Maine internal parasites

10/18/2011

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Internal parasites seminarSHEEPSHEEP ANDAND GOATSGOATS

SUSAN SCHOENIAN (Shāy‐nē‐ŭn) Sheep & Goat Specialist

University of Maryland [email protected] – www.sheepandgoat.com

Today’s seminar topics

I. Parasites and their biology

II. Diagnostic tools Diagnostic tools

III Using anthelmintics effectivelyIII. Using anthelmintics effectively

IV. Integrated parasite management (IPM)

I. Parasites and their biologyI. Parasites and their biologyspecies, life cycles, pathogenicity, interactionsspecies, life cycles, pathogenicity, interactions

Barber pole worms in abomasumImage source: ScienceWatch.com

What is a parasite?A (generally undesirable) living organism that exists by stealing the

resources produced or collected by another living organism.

[Greek: “one who eats at the table of another]

There are two kinds of parasites.

1. Internal (endo) – a parasite that lives inside another organism.

2. External (ecto) – a parasite that lives on the blood of the host or lays eggs on their hide or in their nose.

External parasite: sheep ked (tick)Image from Colorado State University

There are two general kinds of internal parasites.

1. Helminthsmulti‐cellular

a) Nematodes

b) Cestodes

c) Trematodes

2. Protozoasingle cell

a) Coccidia

b) Giardia

c) Cryptosporidium Haemonchus contortus (barber pole worm)Image from University of Georgia

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1. Helminths (parasitic worms)

A. NematodesRoundworms

B. CestodesTapeworms

C. TrematodesFlukes

Barber pole wormImage source: MicrobiologyBytes

A. Nematodes (roundworms)A. Nematodes (roundworms)Phylum Nematoda

• Approximately 1 million– Over 28,000 described– Over 16,000 parasitic

• Round• Elongated• Worm‐like• Have a body cavity• Have digestive systems• Reproduce sexually• Mostly host‐specific• Not all are pathogenic

Most significant kind of internal parasites that affect sheep and goats.

Species Location Light Infection Heavy infection

HaemonchusContortus

Barber pole worm

AbomasumGradual weight lossLoss of color

Lack stamina AnemiaEdema (bottle jaw)ConstipationSudden death

Class Nematoda→ Superfamily Strongyloidea→ Family Strongylidae→ Genera Strongyle

Primary parasites affecting sheep and goats: Strongyles

Sudden death

Teladorsagia spp.(Ostertagia spp.)

Small brown stomach worm

AbomasumUnthriftyDaggy

Rapid loss of conditionProfuse scoursDeath

Trichostrongylus spp.

Black scour wormBankrupt worm

Small intestines(1st 3 m)

UnthriftyDaggy

Rapid loss of conditionBlack scoursDehydrationDeath

Haemonchus contortusBarber pole worm

• Most common in warm, moist climates with summer rainfallssummer rainfalls.

• Adapting to cooler climates.

• Most deadly worm.

• Blood sucker.

• Prolific egg layer.

Western Maryland Pasture‐Based Meat Goat Performance Test (2009)

2011

Strongyle‐ type worms

• Direct life cycles– Weather dependent– 14 to 21 days

• Eggs cannot be differentiated in

L4, adult suck blood

egg fecal analyses.75 – 95 μ m

• Mixed infections common.

Have developed varying levels of resistance to anthelmintics.

L3

L2 L1

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Environmental‐parasite interactions

• Optimal conditions for development of Haemonchus larvae are 82⁰F and humidity above 70%.

• Teladorsagia is better adapted to cooler, temperate climates. They fair poorly in very hot, dry summers.

• Trichostrongylus spp. are more resistant to cold and desiccation than Haemonchus.

Hypobiosisinhibited or arrested larval development

• Period of delayed development whereby 4th stage larvae stop development and remain in the mucosa for 3 to 4 months.

• Occurs when there is insufficient i hmoisture or temperatures that

are too cold for larval development.

– Occurs in winter or summer, depending upon parasite and geographic location.

– Probably involves some immune and environmental cues.

• Survival mechanism• No host response

Strongyles that cause occasional problems

• BunostomumHookworm

• Cooperia spp.Small intestinal worm

• NematodirusNematodirusthreadneck worm

• OesophagastomumNodule worm

• StrongyloidesCommon threadworm

• Trichuris ovisWhipworm

• Muellerius capillarisDictyocaulus filariaLungworms

• Paralaphostrongylus tenius Meningeal worm(brain, deer worm)

Lungworms

• Direct or indirect life cycle

• Prefer cool conditions• Diagnosis is difficult

1. Muellerius capillaris2. Dictyocaulus filaria

– Clinical signsPersistent coughing, respiratory distress, reduced weight gains

– Recovery of 1st stage larvae from feces

– Usually diagnosed at post‐mortem Image source: UPENN Vet School

Meningeal worm

• White‐tailed deer are the normal host.– Infection typically causes no

clinical disease in deer.

• Severe neurological disease occurs when infected snails oroccurs when infected snails or slugs are ingested by other cervids or ungulates.

• Gastropods serve as intermediate host.

• Parasite migrates to spinal cord and brain.– 10 to 14 days after ingestion of

infected snail or slug

CLINICAL SIGNS• Variable• Mimic other

neurologic diseases– Weakness– Lameness– Circling– Blindness

TREAMENT PROTOCOLS

• High doses of anthelmintics– Ivermectin for five days

– Fenbendazole for five days

• Anti‐inflammatory drugs

Blindness– Head tilt– Abnormal behavior– Paralysis– Death

No controlled studies have confirmed or refuted the efficacy of various treatment recommendations.

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Prevention • Limit deer access to pasture.– Eliminate deer via lethal

means.– Deer‐proof fencing for small

operations.– Make pastures less appealing

to deer.Feed in enclosed areas– Feed in enclosed areas.

• Reduce exposure to infected snails and slugs.– Do not allow access to

pastures that contain thick vegetation or moist shaded areas that are favorable snail and slug habits.

• Prophylactic treatment with anthelmintics (every 10‐14 d).

B. Cestodes (tapeworms)

• Flat • Segmented• No body cavityNo body cavity• Hermaphrodites• Indirect life cycle• Some cause symptoms

in the intermediate host.

Tapeworms affecting sheep and goatsGenus Moniezia

• Indirect life cycle– Pasture mites serve as an

intermediate host.– 6 weeks

• Segments visible in feces.Only worm visible in feces

• Generally thought to be non‐pathogenic and of little consequence.– Usually no benefit to treatment

• Treat with albendazole (Valbazen®), fenbendazole (Safe‐Guard®), or praziquantel.

Sheep measles (Ovine cysticercosis)

• Sheep tapeworm of dogs– Transmitted to sheep eating

forages contaminated with tapeworm eggs shed by canines.

– Sheep and goats host larval stage of parasiteg p

– No clinical signs in sheep or goats.

• Causes development of cysts in skeletal and heart muscle.– Cause of carcass

condemnation.

→ Control point: dogs

Image source: Optimal Livestock Services, LLC

C. Trematodes (flukes)

• Flat • Oval shape• No body cavity• No digestive tube• Indirect life cycle• Hermaphrodites

Image source: http://www.flickr.com/photos/peteredin/3386220058/

Liver flukes

• Fasciola hepatica(common liver fluke)

• Gastropods serve as intermediate host.

• In U.S., found mainly in Gulf states, California, and Pacific Northwest.

• Symptoms include pale mucous membranes, bottle jaw, and weight loss.

• Treat with albendazole (Valbazen®).

Image source: Agricultural Research Council in South Africa

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2. Protozoan parasites

A. Eimeria spp.Coccidia

B GiardiaB. Giardia

C. Cryptosporidium sp.

D. Toxoplasma gondii

Image source: FAO United Nations

Eimeria spp. ‐ Coccidia• Single cell

• Life cycle– Complicated– Many stages– Oocytes → sporulation (hatching)– Sexual and asexual reproduction– 21 days

• 10 species known to infect sheep and goats– Host specific– Not all are pathogenic

• Damage cells of small intestines1. Subclinical2. Clinical (diarrhea)

Internal parasites of sheep and goats

Roundworms Teladorsagia (Ostertagia)Trichostronyglus spp.

Barber pole worm

Tapeworms

Liver flukes

CoccidiaProtozoa

HelminthsOther strongyles

LungwormsMeningeal worm

Next topic: diagnostic tools

II. Diagnostic II. Diagnostic toolstoolsFAMACHA© system, Five Point Check©, laboratory and field testsFAMACHA© system, Five Point Check©, laboratory and field tests

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How do you tell if your sheep or goats are infected with internal parasites?

They all are.

• Almost all sheep and goats have parasites, probably of different kinds.

• “Positive” egg or oocyst• Positive egg or oocystcounts are “normal.” Negative tests are rare (during the periods of risk).

• Some level of parasite infection is required for immunity.

They all are. • Clinical disease occurs at

a certain level of infection that can vary by animal.

• Not all parasites areNot all parasites are pathogenic or highly pathogenic.

• Not all strains of parasites are pathogenic or equally pathogenic.

The more important question to ask is:

How do you tell if a sheep or goat is clinically parasitized (suffering negative effects) and requires anthelmintic treatment?

Diagnostic tools

1) On‐farm1) Animal

2) Fecal

2) Laboratory1) Blood

2) Fecal

3) Larvae

Diagnostic tools

ON FARM

• Animal– FAMACHA©

– Five Point Check® NEW!

LABORATORY• Blood

– Packed cell volume

• FecalSi l fl i• Fecal

– Simple flotation

– Fecal egg counts• Fecal egg count reduction test (FECRT)

– Dipstick

• Carla® saliva test

– Simple flotation– Fecal egg counts

• FECRT

– Lectin staining test NEW!– Larvae

• Larvae culture• Larval development assay

[DrenchRite®]• Pasture

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The FAMACHA© System• Develop for small‐scale sheep

producers in South Africa in response to the widespread development of anthelmintic‐resistant worms.

• A practical system for assessing barber pole worm infection in sheep and goats and determining the need for deworming individual animals.

• Named for its originator:Dr. Francois “FAffa” MAlan CHArt

FAMACHA©

General treatment recommendationsDeworm adults at scores 4 and 5*Treat lambs and kids at categories 3, 4, and 5

*The South Africans recommend goats be treated at categories 3 4

Clinical Category

Eye Lid Color

Packed Cell

VolumeDeworm?

1 Red > 28 No

2 Red-Pink 23-27 No

3 Pink 18-22 ?

4 Pink-White 13-17 Yes

5 White < 12 Yes

goats be treated at categories 3, 4, and 5

Using FAMACHA©

• Must take training to get card.

• Use card• Replace card periodically

(colors fade)• Do not use in a vacuum;

consider other factors.• Frequency of checking

varies by risk.• Should incorporate

FAMACHA© into an integrated parasite management program.

Benefits of FAMACHA©

• Reduces number of anthelmintic treatments.

• Reduces dollars spent pon anthelmintics.

• Identifies susceptible and resilient animals.

• Increases refugia • Prolongs effectiveness

of anthelmintics

Using the FAMACHA© system to control internal parasites in grazing lambs

50

60

2

3

3.5Avg FAMACHA Score# Lambs Dewormed

56

% Lambs/No. times treated

0

10

20

30

40

0

0.5

1

1.5

2

2.5

26.2%

41.7%

16.7%

7.1%4.8%1.2%1.2%

0

1

2

345

Limitations of FAMACHA©• Doesn’t save time.

– LESS deworming– MORE monitoring

• Only useful where• Only useful where (when) barber pole worm is the primary parasite.

• Must know which anthelmintics are effective.

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The Five Point Check© (5. ©)

• Expands the FAMACHA© system to include evaluation criteria for other internal parasites.

• Check five places on animal’s body1. FAMACHA© score2. Bottle jaw3. Body condition score4. Dag score5. Nasal discharge

Backbody condition (and coat condition)

Tailsoiling , dags

(scours)

Eyeanemia

FAMACHA© score1 3

2

Nosenasal discharge(nose bots)

Jawswelling, edema “bottle jaw”

FIVE POINT CHECK© (5. ©)FOR TARGETED SELECTIVE TREATMENT OF INTERNAL PARASITES IN SMALL RUMINANTSG.F. BATH AND J.A. VANWYK, FACULTY OF VETERINARY SCIENCE, UNIVERSITY OF PRETORIA, SOUTH AFRICA

4 5

Five Point check©Point What to check Specificity

1 Eye

Paling of ocular membranesFAMACHA© eye anemia score

Barber pole wormLiver fluke

2 Back Body condition score All

3 RearDag scorefecal soilingevidence of scouring

Brown stomach wormHair wormThreadneck wormNodule wormCoccidia

4 JawSub‐mandibular edema (bottle jaw)

Barber pole wormLiver fluke

5 Nose Nasal discharge Nasal bots

Source: G.F. Bath and J.A. van Wyk, Faculty of Veterinary Science, University of Pretoria, South Africa

FAMACHA© eye anemia score

Eye lid colorPacked cell volume

Treatment recommendation

1 Red > 28 Optimal No

2 Red-Pink 23-27 Acceptable No

3 Pink 18-22 Borderline ?3 Pink 18 22 Borderline ?

4 Pink-White 13-17 Dangerous Yes

5 White < 12 Fatal Yes


Bottle jawSub‐mandibular edema


Body condition score (BCS)

SpineTransverse processes

Muscle Fat

1 Individually clearly felt, sharp, obvious

Fingers easily pass underneath Very little No

2 Form a smooth line with deep undulations

Smooth round edges Concave Very thin

3 Only slightly detectable undulations

Well coveredhave to push firmly

to get fingers underneath

Not concaveNot convex

Moderate

4 Only detectable with firm pressure Cannot be

felt at all

Maximally developed

Convex

Thick

5 Not detectable Very thick


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Dag Scoresbritch soiling, evidence of scouring (diarrhea)

Dag score DescriptionTreatment

recommendation

0 No fecal soiling No indication for treatment

1 Very slight soiling on edge of tail

No treatment

2 Slight soiling on edge of tail and on each side

Usually no treatment

3 Moderate soiling of tail and woolDag formation

Consider treatment

4Severe soiling extending far into

woolSevere dag formation

Treatment, crutching recommended

5Very severe

watery diarrhea extending to hocks

Treatment and crutching essential


Nasal discharge


Packed cell volume (PCV)

• Portion of whole blood occupied by red blood cells.

• A measure of anemia• A measure of anemia – Primary symptom of Haemonchosis (or barber pole worms).

• A measure of resilience.

Clinical CategoryPacked Cell

VolumeTx (?)

1 Non-anemic > 28 No

2 Non-anemic 23-27 No

3 Mildly anemic 18-22 ?

4 Anemic 13-17 Yes

5 Severely anemic < 12 Yes

Why look at feces?1. Identify worm eggs and

determine existence and level of infectiona) Simple fecal flotationb) Fecal egg counting

2. Determine parasite species a) Larvae cultureb) Lectin staining test

3. Determine effectiveness of anthelmintic treatmenta) Fecal egg count reduction

test (FECRT)b) Larval development assay (LDA) or

DrenchRite® test

Fecal testingQuantitativeFecal egg count (FEC)

• Use McMaster egg counting slide

• Weigh feces and measure flotation solution

QualitativeSimple fecal flotation

• Use simple slide and cover slip

flotation solution

• Determine general egg typesStrongyle vs. coccidia vs. tape

• Determine level of infection– Eggs per gram of feces

• Determine general egg typesStrongyle vs. coccidia vs. tape

• Determine existence and general level of infection– Eggs per field of view

e.g. Eggs Plus system

What you need to do your own fecal egg counts

1) Microscope40x objective x 10x eye piece = 400Only need 100xMechanical stage recommended

2) Flotation solutionSaturated salt or sugar solutiongSpecific gravity of 1.2Can also purchase

3) McMaster egg counting slidewww.vetslides.comwww.mcmaster.co.za

4) Miscellaneous suppliesscale, beaker, pipettes, vials, craft sticks, cheese cloth or strainer

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Fecal egg countseggs per gram of feces

• Indicate “potential” parasite burden in animal.

• Indicate potential b dparasite burden on

pasture..

• Use to determine level of drug efficacy.

• Use to determine genetic differences in parasite resistance.

Fecal egg counts are not definitive.• Fecal egg counts are

not always well‐correlated with clinical disease.

– Presence of eggs or does not mean that thedoes not mean that the animal is clinically parasitized and needs treatment.

– Absence of eggs or oocytes (coccidia) or a low count does not mean that the animal is parasite‐free and not in need of treatment.

Limitations to fecal egg counts• Some parasite eggs look the same

and cannot be identified at the egg stage).

• There is a fairly regular fluctuation in fecal egg output.

• Egg output varies by season of the year.

• Eggs are not always evenly distributed in the feces

• Not all parasites are pathogenic (disease‐causing)

• Total egg counts may include a mixture of species with different levels of fecundity and pathogenicity.

• Diarrhea increases fecal moisture and may dilute the number of eggs.

• Human error.distributed in the feces.

• Parasite species vary in their egg producing capacity.

– Some parasites are prolific egg producers (e.g. Haemonchus)

– Some parasites do not produce very many eggs. (e.g. Nematodirus)

– Some parasites produce eggs intermittently

– Some parasites can produce asexually– Immature worms (L4’s) do not lay eggs– Inhibited larvae do not lay eggs

Clinical significance of fecal egg counts

Fecal egg count reduction test (FECRT)

• First and most widely used method to access efficacy of anthelmintics.

• Before and after fecal egg counts.– d 0 and d 7‐14 post

treatment

– With or without untreated controls

– Minimum of 10 animals.

DrenchRite® Larval Development Assay (LDA)

• In vitro test for the detection of anthelmintic resistance.

• Evaluates resistance to all major anthelmintics from a single pooled fecal sample.

• Requires pooled fecal sample from 10 or more animals – Mean FEC of > 350 epg minimum– Mean FEC of > 500 epg preferred.– Select feces from animals scored

as FAMACHA© 3, 4, or 5.

• Available through University of Georgia ([email protected])

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Larvae culture and differentiation

• It is difficult to differentiate the eggs of many common species of worms during a worm egg count.

• Culture of the feces for the purpose of hatching parasite eggs and obtaining larvae for morphological identification.

Image source: Dr. Woodgate, Western Australia Department of Agriculture

Western Maryland Pasture‐Based Meat Goat Performance Test (2009)

Lectin staining test

• Fast, easy, less‐expensive way to test for the presence and quantity of barber pole worms.

• Lectin‐staining test based on peanut agglutin that binds to egg of barber pole worm.of barber pole worm.

• Only requires a small amount of feces.

• Results available in as little as two days.

• Available through Oregon State University and University of Georgia.

Image source: University of Georgia College of Veterinary Medicine.

New tests (not available in U.S.)

CARLA® SALIVA TEST• Measures antibodies against

worm larvae.

• Use to select animals which

HAEMONCHUS DIPSTICK TEST

• Detects blood in feces to determine presence of

• Use to select animals which suffer less from parasites and pass fewer eggs onto pasture.

barber pole worm and level of infection.

Next topic: Using anthelmintics effectively

III. Using anthelmintics effectivelyIII. Using anthelmintics effectivelyProducts, usage, resistance, refugia, alternatives, future Products, usage, resistance, refugia, alternatives, future

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What is an anthelmintic?An agent that kills or causes the expulsion of parasitic worms.

Also called dewormer, wormer, drench, or parasiticide.

There are three anthelmintic classes.Based on similar chemistries, modes of action, and cross‐resistance.

1. Benzimidazoles (BZ)

2. Macrocylic lactones (ML)2. Macrocylic lactones (ML)A. Avermectins

B. Milbemycins

3. Nicotinic antagonistsA. Imidazothiazoles (IMID)

B. Tetrahydropyrimidines (TETR)

1 ‐ Benzimidazoles (BZ)First class of modern anthelmintics (1961)

A. FenbendazoleSafe‐guard®Panacur®

B AlbendazoleB. AlbendazoleValbazen®

C. OxfendazoleSynanthic®

D. ThiabendazoleTBZ

Benzimidazoles kill worms by interfering with energy metabolism on a cellular level by binding to beta tubulin.

1 ‐ Benzimidazoles (white drenches)

• Broad spectrum1. Adult and 4th stage larvae of

roundworms2. Adult liver flukes

(Valbazen® only)3. Heads and segments of tapeworms

(Valbazen® or 2x labeled dose of Safe‐Guard®)

4. Effective against hypobiotic larvae5. One of the drugs of choice for

meningeal worm (Safe‐Guard®)

• Wide margin of safety– Do not use Valbazen® during

first 30 days of pregnancy or removal of ram(s).

• Widespread resistance reported.

2‐Macrocylic lactones (ML)Newest family of anthelmintics ‐ circa 1980’s

1) Avermectinsa) Ivermectin

Ivomec®Primectin®

b) EprinomectrinE i ®Eprinex®

c) DoramectinDectomax®

2) Milbemycinsa) Moxidectin

Cydectin®Quest®

Macrocylic lactones interfere with GABA‐mediated neurotransmission, causing paralysis and death of the parasite.

2 ‐Macrocylic lactones (ML)• Potent

• Persistent activity (+/‐)

• Broad spectrum1. Adult and 4th stage larvae of

roundwormsroundworms2. Some external parasites

(Ivermectin: larval stages of nasal bots)3. Effective against hypobiotic larvae4. One of the drugs of choice for

meningeal worm (ivermectin).

• Potential negative effect on dung insects.

• Widespread resistance reported, especially avermectins.

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3‐ Nicotinic agonists

1) Imidazothiazoles (IMID)a) Levamisole

Prohibit®Tramisol®

Act as agonists at nicotinic acetylcholine

receptors of nematodes, causing

Levasol®

2) Tetrahydropyrimidines (TETR)a) Morantel

Rumatel®

b) PyrantelStrongid®

nematodes, causing paralysis of the

worms.

3 ‐ Nicotinic agonists

1. Levamisole– Clear (yellow) dewormer– Broad spectrum

• Adult and 4th stage roundworm larvae

• Hypobiotic larvae (?)– Narrower margin of

safety (esp. injectable)– Resistance varies from high to low.– Resistance is sex‐linked.

2. Rumatel– Oral feed additive– Effective against adult worms only– Not much is known about resistance

levels.

FDA‐approved anthelmintics

SHEEP

1. Ivomec® sheep drenchIvermectin

2. Cydectin® sheep drench

GOATS

1. Safe‐Guard® suspensionFenbendazole

2. Valbazen® liquidy pMoxidectin

3. Prohibit® drenchLevamisole

4. Valbazen® liquidAlbendazole

qAlbendazole[liver flukes only]

3. Rumatel® premixMorantel

Different anthelmintics may be approved and available in different countries.Different anthelmintics may be approved and available in different countries.

Withdrawal periods for FDA‐approved anthelmintics

AnthelminticSheep Goats

Meat Milk Meat Milk

Valbazen® suspension 7 days Not est. 7 days Not est.

Prohibit® drench 3 days Not est. NA NA

Cydectin® drench 7 days Not est. NA NA

Ivomec® drench 11 days Not est. NA NA

Rumatel® premix NA NA 30 days Not est.

Safe‐Guard® suspension NA NA 6 days Not est.

Source: Animal Drugs @ FDA and product labels

Withdrawal periods for extra‐label anthelmintics in goats

Anthelmintic Meat Milk

Valbazen® suspension 9 days 7 days

Safe‐Guard® @ 2x label dose 16 days 4 days

Ivomec® sheep drench 14 days NAIvomec® sheep drench 14 days NA

Prohibit® drench(1 packet/262 ml water)

4 days NA

Cydectin® pour‐on (orally) 23 days NA

Cydectin® sheep drench 14 days NA

Cydectin® injectable 120 days NA

Source: Food Animal Residue Avoidance Database (FARAD) and/orhttp://www.luresext.edu/goats/training/GoatDewormerChart.pdf

Anthelmintic resistanceAbility of the worms to survive anthelmintic treatment

• Official definition: 95% or less reduction in fecal egg count (FECRT).

a) Widespread in parasites of sheep, goats, and horses. Has been reported in all anthelmintics.

b) Developing in cattle parasites.

c) Has been detected in pig parasites.

• Is likely (inevitable) to develop wherever anthelmintics are frequently used.– There will always be some worms that

survive an anthelmintic treatment.

Tx

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Anthelmintic resistanceResearch conducted by Delaware State University (2009)

Anthelmintic % farms

Fenbendazole 97

Ivermectin 56

Moxidectin 50

Anthelmintic Sheep Goat

Fenbendazole 5/5 5/5

Ivermectin 3/4 5/5

Moxidectin 2/4 1/5

Levamisole 2819 goat and 13 sheep farms in MD, DE, PA, VA, and WV were tested for anthelmintic resistance using the larval development assay at the University of Georgia.

• Varies by geographic region and individual farm.

• A result of past anthelmintic use.

• Anthelmintic resistance is PERMANENT.

Levamisole 1/4 0/54 sheep and 5 goat farms in the Mid‐Atlantic region were tested for anthelmintic resistance using the FECRT and larval development assay.

Causes of anthelmintic resistance

❶ Frequent deworming

• Treating all animals at the same time.

• Putting treated animals onto a clean pasture.

Causes of anthelmintic resistance

❷ Under‐dosing– Not weighing animals

– Inability to accurately estimate weights

lib i i f– Not calibrating equipment for heaviest animals in group.

• Using anthelmintics with residual activity– Persistent‐activity anthelmintics

– Injectables

– Pour‐ons

Refugia (Worms in “refuge”)

• Worms that have not been exposed to anthelmintic treatment.

• Worms that are still susceptible to anthelmintic treatment.

• There will always be some worms that are resistant to a particular anthelmintic.

Image source: Meat & Wool New Zealand

How to increase refugiaand slow (delay) anthelmintic resistance

• Selective deworming– Do not treat everyone

every time.– Leave some animals

untreated.

• Pasture management– Do not put treated

animals onto a clean pasture.

– Put untreated animals onto pasture previously grazed by treated animals.

Anthelmintic combinations

• Combining anthelmintics from two (or more) different broad

+different broad spectrum groups– Synergistic effect

– Broaden spectrum of activity

– Delay development of resistant worms

+Temporary “fix”

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Preliminary dataEfficacy of anthelmintic combinations in goats

Treatment FECR %

Albendazole 76

Levamisole 39

Moxidectin 74

Treatment FECR %

Moxidectin 100

Levamisole 14Albandazole + levamisole 85

Albendazole + moxidectin 98

Levamsiole + moxidectin 98

Albendazole + levamisole+ moxidectin

99

Copper oxide wire particles (2 g)

28

Control 14

Initial FECs ranged from 250 to 13,500 and averaged 2,550 epg. 8.6 animals/Tx

Levamisole 14

Albendazole 21

Levamisole + albendazole 94

Levamisole + albendazole + moxidectin

100

4 animals/Tx

Research conducted at Langston University (OK)

Proper anthelmintic use

• Give proper dose based on accurate weight.– Goats require higher doses of

anthelmintics, usually 1.5 to 2x the sheep or cattle dose.

• Administer all anthelmintics orally to sheep and goats.

• Use drench (liquid) formulations of anthelmintics.

• Fasting may improve efficacy of some anthelmintic treatments.

Proper oral drenching technique

• Use proper equipment– Smaller nozzle for

lambs and kids

• Maintain equipment properly• Calibrate equipment for

proper dosageH ld h d h i l f• Hold head horizontal for drenching

• Insert nozzle in side of mouth• Put nozzle over back

of tongue• Don’t rush• Ensure swallowing

before release.• Be gentle.• Avoid injury

Putting the drench in the mouth will activate the esophageal groove and cause the drench to by‐pass the rumen into the lower gut . . . and not work!

CoccidiostatsA chemical agent added to animal feed that serves to retard the life cycle or reduce the population of pathogenic coccidia to the point that disease is minimized and the host develops immunity .

Coccidiostats

1. Ionophoresa) Lasalocid

Bovatec®

b) Rumensin®Monensin

2. Quinolonea) Decoquinate

Deccox®

3. Amprolium (Rx)Corid®

Affect mitochondrial function

Coccidiostats

• Do not kill coccidia.

• Slow down shedding of coccidia into the environment.

• Need to be fed ahead of risk period, at least 21 days before.

• Adequate consumption is a limitation to their effectiveness.

• Should not feed year‐round – risk of resistance developing

• Permissible under USDA natural standards (if declared).

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Coccidiostats FDA‐approved for use in sheep and goats

Trade name Ingredient DosageApproved species and class

Bovatec® Lasalocid15‐70 mg/d20‐30 g/ton of feed

Sheep in confinement

Deccox® Decoquinate22.7 mg/100 lbs. BW Young, non‐lactating

Deccox® Decoquinate13.6 g/ ton of feed sheep and goats

Rumensin® Monensin 20 g/ton of feed Goats in confinement

Source: Animal Drugs @ FDA

Rumensin® can be toxic to equines and dogs.

There is no withdrawal period for slaughter.

Treating coccidiosis (Tx)

• Coccidiostats will not treat coccidiosis.

• Treatment needs to be administered to individual animals.

• None of the drugs that are used to treat coccidiosis are FDA‐approved for sheep and/or goats.

• Use must meet requirements for extra label drug use.

Two treatment choices1. Amprolium (Corid®)2. Sulfa drugs

http://old.cvm.msu.edu/extension/Rook/ROOKpdf/coccidia.PDF

1 ‐ Corid® (amprolium)

• Labeled as an aid in the prevention and treatment of coccidiosis in beef and dairy cattle.

21 day prevention5 day treatment

• Mimics thiamine (vitamin B1), causing a thiamine deficiency in coccidia → starvation from malnutrition.

– Polioencephalomalacia (polio) is a possible side effect of treatment.


2 ‐ SulfonamidesSsulfadimethoxine (Di‐methox®, Albon®), Sulfamethazine (Sulmet®)

• Used to treat many infections.

• Common treatment for coccidiosis.

• Cause folic acid deficiency

• More effective than Corid® (?)


What’s “new” in parasite control?New anthelmintics

ZOLVIX® • Monepantel

STARTECT®• Derquantel + abamectin• New class of anthelmintic:

Spiroindole (SI)• Acts as a channel blocker to

• Monepantel• New class of anthelmintic:

amino‐Acetonitrilederivatives (ADDs)

• Paralyzes worms by attacking a previously undiscovered receptor (Hco‐MPTL‐1) only present in nematodes

• Available in New Zealand, Australia, Europe, UK, and South America.

cause flaccid paralysis in worms.• Acts on different binding sites

than other anthelmintic classes.• Only available in New Zealand

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Copper for internal parasite controlRisk: copper toxicity in sheepRisk: copper toxicity in sheep

1. DietaryMineral mixFeed supplement

2. DrenchCopper sulfate

3. BolusCopper oxide wire particles (COWP) CuSOCuSO44

Copper oxide wire particles (COWP) http://www.attra.org/attra‐pub/PDF/copper_wire.pdf ($)

• Copper boluses are available for use for copper deficiency in cattle.

• Boluses can be repackaged into doses suitable for lambs and kids.

• Minimum dose is 0 5 g; as• Minimum dose is 0.5 g; as much as 2‐4 g may be necessary.

• Effective against barber pole worm only.

• Mechanism of action is not known.

• Form of copper is poorly absorbed.

Natural “anthelmintics”Significant research effort underway

• Garlic juice

• Pumpkin seed

• Mustard seed

• Oregano oil

• Papaya

• Diatomaceous earth (DE)

• Bioactive plants (herbal)– Artemisia spp.

– Sericea lespedeza

– Birdsfoot trefoil

– Chicory

– Pine bark

Sesquiterpene lactonesCondensed tannins

Nematode‐trapping fungusDuddingtonia flagrans

• Spores are fed to livestock as part of their diet.

• Spores pass through digestive tract of livestock and are deposited in the fecesdeposited in the feces.

• Spores germinate alongside worm eggs.

• Spores trap and feed on newly emerging larvae.

No commercial product (yet)Image source: Louisiana State University

Natural “anthelmintics”

• Natural “anthelmintics” are not likely to replace the therapeutic use of anthelmintics.

• However they may reduceHowever, they may reduce the need for anthelmintic treatments disrupting the parasite’s life cycle.

• They may become an important aspect of holistic or integrated parasite management systems.

What about a vaccine?• So far, limited success in

developing vaccines for internal parasites.

• Paravac Consortium received record €9 million EU grant to fund development ofEU grant to fund development of vaccines against parasitic worms.

• Promising vaccine for Haemonchus developed by Moredun Institute (Scotland) and currently being tested in Australia.

• Would the vaccine be available to U.S. producers?

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Next topic: Integrated parasite management (IPM)

IV. Integrated parasite management (IPM)IV. Integrated parasite management (IPM)Controlling internal parasites without or before without or before you need to use anthelmintics: host immunity, grazing and pasture management, nutrition, management, and genetics.

Boer goat grazing chicory

Key points of parasite control

• The goal is not to eradicate worms, but to reduce their adverse effects in practical and economical ways.

• The interaction between parasites, the environment, animals, and management decisions is complex.

• Drug resistance is a seriouschallenge to effective parasite control.

Parasite infection in sheep and goats

• Parasite infection is normal in sheep and goats.

• The number of worms found in individual animals varies, with essentially all animals having some worms (and coccidia).

• It is rare to find animals uninfected.


• The nematode population in a flock is over dispersed.

• A majority of the• A majority of the nematodes are in a minority of the animals.

• The 80‐20 rule: 20 percent of the animals shed 80 percent of the worm eggs.


• The risk and severity of parasite infection varies by . . .

1. Season2. Year (weather)3. Geographic

location (climate)4. Farm5. Production system6. Animal

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Integrated parasite management (IPM)

• Whole farm or systems approach to managing internal parasitism.

• Applying best• Applying best management practices to minimize the effects of parasites and the need for deworming.

• Holistic worm management.

There is no one way or “magical” recipe for controlling parasites.

Integrated parasite management

• Host immunity• Pasture and grazing

managementg• Nutrition• Management• Genetics• Anthelmintic

treatment

Host immunity

• Sheep and goats have several defense mechanisms for dealing with internal gparasites:

1. Immune exclusion2. Self‐cure3. Immunity

a) Innateb) Acquired

IMMUNE EXCLUSION

• Ingested larvae fail to establish in heavily infected animals.

SELF‐CURE PHENOMENON• Adult nematodes are

spontaneously expelled when there is a massive larval invasion over a

hvery short exposure period.– Usually observed after

a heavy rain.

Why does it occur (?)• Increase in

abomasal pH• IgE mediated

hypersensitivity

Immunity (2 kinds)The ability to resist a particular disease.

INNATE

ACQUIRED

• Immunity that is not inherited.

• Immunity that is acquired

St. Croix lambs

INNATE (inborn, natural)

• Infection is limited during the initial exposure.

• Immunity that occurs naturally as part of an individual’s genetic make‐up.

y qduring life.

• Immunity that results from exposure to the disease.

Crossbred lambs

Immunity• Develops with advancing age

and parasite exposure.– Not until >4 months of age,

depending upon breed and nematode species.

• Preventative anthelmintic• Preventative anthelmintic treatments interfere with the development of immunity.

• Adults are generally immune to parasites, but under stress can break down.

• Goats show the weakest degree of immunity of any livestock.

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Periparturient egg riseRelaxation of immunity around the time of parturition

• Lasts for about 4 weeks• May occur earlier (in

pregnancy) if animals are underfed or under stressunderfed or under stress.

• Primary source of infection for new crop of lambs and kids.

• Cause (?) Hypothesis:Lactation after pregnancy– Increasing prolactin levels– Reduction in IgA antibodies

associated with transfer of maternal antibodies in colostrum

“Spring” periparturient egg rise

• If lambing and kidding occur in the spring, it will coincide with the maturation and egg production from previously arrested worm p ylarvae.

• Management strategies1. Deworm all females prior to

parturition with an anthelmintic that is effective against hypobiotic larvae.

2. Increase protein level of ration during late gestation.

3. Selective deworming using FAMACHA© system and Five Point Check©.

Pasture and grazing managementThe “cornerstone” of effective parasite control.

• Clean or safe pastures• Pasture rest/rotation• Stocking rates

l f• Alternative forages• Browsing• Plant height• Plant morphology• Plant moisture• Mixed species grazing

Clean or safe pastureA pasture that is FREE from parasites.

1. A pasture that has never grazed by sheep or goats.

2. A pasture that is grazed once per year by sheep and/or goats.

3. A pasture that has not been grazed by sheep or goats for 6 to 12 months

Newly planted dwarf pearl millet

to 12 months.4. Pasture that has been grazed

by cattle or horses for past 6 to 12 months.

5. Pasture in which a hay or silage crop has been removed.

6. A pasture that has been renovated with tillage.

7. A pasture that has been rotated with row crops.

8. Burnt pasture.9. Annual pastures. Cleaner, safer pastures are usually a more practical option.

Pasture rest/rotationThe primary method for creating safer (less contaminated) pastures.

• Parasite infection is driven by stocking rates and duration of grazing periods.

Overgrazing → parasitism

• The higher the stocking rate• The higher the stocking rate, the more the pasture gets infected and the more likely livestock are to ingest infective worm larvae.

• The longer the grazing period, the more the pasture gets infected and the more likely livestock are to ingest infective parasite larvae.

Rotational grazing• There is no “one‐size fits all”

pasture rotation schedule. There are many variables to manage:– Climate– Season– RainfallRainfall– Number of paddocks– Size of paddocks– Number of livestock– Susceptibility of livestock– Forage type and quality– Supplemental feed

• There is often a trade‐off between parasite control and good pasture management.

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General recommendations

• It takes approximately 60 days for a highly contaminated pasture to become lowly

t i t d ithcontaminated with worm larvae.

• “Take half, leave half”

• Don’t graze below 4 inches (10 cm).

Plant height

• It is estimated that 80 percent of infective worm larvae are found in the first 2 to 3 inches of the ground surface.

• Do not graze pastures below 4 inches.

• Overgrazing is one of the primary causes of internal parasitism in small ruminants.

Alternative forages

• Forages containing condensed tannins and sesquiterpenelactones.

Chicory

– Sericea lespedeza

– Chicory

– Birdsfoot trefoil

– Artemisia spp.

How do they work (?) – reduce egg hatch and development of larvae.

Sericea lespedezaLespedeza cuneata (high tannin variety)

• Warm season legume that grows in acidic soils with low fertility and is tolerant of drought.

G t dil t• Goats readily eat.Sheep will eat.

• For control of barber pole worm only.

• Effective when consumed as– Fresh forage– Loose or ground hay– Pelleted supplementImages from scsrpc.org

Browsing

• Goats that are allowed to browse (their natural grazing behavior) have fewer parasite problems.

• Browse should be managed to provide continuous nutrition for goats.

• Sheep will also browse.

Plant morphology

• There are lower numbers of larvae on non‐grass plants, e.g. legumes, forbs.

N l t d

Red clover

• Non‐grass plants reduce parasite survival on pasture or reduce larval migration up plant.

• Management strategies– Include legumes in pasture

mixes (e.g. 30%).– Plant alternative forages.

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Plant moisture

• Delay grazing until after dew has lifted or the grass has dried after a rain.

• Dry conditions force the larvae to stay at the base of the plant. • Parasites need moisture!

Mixed or multi‐species grazing

• Parasites are mostly host‐specific.– Worms rarely transmit

from one species to another.Cattle and horses have– Cattle and horses have different parasites than sheep and goats.

• Complementary grazing habits– Goats → browse– Sheep → forbs– Cattle → grass

NutritionThere is an interaction between parasites and nutrition.

• Livestock are far more capable of coping with parasites if their nutritional needs are being metbeing met.

• Animals on low protein diets are more susceptible to infection because they produce less IgA.

Nutritional control of parasites

• Improved protein nutrition.• Increased body protein

reserves.

• Feed periparturient f l t i t 130% ffemales protein at 130% of requirements.

• Provide supplemental protein to grazing livestock, especially at‐risk animals and during periods of poor forage quality.

• Manage pastures so that they are grazed in a vegetative state.

Management options

• Sanitation• Biosecurity• Biosecurity• Zero grazing• Timing of lambing and kidding

• Weaning age

Sanitation• Dry, well‐bedded pens

• Clean floors and surfaces

• Feeders which prevent contamination andcontamination and wastage.

Do not feed on ground.

• Clean water that is free from fecal material.

• Discourage congregation on pasture.

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BiosecurityDon’t introduce drug‐resistant worms to your farm

• Quarantine new animals for 30 days

– In a pen away from rest of flock/herd.

– No fence line contact

– Deworm with anthelmintics from 2‐3 drug chemistries, e.g.

• Cydectin® + levamisole• Valbazen® + Ivomec® + levamisole

Zero grazingconfinement, dry lot, feed lot, elevated floors

• Can maintain animals relatively “worm‐free” under zero grazing conditions.– Coccidiosis is still a risk.

• Primary source of infectionPrimary source of infection (and re‐infection) is removed: grazing.

• Pens should be kept dry.

• Feeders and waterers need to be kept clean.– No feeding on pen floor or

ground.Dairy goats in China

Season of lambing and kidding

• Parasite problems can be minimized by lambing and kidding at different times of the year, so that lambs and kids are not on pasture when weather conditions are most conducive to parasite development.

• There can be other advantages to lambing and kidding at different times of the year (e.g. marketing, predator risk).

Weaning

• The influence of weaning on resistance to worms is not clear and is probably more dependent on nutrition. However, . . .

– If lambs or kids will face a substantial parasite challenge, do not wean before 3(‐4) months of age.

Genetic aspects of parasite control

• Some animals mount a significant response to internal parasite infection, while others do not.

• Some animals do not mount a noticeable response to internal parasite infection, but they suffer no obvious loss of production.

• There is significant within and between breed variation in parasite resistance and resilience.

Two genetic traits

RESISTANCE• Ability to prevent infection

from establishing.• Quantified by fecal egg

counts.• Moderately heritable

– h2 ranges from 0.22 to 0.63– Avg. h2 is 0.25

RESILIENCE (tolerance)• Ability to limit damage

caused by parasites• Quantified by clinical signs:

packed cell volume (barber pole worm), dag scores, etc.

• Less heritable than resistance, ~ 0.1

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Resistance and resilienceBoth traits are equally important!

• There is a cost to parasite resistance as resources are directed away from production traits.

• Resilient animals may still carry significant parasite loads and be a

f t i ti t thsource of contamination to the pasture and other animals.

• Correlation between two traits– No correlation between worm

resistance and resilience in New Zealand studies.

– Positive correlation between two traits in Australian work.

– Low (positive) or no correlation in Western Maryland Pasture‐Based Meat Goat Performance Test.

(More) resistant breeds

SHEEP

1. Hair sheep of Caribbean or North African heritage

St. Croix

B b d Bl kb ll

GOATS

• Kiko

• Spanish

• MyotonicBarbados Blackbelly

Katahdin

2. Gulf Coast Native

Naturally‐selected resistant breeds of sheep andgoats have developed resistance over a muchlonger term (decades and perhaps centuries)than short‐term (few years) genetically‐selectedresistant lines within breed.

St. Croix sheep

Breeding for worm resistanceWithin breed selection

RESISTANCE• Cull animals with high fecal egg

counts.• Don’t select replacements with

high fecal egg counts.• Don’t use rams or bucks with high

RESILIENCE

• Cull animals that require frequent deworming.

• Don’t select replacements that Don t use rams or bucks with high egg fecal counts.

• Include fecal egg counts in a selection index.

• Select animals based on a minimum standard for parasite resistance.

• Use EPD’s to select for parasite resistance.

• Use gene markers to select for parasite resistance.

require frequent deworming.

• Don’t use a ram or buck that requires frequent deworming.

Make sure you are comparing animals in the same contemporary group (i.e. similar breed, age, and management).

Maine internal parasites

Education

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