Lecture 9: Equine Clinical Parasitology Flashcards
What type of worms are the following: P. Equorum, S. Westeri, strongyles, O. Equi, O. Cervicalis, S. Equine, H. Muscae, D. Megastoma, gasterophilus, T. Lacrymalis, D. Arnfieldi
Nematodes- roundworms
What type of worm is A. Perfoliata
Cestode- tapeworm
What type of worm is F. Hepatica
Trematode- fluke
What is the mechanism for bendimidazoles
Act upon fumarate reductose to interfere with carbohydrate metabolism
What are some examples of bendimidazoles
Fenbendazole, oxibendazole
What is the mechanism for macrocyclic lactose’s
Increase cell permeability to Cl- resulting in flaccid paralysis and death
What are some examples of macrocyclic lactones
Ivermectin, moxidectin
Why do you need to be careful with moxidectin
Very low therapeutic range
What is the mechanism for tetrahydropyrimidines
Cholinergic agonist
What are some examples of tetrhydripyrimidines
Pyrantel pamoate paste, pyrantel tartrate daily
What is the mechanism for praziquantel
Induces spastic paralysis possibly via calcium channels, disrupts regimental
Praziquantel is formulated with what other drug class
Macrocyclic lactones
What parasites have widespread resistance to bendimidazoles (oxibendazole, fenbendazole)
Cyasthostomes- small strongyles
What parasite shows early indications for resistance against bendimidazoles (oxibendazole, fenbendazole)
P. Equorum
What parasites is it common to see resistance against pyrimidines
Cyasthostomes- small strongyles
What parasite shows early indications for resistance against pyrimidines
P. Equorum
What class of parasites show early indications for resistance against macrocyclic lactones
Cyasthostomes- small stronglyes
What parasite shows widespread resistance to macrocyclic lactones
P. Equorum
P. Equorum is a primary concern in what age group
Foals up to 6 months
What horses might have patent infections with P. Equorum
Adults, especially broodmares
What is the pathway of infection and migration for P. Equorum
Embryonated egg is infectious and hatches in stomach and SI
Migrates to lungs and liver
What is the clinical syndrome for P. Equorum
Intestinal impaction and rupture
What is the first line of defense against P. Equorum
Bendimidazoles (oxibendazole, fenbendazole)
What age group does S. Westeri typically inhabit
SI of nursing foals
What are the three routes of infection for S. Westeri
- Skin penetration via L3
- Ingestion
- Lactogenic transmission from mare
What can be done to prevent S. Westeri in foals
Deworm mare prior to foaling
Foals with S. Westeri are often asymptomatic but high egg counts can cause ___
Diarrhea
What anthelmintics should be used to tx S. Westeri
Bendimidazoles and macrocyclic lactones
What is the recommended deworming schedule for foals from 8 weeks to 12 months
8-12 weeks: bendimidazoles
Just prior to weaning (4-6 months): FEC to determine ascarid/strongyle burden
9 months: strongyles and tapeworms (ivermectin and praziquantel)
12 months: strongyles
What is the most clinically significant large strongyle
S. Vulgarus
What is the clinical syndrome associated with large strongyles/ S. Vulgarus
Verminous arteriosus
L3 damage from migration and associated inflammation
L4 migrates to arterioles and migrates to cranial mesenteric artery
Results in thrombosis and infarction of intestines results in colic
What anthelmintic should be used to tx large strongyles/ S. Vulgarus
Macrocyclic lactones
What are small strongyles also called
Cyasthostomes
Small stronglyes are very resistant to ___ and ___
Freezing and desiccation
What is the clinical syndrome associated with small strongyles
Larval cyathostominosis
Synchronous emergence of L4 larvae resulting in diarrhea, hypoproteinemia
Fatality rates for small strongyles are up to __%
50%
What anthelmintic should be used to tx small strongyles
Moxidectin, panacur powerpack, daily strongid tablet
What is the most clinically significant tapeworm
A. Perfoliata
What can tapeworms/ A. Perfoliata cause
Ulceration and inflammation, colic, intussusceptions, ruptures
What anthelmintic should be used to tx tapeworms/ A. Perfoliata
Praziquantel
How does O. Equi infect/ cause clinical signs
Adults reside in descending colon and rectum and eggs laid perianally- horses become itchy
What anthelmintic should be used to tx O. Equi
Ivermectin
How is Onchocera cervicalis and steria equina transmitted
Bloodsucking arthropods
What is the preferred site for onchocera cervicalis
Connective tissue- nuchal ligament
What is the preferred site for setaria
Abdominal cavity
What does Onchocera result in/ what clinically
Verminous dermatitis, pruritic on ventral midline and face
Can also migrate to palpebral corneal, and conjunctival structures resulting in uveitis and keratoconjunctivitis
What is the anthelmintic to tx O. Cervicalis and S. Equina
Macrocyclic lactones
Habronema spp and Draschia spp are also known as ___
Stomach worms
How is Habromena spp and Draschia spp transmited
Muscid flies
What does Habronema spp and Draschia spp result in
Infect wounds and mucocutaneous junctions resulting in massive inflammatory reaction in host—> Eosinophilic granulomatous, sulfur granules
How to you tx inflammatory reactions to Habronema spp and Draschia spp
Oral or intralesional steroids or surgical excision
What anthelmintic is used to tx Habronema spp, Draschia spp
Macrocyclic lactones
How does Gasterophilus spp infect/ cause clinical signs
Larvae spend winter in GI tract, passed in manure, eggs laid on hair coat and horses infected by licking themselves or other horses
Lesions in oral cavity and stomach
What anthelmintic is used to tx gasterophilus
Macrocyclic lactones
What is Thelazia lacrymalis also known as
Eyeworm
How is T. Lacrymalis transmitted
Muscid flies
What does T. Lacrymalis result in
Inflammation of Lacrimal glands
What is the anthelmintic to tx T. Lacrymalis
Bendimidazoles
Who is the natural reservoir for Dictyocaulus arnfieldi
Donkeys and mules- infect horses if cohabitated
How does D. Arnfieldi do damage/ show clinical signs
L4 in mesenteric LN and L5 in bronchioles.
Eggs laid in bronchi transported to pharynx via mucociliary elevator, eggs swallowed and passed in manure
What dx test can we do for D. Arnfieldi
Baermann test
What anthelmintic is used to tx D. Arnfieldi
Macrocyclic lactones
What drugs are used to tx F. Hepatica
Triclabendazole and albendazole
What is the approach to individualized parasite control in horses
- FEC- basis of adult plan, 200EPG threshold for tx
- FECRT- just prior to tx and 10-14 days after, below 90% means some resistance
Horses with ___may require more intensive parasite management
PPID
What is the EPG threshold for tx
200
What are the diagnostics commonly used for parasites
McMaster FEC, fecal floats
These eggs are common on fecal float or McMasters, identify 1-3
- P. Equorum
- O. Equi
- Strongyle type