Strongyles- Equine Flashcards
What are common characteristics of cyathostomins?
- Free living stages on pasture
- Parasitic stage inside the horse within the large intestine
- A common parasite of horses >1 year of age
- No protective immunity so horses become infected their whole lives
What are cyathostomins also known as?
Small stronglyes
What parasite is this and what stages are they?
Cyathostomins
Describe the life cycle of the cyathostomin, how long is the PPP
Cyathostomin have a direct, non-migratory life cycle
- Infective L3 are eaten on pasture and pass to large intestine
- Early L3 enter the mucosa and develop to late L3 then developing L4
- Leave the mucosa and develop to L5
- L5 pass eggs into faeces onto pasture
- Eggs to L2 to L2 to L3
- PPP- 6-8 weeks
What stages of cyathostomins are these?
A) Developing fourth stage in the mucosa (DL4) are visible by transillumination of mucosa at x40 magnification
B) Early stage L3- have to be digested out of mucosa to be visible
How are species of cyathostomin distinguished?
Head end allows species identification based on morphological characteristics
Total length of worms ranges from 0.5-1.0cm depending on species of cyathostomin
When do cyathostomins hypobiose?
Hypobiose as early L3 in the mucosa of the large intestine
What is the drug of choice for cyathostomins?
Moxidectin is drug of choice for mucosal larval stages, including hypobiosed
5 day panacur is effective when benzimidazole resistance is not present
How does cyathostomins cause disease?
Larval cyathostominosis
Occurs when large numbers of mucosal-stage larvae build up in the mucosa of large intestine
Mass emergence of mucosal-stage hypobiosed larvae
50% fatality rate
What are the clinical signs of cyathostomins?
What are the predisposing factors?
Sudden onset diarrhoea/weight loss
Sudden weight loss/oedema
Acute diarrhoea, weight loss and collapse
Colic
Factors- Age, high stocking density, history of poor parasite control, history of grazing heavily contaminated pasture
When is larval cyathostominosis prominent?
October to may
What factors affect epidemiology of cyathostomins?
Age and immune status- horses do not develop strong immunity, animals <3 years of age have highest levels of infection
Over dispersion- small portion of the host population carries the majority of the parasite population- 80% eggs from 20% horses
Environmental- continuous source from infected horses, eggs to L3 temp development, L3 can over winter
Describe the normal year for a cyathostomins?
April- June- overwintered to L3, once ingested L3 mature, eggs start to be passed, hypobiotic larvae within the host mature and become adult
July-Sep- highest egg shedding July/Aug, Peak of L3 late summer
Oct-Dec- L3 experience lower temps, ingested hypobiose
Jan-mar- larval development resumes
What is the family of large strongyles called?
Strongylus spp
What is the range of sizes of stronglysus spp?
Large strongyles- S. edentatus, S. equinus- 2.5-5cm
Strongylus vulgaris 1.5-2.5cm
Describe the general life cycle of the strongyles
- Eggs to L3 on pasture
- L3 ingested, penetrates LI mucosa
- Larvae migrate and return as L5 into lumen
- L5 in lumen release egg
Why is the PPP for strongyles longer then cyathostomins?
Stronglyes migrate out and back of the SI
Therefore process takes a lot longer
How can adult strongylus spp and cyathostomins be differentiated?
Eggs are same- typical strongyle
Large strongyle L3 morphologically similar to cyathstomin but have >8 midgut cells
Head end of adult allows species differentiation
What are the differences of the head end of the adult strongly species?
Size first
S. vulgaris- two teeth (most important)
S. edentatus (no teeth- not common, dorsal gutta- line)
S. equinus (three teeth)
Where do each of the stronglye species migrate?
S. vulgaris- migrate to cranial mesenteric artery - PPP 6 months
S. edentatus- flanks and hepatic ligament- PPP 10 months
S. equinus in liver then pancreas- PPP 8 months
What is the clinical relevance of the stronglye species?
Adult parasites cause little pathology, occasionally do with large numbers
Larvae most relevant- migration
Which strongly species of strongly causes most significant disease?
Larvae have a prediction for the cranial mesenteric artery
Can cause a non-strangulating infection secondary to larvae in cranial mesenteric arteries
Describe the general features of triodontrophorus spp?
Low pathogenicity
Non-migratory
Contribute to damage casued by other adult worms
Feed in groups
Eggs double the size of stronglyes
What are the similarities and differences between stronglyes and cyathostomins epidemiology?
Similarities-
Horses don’t develop immunity to either
Over-dispersion- small population carries the majority of parasites
Egg to L3 simular- can over winter
Differences-
Cyathostomins hypobiose
Longer PPP due to somatic migration
Lower levels of strongyles are needed to cause disease
What are the signs of a worm infestation?
Most horses tolerate worm burdens with little outward sign
Problems often only apparent when clinical disease imminent
Problems usually associated with high levels of infection
Emphasis is on control of parasite levels
What is the goals of parasite control?
Minimise the risk of parasite associated disease
To reduce parasite transmission- reduce parastie egg shedding
To preserve drug efficacy and avoid further resistance
How can pasture be managed for parasites?
Poo picking
Pasture rotation- do not over graze or use year on year
Mixed species grazing- graze lifestock on horse pasture
‘Clean pasture’ at turnout
Harrowing- only effective in very dry, warm climates
What anthelmintics can be used for de-wormers and where is there resitance?
Fenbendazole- cyathstomin resistance
Pyrantel- cyathstomin resistance
Ivermectin- emerging resistance
Moxidectin- drug of choice
Strongyles- Ivermectin/Moxidectin used
How can targeted treatements be achieved?
- Identify parasites present- ELISA, FEC
- Generate data for each horse- High/Low burden
- Low burden- don’t treat
- High burden- treat
- Repeat 3-6 months
What are the challenges of livery yards and studs in regards to paratsite control?
Livery-
Multiple owners
restricted grazing
high turnover- quartantine
Studs-
Yound horses
Visiting horses
Intensive grazing
High value stock
Economics
