Equine strongylosis (Strongylus, Cyathostoma). Flashcards
(29 cards)
What are the species of large strongyles?
- Strongylus vulgaris
- Strongylus edentatus
- Strongylus equinus
- Triodontophorous serratus
- T. tenuicollis
- T. brevicauda
- T. minor
Where do large strongyles primarily reside in their host?
Large intestine of horse, can also appear in caecum
What is the size range of Strongylus species?
Male: 2.5 – 4 cm
Female: 4 – 6 cm
What type of life cycle do large strongyles have?
Direct LC
The adult parasites live in cecum and large intestine. The eggs are passed in the faeces and development from egg to L3 requires 2 weeks (moist and temperate climate). Infection is by ingestion of L3.
.
Parasitic larval development of the three species differ from each other:
- Strongylus vulgaris: L3 penetrate the mucosa and moult into L4 in the submucosa. Then they enter the small arteries and migrate to endothelium to their predilection site via the arterial lumina. After a period of several months, the larvae moult to L5 and return to the intestinal wall via the arterial lumina. Nodules are formed around the larvae in the wall of cecum and colon. Due to their size, the nodules rupture and the young adult parasites are released in the lumen of the intestine. PP: 6-7 months.
- Strongylus equinus: The preparasitic phase of this life cycle is virtually identical to that of strongylus vulgaris. Of the three species of Strongylus, we know the least about S. equinus because it is less common. Infection is by ingestion of the L3 larva. L3 invade the wall of small intestine, cecum and colon and become encapsulated in nodules where they moult to L4 by 12-14 days. L4 leave nodules and cross peritoneal cavity to the liver. Most L4 reach liver by 19-20 days. Stay there for 12 weeks. Finally, L4 migrate back to the large intestine (crossing the abdominal cavity directly or first passing through pancreas). The final moult to L5 occurs 15 weeks after infection during migration back to large intestine. PP: 9 months.
- Strongylus edentatus: L3 exsheaths in small intestine, penetrate gut wall to subserosa and moults to L4. It remains there (often in nodules) for 3 months before it migrate to root of mesentery, some go to liver and lungs before wall of cecum and right, ventral colon. Immature adults then appear in lumen of the large intestine. PP: 11 months.
How long does it take for Strongylus species eggs to develop to L3?
2 weeks
What is the prepatent period for Strongylus vulgaris?
6-7 months
What happens to L3 larvae of Strongylus vulgaris after penetrating the mucosa?
Moult into L4 in the submucosa, then migrate to small arteries
What is the prepatent period for Strongylus equinus?
9 months
How long do L4 larvae of Strongylus equinus stay in the liver?
12 weeks
What is the prepatent period for Strongylus edentatus?
11 months
What pathogenesis occurs due to the migration of large, young strongyles?
Causes inflammation and obstruction of blood vessels
Pathogenesis of young worms:
- Larvae migrate through intestinal- & liver blood vessels, and can cause inflammation & obstruction of the blood vessels –> damage to intestine supplied by the damaged vessel.
- Migrating larvae of Strongylus equinus and edentatus do not appear to cause pathological changes.
- Migrations through liver may produce nodules and formation of fibrous tissue seen on necropsies.
- Early migrations of S. equinus larvae: hemorrhagic nodules in intestinal mucosa, can be seen on necropsy or in abdominal surgery in horses with colic.
- S. edentatus migrates to flanks where L4 enclosed in subperitoneal cysts, can be found in necropsies
Inflammation and obstruction of bv´s
Nodules & fibrous tissue formation of liver
Hemorrhagic nodules in intestinal mucosa
L4 enclosed in subperitoneal cysts
What clinical signs are associated with large strongyle infection?
- Colic
- Ill thrift
- Diarrhoea
What are the main treatments for large strongyles?
- Moxidectin - best to date
- Ivermectin
- Avermectins
- Fenbendazole
- Pyrantel salt
What are the control measures for both small & large strongyles?
- Clean bedding in stalls
- No running foals with older immune horses
- Rotation onto clean pastures
- Treatment programs
- Dewormer annually
How can large strongyle infections be diagnosed?
- Eggs identify family
- Larval culture for species identification
- Faecal flotation
- Necropsy
What are the species of small strongyles?
- Cyathostomum - most common
- Cabellonema
- Coronocyclus
- Cylicocyclus
.
Where do small strongyles reside in their host?
Large intestine lining
What is the size range of small strongyles?
2-5 cm
What is the infective stage of small strongyles?
L3
What is the prepatent period for small strongyles?
4-6 weeks and up to 3-4 months
What clinical signs are associated with small strongyle infection?
- Severe diarrhoea
- Weight loss
What disease is caused by small strongyles?
Cyathostominosis
What pathogenesis occurs due to small strongyles?
- Under-performance of the horse;
- loss of condition
- feed inefficiency
- predisposition to secondary diseases.
- Severe enteritis
Extremely prolific; emerge from lining of intestines & leave an ulcerated gut wall.
Disease is called cyathostominosis.
What are the life cycle for small strongyles?
- Live in the lining of large intestine, develop into adults, lay eggs that are passed in faeces onto pasture, develop into larvae to complete the cycle.
- Larvae picked up in autumn can go through hibernation in cysts in the intestinal wall. These “encysted larvae” can survive in this state for a considerable length of time and develop to adult when the time is right for them (typically spring). In hibernating state, they are resistant to most dewormers.
- L3 is the infective stage – they exsheath in the stomach & SI, but do not migrate.
- They only form nodules.
- L3 enters the wall of cecum and large intestine, develop and moult.
- Return to lumen as early L5.
Prepatent period: 4 – 6 weeks and up to 3 – 4 months.
