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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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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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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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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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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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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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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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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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”
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