GI - equine parasites

Question 1

What parasite causes massive inflammatory reaction, severe diarrhoea and often death in horses when they all emerge at once?

Answer 1

Cyathostomes

Question 2

What do cyathostomes look like?

Answer 2

Small redworm

Question 3

Where do the cyathostomes encyst? For how long?

Answer 3

Encyst in the large intestinal mucosa for 2-3 years

Question 4

How do you treat cyathostomiasis?

Answer 4

Moxidectin - be careful of inflammation from dead worms causing colitis
Concurrent corticosteroids to reduce inflammation

Question 5

What do strongyles cause in horses?

Answer 5

Verminous arteritis - block the blood vessels

Question 6

Where do the strongyles reside/migrate in horses?

Answer 6

Migrate from the GI tract to the cranial mesenteric artery and back

Question 7

What is used to treat strongyles?

Answer 7

Avermectins - so now rare

Question 8

What worm parasite affects foals?

Answer 8

Strongyloides westeri

Question 9

How do foals get infected by strongyloides?

Answer 9

Through dams milk
Skin penetration

Question 10

What does strongyloides westeri cause in foals?

Answer 10

Induces diarrhoea 6 months later

Question 11

What is an example of an ascarid in horses?

Answer 11

Parascaris equorum

Question 12

When are horses at greatest risk of parascaris ascarid?

Answer 12

From 6 months to 2 years - after this they gain immunity

Question 13

What does parascaris equorum cause in horses?

Answer 13

Small intestinal obstruction - surgical colic

Question 14

When are horses at greatest risk of parascaris equorum causing surgical colic?

Answer 14

After using an effective anthelmintic when there is a high burden

Question 15

What are the organs affected by the parascaris lifecycle?

Answer 15

Intestinal wall > Liver > Bronchi in lungs > Small intestines

Question 16

What is to note about the dictyocaulus arnfieldi life cycle?

Answer 16

Not completed in the horse - the donkey is the usual host

Question 17

What worms cause anal pruritis? Why?

Answer 17

Oxyuris equi - live in colon, females migrate down and stick eggs to anus

Question 18

What tapeworm can horses get?

Answer 18

Anoplocephela

Question 19

What is the intermediate host of anoplocephela tapeworm?

Answer 19

Oribatid mite

Question 20

What do anoplocephela tapeworms cause in horses?

Answer 20

Spasmodic colic
Intussuseption
Thickened ilio-caecal junction wall - ileal food impaction

Question 21

What red eggs can be found in the stomach as an incidental finding/dont cause a problem?

Answer 21

Gasterophilus - bot fly

Question 22

How do bot fly eggs get into the stomach?

Answer 22

Bot fly lays eggs on horses legs
Horse grooms itself and eats them

Question 23

What horse wormer has the highest resistance?

Answer 23

Fenbendazole

Question 24

What is resistance?

Answer 24

The genetically transmitted loss of sensitivity in parasite populations previously sensitive to the same drug

Question 25

What is refugia?

Answer 25

Parasites in the horses environment that are not exposed to an anthelmintic at each dose Eg. on pasture, untreated horses, some larval stages

Question 26

How does refugia impact resistance?

Answer 26

Increasing refugia is likely to slow development of resistance

Question 27

What is a way of measuring resistance?

Answer 27

Faecal egg count reduction test

Question 28

How do you do a faecal egg count reduction test?

Answer 28

No wormer for 8 weeks prior FEC before treatment Give wormer Repeat FEC 2 weeks later

Question 29

How many horse owners are using a targeted parasite control now?

Answer 29

50%

Question 30

What are ways of using parasite control to cause minimal resistance?

Answer 30

Targeted worming Poo pick fields Dont overgraze Different things at different times of year

Question 31

What are the challenges of using parasite control to cause minimal resistance?

Answer 31

Owners want to give anthelmintics Cheaper than targeted parasite control

Question 32

What are the 4 main groups of anthelmintics in horses?

Answer 32

Avermectins Benzimidazoles PRaziquantel Pyrantel

Question 33

What wormer do you use for cyathostomes? When?

Answer 33

Moxidectin - kills encysted too Once a year in winter

Question 34

What wormer do you use for strongyles?

Answer 34

Ivermectin - least resistance

Question 35

When should you worm for strongyles?

Answer 35

If FEC greater than 200 eggs/gram Do FEC every 12 weeks

Question 36

What wormer is most sensitive for parascaris?

Answer 36

Pyrantel

Question 37

What wormer do you use for strongyloides westeri?

Answer 37

Ivermectin - in foal or de-worm mare 2 weeks before due date

Question 38

What wormer do you use for tapeworms (anaplocephala)? When?

Answer 38

Praziquantel Twice a year, after tapeworm ELISA

Question 39

What wormer do you use to treat dictocaulus, gasterophilus and oxyuris?

Answer 39

Ivermectin

Question 40

What are the problems of FEC?

Answer 40

Costs same as wormer tube - (£10) Only counts eggs - misses encysted, non producing adults) More expensive if find all horses have it

Question 41

What are the problems with the tapeworm ELISA?

Answer 41

Looks for tapeworm antibodies so can tell if has been exposed but antibodies stay high for 6 months after treatment so cant tell if you have resistance

Question 42

How can you use pasture management to reduce worms?

Answer 42

Poo pick Reduce stocking density Graze with ruminants

Question 43

How should you worm pregnant mares?

Answer 43

Treat with ivermectin a few weeks before due date

Question 44

How should you worm a new horse to the yard?

Answer 44

Moxidectin and praziquantel Keep off pasture for 3 days

Question 45

What worm eggs does a faecal egg count test?

Answer 45

Strongyles