Non strongyle parasites of horses

What nematodes affect horses?

• Parascaris equorum

• Oxyuris equi

• Dictyocaulus arnfieldi

• Filarial nematodes

what cestodes affect horses?

Anoplocephala perfoliata

what ectoparsites affect horses?

• lice

• Chorioptes

• Bots - Gastrophilus

• Sweet itch - Culicoides spp

what trematodes affect horses?

Fasciola hepatica

what are the characteristics of tapeworms?

• adult parasites primarily found in small intestine

• indirect life cycle - involves oribatid mite as intermediate host

what are features of Anoplocephala perfoliata?

• most common and most significant species

• adult tapeworms found at ileo-caecal junction

• short, broad segments

• lappets behind each of four suckers

what is the life cycle of A. perfoliata?

• eggs ingested by free-living oribatid mites

• develop to metacestode stage

  • found in soil, shavings and hay

• infected mite ingested by horse

• adult tapeworm at ileo-caecal junction

• proglottids passed in faeces, disintegrate and eggs released

what is the appearance of A. perfoliata eggs?

• irregularly spherical (D shape)

• 60-80um

• onchosphere supported by pyriform apparatus

what is the pathogenesis of A. perfoliata?

• spasmodic colic

• intussusception

• ileal impaction

• rupture

what are the clinical signs of A. perfoliata?

• ulceration and pathological changes in intestine

• unthriftiness

• enteritis

• colic

what animals are affected by A. perfoliata and when?

• all ages infected (<3 years old have highest levels of infection)

• peak levels detected in autumn/winter but possible all year round

how do we diagnose A. perfoilata?

• eggs in faeces - FEC (sensitivity is 60%)

• ELISA to detect circulating antibody (sensitivity 68%, specificity 95%)

• EquiSal saliva test - improved sensitivity, antibody based

how do we treat A. perfoliata?

• double dose pyrantel

• praziquantel

what are the ascarid nematodes?

large white roundworms, adults found in small intestine

what are general features of ascarid nematodes?

• females lay huge numbers of eggs

• eggs are highly resistant

• L2/L3 develop in the egg and are the infective stages

• direct life cycle

• hepato-tracheal migration - stimulates profound inflammatory response

• adult worms can cause mechanical blockage

• no damage to mucosa

what is Parascaris equorum?

the ascarid of horses and donkeys, common world wide

what is the life cycle of Parascaris equorum?

• eggs passed in faeces

• develop on the ground (approx 4 weeks) - temperature dependent

• egg containing L2/3 is eaten by horse

• L2/3 migrates to liver and lung

• coughed up and swallowed, L4-5 in small intestine

• PPP = 12 weeks

what animals are usually affected by Parascaris equorum?

typically affects foals - adult horses usually immune

what are clinical signs of Parascaris equorum infection?

• transient cough

• poor weight gain and unthriftiness

• no diarrhoea

• possible obstruction in heavily infected individuals

how do we control Parascaris equorum?

anthelmintic treatment

• drug resistance is reported to ivermectin, moxidectin (possibly also BZ and PYR)

what is oxyuris equi?

horse pinworm, found in large intestine, causes ‘anal rust’

what is the appearance of oxyuris equi?

• pointed tails

• 1-10cm

• eggs 80um

what is the lifecycle of oxyuris equi?

• direct

• female lays eggs on peri-anal skin

• eggs fall to the ground

• develop to L3 in the egg (approx 5 days)

• ingested by horse

• larvae develop in mucosal crypts in large intestine

• adults in lumen of large intestine

• PPP = 5 months

what are clinical signs of Oxyuris equi?

• pruritis

• excoriation (tail)

how do we diagnose Oxyuris equi?

• eggs on perianal area

• sellotape / scotchtape test

how do we control Oxyuris equi?

• anthelmintics - challenging due to lack of efficacy and rapid reinfection

• high hygiene environment reduces transmission