Equine parasites and parasite-associated disease

Question 1

Equine roundowrm

Answer 1

Parascarus equorum

Question 2

Parascarus equorum mostly affects…?

Answer 2

Foals, weanlings, yearlings
Adults usually resistant

Question 3

P. equorum life cycle

Answer 3

1. L3 hatches in stomach and SI and penetrates veins
2. Larvae reaches liver via portal and migrates in liver tissue and penetrates Liver vein
3. Larvae reaches lung and right heart via vena cava and penetrates lung alveoles
4. Migrate into trachea then to SI again ( moulting to L4)

Question 4

P. equorum diagnosis

Answer 4

faecal egg count (Faecal Flotation, typical appearance of eggs)
If one horse positive, assume all in the group are infected

Question 5

P. equorum treatment

Answer 5

Pyrantel embonate (dose 19 mg/kg) or fenbendazole to kill adults.
Ivermectin larval stages

Question 6

Suggest diet of horse infected with P. equorum

Answer 6

Low bulk diet
NGT with liquid paraffin (lubricate)
Treat with fenbendazole
Day 1: 2.5 mg/kg
Day 4: 2.5 mg/kg
Day 7-11: 10 mg/kg once daily for 5 days
Repeat FWEC 3 weeks after last dose

Question 7

Strongylus vulgaris, Strongylus edentatus, Strongylus equinus adults infect…?

Answer 7

Adults infect the cecum and ventral colon (large intestine).

Question 8

Strongylus vulgaris is what kind of parasite

Answer 8

blood worm, is a common horse parasite in the phylum Nematoda. It looks like a long worm with a large biting mouth. They are usually reddish in color because of all the blood they take from the equine host.

Question 9

Strongylus vulgaris diagnosis

Answer 9

Faecal flotation

Question 10

What condition is associated with strongylus

Answer 10

Colic

Question 11

Strongylus vulgaris life cycle

Answer 11

Egg Ingestion: Horses ingest L3 of Strongylus vulgaris while grazing on contaminated pasture or consuming contaminated food, water, or bedding.

Migration through Tissues: After ingestion, the larvae penetrate the intestinal wall and migrate through the blood vessels to various organs, particularly the cranial mesenteric artery.

Arterial Migration: Once in the arteries, larvae molt and develop into fourth-stage larvae, causing damage to the arterial walls.

Return to Intestines: Mature larvae return to the intestinal lumen, where they molt into adult worms.

Maturation to Adult Worms: In the intestines, the larvae mature into adult worms.

Egg Production: Adult female worms lay eggs, which are passed in the horse’s feces.

Environmental Contamination: The eggs are released into the
environment through the horse’s feces, contaminating pasture, water sources, and bedding.

Ingestion by Host: Horses ingest the infective eggs from contaminated environments, restarting the life cycle.

Question 12

S. vulgaris how does it cause colic

Answer 12

Migration through mesenteric arteries leads to thrombosis, infarctions, and necrosis of the intestine.
Non-strangulating infarction
Surgical colic

Question 13

S. vulgaris control/treatment

Answer 13

ivermectin and moxidectin: larval stages.
oxibendazole, fenbendazole, or pyrantel pamoate: adult worms

Question 14

Small strongyles Cyathostomins, Redworm life cycle

Answer 14

Egg Ingestion: Horses ingest infective larvae (L3) of small strongyles while grazing on contaminated pasture or consuming contaminated food, water, or bedding.

Migration and Encystment in Intestinal Mucosa: After ingestion, the larvae migrate through the intestinal wall and encyst in the mucosa of the large intestine.

Hypobiosis (Arrested Development): Encysted larvae undergo hypobiosis, a state of arrested development, where they can remain dormant for extended periods, sometimes over winter or during dry seasons.

Emergence and Maturation: Under certain environmental conditions or upon the administration of anthelmintic drugs, encysted larvae emerge from the intestinal mucosa and resume development into adult worms.

Maturation to Adult Worms: Once emerged, the larvae mature into adult worms in the large intestine.

Egg Production: Adult female worms lay eggs, which are passed in the horse’s feces.

Environmental Contamination: The eggs are released into the environment through the horse’s feces, contaminating pasture, water sources, and bedding.

Ingestion by Host: Horses ingest the infective eggs from contaminated environments, restarting the life cycle.

Question 15

Cyathostomins disease

Answer 15

Larval cyathostominiasis
Sudden onset diarrhoea late winter/spring
Synchronous emergence of fourth-stage larvae from mucosa
Life threatening colitis/diarrhoea
50% case fatality rate reported

Question 16

Cyathostomins disease- Treatment

Answer 16

Replace lost fluid and protein
Enteral or IV fluids
Plasma transfusion/synthetic colloids

Anti-inflammatories (corticosteroids)

Deworming
moxidectin vs fenbendazole

Supportive care and nursing

Question 17

Cyathostomins control

Answer 17

Encysted larval burden NOT detected by FWEC
But new serum ELISA may provide the answer
Limited number of anthelmintics active against encysted larvae (treat in winter)
None 100% effective
Moxidectin (Equest/Equest Pramox or Quest/QuestPlus (USA))
Fenbendazole (10mg/kg PO once daily for 5 days) – widespread resistance

Question 18

How do foals get infected with strongyloides westeri

Answer 18

Arrested larvae in dam’s abdominal wall mobilized and excreted in milk, Foals infected immediately after birth

Question 19

Gravid Oxyuris equi female migrates to…?

Answer 19

anus, eggs deposited in the perianal area

Question 20

Diagnosis Oxyuris equi

Answer 20

Acetate tape prep

Question 21

Oxyuris equi control

Answer 21

Scrub the environment
Washing perineal area can reduce itch
Fenbendazole (5 days) or pyrantel

Question 22

Most common equine cestode

Answer 22

Anoplocephala perfoliata

Question 23

Anoplocephala perfoliata resides…?

Answer 23

in caecum
Particularly adjacent to ileo-caecal junction
Cause inflammation at this site

Question 24

Intermediate host of Anoplocephala perfoliata

Answer 24

forage mites

Question 25

Anoplocephala perfoliata is associated with what disease

Answer 25

Colic

Question 26

Is it easy to detect Anoplocephala perfoliata using egg count

Answer 26

Difficult to detect eggs in faeces
NOT detected on routine FWEC

Question 27

Anoplocephala perfoliata- Diagnosis

Answer 27

Serum/saliva ELISA more sensitive

Question 28

Anoplocephala perfoliata- Life cycle

Answer 28

Egg Production: Adult tapeworms, which inhabit the ileocecal junction and cecum of the horse, produce eggs within their segments.
Egg Release: Mature segments of the tapeworm containing eggs detach from the adult tapeworm and are passed in the horse’s feces.
Environment Contamination: Eggs are released into the environment through the horse’s feces, contaminating pasture, water sources, and bedding.
Oral Ingestion by Intermediate Host: Free-living oribatid mites, the intermediate host, ingest the tapeworm eggs while feeding on contaminated vegetation or bedding.
Egg Development in Intermediate Host: Inside the mite, the tapeworm eggs develop into infective larvae (cysticercoid larvae).
Ingestion by Definitive Host: Horses ingest the oribatid mites containing the infective larvae while grazing on contaminated pasture or consuming contaminated food or water.
Larval Development in Horse: Once ingested, the larvae are released from the mites’ bodies in the horse’s small intestine.
Penetration of Intestinal Wall: The larvae penetrate the intestinal wall and migrate to the ileocecal junction and cecum, where they mature into adult tapeworms.
Attachment and Egg Production: Adult tapeworms attach to the intestinal mucosa and begin producing eggs, completing the life cycle.

Question 29

Gasterophilus also known as

Answer 29

Atrophods/Bot flies

Question 30

Gasterophilis haemorrhoidalis/nasalis

Answer 30

Attached to rectal mucosa
Cause of rectal prolapse

Question 31

3 Goals of parasite control

Answer 31

To minimize the risk of parasitic disease
To control parasite egg shedding.
To maintain efficacious drugs and avoid further development of anthelmintic resistance as much as possible.

Question 32

4 reasons to perform Faecal Egg counts

Answer 32

1. To evaluate the anthelmintic efficacy using the FECRT.
2. To evaluate and monitor the egg reappearance period (ERP) of the most recently administered dewormer.
3. To determine the shedding status of the horse at the time of sampling.
4. To determine whether parasite burdens in foals and weanlings are primarily Parascaris spp. or strongyle.

Question 33

4 Limitations of Faecal Egg counts

Answer 33

1. They do not accurately reflect the total adult strongyle or Parascaris spp. burden of the horse.
2. They do not detect immature or larval stages of parasites including migrating large strongyles and ascarids, and/or encysted cyathostomins.
3. Tapeworm infections are often missed or underestimated by faecal techniques (ELISA).
4. Pinworm eggs are usually missed since they are adhered as egg packets around the anus rather than being shed in the faeces.

Question 34

Adult horses with FEC (strongyles) >???epg are treated

Answer 34

≥200 epg

Question 35

Non-adult (<2 years) or geriatric horses with FEC ≥ ???epg are treated

Answer 35

100

Question 36

Is Targeted treatments (selective therapy) based on FEC recommended in foals, weanling, yearling?

Answer 36

No
During the first year of life foals should receive a minimum of four anthelmintic treatments.
First deworming should be carried out at about 2-3 months of age, and a benzimidazole drug is recommended to ensure efficacy against ascarids.
Second deworming is recommended just before weaning (approximately 4-6 months of age).
At weaning FEC are recommended to determine whether worm burdens are primarily strongyles or ascarids, to facilitate the right choice of drug class.
Third and fourth treatments should be considered at about 9 and 12 months of age, respectively, and treatment should primarily be targeting strongyles.
Tapeworm treatment should be included in the 9-month treatment.

Question 37

Oxyuris equi is also known as …?

Answer 37

Pinworm

Question 38

Suggest methods to carry out deworming programs

Answer 38

Evaluate the efficacy of the dewormers used on each farm at least every three years using the FECRT.
Basic anthelmintic treatments considered to all horses.
One or two yearly treatments.
All further treatments should be targeting horses with a high strongyle contamination potential.
Focus anthelmintic treatments during seasons of peak transmission (usually spring and fall when pasture refugia is at its highest).