introduction morphology life cyle larvae pathogenesis clinical sign diagnosis treatment control

1. Dr. Dhaval F. Chaudhary
(B.V.Sc & A.H.)
COLLEGE OF VETERINARY SCIENCE AND ANIMAL HUSBANDRY, AAU, ANAND.

2.  The members belonging to this super family are known as “bursate nematodes”.
 Common name : Red worm of Horse
 Family: Strongylidae
 Genus: Strongylus
 Species: Strongylus vulgaris
Strongylus edentates
Strongylus equinus
 Host: Equine
 Location: Large intenstine

3.  Worms are smaller than other two species. Buccal capsule roughly oval in shape.
 Buccal capsule contain two ear shaped dorsal teeth.
 Both internal and external leaf crowns are present.
 External leaf crowns fringed at distal extremity.
 Spicules are equal.
Size
1.4-1.6 cm(Male)
2.0-2.4 cm(Female)

4.  Eggs are passed in faeces of host, oval in shape, thin shell contains early segmentation
of yolk.
 The development and hatching of eggs is controlled by various factors like moisture,
temperature and O2.
 At 26C the first stage larvae is produced within 24 hrs.
Strongyle larvae

5. LIFE CYCLE

6.  The L1 hatch out from the eggs, L1 have rhabditiform oesophagus.
 L1 mainly feeds on bacteria and grows rapidly, then enter into the lethargic state and
moult to L2.
 L2 also feeds on bacteria, soon after lethargic state the L2 moult to L3. L2 have less
rhabditifrom oesophagus.
 L3 have filariform oesophagus, it is a infective stage. Cuticle of L2 is retained as a
protective sheath around L3. Which is very important for survival of infective stage.
Since L3 wrapped with cuticle of L2 it does not feed. L3 thrive on the stored food
materials in the intestinal cells. Infective stage is negatively geotropic and positively
phototropic to mild sunlight, but it will be repelled by strong sun light. L3 larva crawls
on grass blades in early morning, evening and during dull weather. L3 survive upto 3
months.

7.  Infection of horse by ingestion of L3 along with herbage or vegetations.
 Exsheathment occurs in the small intestine of horse.
 After exsheathment, L3 penetrate the intestine wall where L3 moult to become L4 in
about 3 days of infection. These L4 penetrate the intima of submucosal arterioles and
migrate towards the cranial mesenteric artery. In the cranial mesenteric artery it
produces thrombus and later aneurysm in about 14 days of infection. From 45 days of
infection onwards the L4 pass back to submucosa of caecum and colon via arterial
system. In the submucosa of caecum and colon L4 moult to L5. Then L5 enter into the
lumen of intestine and reach maturity in about 3 months.

8.  L4 in the cranial mesenteric artery causes inflammatory
reaction lesions like endarteritis and thrombus formation.
 Due to thrombus formation, initial thickening and later
dilatation of arterial wall may occur.
 Sometimes the thrombus detached leads to fatal results like
occlusion of coronary artery or brachio cephalic trunk.
 Infarction of iliac artery leads to temporary lameness.
 Thrombus in the testicular artery results in passive congestion
of one or both testicle.
 Diarrhoeic syndrome may occur and is associated with
ulceration of caecum and colon due to thromboembolism
caused by migrating larvae.

9.  Colic is due to pressure of cranial mesenteric artery on nerve plexuses.
 Rough coat, diminished appetite, diarrhoea, edematous swelling on the abdomen and
leg, emaciation and anaemia.
 Adult worm causes heavy blood loss due to blood sucking activity resulting in
anaemia. (Normocytic, normochromic anaemia).
 Large number of haemorrhagic ulcers are seen in the intestine which indicates the site
of attachment of worm.

10.  Faecal examination for eggs.
 Detection of anterior mesenteric aneurysm by rectal palpation.
 PM examination reveals ascitis, emaciation and anaemia.

11.  Diagnosis of the presence of strongylus can be determined by a fecal flotation
examination, but this test does not differentiate between large and small strongyles.
However, a fecal culture will allow for the maturation of the larvae and the subsequent
identification of the parasites infecting the horse.
 Horses usually do not get a strictly large or small strongylus infection; typically, they
are infected with both.
 Colic or abdominal distress due to Strongylus vulgaris infection may result from
inflammation and obstruction of the cranial mesenteric artery. This artery can be
palpated on rectal examination, and a veterinarian may be able to identify changes
consistent with Strongylus vulgaris infestation.

12. Cyathostome larvae feaces in horse
Strongylus vulgaris
with the thickened cranial mesenteric
artery in horse

13.  Fenbendazole – 7.5mg / Kg b wt. (oral).
 Thiabendazole – 440mg / Kg b wt. (oral).
 Ivermectin 0.2mg / Kg b wt s/c.

14.  Periodic deworming of horse.
 Proper disposal.
 Use clean pasture.