Cyathostomins Flashcards
Which parasite is the horse equivalent of Teladorsagia in sheep and Ostertagia in cattle?
Cyathostomin spp
Where do the parasitic stages of Cyathostomins live in the horse?
Large intestine
Cyathostomins are a common parasite of horses of which age?
More than one year old
The eggs of Cyathostomin spp are what size?
80-100um
What are some features of the Cyathostomin spp life cycle?
- Direct
- Non-migratory – parasite stays within the GI tract
- Infective stage is L3
What are the 3 further defined stages of the Cyathostomin spp lifecycle within the host?
Within the large intestinal mucosa the parasites stages have been further defined
- EL3 = Early L3
- LL3 = Late L3
- DL4 = Developing L4
How are the stages of Cyathostomin visualised under magnification?
- Early third stage in the mucosa (EL3) have to be digested out of the mucosa to be visible under x40 magnification
- Developing fourth stage in the mucosa (DL4) are visible by transillumination of mucosa at x40 magnification
How long is the ppp of Cyathostomin spp?
6-8 weeks
Total length of Cyathostomin worms ranges from ?
0.5-1cm
Describe hypobiosis of Cyathostomin spp
- Inhibited larvae may constitute >70% of total worm burden in autumn/winter in UK
- Complex process of arrested development and reactivation not well understood
Which factors may contribute to the occurrence of hypobiosis?
- Cold conditioning
- Heavy parasite burden
- Age - young horses have higher mucosal burden
What is the drug of choice to treat mucosal-stage larvae (including hypobiosed larvae).
Moxidectin
Describe the features of disease with Cyathostomin
- Larval cyathostominosis
- Occurs when large numbers of mucosal-stage larvae (L3, L4) build-up in the mucosa of large intestine
- Mass emergence of mucosal-stage hypobiosed larvae
- 50% fatality rate
What are the clinical signs of Cyathostomin infection?
- Sudden onset diarrhoea/ weight loss
- Sudden weight loss/oedema
- Acute diarrhoea, weight loss and collapse
- Colic
What are 3 predisposing factors for Cyathostomin infection?
- Age (≤5yrs)
- High stocking density
- History of poor parasite control
Larval cyathostominosis occurs at what time of year?
October - may
Which host factors affect the epidemiology of Cyathostomin?
- Hypobiosis = Arrested, mucosal cyathostomins are a major source of infection year to year
- Age and Immune status
- Animals <3 years of age have highest levels of infection
Describe over dispersion in Cyathostomin infections
Over dispersion – small proportion of the host population carries the majority of the parasite population
80% egg shedding by 20% horses - small portion of the population will have high FECs
Give some environmental factors which influence the epidemiology of Cyathostomin
- Continuous source of eggs being passed onto pasture by infected horses
- Eggs to L3 development is temperature dependent
- L3 can survive overwinter on pasture
Describe April-June in a typical year of Cyathostomin
- Overwintered L3 on pasture
- Once ingested L3 mature, PPP = six-eight weeks
- Eggs start to be passed onto pasture in faeces: continuous excretion of eggs
- Hypobiotic larvae within the host are mature and become adults. They are a source of eggs passed onto pasture
- Ambient temperatures gradually start to increase, eggs start to develop more rapidly
Describe July-September in a typical year of Cyathostomin
- Egg and L1-L3 development is temperature dependent
- Highest egg shedding is seen in July/August
- Peak of L3 on pasture in late summer (August/September)
Describe October - December in a typical year of Cyathostomin
- L3 on pasture exposed to drop in temperatures
* Cyathostomins: L3 ingested undergo hypobiosis. Accumulation of hypobiosed EL3/L4 in large intestinal mucosa.
Describe January-March in a typical year of Cyathostomin
Cyathostomins: Larval development resumes and mucosal stages mature and trickle emerge
