SUSAN SCHOENIAN (Shāy-ne-ŭn)EXTENSION SHEEP & GOAT SPECIALISTWESTERN MARYLAND RESEARCH & EDUCATION CENTERsschoen@umd.edu - www.sheepandgoat.com

PA R A S I T E C O N T R O L I N D A I RY S H E E P

Gastro-intestinal parasites

Primary health problem affecting sheep and lambs, especially east of the Rockies.

Severity varies by • Geographic region• Production system

Control is limited by effectiveness of anti-parasitic drugs (called anthelmintics).

Goals of internal parasite control

Eliminate parasites

1. Prevent clinical disease, production losses, and mortality, and …

2. Slow down drug resistance.

Critical control points in dairy sheep

LACTATING EWESPERI-PARTURIENT EGG RISE

EARLY WEANED LAMBS

Parasite control in dairy sheep

Parasite biology

Integrated parasite management (IPM)

1. Pasture management2. Animal factors/

management3. Deworming

Anthelmintics

Anthelmintic resistance

Internal parasite species affecting sheepIt is normal for healthy sheep to have various kinds of parasites in their gut.

1. Multi-cellular(Helminths)

a) Nematodes(roundworms)

b) Cestodes(tapeworms)

c) Trematodes(flukes)

2. Single-cell(protozoa)

Nematodes - roundworms

1. Strongyle

2. Lungworms

3. Meningeal worm

Strongyle-type worms

Haemonchus contortus

Teladorsagia (Ostertagia)

TrichostrongylusNematodirusOesophagostomumCooperiaTrichuris ovisBunostomum

Haemonchus – Trichostrongylus – Teladorsagiabarber pole worm – bankrupt worm – small brown stomach worm

Short, direct life cycles that are weather-dependent.

Can overwinter on pasture.

Ability to go into hypobiotic (arrested) state (in host) when environmental conditions are not conducive to their development.

Vary in their egg laying ability.

Eggs look same under microscope.

L3

L4, adult

L2

L1

Haemonchus contortusbarber pole worm

Primary parasite affecting sheep and lambs in warm, moist climates and/or with summer-dominated rainfall.

Most pathogenic species

Blood-sucker

Prolific egg layer

Image from University of Georgia

Haemonchus contortusbarber pole wormSYMPTOMS(due to blood and protein loss)

Anemia (paleness) Edema - “bottle jaw”

(accumulation of fluid)

Not usually diarrhea Weight loss Loss of body condition Poor stamina Sudden death

Other strongylesPrimarily Teladorsagia and TrichostrongylusSYMPTOMS(usually additive w/barber pole worm)

Production lossWeight lossDagginessScours (diarrhea)Only occasional

deathImage source: NADIS UK

Lungworms

Usually not significant

Usually additive in effect

Possible respiratory symptoms Coughing Irritated airways Pneumonia

Difficult to diagnose Usually no clinical signs Larvae (not eggs) in feces Post-mortem diagnosis

Meningeal wormdeer worm, brain worm

Normal parasite of white tail deer.

Sheep are an abnormal host. Ingest intermediate host

(snail or slug) Larvae migrates into central

nervous system where itcauses neurological disease (various symptoms).

Treat with repeated doses of fenbendazole and anti-inflammatory drugs.

Monthly treatments with ivermectin have been used as a preventative (camelids). Paralaphostrongylus tenius

Cestodes - Tapeworms Indirect life cycle; require

pasture mite as an intermediate host.

Tend to be non-pathogenic

Usually no benefit to treatment.

Treat with albendazole (Valbazen®), fenben-dazole (Safeguard®, or praziquantel (Quest Plus®). Moniezia expansa

Trematodes - Liver flukes Regional problem

(Gulf States, Pacific Northwest) Require an intermediate

host (snail or slug) Infect bile ducts - liver damage Diagnosis based on finding eggs

in feces and post-mortem Similar symptoms as barber

pole worm (anemia and bottle jaw) Treat with albendazole (Valbazen®)

or clorsulon (Ivomec® Plus).

Fasciola hepatica

Single-cell protozoa - Coccidia Species-specific

10 species known to infect sheep, but not all are pathogenic.

More complicated life cycle than most roundworms.

Cause damage to cells lining small intestines.

Most prevalent Indoor pens Feed lots Intensive grazing areas

Eimeria spp.

Coccidiosis - diagnosisFECAL EXAM

Of limited value – shouldn’t use as sole diagnostic tool Can have clinical

coccidiosis with low oocyte count and vice versa.

Not all species of coccidia are pathogenic.

Is normal to find coccidia oocytes in fecal samples.

CLINICAL SIGNS

Adults are largely immune, but serve as a reservoir of infection.

Lambs (1-6 mos., esp. 4-8 wks.) are very susceptible. Scours (diarrhea) Open fleece Weight loss Anorexia Dehydration Weakness

Coccidiosis - prevention

Good sanitation

Coccidiostats in feed, mineral, water, and/or milk replacer.

Lasalocid (Bovatec®) Monensin (Rumensin®) Decoquinate (Deccox®) Amprolium (Corid)

Coccidiosis - treatment Medicate water or

drench individual animals (preferable).

Anthelmintics1. Amprolium (Corid)2. Sulfa antibiotics▪ Di-Methox®▪ Sulmet®

Supportive therapies All Tx’s require veterinary Rx.

A method of controlling parasites using a combination of chemical and non-chemical means.

1. Non-chemical▪ Pasture management▪ Animal management

2. Chemical▪ Proper and judicious

use of drugs

Integrated parasite management (IPM)

Pasture and grazing management

1) Safe pastures2) Low risk

pastures3) Evasive grazing4) Strip grazing5) Rotational

grazing6) Multi-species

grazing

Pasture and grazing management

7) Compost manure before spreading

8) Alternative forages

9) Minimum grazing height

10) Delay grazing11) Night penning12) Zero grazing

Chicory

Sericea lespedeza

Animal management

1) Host immunity2) Lambing

management3) Nutrition4) Genetics

Targeted, selective deworming

1. FAMACHA© System

2. Five Point Check©

Fecal egg counting

FAMACHA© system

A system developed in South Africa to assess barber pole worm infection and determine the need for deworming.

Scores estimate packed cell volume (PVC) by measuring anemia using a color eye chart.

Each score has a treatment recommendation.

Eye lid color

PCV Treatment recommendation

1 Red > 28 Optimal No

2 Red-Pink 23-27 Acceptable No

3 Pink 18-22 Borderline ?

4 Pink-White 13-17 Dangerous Yes

5 White < 12 Fatal Yes

Five Point Check©

An extension of the FAMACHA© system that includes evaluation criteria for other important internal (and external) parasites.

Includes five check points on the animal:

1. Ocular membrane (eye)2. Bottle jaw3. Body condition score 4. Dag score (scours)5. Nasal discharge (nose bots)

Fecal egg counting

Determining the number of worm eggs per gram of feces (EPG) in order to estimate the worm burden in an animal.

Egg count includes all strongyle eggs; cannot differentiate at egg stage.

Requires a measured amount of feces and flotation solution. A McMaster slide is used to count eggs.

Most veterinarians and many diagnostic labs do not perform quantitative egg counts (only simple fecal flotations).

Fecal egg count uses

Individual sample to determine need for deworming individual animal.

Individual or pooled samples to determine level of pasture contamination.

Pooled sample to determine treatment need in a large flock, where FAMACHA© and Five Point Check® are not practical.

Individual samples to determine effectiveness of anthelmintic treatment (FECRT) or management strategy.

Individual samples to determine genetic differences in parasite resistance.

Anthelmintics

A limited resource that should be used judiciously.

Anthelmintic families (3)Drugs in the same family have the same way of killing worms.BENZIMIDAZOLES

1.FenbendazoleSafeGuard®Panacur®

2.AlbendazoleValbazen®

3.OxybendazoleSynanthic®

MACROCYLIC LACTONES

1. AvermectinsIvermectin(Ivomec®)Eprinomectin(Eprinex®)Doramectin(Dectomax®)

2. MilbimycinsMoxidectin(Cydectin®)

NICOTINICS

1. Levamisole(Prohibit®)

2. Pyrantel(Strongid®)

3. Morantel(Rumatel®)

FDA-approved anthelmintics

SHEEP AND LAMBS

Ivermectin (Ivomec® drench)

Albendazole(Valbazen® liquid)First 30-d gestation

Moxidectin (Cydectin® drench)

Levamisole(Prohibit® drench)

LACTATING DAIRY EWES Withdrawal periods

have not been established for lactating dairy ewes.

Requires extra-label drug use, as prescribed by a licensed veterinarian.

Work with veterinarian to establish safe withdrawal periods for milk.

Anthelmintic formulationsORAL DRENCHES

FDA-approved for sheep.

Easier to administer.

Clear system faster.

Shorter withdrawal periods.

More effective

INJECTABLES

Not FDA-approved.

Sub-therapeutic levels select for resistant worms.

Longer withdrawal periods.

POUR-ONS

Not-FDA approved.

Not developed for sheep skin.

Less effective.

Sub-therapeutic levels select for resistant worms.

Anthelmintic resistanceInevitable: no treatment is 100% effective.

1) When an anthelmintic treatment fails to reduce fecal egg counts by 95% or more; severe when less than 60%.

2) There is varying degrees of resistance to all anthelmintic classes. Benzimidazoles - widespread Avermectins - widespread Moxidectin - emerging Levamisole - variable

3) Resistance varies by geographic location and farm and is influenced by past anthelmintic use.

Anthelmintic resistance Each anthelmintic family has

a different way to kill worms.

Worms develop resistance to the mechanism of worm control not individual drugs.

There is cross resistance among drugs in the same family.

If a different drug in the same family appears to work, its efficacy will be short-lived.

Determining anthelmintic resistance1) Treatment response

2) Fecal egg count reduction test (FECRT)▪ Before (d-0) and after fecal

egg counts (d 10-14)

3) DrenchRite® testLarval development assay (LDA)

Slow drug resistance by increasing refugia

Decrease frequency of treatments.

Do not treat everyone; leave some animals untreated.

Do not move treated animals to a clean pasture.

Do not deworm when there is a low level of pasture contamination.

Re-introduce suceptable worms.

Do not make it easier for worms to develop resistance to drugs By exposing worms

to sub-therapeutic levels of drugs.1) Underdosing2) Using injectable

dewormers3) Using pour-on

dewormers4) Depositing drug into

mouth instead of esophagus.

5) Persistent activity dewormers (?)

Do not introduce resistant worms to your farm To prevent the

introduction of resistant worms to your farm, deworm all newly acquired animals with anthelmintics from all three chemical classes.

For saleRam - $1,000Resistant worms - free

OTHER

NATURAL “ANTHELMINTICS”

Copper oxide wire particles

Copper sulfate Nicotine sulfate Diatomaceous earth Pumpkin seed Garlic Papaya Sericea lespedeza

(leaf meal)? Pine bark? Others

NEW ANTHELMINTICS

Monepantel (Zolvix®) Derquantel +

abamectin (Startect®)

Nematode trapping fungus

FUTURE (?) Vaccine for

Haemonchus contortus (in development)

Internal parasite resources American Consortium for Small Ruminant Parasite

Controlwormx.orgacsrpc.orgwormcontrol.orgcontrolworms.org

Maryland Small Ruminant Pagewww.sheepandgoat.com

Sheep 201: A Beginner’s Guide to Raising Sheepwww.sheep101.info/201/parasite.html

Today’s PowerPoint presentationwww.slideshare.com/schoenian

Thank ewe for your attention.

Lambs are 69% Katahdin x 31% Lacaune.