthelmintic resistanceWhen an anthelmintic treatment fails to reduce fecal egg counts by 95% or more.

Anthelmintic resistance was (is) inevitable.No treatment will kill 100% of worms.

Numerous on-farm practices have accelerated the development of resistant worms in small ruminants.

Frequent deworming, especially without regard to clinical need.

Underdosing drugs (failure to dose based on accurate weights).

Injecting an anthelmintic instead of using a drench.

Pouring an anthelmintic on the back instead of using a drench.

Improper administration of drenches, e.g. depositing drug in mouth

Use of persistent-activity dewormers (e.g. moxidectin).

Treating all animals in flock/herd, leaving no refugia.

Putting treated animals onto a clean pasture: no refugia.

Treating animals when pasture contamination is low.

Giving more than one dewormer at a time.

Introduction of resistant worms to a farm via new animals; failure to quarantine drench.

Anthelmintic resistance

Is not fully appreciated by some producers and veterinarians.

Varies by geographic region and farm.

Is result of past deworming practices.

On most farms, resistance is probably still at a level where there is still time to slow it down and enable the continued use of (some) anthelmintics.

Most small ruminant producers do not know which dewormers work on their farm.

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Dealing with anthelmintic resistance on the farm.

The first thing you need to do is determine which dewormer(s) still work on your farm.

All producers need to devise production/ management systems that minimize the need for deworming.

There are two methods to determine anthelmintic (dewormer) resistance.

Fecal egg count reduction test (FECRT) Comparison of pre- and post-

treatment fecal egg counts.

Must compare egg counts for each individual anthelmintic.

DrenchRite® larval development assay (LDA) In vitro test for anthelmintic

resistance (for all drugs).

Fecal egg count reduction test (FECRT)

Collect samples at the time of treatment (deworming).

Collect post-treatment samples 8-10 days, benzimidazoles 14-17 days, macrocylic lactones 5-7 days, levamisole 10-14 days, all dewormers

Need FECs > 250 epg

Favor animals with higher FAMACHA© scores and positive dag scores.

Should include a control group for comparison. DrenchRite® larval

development assay (LDA)

Collect pooled fecal sample from at least 10 animals.

Need FECs > 350-500 epg

Favor animals with higher FAMACHA© scores and positive dag scores.

Fecal egg count reduction test (FECRT)

Takes 7-14 days (or more) to get results, longer if done by someone else.

Cost of testing varies (15 samples x 4 anthelmintics + control group)

75 x free labor = no cost75 x $5/sample = $35075 x $10/sample = $750

Requires a lot more animals (ideally, 12-15 per treatment group); many producers don’t have enough animals for accurate testing.

Results% reduction (whole flock/herd)Results from individual animals vary

DrenchRite® larval development assay (LDA)

Takes 3-4 weeks to get results

Only one lab in US that does test:Dr. Ray Kaplan’s lab at the University of Georgia College of Veterinary Medicine.

$450 per sample

ResultsResistant (R)Susceptible (S)Suspected resistance (SR)

There are many things a producer can do to potentially reduce the number of animals that require deworming and/or the frequency of deworming.

Pasture and grazing management

General management

Animal management

Nutritional management

Genetic selection

Targeted selective treatment (TST)

“Natural” dewormers

The foundation of parasite control is good pasture and grazing management.

Evasive grazing: pasture rest and rotation

Maintaining minimum grazing heights (> 3 in.)

Browsing

Mixed swards

Clean pastures

Annual pastures

Tannin-rich forages

Mowing, haying, cropping

Mixed species grazing w/alpacas, llamas

Low/reduced stocking rates ****

Certain management practices may reduce the need for deworming.

Management Winter or fall lambing/kidding

Early marketing

“Early” weaning

Night penning

Zero grazing

Delay grazing until after dew lifts

Put treated animals in dry lot for 48 hours after deworming

Good sanitation/hygiene

Nutrition Manage pastures so that plants are in a vegetative

stage for grazing.

Plant annuals, legumes, and warm season plants to improve nutrition of pasture.

Provide supplemental nutrition when pasture quantity or quality is low/poor and/or to susceptible animals. Soy hulls

Distiller’s grains (DDSG)

By-pass protein (?)

Increase protein in late gestation ration to counter periparturient egg rise.

Maintain animals in good body condition (BCS > 2.5)

Genetic selection can reduce the number of animals that require deworming.

Between species/breed Goats are usually more susceptible

to parasites than sheep.

Some sheep breeds are more resistant to parasites.

Hair sheep of tropical origin:St. Croix, Barbado, Katahdin

Native breeds of the Southeast:Gulf Coast, Florida, Louisiana

Other breeds: Texel (?)

Some goat breeds seem to be more resistant to parasites than others: Kiko, Spanish, Myotonic.

Within breed 80:20 rule

20 percent of flock/herd is responsible for 80% of pasture contamination (egg shedding).

Can select any breed for improved resistance to parasites

Select individuals with lower FECs.

Use EBVs (estimated breeding values) to choose resistant males for breeding.

Parasite resistance (fecal egg counts) is a moderately heritable trait (20-40%): heritability of prolificacy is only 10%.

Resilience is less heritable.

Targeted Selective Treatment (TST)Only treating animals that require treatment or would benefit from treatment; increases refugia.

FAMACHA© SYSTEM

Uses color eye chart to estimate level of anemia (packed cell volume/PCV); thus, need for deworming.

Only useful for blood-feeding parasites, such as barber pole worm.

Category Color PCV Tx?

1 Red > 28 No

2 Red-Pink 23-27 No

3 Pink 18-22 ?

4 Pink-White 13-17 Yes

5 White < 12 Yes

Refugia – worms not exposed to anthelmintic(s).

Targeted Selective Treatment (TST)Only treating animals that require treatment or would benefit from treatment; increases refugia.

FIVE POINT CHECK© - 5. Extension of FAMACHA© system: decision-making

tool for all parasites that commonly affect small ruminants.

Involves 5 check points on animal’s body

1. Eye FAMACHA© score (anemia) (1-5)

2. Jaw Submandibular edema (bottle jaw)

3. Back Body condition score (1-5)

4. Tail Dag score, fecal soiling (scouring) (0-5)

5. Nose Sheep: nasal discharge (bot flies)Goats: coat condition

The FAMACHA© system is a perfect example of the land grant mission: get producers to apply research-based knowledge to solve a problem.

Producers must take an approved training in order to receive a FAMACHA© card.

Since 2003, over 29,000 FAMACHA© cards have been sold to over 40 states and various Caribbean and Latin American countries.

Two formal evaluations of FAMACHA© workshops have been conducted.

Using FAMACHA

Deworming less Saving money0

10

20

30

40

50

60

70

80

90

100

91%

78% 76%

95%

74% 75%

2004 2009

What are limitations to producers adopting the FAMACHA© system/Five Point Check©?

Conflicting informationMany veterinarians still give contrary advice.

TraditionMany producers still think of deworming as a preventative and best management practice.

Availability of trainingWorkshops are not always available at convenient locations or times.

New anthelminticThere is a new anthelmintic in the pipeline (Zolvix®); the urgency of anthelmintic resistance may be abandoned (?).

The FAMACHA© system was developed for “small” farms; FAMACHA© scoring is labor-intensive.

It is easier to deworm all members of the flock/herd than to check their FAMACHA© and other scores.

Sub-clinical parasitism is not treated; it is a cost of Targeted Selective Treatment.

“Natural” dewormersSOME: (GENERALLY) EFFECTIVE Kill parasites

Copper oxide wire particles (COWP)

Copper sulfate ()

Tobacco and nicotine sulfate ()

Reduce treatment #’s Condensed tannins

Sericea lespedeza

Duddingtonia flagransnematode-trapping fungus***not commercially available yet**

MOST: INEFFECTIVE AND/OR UNPROVEN

Diatomaceous earth (DE)

Garlic

Papaya

Paprika

Pine bark

Pumpkin seeds

Commercial herbal dewormers(e.g. Hoegger’s herbal dewormer)

Many, many more…

Copper oxide wire particles (COWP) Copper oxide wire particles have been shown to

reduce parasite burdens (H. contortus) in lambs and kids.

Less effective in mature animals.

Copper oxide wire particles are a slow-release form of copper

Less potential for toxicity in sheep; sheep are sensitive to excess copper in the diet.

Copasure® is a copper supplement (12.5 and 20 g) for cattle that can be repackaged into smaller doses for sheep and goats (0.5 to 4 g).

Copasure® capsules are now available in 2 g and 4 g dosages for sheep and goats (as Cu supplement).

Selective treatment with COWP advised.

FAMACHA© scores of 3, 4, 5 only.

Condensed tannins

Tannins are plant compounds that bind to proteins and other molecules.

Effects of tannins vary depending upon type, concentration, and the animal consuming the tannin.

Tannins can have both negative or positive effects.

Sericea lespedeza (AU Grazer™) is a high-tannin forage (warm season legume) that has been scientifically-proven to reduce parasite burdens in sheep and goats.

Fresh forage Hay Leaf meal (pellets) [simsbrothers.com]

Sericea cuneata

“Natural” dewormers (IMO)

Most likely effect of “natural” dewormers will be to reduce the number of animals that require deworming by . . .

Disrupting the free-living stage of the parasite (e.g. egg hatching, larval development)

Improving the immune function of the host.

THANK YOU. QUESTIONS? COMMENTS.

American Consortium for Small Ruminant Parasite Control - www.acsrpc.org