Equine Parasitology

Question 1

what are the equine stomach worms?

Answer 1

Draschia megastoma
Habronema muscae
Habronema microstoma

Question 2

what equine stomach worm causes the most severe lesions?

Answer 2

Draschia megastoma

Question 3

what is the life cycle of the equine stomach worms?

Answer 3

indirect
intermediate host: muscid fly
L3 infective: swallowed to stomach and produce L1 or cutaneous lesions with immature larvae

Question 4

what is the most common equine stomach worm?

Answer 4

Habronema muscae

Question 5

what are the clinical signs of equine stomach worms?

Answer 5

usually none, can be gastritis
Draschia megastoma is rare: nodules of necrotic material and worms
if deposited in skin: cutaneous habronemiasis aka summer sores

Question 6

what are the equine small intestinal worms?

Answer 6

Strongyloides westeri
Parascaris equorum

Question 7

what is the life cycle of Strongyloides westeri?

Answer 7

direct but complex with free-living option
infectious L3 penetrate skin or transmammary

Question 8

what does Strongyloides westeri cause?

Answer 8

small intestinal enteritis and diarrhea
skin irritation
“frenzied behavior”
foals affected primarily

Question 9

how can you prevent Strongyloides westeri from being transmitted to a foal?

Answer 9

ivermectin to mare within 24 hours after foaling

Question 10

what is the life cycle of Parascaris equorum?

Answer 10

direct
infective L2 within egg
hatch in gut, migrate to liver to lung
L3 up to trachea and swallowed, mature fully in small intestine

Question 11

what are the clinical signs of Parascaris equorum?

Answer 11

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

Question 12

what are the equine large intestinal worms?

Answer 12

large strongyles
small strongyles
Oxyuris equi

Question 13

what are the species of large strongyles?

Answer 13

Strongylus vulgaris
Strongylus edentatus
Strongylus equinus

Question 14

what is the life cycle of Anoplocephala perfoliata?

Answer 14

indirect
intermediate host: Oribatid (forage) mite

Question 15

where does Anoplocephala perfoliata attach?

Answer 15

ileocecal junction

Question 16

what are the clinical signs of Anoplocephala perfoliata?

Answer 16

usually none
damage to intestinal mucosa can lead to: ileal impaction, spasmodic colic, cecal intussusception and rupture
large numbers can obstruct bowel

Question 17

how do you treat Anoplocephala perfoliata?

Answer 17

praziquantel or pyrantel pamoate at a double dose

Question 18

what is the life cycle of the large strongyles?

Answer 18

direct
L3 larvae infective and ingested
migrate via vasculature in abdomen
return to cecum once mature

Question 19

where does Strongylus vulgaris migrate?

Answer 19

cranial mesenteric artery and its branches

Question 20

what are the clinical signs of the large strongyles (general)?

Answer 20

unthriftiness
lethargy
anemia
hypoproteinemia
dependent edema
diarrhea

Question 21

how do the clinical signs of the large strongyles differ between species?

Answer 21

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

Question 22

what is the most numerous parasite of the horse?

Answer 22

small strongyles

Question 23

what is the life cycle of the small strongyles?

Answer 23

direct
no migration
larvae can undergo hypobiosis within nodules in GI tract

Question 24

what are the clinical signs of the small strongyles?

Answer 24

usually harmless unless heavily parasitized
irritation/inflammation if nodules erupt all at once: unthriftiness, lethargy, anemia, hypoproteinemia, dependent edema, diarrhea

Question 25

how do you treat small strongyles?

Answer 25

double dose panacur to get nodules too

Question 26

what are Oxyuris equi?

Answer 26

equine pinworms

Question 27

what is the life cycle of Oxyuris equi?

Answer 27

egg of L3 are ingested larvae emerge and go to large intestine adults females to anus and lay eggs on perianal skin

Question 28

what are the clinical signs of Oxyuris equi?

Answer 28

heavily infected: nervous and lose appetite rubbing/scratching on perianal region: irritation, dull hair coat, loss of hair on tail ulceration in intestine

Question 29

how is Oxyuris equi diagnosed?

Answer 29

scotch tape test

Question 30

what worms infect the respiratory system of equines?

Answer 30

Dictyocaulus arnfieldi

Question 31

what is the life cycle of Dictyocaulus arnfieldi?

Answer 31

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

Question 32

what are the clinical signs of Dictyocaulus arnfieldi?

Answer 32

pulmonary disease: chronic, nonsuppurative, eosinophilic, granulomatous pneumonia coughing, dyspnea, unthriftiness, exercise intolerance, death donkey: no signs, can handle higher worm burden

Question 33

where does Thelazia lacrymalis infect?

Answer 33

eyes

Question 34

what is the life cycle of Thelazia lacrymalis?

Answer 34

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

Question 35

what are the species of Onchocerca and what do they infect?

Answer 35

Onchocerca cervicalis Onchocerca reticulata Onchocerca railliti integument

Question 36

what is the life cycle of Onchocerca?

Answer 36

indirect intermediate: black fly infective L3 to subcutaneous tissue, L1 migrate distally L1 picked up by fly when feeding

Question 37

where does Onchocerca reticulate affect?

Answer 37

connective tissue of distal limb

Question 38

where does Onchocerca cervicalis affect?

Answer 38

connective tissue of nuchal ligament