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Glossary of Endoparasites of Horses

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Equine ascarid, equine roundworm
Parascaris equorum
Prepatent is 75-80 days
Parascaris equorum
Largest of the equine nematodes
Parascaris equorum
Adults may be passed in feces and may grow to 50cm
Parascaris equorum
Nematodes found in the small intestine of young foals
Parascaris equorum

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Parascaris equorum

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Parascaris equorum

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Parascaris equorum

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Parascaris equorum
Strongylus vulgarus, S edentatus, S. equinus
Large Strongyles
eggs (large or small) are virtually identical, species identification is achieved by fecal culture
Large Strongyles
Listed as “strongyle type” in medical record when found on flotation
Large Strongyles

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Strongyles

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Strongyles

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Strongyles

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Strongyles

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Strongyles

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Strongyles
Intestinal threadworm of horses
Nematodes
Strongyloides westeri
Only the female is parasitic in the host
Strongyloides westeri
Prepatent period 5-7 days
Strongyloides westeri
Can be passed through milk to foal
Strongyloides westeri
Causes diarrhea in foals
Strongyloides westeri

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Strongyloides westeri

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Strongyloides westeri

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Strongyloides westeri
Pinworm of horses
Oxyuris equi
Adults found in cecum, colon and rectum
Oxyuris equi
Adult females attach eggs to exterior of anus with sticky material that causes anal puritis in infected horses
Oxyuris equi
Adult worms often seen protruding from the anus
Oxyuris equi
Eggs may be larvated
Oxyuris equi
Prepatent 4-5 months
Oxyuris equi
Eggs can be recovered by using tape impressions of anus, as well as a scarping the surface of the anus
Oxyuris equi
Due to the intense itching, horses will rub their rumps against solid objects, causing broken hairs on the tail head
Oxyuris equi

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Oxyuris equi

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Oxyuris equi

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Oxyuris equi
Equine lungworm
Dictyocaulus arnfieldi
Found in bronchi and bronchioles of horses, mules and donkeys
Dictyocaulus arnfieldi
Embryonated eggs
Dictyocaulus arnfieldi
Eggs can be found on fresh (<24 hrs old) feces
Dictyocaulus arnfieldi
Larvae hatch from eggs within a few hours
Dictyocaulus arnfieldi
Prepatent 42-56 days
Dictyocaulus arnfieldi

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Dictyocaulus arnfieldi
Adult gastrointestinal nematodes
Habronema sp
Aberrant larvae (deposited by flies) produce cutaneous habronemiasis, aka summer sores
Habronema sp
Lesions vary in size and have an uneven surface that consists of a soft reddish-brown material and covers a mass of firmer granulation tissue
Seen on parts of the body that are liable to be injured: legs, withers, male genitalia, and medial canthus
Habronema sp
Wounds increase in size and do not respond to treatment until the following winter, when they spontaneously heal
Habronema sp
Diagnosis is based on biopsies and clinical signs
Habronema sp

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Habronema sp

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Habronema sp

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Habronema sp
Equine filarial parasite
Onchocerca cervicalis
Produce recurrent dermatitis
Onchocerca cervicalis
Periodic opthalmia
Onchocerca cervicalis
Adults live in the ligamentum nuchae (ligament that runs from the skull down the cervical spine)
Onchocerca cervicalis
Females produce microfilrariae that migrate to the dermis via connective tissues
Onchocerca cervicalis
Spread by biting midges
Onchocerca cervicalis
Cause cutaneous onchocerciasis
patchy alopecia and scaling on head, neck, shoulders and ventral midline, may be accompanied by intense puritis
Onchocerca cervicalis
Many horses are asymptomatic
Onchocerca cervicalis
Biopsy can be examined for microfilaria
Onchocerca cervicalis

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Onchocerca cervicalis
Lives within the conjunctival sac and on the surface of the eye
Thelazia sp
Remove while eye is anesthetized
Thelazia sp
Equine tapeworms
Anoplocephala perfoliata and A. magna
found in the SI, LI and cecum
Anoplocephala perfoliata
found in the SI and sometimes the stomach
A. magna
Proglottids are wider than long
Anoplocephala perfoliata and A. magna
has only one set of male and female reproductive organs in each proglottid
Eggs are thick walled with one or more flattened sides
Anoplocephala perfoliata
Grain mites are the intermediate host
Anoplocephala perfoliata and A. magna

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Anoplocephala sp.

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Anoplocephala sp.

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Anoplocephala perfoliata

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Anoplocephala perfoliata

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