Bursate Nematodes 5 - Redworms Of Horses

Question 1

Strongyloidea

Answer 1

Direct life cycles GIT in horses

Question 2

“Strongyles”

Answer 2

Has a number of families, affects the large intestine

Question 3

Hookworms

Answer 3

Anclostomatidae, affects the small intestine

Question 4

Groups of interest:

Answer 4

1. Cyathostomins (aka small Strongyle)
2. Strongyles (aka large Strongyles)
3. Contributors to PGE -> Oesophagostomum, Chabertia
4. Hookworms -> Ucinaria, Ancylostoma, Bunostomum
5. Syngamus trachea

Question 5

Strongyloidea Characteristics:

Answer 5

-comparatively “stout” worms
-well developed baccal capsule (often “teeth” / cutting plates
-on mucosa GIT = plug feeders
-reddish appearance

Question 6

What are some characteristic common to ALL the Strongyloidea

Answer 6

1. Large, well developed buccal capsule w/ features
2. Bursate nematodes
3. Typical strongyle eggs
4. Direct lifecycle

Question 7

Strongyloidea are __ __ of horses

Answer 7

Ubiquitous parasites; encyst and develop in the large colon and caecum

Question 8

Large strongyles species are all

Question 9

Large strongyle characteristics:

Answer 9

-dark, red worms (1-5 cm long)
-well developed buccal capsule
Strongylus vulgaris (least rare, most pathogenic)
Strongylus edentatus -> no teeth
Strongylus equinus -> 3 teeth
Triodontophorus tenuicollis -> 6 teeth

Question 10

Strongylus vulgaris life cycle

Answer 10

1. Eggs, L1 -> L3 on pasture (2 weeks)
2. L3 exsheath in small intestine penetrate mucosa -> mount to L4 (7 days)
3. Enter small arteries
4. Migrate in arterial system to predilection site (by day 21)
5. Develop L5 in endothelium cranial mesenteric artery (3-4 months)
   *migration via arterial lumen to large intestine
6. Adults mature (6-8 weeks)
   PPP = 6-7 months

Question 11

PPP

Answer 11

Pre Patent Period

Question 12

S. vulgaris - damage to arteries:

Answer 12

-Cranial Mesenteric Artery is predilection site
-Other arteries may also be affected (renal, iliac, etc)
-Endarteritis & progressive thickening of the arterial walls
-Aneurysm
-Sequelae

Question 13

S. vulgaris damage to the arteries (broken down - normal course of events that may happen):

Answer 13

Endareritis -> Thrombosis -> Blockage of arterioles -> Infarcations -> Colic

Question 14

Large Stronglyes Pathogenesis

Answer 14

Adults -> formation of nodules in the gut wall when they return (minor clinical consequences)
Adult worms - aggressive plug feeders on mucosa (small erosions: loss of albumin & blood)
Effect “cumulative” with other parasites

Question 15

Plug Feeding

Answer 15

-Bite and move on
-Each bite leaves a tiny, bleeding erosion
-Very large burdens (mixed species)
-Widespread erosion, petechial have haemorrhage and scarring of large intestine mucosa
-Significant blood loss!

Question 16

Genus Triodontophous

Answer 16

-Large strongyles, but NON-MIGRATORY
-Cylindrical buccal capsule, 3 pairs of oesophageal teeth
-Right dorsal colon, larvae encysts wall large intestine -> emerge & develop into adults
-Typical strongyle eggs, but larger slightly (130-140)
-PP: 2-3 months
-Several species - triodontophorus tenuicollis is most pathogenic, feeds in groups and leaves larger erosions

Question 17

Cyastostomins (“Small Strongyles”)

Answer 17

40-50 species occur in equids
A smaller # of species known to be common
Live as adults in the lumen of the large intestine (caecum & colon)
Can undergo hypobiosis (L4, L5) in the mucosa of the large intestine

Question 18

Cyathostomins

Answer 18

Encyst and develop in the large colon and caecum

Question 19

What is hypobiosis?

Question 20

Chronic Infection of Cyathostomins

Answer 20

“The wormy horse”
Ill-thrift
Poor coat

Question 21

Acute infection of Cyathostomins

Answer 21

-larval cyathostominosis -> larvae emerging from mucosa in waves
-“Type 2 disease”
-Rapid weight loss or “melt”
-+/- diarrhea
-lowered albumin or “leaky gut”
-Dysbiosis
-Lower limb oedema
-up to 50% mortality

Question 22

Potential triggers of acute larval cyathostominosis

Answer 22

Seasonality - cold conditioning?
Springtime peak - but can occur anytime
Recent anthelmintic TX, removal of adults may trigger larval emergence

Question 23

Chronic clinic sings - Cyathostominosis

Answer 23

1. Inappetence
2. Emaciation
3. Rough coat
4. Recurrent colic

Question 24

Acute clinic sings - Cyathostominosis (relatively rare)

Answer 24

1. Inappetence
2. Fever
3. Colic
4. Death

Question 25

Cyathostominosis Diagnosis

Answer 25

• History and clinical signs
  -Diagnosis is difficult during the PPP, migratory phase
  -ALC horses may have negative egg counts!
  -After adult worms have developed typical strongyle eggs in feces
  -Egg counts don’t represent burden