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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

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

Major Worms Affecting Ruminats

GI nematodes (Haemonchus, Ostertagia)


Lungworms


Liver flukes


Rumen flukes


Tapeworms


Peritoneal nematodes

Major Worms Affecting Horses

Large & small strongyles


Pinworms


Ascarids

Major Worms Affecting Swine

Ascarids


Strongyles


Whipworms

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

_______ & _________ account for over 80% of the product available to treat for worms in ruminants

Avermectin & benzimidazoles

_________ is a ruminant dewormer specifically targeted against flukes

Corsulon

Avermectin Structure

Pentacyclic macrocyclic lactone

__________ are a naturally occurring avermectin

Ivermectin & doramectin

Is ivermectin water soluble? Can it cross the BBB?

NO & NO (in most mammals at therapeutic doses)

Which has a longer half life: ivermectin or doramectin?

Doramectin - Almost double that of ivermectin

Eprinomectin Structure

Amino-avermectin derivative

Avermectin MOA

Binds to a receptor on invertebrate glutamate-gated chloride channel




Causes influx of calcium into the parasite causing hyperpolarization and neuromuscular paralysis

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

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

Doramectin is no longer effective against.....

Screwworm


Cochliomyia


Biting lice


Chorioptes

Avermectin Spectrum of Activity in Horses

Large & small strongyles


Other GI nematodes


Pinworms


Ascarids


Lungworms


Gastric bots


Habronema


Onchocerca

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

Ivermectin Routes of Administration

Cattle: Injectable, pour-on, oral products




Swine: Injectable




Horses: Oral

_________ & _________ may require 1.5-2x the label dose for most dewormers

Goats & camelids




Possible exceptions: levamisole, moxidectin, albendazole

Which dewormers are better absorbed orally compared to topically?

Avermectins


Benzamidazoles




Can also restrict food in ruminants to slow gastric emptying to prolong effects

Which avermectin can be used in lactating dairy cattle with no milk discard?

Eprinomectin


Moxidectin

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

Avermectin Environmental Concerns

Activity is retained in the feces, may harm insects (ex: dung beetles)

How does moxidectin differ from avermectin?

Longer half life, especially in body fat

________ may enhance neurotoxicosis when using moxidectin

Low body fat




Do not use in animals <4 months of age

Which agent is best for encysted worm larvae in horses?

Moxidectin

What species should moxidectin NOT be used in?

Discouraged to use in goats in order to delay the development of resistance

Benzimidazole Drugs

Fenbendazole


Oxyfendazole


Albendazole


Oxibendazole


Triclabendazole

Benzimidazole Solubility

Limited water solubility





Benzimidazole MOA

Inhibition of microtubules -> Impaired glucose uptake -> Release of lysozomes from the worm ER -> Decreased ATP production




Ultimately the parasite is immobilized

Where to benzimidazoles bind?

Colchicine-sensitive site of beta tubulin

Why are benzimidazoles safe?

Poor absorption




Higher affinity for parasite vs mammalian microtubules

Are benzimidazoles time or concentration dependent?

Time dependent




Slow GI transit time prolongs contact with target invertebrates

A secondary mechanism of benzimidazoles is inhibition of __________

Helminth specific fumarate reductase - involved in NADH production

Benzimidazole Absoprtion

Most have poor oral absorption, but they are so insoluble that other route of administration are impractical



Benzimidazoles have a ________ volume of distribution and a ___________ rate of elimination

High volume of distribution




Fast rate of elimination

Benzimidazole Spectrum

Most internal worms - larvae & adults




Also giardia

___________ are the only ruminant dewormers labeled for use against tapeworms

Benzimidazoles

Which benzimidazoles are effective against Fasciola?

Albendazole


Triclabendazole

Benzimidazole resistance is due to....

Point mutations in parasite beta tubulin

Benzimidazoles should not be used with ______ because it may lead to abortion

Flukicides (Ex: clorsulon)

Benzimidazole Adverse Effects

Bone marrow suppression




Albendazole is tetratogenic & embryotixic (fenbendazole is slightly so)




Abortion risk when combined with flukicides





Levamisole MOA

Nicotinic agnoist - neuromuscular stimulation leads to parasite paralysis




Also interferes with fumarate reduction

Which dewormer is a nicotinic agonist?

Levamisolae

Levamisole Spectrum

GI nematodes & lungworms




Encysted larvae are refractory

Levamisole is often combined with _________ to treat tapeworms in ruminants

Praziquantel

Levamisole is primarily used in herds that....

Have worms resistant to avermectins and benzimidazoles

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

Cocaine is often mixed with which dewormer?

Levamisole

Corsulon Spectrum

Liver flukes

Corsulon Administration

Only available as an injectable combination with ivermectin

Praziquantal Classification

Isoquinolone

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

Praziquantel Spectrum

Cestodes & trematodes

All current praziquantel LA products licensed in the US are.....

Combination products for horses




Sometimes used extra-label in small ruminants & camelids

Piperazine MOA

GABA-receptor agonist leading to influx of chloride, hyperpolarization, and spastic paralysis

Piperazine Absorption & Excretion

Rapid oral absorption




Rapid excretion in the urine

Piperazine is very _________ meaning that some worms may recover before expulstion

Short-acting

Piperazine is most commonly used in ________ in conjunction with ______________

Used in horses and pigs in conjunction with benzimidazoles




Rarely used in ruminants

Piperazine Spectrum

Ascarids


Adult cyanthostomes


Tapeworms

Which dewormers are nicotinic agonists (cholingerig antihelmintics)?

Levamisole

Pyrantel


Morantel


Pyrantel/Morantel MOA

Nicotinic agonist leading to spastic paralysis

Pyrantel/Morantel is _________ metabolized in ruminants

Rapidly

What forms of pyrantel are used in horses?

Pyrantel pamoate




Pyrantel tartrate

Which dewormer is used as a daily feed supplement in horses?

Pyrantel tartrate

Morantel is used in which species?

Cattle & goats




(no milk discard)

Pyrantel/Morantel Spectrum

Nematodes




Pyrantel pamoate is used extralabel at triple dose as a tapeworm treatment

Dichlorvos Classification

Organophosphate

Dichlorvos MOA

Inactivates ACH

Dichlorvos currently is only used in _______

Swine (dewormer)




Ectoparasite control in cattle

Antiprotozoal Drugs

Amprolium


Sulfa antibiotics


Ionophores


Decoquinate


Ponazuril


Fenbendazole


Metronidazole

Amprolium Spectrum

Coccidia - most effective against first generation schizonts (extracellular stage)

Amprolium is often supplemented with ______

Thiamine (its an inactive thiamine analog)

Amprolium Side Effects

Polioencephalomalacia (central blindness, ataxia, seizures)

Sulfa antibiotic are used extralabelly in ________ to treat _______________

Used in swine & ruminants to treat coccidia

Sulfa Antibiotic MOA

Disrupts folate metabolism

Sulfa antibiotics are licensed as a parasite treatment for.....

Coccidiosis in poultry

Ionophore MOA

Forms NA or P complexes that increase the parasite's membrane permeability and affect mitochondrial function

Ionophores are most effective aginst what stage of protozoa?

Trophozoites (intracellular stage)




Most useful as preventatives

Ionophore Side Effects

Cardiotoxicity

Ionophores should NEVER be given to...

Horses - Carditoxic at any dose

Ionophore administration

Usually given as a feed additive

Ionophore Drug Names

Monensin


Lasalocid


Salinomycin (swine)

Decoquinate MOA

Disrupts electron transport in the parasite's mitochondrial cytochrome system

Decoquinate is most effective against which stage of parasite?

Sporozoite

Decoquinate Spectrum

Coccidia prophylaxis

Decoquinate is used in which species?

Ruminants (coccidia prophylaxis)

Which bezacetonitrile drug is used in the US?

Ponazuril




(toltrazuril & dicazuril outside the US)

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

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

Ponazuril MOA

Affects nuclear division, mitochondira activity, body formation, and causes vacuolization of the ER




Effective on intracellular & extracellular stages

Ponazuril Side Effects

Oral rash




Minimal possibility of birth defects

Fendendazole Spectrum

Giardia

Metronidazole is legal in food animals only when....

Following the label

Ectoparasite Drugs

Avermectins


Organophosphates


Amitraz


Pyrethrins

Avermectin for Ectoparasites

Good for killing, but not as a repellant




Used for ticks, lice, and burrowing mites - Not as good for surface feeders

Which ectoparasite treatment is safe to use in lactating cows?

Organophosphates (dichlorvos)


Amitraz

Dichlorvos is often mixed with _________ and sprayed onto cattle for fly control

Diesel or water

Dichlorvos is used as an ectoparasite treatment in which species?

Cattle, horses, swine

Organophosphate Side Effects

SLUD


Miosis


Vomiting


Dyspnea


Bradycardia


Hypotension


Muscle fasiculation/weakness




Chronic- Nerve degeneration, ataxia, proprioceptive defects, weakness



Amitraz MOA

Octopaminergic agonist




Affects ectoparasite adenylate cyclase

Amitraz is discouraged from use in which species?

Horses due to risk of colonic impaction

Pyrethroids are synthetic versions of....

Pyrethrins (ectoparasite drugs)

Pyrethrin MOA

Disruption of NA & K transport on parasite nervous membranes, affects neurotransmission




Also has some repellent efficacy

Pyrethrins are toxic to....

Fish




Occasionally neonates

How long do pyrethrin treatments last?

Topicals last 2-3 weeks




Ear tags can last up to 5 months!





Which ectoparasite treatment is showing some signs of resistance?

Pyrethrins

What is Monepantel?

Amino-acetonitrile derivative nematode treatment and is not available in the US

What are spiroindoles (derquantel)?

Nicotinic antagonist anti-helmintic that is not available in the US

What are some "alternative" dewormer products?

Tobacco (nicotine sulfate)


Diatomaceous earth


Tannins


Copper oxide wire


Nematophagus fungus


Herbal products