Equine Parasitology Flashcards
what are the equine stomach worms?
Draschia megastoma
Habronema muscae
Habronema microstoma
what equine stomach worm causes the most severe lesions?
Draschia megastoma
what is the life cycle of the equine stomach worms?
indirect
intermediate host: muscid fly
L3 infective: swallowed to stomach and produce L1 or cutaneous lesions with immature larvae
what is the most common equine stomach worm?
Habronema muscae
what are the clinical signs of equine stomach worms?
usually none, can be gastritis
Draschia megastoma is rare: nodules of necrotic material and worms
if deposited in skin: cutaneous habronemiasis aka summer sores
what are the equine small intestinal worms?
Strongyloides westeri
Parascaris equorum
what is the life cycle of Strongyloides westeri?
direct but complex with free-living option
infectious L3 penetrate skin or transmammary
what does Strongyloides westeri cause?
small intestinal enteritis and diarrhea
skin irritation
“frenzied behavior”
foals affected primarily
how can you prevent Strongyloides westeri from being transmitted to a foal?
ivermectin to mare within 24 hours after foaling
what is the life cycle of Parascaris equorum?
direct
infective L2 within egg
hatch in gut, migrate to liver to lung
L3 up to trachea and swallowed, mature fully in small intestine
what are the clinical signs of Parascaris equorum?
larval migration: fibrous tissue in liver, coughing, nasal discharge
small intestine: weight loss, hyporexia, decreased albumin, death due to impaction
nursing and weaned foals less than a year old
what are the equine large intestinal worms?
large strongyles
small strongyles
Oxyuris equi
what are the species of large strongyles?
Strongylus vulgaris
Strongylus edentatus
Strongylus equinus
what is the life cycle of Anoplocephala perfoliata?
indirect
intermediate host: Oribatid (forage) mite
where does Anoplocephala perfoliata attach?
ileocecal junction
what are the clinical signs of Anoplocephala perfoliata?
usually none
damage to intestinal mucosa can lead to: ileal impaction, spasmodic colic, cecal intussusception and rupture
large numbers can obstruct bowel
how do you treat Anoplocephala perfoliata?
praziquantel or pyrantel pamoate at a double dose
what is the life cycle of the large strongyles?
direct
L3 larvae infective and ingested
migrate via vasculature in abdomen
return to cecum once mature
where does Strongylus vulgaris migrate?
cranial mesenteric artery and its branches
what are the clinical signs of the large strongyles (general)?
unthriftiness
lethargy
anemia
hypoproteinemia
dependent edema
diarrhea
how do the clinical signs of the large strongyles differ between species?
Strongylus vulgaris: fatal infarction of bowel, damaged vascular endothelium leads to arteritis, thrombosis, embolism of artery
Strongylus edentates: relatively harmless because migration confined to liver
Strongylus equinus: relatively harmless because migration confined to liver and pancreas
what is the most numerous parasite of the horse?
small strongyles
what is the life cycle of the small strongyles?
direct
no migration
larvae can undergo hypobiosis within nodules in GI tract
what are the clinical signs of the small strongyles?
usually harmless unless heavily parasitized
irritation/inflammation if nodules erupt all at once: unthriftiness, lethargy, anemia, hypoproteinemia, dependent edema, diarrhea
how do you treat small strongyles?
double dose panacur to get nodules too
what are Oxyuris equi?
equine pinworms
what is the life cycle of Oxyuris equi?
egg of L3 are ingested
larvae emerge and go to large intestine
adults females to anus and lay eggs on perianal skin
what are the clinical signs of Oxyuris equi?
heavily infected: nervous and lose appetite
rubbing/scratching on perianal region: irritation, dull hair coat, loss of hair on tail
ulceration in intestine
how is Oxyuris equi diagnosed?
scotch tape test
what worms infect the respiratory system of equines?
Dictyocaulus arnfieldi
what is the life cycle of Dictyocaulus arnfieldi?
direct
primary host is donkeys but also horses
L3 larvae infective, penetrate GI mucosa and migrate via lymphatics and vasculature to lungs
mature in bronchioles and bronchi
eggs and/or larvae are swallowed and passed in stool
what are the clinical signs of Dictyocaulus arnfieldi?
pulmonary disease: chronic, nonsuppurative, eosinophilic, granulomatous pneumonia
coughing, dyspnea, unthriftiness, exercise intolerance, death
donkey: no signs, can handle higher worm burden
where does Thelazia lacrymalis infect?
eyes
what is the life cycle of Thelazia lacrymalis?
indirect
intermediate host: muscoid flies (face fly and house fly)
L3 larvae infective, deposited in ocular mucosa
eggs ingested by flies, mature to L3 larvae in ovarian follicles of fly
what are the species of Onchocerca and what do they infect?
Onchocerca cervicalis
Onchocerca reticulata
Onchocerca railliti
integument
what is the life cycle of Onchocerca?
indirect
intermediate: black fly
infective L3 to subcutaneous tissue, L1 migrate distally
L1 picked up by fly when feeding
where does Onchocerca reticulate affect?
connective tissue of distal limb
where does Onchocerca cervicalis affect?
connective tissue of nuchal ligament
