Anthelmintics

Uploaded on May 26, 2011

This is the 4th webinar in a series of webinars on worms in sheep and goats. This presentation focuses on anthelmintics and other treatment options. The presentation was prepared by Susan Schoenian, ...

This is the 4th webinar in a series of webinars on worms in sheep and goats. This presentation focuses on anthelmintics and other treatment options. The presentation was prepared by Susan Schoenian, University of Maryland Extension Sheep & Goat Specialist.

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1. IV. Using anthelmintics effectively
Products, usage, resistance, refugia, alternatives, future
2. What is an anthelmintic?
An agent that kills or causes the expulsion of parasitic worms.
Also called dewormer, wormer, drench, or parasiticide.
3. There are three anthelmintic classes.Based on similar chemistries, modes of action, and cross-resistance.
Benzimidazoles (BZ)
Macrocylic lactones (ML)
Avermectins
Milbemycins
Nicotinic antagonists
Imidazothiazoles (IMID)
Tetrahydropyrimidines (TETR)
4. 1 - Benzimidazoles (BZ) First class of modern anthelmintics (1961)
FenbendazoleSafe-guard®Panacur®
AlbendazoleValbazen®
OxfendazoleSynanthic®
ThiabendazoleTBZ
Benzimidazoles kill worms by interfering with energy metabolism on a cellular level by binding to beta tubulin.
5. 1 - Benzimidazoles (white drenches)
Broad spectrum
Adult and 4th stage larvae of roundworms
Adult liver flukes (Valbazen® only)
Heads and segments of tapeworms (Valbazen® or 2x labeled dose of Safe-Guard®)
Effective against hypobiotic larvae
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.
6. 2- Macrocylic lactones (ML) Newest family of anthelmintics - circa 1980’s
Avermectins
Ivermectin Ivomec®Primectin®
EprinomectrinEprinex®
DoramectinDectomax®
Milbemycins
Moxidectin Cydectin®Quest®
Macrocylic lactones interfere with GABA-mediated neurotransmission, causing paralysis and death of the parasite.
7. 2 - Macrocylic lactones (ML)
Potent
Persistent activity (+/-)
Broad spectrum
Adult and 4th stage larvae of roundworms
Some external parasites
(Ivermectin: larval stages of nasal bots)
Effective against hypobiotic larvae
One of the drugs of choice for meningeal worm (ivermectin).
Potential negative effect on dung insects.
Widespread resistance reported, especially avermectins.
8. 3- Nicotinic agonists
Imidazothiazoles (IMID)
LevamisoleProhibit®Tramisol®Levasol®
Tetrahydropyrimidines (TETR)
MorantelRumatel®
PyrantelStrongid®
Act as agonists at nicotinic acetylcholine receptors of nematodes, causing paralysis of the worms.
9. 3 - Nicotinic agonists
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.
Rumatel
Oral feed additive
Effective against adult worms only
Not much is known about resistance levels.
10. FDA-approved anthelmintics
SHEEP
GOATS
Ivomec® sheep drenchIvermectin
Cydectin® sheep drenchMoxidectin
Prohibit® drenchLevamisole
Valbazen® liquidAlbendazole
Safe-Guard® suspensionFenbendazole
Valbazen® liquidAlbendazole[liver flukes only]
Rumatel® premixMorantel
Different anthelmintics may be approved and available in different countries.
11. Withdrawal periods for FDA-approved anthelmintics
Source: Animal Drugs @ FDA and product labels
12. Withdrawal periods for extra-label anthelmintics in goats
Source: Food Animal Residue Avoidance Database (FARAD) and/or http://www.luresext.edu/goats/training/GoatDewormerChart.pdf
13. Anthelmintic resistanceAbility of the worms to survive anthelmintic treatment
Official definition: 95% or less reduction in fecal egg count (FECRT).
Widespread in parasites of sheep, goats, and horses. Has been reported in all anthelmintics.
Developing in cattle parasites.
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
14. Anthelmintic resistanceResearch conducted by Delaware State University (2009)
Varies by geographic region and individual farm.
A result of past anthelmintic use.
Anthelmintic resistance is PERMANENT.
15. Causes of anthelmintic resistance
- Frequent deworming
Treating all animals at the same time.
Putting treated animals onto a clean pasture.
16. Causes of anthelmintic resistance
- Under-dosing
Not weighing animals
Inability to accurately estimate weights
Not calibrating equipment for heaviest animals in group.
Using anthelmintics with residual activity
Persistent-activity anthelmintics
Injectables
Pour-ons
17. 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
18. 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.
19. Anthelmintic combinations
Combining anthelmintics from two (or more) different broad spectrum groups
Synergistic effect
Broaden spectrum of activity
Delay development of resistant worms
+
+
Temporary “fix”
20. Preliminary dataEfficacy of anthelmintic combinations in goats
4 animals/Tx
Research conducted at Langston University (OK)
Initial FECs ranged from 250 to 13,500 and averaged 2,550 epg. 8.6 animals/Tx
21. 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.
22. Proper oral drenching technique
Use proper equipment
Smaller nozzle for lambs and kids
Maintain equipment properly
Calibrate equipment for proper dosage
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!
23. Coccidiostats
A 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 .
24. Coccidiostats
Ionophores
LasalocidBovatec®
Rumensin®Monensin
Quinolone
DecoquinateDeccox®
Amprolium (Rx)Corid®
Affect mitochondrial function
25. 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).
26. Coccidiostats FDA-approved for use in sheep and goats
Source: Animal Drugs @ FDA
Rumensin® can be toxic to equines and dogs.
There is no withdrawal period for slaughter.
27. 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 choices
Amprolium (Corid®)
Sulfa drugs
http://old.cvm.msu.edu/extension/Rook/ROOKpdf/coccidia.PDF
28. 1 - Corid® (amprolium)
Labeled as an aid in the prevention and treatment of coccidiosis in beef and dairy cattle.
- 21 day prevention
- 29. 5 day treatment
Mimics thiamine (vitamin B1), causing a thiamine deficiency in coccidia -> starvation from malnutrition.
Polioencephalomalacia (polio) is a possible side effect of treatment.
http://old.cvm.msu.edu/extension/Rook/ROOKpdf/coccidia.PDF
30. 2 - SulfonamidesSsulfadimethoxine (Di-methox®, Albon®), Sulfamethazine (Sulmet®)
Used to treat many infections.
Common treatment for coccidiosis.
Cause folic acid deficiency
More effective than Corid® (?)
http://old.cvm.msu.edu/extension/Rook/ROOKpdf/coccidia.PDF
31. What’s “new” in parasite control?
32. New anthelmintics
STARTECT®
Derquantel + abamectin
New class of anthelmintic: Spiroindole (SI)
Acts as a channel blocker to cause flaccid paralysis in worms.
Acts on different binding sites than other anthelmintic classes.
Only available in New Zealand
ZOLVIX®
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.
33. Copper for internal parasite controlRisk: copper toxicity in sheep
Dietary
- Mineral mix
- 34. Feed supplement
DrenchCopper sulfate
BolusCopper oxide wire particles (COWP)
CuSO4
35. 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 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.
http://www.attra.org/attra-pub/PDF/copper_wire.pdf
36. Natural “anthelmintics”Significant research effort underway
Garlic juice
Pumpkin seed
Mustard seed
Oregano oil
Papaya
Diatomaceous earth (DE)
Bioactive plants (herbal)
Artemisia spp.
Sericealespedeza
Birdsfoot trefoil
Chicory
Pine bark
Sesquiterpene lactones
Condensed tannins
37. Nematode-trapping fungusDuddingtoniaflagrans
Spores are fed to livestock as part of their diet.
Spores pass through digestive tract of livestock and are deposited 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
38. Natural “anthelmintics”
Natural “anthelmintics” are not likely to replace the therapeutic use of anthelmintics.
However, 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.
39. 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 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?
40. Small Ruminant Program
Thank you for your attention.
Any questions?
SUSAN SCHOENIANsschoen@umd.eduwww.sheepandgoat.com
41. Recordings of the 2011 Worm Webinar series are available at http://www.sheepandgoat.com/ recordings.html.
PowerPoint presentations from the 2011 Worm webinar series may be viewed or downloaded from http://www.slideshare.net/schoenian.
Additional questions may be sent to Susan @ sschoen@umd.edu.
Small Ruminant Program