Copy of PowerPoint slides for Sheep & Goat Internal Parasite Seminar in Maine (October 22, 2011).

1. 10/18/2011
Today’s seminar topics
Internal parasites seminar I. Parasites and their biology
SHEEP AND GOATS II. Diagnostic tools
Diagnostic tools
III Using anthelmintics effectively
III. Using anthelmintics effectively
IV. Integrated parasite management (IPM)
SUSAN SCHOENIAN (Shāy‐nē‐ŭn)
Sheep & Goat Specialist
University of Maryland Extension
sschoen@umd.edu – www.sheepandgoat.com
Barber pole worms in abomasum
Image source: ScienceWatch.com
What is a parasite?
I. Parasites and their biology A (generally undesirable) living organism that exists by stealing the
species, life cycles, pathogenicity, interactions resources produced or collected by another living organism.
[Greek: “one who eats at the table of another]
There are two general kinds
There are two kinds of parasites. of internal parasites.
1. Internal (endo) – a 1. Helminths
parasite that lives multi‐cellular
inside another a) Nematodes
organism. b) Cestodes
c) Trematodes
2. External (ecto) – a
parasite that lives on 2. Protozoa
the blood of the host single cell
or lays eggs on their a) Coccidia
hide or in their nose. b) Giardia
c) Cryptosporidium Haemonchus contortus (barber pole worm)
External parasite: sheep ked (tick)
Image from University of Georgia
Image from Colorado State University
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2. 10/18/2011
1. Helminths (parasitic worms) A. Nematodes (roundworms)
Phylum Nematoda
A. Nematodes • Approximately 1 million
– Over 28,000 described
Roundworms – Over 16,000 parasitic
• Round
• Elongated
B. Cestodes • Worm‐like
Tapeworms • Have a body cavity
• Have digestive systems
• Reproduce sexually
C. Trematodes • Mostly host‐specific Most significant kind of internal
Flukes • Not all are pathogenic parasites that affect sheep and goats.
Barber pole worm
Image source: MicrobiologyBytes
Class Nematoda → Superfamily Strongyloidea → Family Strongylidae → Genera Strongyle
Haemonchus contortus
Primary parasites affecting sheep and goats: Strongyles Barber pole worm
Species Location Light Infection Heavy infection
• Most common in
Haemonchus
Lack stamina warm, moist
Anemia
Contortus Gradual weight loss
Abomasum
Loss of color
Edema (bottle jaw) climates with
Constipation
Barber pole worm
Sudden death
Sudden death summer rainfalls.
summer rainfalls
Teladorsagia spp. • Adapting to cooler
(Ostertagia spp.) Rapid loss of condition
Abomasum
Unthrifty
Daggy
Profuse scours climates.
Small brown Death
stomach worm • Most deadly worm.
Trichostrongylus spp.
Small
Rapid loss of condition
Black scours
• Blood sucker.
Unthrifty
intestines Dehydration
Black scour worm
Bankrupt worm
(1st 3 m)
Daggy
Death • Prolific egg layer.
Western Maryland Pasture‐Based Strongyle‐ type worms
Meat Goat Performance Test (2009)
• Direct life cycles
– Weather dependent L4, adult suck blood
– 14 to 21 days
• Eggs cannot be
differentiated in
2011 egg fecal analyses.
75 – 95 μ m
L3
• Mixed infections common.
Have developed varying L1
levels of resistance to L2
anthelmintics.
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3. 10/18/2011
Environmental‐parasite interactions Hypobiosis
inhibited 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
moisture or temperatures that
i h
are too cold for larval
development.
– Occurs in winter or summer,
• Optimal conditions for development of Haemonchus larvae are 82⁰F and depending upon parasite and
humidity above 70%. geographic location.
– Probably involves some immune and
• Teladorsagia is better adapted to cooler, temperate climates. They fair poorly environmental cues.
in very hot, dry summers.
• Survival mechanism
• Trichostrongylus spp. are more resistant to cold and desiccation than • No host response
Haemonchus.
Strongyles that cause occasional problems Lungworms
• Bunostomum • Direct or indirect 1. Muellerius capillaris
Hookworm life cycle 2. Dictyocaulus filaria
• Cooperia spp. • Prefer cool conditions
Small intestinal worm
• Nematodirus • Diagnosis is difficult
threadneck worm – Clinical signs
Persistent coughing, respiratory
• Oesophagastomum • Muellerius capillaris distress, reduced weight gains
Nodule worm Dictyocaulus filaria – Recovery of 1st stage
• Strongyloides Lungworms larvae from feces
Common threadworm • Paralaphostrongylus tenius – Usually diagnosed at
• Trichuris ovis Meningeal worm post‐mortem Image source: UPENN Vet School
Whipworm (brain, deer worm)
CLINICAL SIGNS TREAMENT PROTOCOLS
Meningeal worm • Variable • High doses of anthelmintics
• Mimic other – Ivermectin for five days
• White‐tailed deer are the neurologic diseases
normal host. – Fenbendazole for five days
– Infection typically causes no – Weakness
clinical disease in deer.
• Anti‐inflammatory drugs
– Lameness
– Circling
• Severe neurological disease
occurs when infected snails or
occurs when infected snails or – Blindness
slugs are ingested by other – Head tilt
cervids or ungulates.
– Abnormal behavior
– Paralysis
• Gastropods serve as
intermediate host. – Death
• Parasite migrates to spinal
cord and brain.
– 10 to 14 days after ingestion of
infected snail or slug
No controlled studies have confirmed or refuted the
efficacy of various treatment recommendations.
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4. 10/18/2011
Prevention • Limit deer access to
pasture.
B. Cestodes (tapeworms)
– Eliminate deer via lethal
means.
– Deer‐proof fencing for small
operations. • Flat
– Make pastures less appealing • Segmented
to deer.
Feed in enclosed areas.
– Feed in enclosed areas • No body cavity
No body cavity
• Hermaphrodites
• Reduce exposure to
infected snails and slugs. • Indirect life cycle
– Do not allow access to • Some cause symptoms
pastures that contain thick
• Prophylactic treatment vegetation or moist shaded in the intermediate
with anthelmintics areas that are favorable snail host.
(every 10‐14 d). and slug habits.
Tapeworms affecting sheep and goats Sheep measles (Ovine cysticercosis)
Genus Moniezia
• Indirect life cycle • Sheep tapeworm of dogs
– Pasture mites serve as an – Transmitted to sheep eating
intermediate host. forages contaminated with
tapeworm eggs shed by
– 6 weeks canines.
– Sheep and goats host larval
• Segments visible in feces. stage of parasite
g p
Only worm visible in feces – No clinical signs in sheep or
goats. Image source: Optimal Livestock Services, LLC
• Generally thought to be
non‐pathogenic and of little • Causes development of cysts
consequence. in skeletal and heart muscle.
– Usually no benefit to treatment – Cause of carcass
condemnation.
• Treat with albendazole
(Valbazen®), fenbendazole (Safe‐ → Control point: dogs
Guard®), or praziquantel.
Liver flukes
C. Trematodes (flukes)
• Fasciola hepatica
(common liver fluke)
• Flat • Gastropods serve as
intermediate host.
• Oval shape
• No body cavity • In U.S., found mainly in Gulf
states, California, and Pacific
• No digestive tube Northwest.
• Indirect life cycle • Symptoms include pale
• Hermaphrodites mucous membranes, bottle
jaw, and weight loss.
Image source:
Image source:
http://www.flickr.com/photos/peteredin/3386220058/ • Treat with albendazole Agricultural Research Council in South Africa
(Valbazen®).
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5. 10/18/2011
2. Protozoan parasites Eimeria spp. ‐ Coccidia
• Single cell
A. Eimeria spp. • Life cycle
Coccidia – Complicated
– Many stages
– Oocytes → sporulation (hatching)
– Sexual and asexual reproduction
B.
B Giardia – 21 days
• 10 species known to infect sheep
C. Cryptosporidium sp. and goats
– Host specific
– Not all are pathogenic
D. Toxoplasma gondii • Damage cells of small intestines
1. Subclinical
2. Clinical (diarrhea)
Image source: FAO United Nations
Internal parasites of sheep and goats
Barber pole worm
Roundworms Teladorsagia (Ostertagia)
Trichostronyglus spp.
Helminths Tapeworms
Other strongyles
Lungworms
Liver flukes Meningeal worm
Protozoa Coccidia
II. Diagnostic tools
II. Diagnostic tools
FAMACHA© system, Five Point Check©, laboratory and field tests
Next topic: diagnostic tools
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6. 10/18/2011
They all are.
• Almost all sheep and goats
have parasites, probably of
different kinds.
• “Positive” egg or oocyst
Positive egg or oocyst
counts are “normal.”
Negative tests are rare
(during the periods of risk).
How do you tell if your sheep or goats • Some level of parasite
infection is required for
are infected with internal parasites? immunity.
They all are.
• Clinical disease occurs at
a certain level of infection
that can vary by animal.
• Not all parasites are
Not all parasites are
pathogenic or highly
pathogenic.
• Not all strains of parasites The more important question to ask is:
are pathogenic or equally
pathogenic. How do you tell if a sheep or goat is clinically parasitized
(suffering negative effects) and requires anthelmintic treatment?
Diagnostic tools Diagnostic tools
ON FARM LABORATORY
1) On‐farm
• Animal • Blood
1) Animal – Packed cell volume
– FAMACHA©
2) Fecal – Five Point Check® NEW! • Fecal
– Si l fl
Simple flotation
i
• Fecal
– Fecal egg counts
2) Laboratory – Simple flotation • FECRT
1) Blood – Fecal egg counts – Lectin staining test NEW!
• Fecal egg count – Larvae
2) Fecal reduction test (FECRT) • Larvae culture
3) Larvae – Dipstick • Larval development assay
[DrenchRite®]
• Carla® saliva test • Pasture
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7. 10/18/2011
The FAMACHA© System FAMACHA©
• Develop for small‐scale sheep
producers in South Africa in
response to the widespread General treatment recommendations
Deworm adults at scores 4 and 5*
development of anthelmintic‐ Treat lambs and kids at categories 3,
4, and 5
resistant worms.
*The South Africans recommend
goats be treated at categories 3 4,
3, 4
and 5
• A practical system for assessing
barber pole worm infection in Packed
sheep and goats and Clinical Eye Lid
Cell Deworm?
determining the need for Category Color
Volume
deworming individual animals. 1 Red > 28 No
2 Red-Pink 23-27 No
• Named for its originator:
Dr. Francois “FAffa” MAlan CHArt 3 Pink 18-22 ?
4 Pink-White 13-17 Yes
5 White < 12 Yes
Using FAMACHA© Benefits of FAMACHA©
• Must take training
to get card. • Reduces number of
• Use card anthelmintic
• Replace card periodically treatments.
(colors fade) • Reduces dollars spent
p
• Do not use in a vacuum; on anthelmintics.
consider other factors. • Identifies susceptible
• Frequency of checking and resilient animals.
varies by risk.
• Should incorporate • Increases refugia
FAMACHA© into an • Prolongs effectiveness
integrated parasite of anthelmintics
management program.
Using the FAMACHA© system to control Limitations of FAMACHA©
internal parasites in grazing lambs
• Doesn’t save time.
– LESS deworming
% Lambs/
3.5 60
No. times treated
– MORE monitoring
Avg FAMACHA Score
3 50 6
# Lambs Dewormed
2.5
2
40
5 • Only useful where
Only useful where
2
1.2%
1.2%
4
3
(when) barber pole
1.5
30 4.8%
7.1% 2
worm is the primary
1
20
16.7% 1
parasite.
0.5 10
41.7%
0 0 0
• Must know which
26.2% anthelmintics are
effective.
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8. 10/18/2011
Back
body condition (and coat condition)
The Five Point Check © (5. ©)
2
• Expands the FAMACHA©
system to include Eye Tail
evaluation criteria for anemia 1 3 soiling , dags
other internal parasites. FAMACHA© score (scours)
• Check five places on
animal’s body
1. FAMACHA© score 4 5
2. Bottle jaw
3. Body condition score Jaw Nose
swelling, edema nasal discharge
4. Dag score “bottle jaw” (nose bots)
5. Nasal discharge
FIVE POINT CHECK© (5. ©)
FOR TARGETED SELECTIVE TREATMENT OF INTERNAL PARASITES IN SMALL RUMINANTS
G.F. BATH AND J.A. VAN WYK, FACULTY OF VETERINARY SCIENCE, UNIVERSITY OF PRETORIA, SOUTH AFRICA
Five Point check© FAMACHA© eye anemia score
Point What to check Specificity
Paling of ocular Packed cell Treatment
Eye lid color
volume recommendation
membranes Barber pole worm
1 Eye
FAMACHA© eye Liver fluke 1 Red > 28 Optimal No
anemia score
2 Red-Pink 23-27 Acceptable No
2 Back Body condition score All
3 Pink 18 22
18-22 Borderline ?
Brown stomach worm
Dag score Hair worm
4 Pink-White 13-17 Dangerous Yes
3 Rear fecal soiling Threadneck worm 5 White < 12 Fatal Yes
evidence of scouring Nodule worm
Coccidia
Sub‐mandibular edema Barber pole worm
4 Jaw
(bottle jaw) Liver 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 Source: G.F. Bath and J.A. van Wyk, Faculty of Veterinary Science, University of Pretoria, South Africa
Bottle jaw Body condition score (BCS)
Sub‐mandibular edema
Transverse
Spine Muscle Fat
processes
Fingers easily pass
Individually clearly
1 felt, sharp, obvious
underneath Very little No
Form a smooth line Smooth round
2 with deep undulations edges
Concave Very thin
Well covered
Only slightly have to push firmly Not concave
3 detectable undulations to get fingers Not convex
Moderate
underneath
Only detectable with
4 firm pressure Cannot be
Maximally Thick
developed
felt at all
5 Not detectable Convex Very thick
Source: G.F. Bath and J.A. van Wyk, Faculty of Veterinary Science, University of Pretoria, South Africa
Source: G.F. Bath and J.A. van Wyk, Faculty of Veterinary Science, University of Pretoria, South Africa
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9. 10/18/2011
Dag Scores Nasal discharge
britch soiling, evidence of scouring (diarrhea)
Treatment
Dag score Description
recommendation
No indication for
0 No fecal soiling
treatment
Very slight soiling on edge of
1 tail
No treatment
Slight soiling on edge of tail and
2 on each side
Usually no treatment
Moderate soiling of tail and wool
3 Dag formation
Consider treatment
Severe soiling extending far into
Treatment, crutching
4 wool
recommended
Severe dag formation
Very severe
Treatment and crutching
5 watery diarrhea extending to
hocks
essential
Source: G.F. Bath and J.A. van Wyk, Faculty of Veterinary Science, University of Pretoria, South Africa
Source: G.F. Bath and J.A. van Wyk, Faculty of Veterinary Science, University of Pretoria, South Africa
Packed cell volume (PCV) Why look at feces?
• Portion of whole 1. Identify worm eggs and
determine existence and
blood occupied by level of infection
a) Simple fecal flotation
red blood cells. b) Fecal egg counting
• A measure of anemia
A measure of anemia 2. Determine parasite species
– Primary symptom of a) Larvae culture
b) Lectin staining test
Haemonchosis (or Clinical Category
Packed Cell
Volume
Tx (?)
barber pole worms). 1 Non-anemic > 28 No 3. Determine effectiveness of
2 Non-anemic 23-27 No anthelmintic treatment
• A measure of 3 Mildly anemic 18-22 ?
a) Fecal egg count reduction
4 Anemic 13-17 Yes test (FECRT)
resilience. 5 Severely anemic < 12 Yes b) Larval development assay (LDA) or
DrenchRite® test
Fecal testing What you need to do your own fecal egg counts
Quantitative
Fecal egg count (FEC) 1) Microscope
Qualitative 40x objective x 10x eye piece = 400
Simple fecal flotation • Use McMaster egg Only need 100x
Mechanical stage recommended
counting slide
• Use simple slide and cover slip • Weigh feces and measure 2) Flotation solution
flotation solution
flotation solution Saturated salt or sugar solution
g
Specific gravity of 1.2
• Determine general egg types Can also purchase
Strongyle vs. coccidia vs. tape • Determine general egg types
• Determine existence and 3) McMaster egg
Strongyle vs. coccidia vs. tape
general level of infection
counting slide
• Determine level of infection www.vetslides.com
– Eggs per field of view www.mcmaster.co.za
– Eggs per gram of feces
e.g. Eggs Plus system
4) Miscellaneous supplies
scale, beaker, pipettes, vials, craft
sticks, cheese cloth or strainer
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10. 10/18/2011
Fecal egg counts Fecal egg counts are not definitive.
eggs per gram of feces
• Fecal egg counts are
• Indicate “potential” not always well‐
parasite burden in correlated with clinical
animal. disease.
– Presence of eggs or
• Indicate potential does not mean that the
does not mean that the
parasite burden on
b d animal is clinically
pasture.. parasitized and needs
treatment.
• Use to determine level of – Absence of eggs or
drug efficacy. oocytes (coccidia) or a
low count does not
• Use to determine genetic mean that the animal is
differences in parasite parasite‐free and not in
need of treatment.
resistance.
Limitations to fecal egg counts Clinical significance of fecal egg counts
• Some parasite eggs look the same • Not all parasites are pathogenic
and cannot be identified at the egg (disease‐causing)
stage). • Total egg counts may include a mixture of
• There is a fairly regular fluctuation in species with different levels of fecundity
fecal egg output. and pathogenicity.
• Egg output varies by season of the • Diarrhea increases fecal moisture and may
year. dilute the number of eggs.
• Eggs are not always evenly • Human error.
distributed in the feces
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
Fecal egg count reduction test (FECRT) DrenchRite® Larval Development Assay (LDA)
• First and most widely • In vitro test for the detection of
anthelmintic resistance.
used method to access
efficacy of anthelmintics. • Evaluates resistance to all major
anthelmintics from a single
pooled fecal sample.
• Before and after fecal • Requires pooled fecal sample
egg counts. from 10 or more animals
– Mean FEC of > 350 epg minimum
– d 0 and d 7‐14 post – Mean FEC of > 500 epg preferred.
treatment – Select feces from animals scored
as FAMACHA© 3, 4, or 5.
– With or without
untreated controls • Available through University of
Georgia (jscb@uga.edu)
– Minimum of 10 animals.
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11. 10/18/2011
Western Maryland Pasture‐Based
Larvae culture and differentiation
Meat Goat Performance Test (2009)
• 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 Image source: Dr. Woodgate, Western
parasite eggs and Australia Department of Agriculture
obtaining larvae for
morphological
identification.
Lectin staining test
New tests (not available in U.S.)
• Fast, easy, less‐expensive way to
test for the presence and
quantity of barber pole worms. CARLA® SALIVA TEST
HAEMONCHUS DIPSTICK TEST
• Lectin‐staining test based on • Measures antibodies against
• Detects blood in feces to
peanut agglutin that binds to egg worm larvae.
of barber pole worm.
of barber pole worm. determine presence of
• Use to select animals which
Use to select animals which barber pole worm and
suffer less from parasites and level of infection.
• Only requires a small amount of
feces. pass fewer eggs onto pasture.
• Results available in as little as two
days.
Image source: University of Georgia
• Available through Oregon State College of Veterinary Medicine.
University and University of
Georgia.
III. Using anthelmintics effectively
Products, usage, resistance, refugia, alternatives, future
Next topic: Using anthelmintics effectively
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12. 10/18/2011
There are three anthelmintic classes.
Based on similar chemistries, modes of action, and cross‐resistance.
1. Benzimidazoles (BZ)
Macrocylic lactones (ML)
2. Macrocylic lactones (ML)
A. Avermectins
B. Milbemycins
3. Nicotinic antagonists
What is an anthelmintic? A. Imidazothiazoles (IMID)
An agent that kills or causes the expulsion of parasitic worms.
Also called dewormer, wormer, drench, or parasiticide. B. Tetrahydropyrimidines (TETR)
1 ‐ Benzimidazoles (BZ) 1 ‐ Benzimidazoles (white drenches)
First class of modern anthelmintics (1961)
• Broad spectrum
A. Fenbendazole 1. Adult and 4th stage larvae of
roundworms
Safe‐guard® 2. Adult liver flukes
Panacur® (Valbazen® only)
3. Heads and segments of tapeworms
(Valbazen® or 2x labeled dose of
Safe‐Guard®)
B.
B Albendazole 4. Effective against hypobiotic larvae
Valbazen® 5. One of the drugs of choice for
meningeal worm (Safe‐Guard®)
C. Oxfendazole • Wide margin of safety
Synanthic® – Do not use Valbazen® during
first 30 days of pregnancy or
removal of ram(s).
D. Thiabendazole • Widespread resistance reported.
TBZ Benzimidazoles kill worms by interfering with energy
metabolism on a cellular level by binding to beta tubulin.
2‐ Macrocylic lactones (ML) 2 ‐ Macrocylic lactones (ML)
Newest family of anthelmintics ‐ circa 1980’s
• Potent
1) Avermectins
a) Ivermectin • Persistent activity (+/‐)
Ivomec®
Primectin® • Broad spectrum
b) Eprinomectrin 1. Adult and 4th stage larvae of
roundworms
Eprinex®
E i ® 2. Some external parasites
c) Doramectin (Ivermectin: larval stages of nasal bots)
Dectomax® 3. Effective against hypobiotic larvae
4. One of the drugs of choice for
meningeal worm (ivermectin).
2) Milbemycins • Potential negative effect on
a) Moxidectin dung insects.
Cydectin®
Quest® • Widespread resistance reported,
especially avermectins.
Macrocylic lactones interfere with GABA‐mediated
neurotransmission, causing paralysis and death of the parasite.
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13. 10/18/2011
3‐ Nicotinic agonists 3 ‐ Nicotinic agonists
1. Levamisole
1) Imidazothiazoles (IMID) – Clear (yellow) dewormer
a) Levamisole – Broad spectrum
Act as agonists at • Adult and 4th stage
Prohibit® nicotinic acetylcholine roundworm larvae
receptors of
Tramisol® nematodes, causing
nematodes, causing
• Hypobiotic larvae (?)
Levasol® paralysis of the – Narrower margin of
worms. safety (esp. injectable)
– Resistance varies from high to low.
2) Tetrahydropyrimidines (TETR) – Resistance is sex‐linked.
a) Morantel 2. Rumatel
Rumatel® – Oral feed additive
b) Pyrantel – Effective against adult worms only
Strongid® – Not much is known about resistance
levels.
FDA‐approved anthelmintics Withdrawal periods for
SHEEP GOATS FDA‐approved anthelmintics
1. Ivomec® sheep drench 1. Safe‐Guard® suspension Sheep Goats
Anthelmintic
Ivermectin Fenbendazole Meat Milk Meat Milk
y p
2. Cydectin® sheep drench q
2. Valbazen® liquid Valbazen® suspension 7 days Not est. 7 days Not est.
Moxidectin Albendazole Prohibit® drench 3 days Not est. NA NA
3. Prohibit® drench [liver flukes only] Cydectin® drench 7 days Not est. NA NA
Ivomec® drench 11 days Not est. NA NA
Levamisole 3. Rumatel® premix
Rumatel® premix NA NA 30 days Not est.
4. Valbazen® liquid Morantel
Safe‐Guard® suspension NA NA 6 days Not est.
Albendazole
Source: Animal Drugs @ FDA and product labels
Different anthelmintics may be approved and available in different countries.
Withdrawal periods for extra‐ Anthelmintic resistance
Ability of the worms to survive anthelmintic treatment
label anthelmintics in goats
• Official definition: 95% or less reduction
Anthelmintic Meat Milk in fecal egg count (FECRT).
Valbazen® suspension 9 days 7 days
a) Widespread in parasites of sheep, goats,
Safe‐Guard® @ 2x label dose 16 days 4 days and horses. Has been reported in all
anthelmintics.
Ivomec® sheep drench
Ivomec® sheep drench 14 days
14 days NA
Prohibit® drench b) Developing in cattle parasites.
4 days NA
(1 packet/262 ml water)
Cydectin® pour‐on (orally) 23 days NA c) Has been detected in pig parasites.
Tx
Cydectin® sheep drench 14 days NA
• Is likely (inevitable) to develop wherever
Cydectin® injectable 120 days NA anthelmintics are frequently used.
– There will always be some worms that
Source: Food Animal Residue Avoidance Database (FARAD) and/or survive an anthelmintic treatment.
http://www.luresext.edu/goats/training/GoatDewormerChart.pdf
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14. 10/18/2011
Anthelmintic resistance Causes of anthelmintic resistance
Research conducted by Delaware State University (2009)
Anthelmintic % farms Anthelmintic Sheep Goat
Fenbendazole 97 Fenbendazole 5/5 5/5
Ivermectin 56 Ivermectin 3/4 5/5
❶ Frequent deworming
Moxidectin 50 Moxidectin 2/4 1/5
Levamisole 28 Levamisole 1/4 0/5
4 sheep and 5 goat farms in the Mid‐Atlantic region were tested for anthelmintic resistance
• Treating all animals at
19 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. using the FECRT and larval development assay.
the same time.
• Varies by geographic region and individual farm.
• A result of past anthelmintic use. • Putting treated animals
• Anthelmintic resistance is PERMANENT. onto a clean pasture.
Causes of anthelmintic resistance Refugia (Worms in “refuge”)
❷ Under‐dosing • Worms that have not
– Not weighing animals been exposed to
– Inability to accurately anthelmintic treatment.
estimate weights
lib i i f
– Not calibrating equipment for • Worms that are still
heaviest animals in group. susceptible to
anthelmintic treatment.
• Using anthelmintics
with residual activity • There will always be
– Persistent‐activity anthelmintics some worms that are
resistant to a particular
– Injectables
anthelmintic.
– Pour‐ons
Image source: Meat & Wool New Zealand
How to increase refugia Anthelmintic combinations
and slow (delay) anthelmintic resistance
• Selective deworming • Combining
– Do not treat everyone
every time.
– Leave some animals
anthelmintics from
two (or more) +
untreated. different broad
different broad
• Pasture management spectrum groups
– Do not put treated – Synergistic effect
animals onto a clean
+
– Broaden spectrum of
pasture. activity
– Put untreated animals – Delay development of
onto pasture resistant worms
previously grazed by
treated animals. Temporary “fix”
14