Antiparasitics Flashcards
Ectoparasitics
Treat Ectoparasites
Anthelmintics
Treat worm infections
Antiprotozoals
treat protozoan parasite infections
Endectocides
treat internal parasitic infections and
external parasitic infestations
2 groups of Helminths
Nematodes, Platyhelminthes
Platyhelminthes
flattened worms that are subdivided into two groups: Cestodes (tapeworms) Trematodes (flukes)
Nematodes
cylindrical,
nonsegmented worms
commonly called
roundworms
Anti nematodals (6 groups)
Benzimidazole drugs Imidazothiazoles Tetrahydropyrimidines Organophosphates Piperazine compounds Macrocyclic lactones (Avermectins)
Benzimidazoles (facts)
Work by interfering with energy metabolism of the worm
Recognize by –azole ending in drug name
Always read the label to determine which parasites a drug
is effective against
All can be administered orally, either as a paste, a
granulated powder, or a solution.
Side effects are rare with benzimidaloles, but may include
vomiting, diarrhea, and lethargy
Benzimidazoles (Groups)
Droncit plus (fenbantel) also contains praziquantel/pyrantel pamoate
Tresaderm (thiabendazole)
Anthelcide EQ Equine Wormer Paste (oxibendazole)
Telmintic (mebendazole) -
Panacur (fenbendazole)
Valbazen (albendazole)
Thiabendazole (facts)
Effective against strongyles and ascarids
Also has antifungal and anti-inflammatory effects
Suitable for otic preparations such as Tresaderm®
Tresaderm® also contains dexamethasone and neomycin
sulfate
Dexamethasone is a synthetic adrenocorticoid steroid
that inhibits the reaction of connective tissue to injury
and suppresses the classic inflammatory manifestations
of skin disease.
Neomycin is a broad-spectrum aminoglycoside
Anticoccidials
Coccidiosis is a protozoal infection that causes intestinal
disorders
Most anticoccidial drugs are coccidiostats (do not actually
kill the parasite, so hygiene is crucial)
Sulfadimethoxine (Albon®)
Reduces the number of oocysts shed, thus reducing spread of
disease
Ponazuril (Marquis®)
Equine antiprotozoal oral paste ; used off-label in dogs/cats
Kills coccidia
Given in 3 doses – days 1, 2, and 9.
30 mg/kg of a 50 mg/mL solution
Others (work mainly by affecting the protozoan’s
metabolism)
Nicarbazine, Amprolium, Monensin, Decoquinate, Robenidine
Antiprotozoals
Giardiosis is a protozoal disease caused by Giardia
spp.
Antiprotozoal drugs
Metronidazole (Flagyl®) (enters the protozoal cell and
interferes with its ability to function and replicate)
Fenbendazole (Panacur®)
Albendazole (Valbazen®)
Giardia Vaccine (GiardiaVax®)
Blood protozoan Babesia sp. is transmitted by ticks
Imidocarb (injectable) has cholinergic effects on the
protozoan
Tick prevention also important
Oxibendazole
Used as a horse dewormer and in combination products for dogs.
Can cause liver toxicity in dogs
Anthelcide EQ Equine Wormer Paste ®
Mebendazole
A granular powder used in dogs and horses to treat ascarid,
hookworm, and cestode infections.
Severe liver toxicity has been reported
Also used in humans for roundworms, pinworms, tapeworms,
and hookworms
Telmintic®
Approved for use in dogs; not cats; not dewormer of choice; safer
alternatives are available
Fenbendazole
Wide spectrum of activity (roundworms,
hookworms, whipworms, and Taenia
pisiformis)
Must be given for 3 consecutive days
Also used to treat metronidazole-resistant
giardiasis.
Side effects include vomiting and diarrhea
Not approved for use in lactating dairy
animals
Panacur® - available in granules,
suspensions, and pastes.
Imidazothiazoles
Work by stimulating the nematode’s cholinergic
nervous system, leading to paralysis of the
parasite (therefore, not ovicidal)
Effective against ascarids, strongyles, whipworms,
and hookworms
Was used as a microfilaricide in the past
An example is levamisole (Levasol®)
Expels most nematodes in 24 hours (some may be
passed alive)
Available in oral forms such as pellets, powder,
suspensions, and pastes
Also has anti-inflammatory and immunostimulant
properties
May cause toxicity in host animal due to
cholinergic effects
Tetrahydropyrimidines
Mimic the action of ACh and cause initial stimulation then paralysis of the worm Effective against ascarids, pinworms, strongyles, and hookworms Examples include pyrantel pamoate, pyrantel tartrate, and morantel tartrate Taste = somewhat pleasant Very safe. Nemex®, Strongid-T®
Organophosphates
Inhibit cholinesterase activity, causing
ACh to remain active in the
neuromuscular junction of the parasite
Are neurotoxic to parasites; some cause
neurologic side effects in the host
Both endoparasitic and ectoparasitic
Narrow range of safety; not for use in
heartworm-positive dogs
Effective against bots and a variety of
nematodes
Dichlorvos (Task®)
Not safe to use OPs off-label!!!
Organophosphates (side effects)
Salivation Lacrimation Urination Dyspnea Defecation Emesis Also ataxia, anxiety, abdominal pain, muscle twitching, pupillary constriction, seizures…
Piperazine
Blocks neuromuscular transmission in the parasite Effective only against ascarids Clients should be made aware that piperazines often result in intact worms being vomited or passed in stool. Practically nontoxic Sold OTC Hartz Health Measures Once-a-Month Wormer® for Puppies Pipa-Tabs®
Macrocyclic Lactones
Avermectins (macrocyclic lactones)
Bind to certain chloride channels in the parasite nerve and
muscle cells, causing paralysis and death of the parasite
The representative of this group is ivermectin, used for a
wide variety of endo- and ectoparasites
May be combined with other antiparasitic agents to broaden its
spectrum of activity
Heartgard Plus® (contains ivermectin and pyrantel pamoate)
Oral (Heartgard®) and parenteral forms (Ivomec®) available
Used for heartworm prevention
Collies are ivermectin sensitive
Another example in this group is moxidectin (ProHeart-6®,
Advantage Multi®)
Not effective against cestodes or trematodes
Anticestodals (3 groups)
Praziquantel, Epsiprantel,Fenbendazole
Epsiprantel
Effective against Taenia spp. and Dipylidium caninum, but not
Echinococcus spp.
Like praziquantel, disintegrates cestode so that it can be digested
by host
Unlike praziquantel, not absorbed well by GI tract, so systemic side
effects are minimal.
-Cestex
Praziquantel
Works by increasing the cell membrane
permeability of the cestode, thus reducing its
resistance to digestion in the host’s intestinal
tract. Ultimately, after administration of
praziquantel, the entire tapeworm
disintegrates (including the scolex).
Owners will not see tapeworm or segments
passed after treatment
Works on all cestode species
With Dipylidium caninum, it is especially
important to also eradicate fleas to prevent
reinfection.
Available as oral tablet or injectable
Side effects are rare; include anorexia,
vomiting, diarrhea, and lethargy
Fenbendazole (Anticestodal)
A benzimidazole (covered previously – antinematodals)
Effective against Taenia spp. but not Dipylidium caninum
Unless other parasites are present in animal that can be treated with
fenbendazole, praziquantel or epsiprantel are recommended.
Antitrematodals (Groups)
Clorsulon, Albendazole, Praziquantel
Praziquantel (Antitrematodals)
Covered previously (anticestodal)
Also effective against lung flukes in dogs and cats
Albendazole
Benzimidazole that interferes with the energy
metabolism of the worm
Also effective against some nematodes (broadspectrum)
Not approved for use in lactating animals
Clorsulon
A benzene sulfonamide Works by inhibiting the trematode’s enzyme systems for energy production (robs fluke of energy) Effective against Fasciola hepatica Adult and immature forms OTC Drench Not recommended in dairy animals
