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112 Cards in this Set
- Front
- Back
__________ represent a particular problem in regards to parasite treatment because not many drugs are specifically labeled for them |
Goats Also because their browsing eating behavior may speed up hepatic detoxicification of drugs |
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In general, how are parasite treatments dosed in large animals? |
Based on best estimates of BW with a large margin of safety The actual BW is rarely known |
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Major Worms Affecting Ruminats |
GI nematodes (Haemonchus, Ostertagia) Lungworms Liver flukes Rumen flukes Tapeworms Peritoneal nematodes |
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Major Worms Affecting Horses |
Large & small strongyles Pinworms Ascarids |
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Major Worms Affecting Swine |
Ascarids Strongyles Whipworms |
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Primary Ingredients for Treatment of Worms in Cattle (+number of compounds utilizing those ingredients) |
Avermectin (includes ivermectin) - 28 Benzimidazole (includes fendendazole) - 12 Levamisole - 5 Moxidectin - 2 Clorsulon - 1 Morantel - 1 |
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_______ & _________ account for over 80% of the product available to treat for worms in ruminants |
Avermectin & benzimidazoles |
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_________ is a ruminant dewormer specifically targeted against flukes |
Corsulon |
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Avermectin Structure |
Pentacyclic macrocyclic lactone |
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__________ are a naturally occurring avermectin |
Ivermectin & doramectin |
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Is ivermectin water soluble? Can it cross the BBB? |
NO & NO (in most mammals at therapeutic doses) |
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Which has a longer half life: ivermectin or doramectin? |
Doramectin - Almost double that of ivermectin |
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Eprinomectin Structure |
Amino-avermectin derivative |
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Avermectin MOA |
Binds to a receptor on invertebrate glutamate-gated chloride channel Causes influx of calcium into the parasite causing hyperpolarization and neuromuscular paralysis |
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Avermectin PK |
Lipid soluble High volume of distribution Highly protein bound Low oral bioavailability in ruminants - leads to unpredictable blood concentrations with likely under dosing in some animals |
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Avermectin Spectrum of Activity in Ruminats |
Most internal nematodes + external parasites NOT effective against flukes or tapeworms (lack of receptor) Doramectin is no longer effective against some parasites |
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Doramectin is no longer effective against..... |
Screwworm Cochliomyia Biting lice Chorioptes |
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Avermectin Spectrum of Activity in Horses |
Large & small strongyles Other GI nematodes Pinworms Ascarids Lungworms Gastric bots Habronema Onchocerca |
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Resistance to Ivermectins |
Increasingly important! Related to mutations in ligand-gated channels and P-glycoproteins Resistance to one member of the class implies resistant to all members of it |
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Ivermectin Routes of Administration |
Cattle: Injectable, pour-on, oral products Swine: Injectable Horses: Oral |
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_________ & _________ may require 1.5-2x the label dose for most dewormers |
Goats & camelids Possible exceptions: levamisole, moxidectin, albendazole |
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Which dewormers are better absorbed orally compared to topically? |
Avermectins Benzamidazoles Can also restrict food in ruminants to slow gastric emptying to prolong effects |
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Which avermectin can be used in lactating dairy cattle with no milk discard? |
Eprinomectin Moxidectin |
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Avermectin Adverse Effects |
Can cross the BBB in in dogs with the MDR-1 (P-glycoprotein drug pump) Does not normally cross the BBB, but use caution in animals with damage to the BBB |
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Avermectin Environmental Concerns |
Activity is retained in the feces, may harm insects (ex: dung beetles) |
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How does moxidectin differ from avermectin? |
Longer half life, especially in body fat |
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________ may enhance neurotoxicosis when using moxidectin |
Low body fat Do not use in animals <4 months of age |
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Which agent is best for encysted worm larvae in horses? |
Moxidectin |
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What species should moxidectin NOT be used in? |
Discouraged to use in goats in order to delay the development of resistance |
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Benzimidazole Drugs |
Fenbendazole Oxyfendazole Albendazole Oxibendazole Triclabendazole |
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Benzimidazole Solubility |
Limited water solubility |
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Benzimidazole MOA |
Inhibition of microtubules -> Impaired glucose uptake -> Release of lysozomes from the worm ER -> Decreased ATP production Ultimately the parasite is immobilized |
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Where to benzimidazoles bind? |
Colchicine-sensitive site of beta tubulin |
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Why are benzimidazoles safe? |
Poor absorption Higher affinity for parasite vs mammalian microtubules |
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Are benzimidazoles time or concentration dependent? |
Time dependent Slow GI transit time prolongs contact with target invertebrates |
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A secondary mechanism of benzimidazoles is inhibition of __________ |
Helminth specific fumarate reductase - involved in NADH production |
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Benzimidazole Absoprtion |
Most have poor oral absorption, but they are so insoluble that other route of administration are impractical |
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Benzimidazoles have a ________ volume of distribution and a ___________ rate of elimination |
High volume of distribution Fast rate of elimination |
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Benzimidazole Spectrum |
Most internal worms - larvae & adults Also giardia |
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___________ are the only ruminant dewormers labeled for use against tapeworms |
Benzimidazoles |
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Which benzimidazoles are effective against Fasciola? |
Albendazole Triclabendazole |
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Benzimidazole resistance is due to.... |
Point mutations in parasite beta tubulin |
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Benzimidazoles should not be used with ______ because it may lead to abortion |
Flukicides (Ex: clorsulon) |
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Benzimidazole Adverse Effects |
Bone marrow suppression Albendazole is tetratogenic & embryotixic (fenbendazole is slightly so) Abortion risk when combined with flukicides |
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Levamisole MOA |
Nicotinic agnoist - neuromuscular stimulation leads to parasite paralysis Also interferes with fumarate reduction |
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Which dewormer is a nicotinic agonist? |
Levamisolae |
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Levamisole Spectrum |
GI nematodes & lungworms Encysted larvae are refractory |
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Levamisole is often combined with _________ to treat tapeworms in ruminants |
Praziquantel |
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Levamisole is primarily used in herds that.... |
Have worms resistant to avermectins and benzimidazoles |
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Levamisole Adverse Effects |
Mild local irritation at injection sites Occasional tremors, salivation, lip-licking, and increased alertness in sheep Bone marrow suppression at high doses |
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Cocaine is often mixed with which dewormer? |
Levamisole |
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Corsulon Spectrum |
Liver flukes |
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Corsulon Administration |
Only available as an injectable combination with ivermectin |
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Praziquantal Classification |
Isoquinolone |
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Praziquantel MOA |
Affects calcium ion permeability leading to increased neuromuscular activity and flaccid paralysis Tegmental damage at high doses - allows the host immune system to attack the parasite |
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Praziquantel Spectrum |
Cestodes & trematodes |
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All current praziquantel LA products licensed in the US are..... |
Combination products for horses Sometimes used extra-label in small ruminants & camelids |
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Piperazine MOA |
GABA-receptor agonist leading to influx of chloride, hyperpolarization, and spastic paralysis |
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Piperazine Absorption & Excretion |
Rapid oral absorption Rapid excretion in the urine |
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Piperazine is very _________ meaning that some worms may recover before expulstion |
Short-acting |
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Piperazine is most commonly used in ________ in conjunction with ______________ |
Used in horses and pigs in conjunction with benzimidazoles Rarely used in ruminants |
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Piperazine Spectrum |
Ascarids Adult cyanthostomes Tapeworms |
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Which dewormers are nicotinic agonists (cholingerig antihelmintics)? |
Levamisole
Pyrantel Morantel |
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Pyrantel/Morantel MOA |
Nicotinic agonist leading to spastic paralysis |
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Pyrantel/Morantel is _________ metabolized in ruminants |
Rapidly |
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What forms of pyrantel are used in horses? |
Pyrantel pamoate Pyrantel tartrate |
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Which dewormer is used as a daily feed supplement in horses? |
Pyrantel tartrate |
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Morantel is used in which species? |
Cattle & goats (no milk discard) |
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Pyrantel/Morantel Spectrum |
Nematodes Pyrantel pamoate is used extralabel at triple dose as a tapeworm treatment |
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Dichlorvos Classification |
Organophosphate |
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Dichlorvos MOA |
Inactivates ACH |
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Dichlorvos currently is only used in _______ |
Swine (dewormer) Ectoparasite control in cattle |
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Antiprotozoal Drugs |
Amprolium Sulfa antibiotics Ionophores Decoquinate Ponazuril Fenbendazole Metronidazole |
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Amprolium Spectrum |
Coccidia - most effective against first generation schizonts (extracellular stage) |
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Amprolium is often supplemented with ______ |
Thiamine (its an inactive thiamine analog) |
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Amprolium Side Effects |
Polioencephalomalacia (central blindness, ataxia, seizures) |
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Sulfa antibiotic are used extralabelly in ________ to treat _______________ |
Used in swine & ruminants to treat coccidia |
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Sulfa Antibiotic MOA |
Disrupts folate metabolism |
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Sulfa antibiotics are licensed as a parasite treatment for..... |
Coccidiosis in poultry |
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Ionophore MOA |
Forms NA or P complexes that increase the parasite's membrane permeability and affect mitochondrial function |
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Ionophores are most effective aginst what stage of protozoa? |
Trophozoites (intracellular stage) Most useful as preventatives |
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Ionophore Side Effects |
Cardiotoxicity |
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Ionophores should NEVER be given to... |
Horses - Carditoxic at any dose |
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Ionophore administration |
Usually given as a feed additive |
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Ionophore Drug Names |
Monensin Lasalocid Salinomycin (swine) |
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Decoquinate MOA |
Disrupts electron transport in the parasite's mitochondrial cytochrome system |
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Decoquinate is most effective against which stage of parasite? |
Sporozoite |
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Decoquinate Spectrum |
Coccidia prophylaxis |
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Decoquinate is used in which species? |
Ruminants (coccidia prophylaxis) |
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Which bezacetonitrile drug is used in the US? |
Ponazuril (toltrazuril & dicazuril outside the US) |
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What is the only approved treatment for equine protozoal myelitis in the US? |
Ponazuril Toltrazuril & dicazuril are approved outside the US Remember: PEM is caused by Sarcosystis neurona |
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Toltrazuril & Dicazuril What are these? How are they used in the US? |
Treatments for equine protozoal myelitis NOT approved for us in the US Used extralabelly in the US for small animals, small ruminants, & camelids as coccidiocides |
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Ponazuril MOA |
Affects nuclear division, mitochondira activity, body formation, and causes vacuolization of the ER Effective on intracellular & extracellular stages |
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Ponazuril Side Effects |
Oral rash Minimal possibility of birth defects |
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Fendendazole Spectrum |
Giardia |
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Metronidazole is legal in food animals only when.... |
Following the label |
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Ectoparasite Drugs |
Avermectins Organophosphates Amitraz Pyrethrins |
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Avermectin for Ectoparasites |
Good for killing, but not as a repellant Used for ticks, lice, and burrowing mites - Not as good for surface feeders |
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Which ectoparasite treatment is safe to use in lactating cows? |
Organophosphates (dichlorvos) Amitraz |
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Dichlorvos is often mixed with _________ and sprayed onto cattle for fly control |
Diesel or water |
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Dichlorvos is used as an ectoparasite treatment in which species? |
Cattle, horses, swine |
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Organophosphate Side Effects |
SLUD Miosis Vomiting Dyspnea Bradycardia Hypotension Muscle fasiculation/weakness Chronic- Nerve degeneration, ataxia, proprioceptive defects, weakness |
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Amitraz MOA |
Octopaminergic agonist Affects ectoparasite adenylate cyclase |
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Amitraz is discouraged from use in which species? |
Horses due to risk of colonic impaction |
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Pyrethroids are synthetic versions of.... |
Pyrethrins (ectoparasite drugs) |
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Pyrethrin MOA |
Disruption of NA & K transport on parasite nervous membranes, affects neurotransmission Also has some repellent efficacy |
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Pyrethrins are toxic to.... |
Fish Occasionally neonates |
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How long do pyrethrin treatments last? |
Topicals last 2-3 weeks Ear tags can last up to 5 months! |
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Which ectoparasite treatment is showing some signs of resistance? |
Pyrethrins |
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What is Monepantel? |
Amino-acetonitrile derivative nematode treatment and is not available in the US |
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What are spiroindoles (derquantel)? |
Nicotinic antagonist anti-helmintic that is not available in the US |
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What are some "alternative" dewormer products? |
Tobacco (nicotine sulfate) Diatomaceous earth Tannins Copper oxide wire Nematophagus fungus Herbal products |