Download Know the parasites that threaten your horse

What Worm Where?
LUNGWORM
(Dictyocaulus arnfieldi)
Description: Primarily found
in donkeys. Horses are typically only
infected if grazed alongside donkeys.
Infections in horses (with the exception
of foals and yearlings) rarely result in the
development of egg producing adults.
Size/Appearance: Up to 8cm long,
slender worms.
Know the parasites that threaten your horse
Location: Lungs
Symptoms: Persistent cough and
increased respiratory rate. May cause
secondary pneumonia.
NECK THREADWORM
(Onchocerca spp.)
Description: Involve an intermediate host –
midges, which spread the microfilariae produced
by the adult worms.
Size/Appearance: A slender worm – males are up
to 6cm long and females are up to 30cm long.
Location: Skin
BOTS (Gasterophilus spp.)
PINWORM (Oxyuris)
Symptoms: Skin irritation and swelling of
ligaments and tendons. Potential blindness.
Description: The two most common species are
G. intestinalis and G. nasalis.
Description: Not thought to be
harmful, more an irritation.
Size/Appearance: Up to 10cm long, white in colour.
Size/Appearance: Eggs (laid on horse’s coat) – up to
2mm long, creamy white in colour. Larvae – up to 20mm long,
reddish-orange in colour.
Location: Large intestine
Symptoms: Itchy anus – causing tail rubbing.
Location: Stomach
Symptoms: Mild damage to mouth and gums, and may cause
damage to stomach lining.1
TAPEWORM (Anoplocephala spp.)
STOMACH WORM (Habronema spp.)
Description: Involve an intermediate host – the muscid fly.
ASCARID/LARGE ROUNDWORM
Size/Appearance: 1-2.5cm long, slender white worms.
(Parascaris equorum)
Location: Stomach
Description: Mainly found in foals, as horses
develop immunity to infection by around
18 months of age.
Symptoms: Mild gastritis, ‘summer sores’ (non-healing wounds)
and conjunctivitis.
Size/Appearance: Up to 40cm long, white in
colour.
HAIRWORM (Trichostrongylus axei)
Description: Anoplocephala perfoliata is the main
species causing disease in horses. The lifecycle involves
an intermediate host – the forage mite.
Size/Appearance: White in colour with a segmented body
– eggs are contained in segments. Usually around 4-5cm long,
some up to 20cm.
Location: Junction between small and large intestine
Symptoms: Unthriftiness, hair loss and enteritis. Proven role in
colic – spasmodic, ileocaecal and intussusception.5
Location: Small intestine
Description: Horses sometimes become infected by
hairworm if grazed alongside sheep and cattle.
SMALL REDWORM
Size/Appearance: Up to 7mm long, small and hair-like.
(small strongyle/cyathostomin)
Location: Stomach, larvae on skin
Description: Now the most common and
pathogenically significant parasite to affect horses today.2
Over 50 species recognised.3
Symptoms: Low infestations result in loss of appetite, poor
growth rate and soft faeces. Heavy infestations lead to weight
loss and diarrhoea.
Size/Appearance: Up to 2.5cm long, thin and reddish in colour.
Location: Large intestine
Symptoms: Diarrhoea, rapid and severe weight loss, oedema,
colic and with severe encysted larval infection, potentially fatal.4
Information brought to you by Zoetis UK Ltd, manufacturers of:
Symptoms: Coughing, poor growth rates,
dull coats and because of worm’s
size, large numbers can cause
fatal blockages or ruptures
in the gut.
INTESTINAL THREADWORM
(Strongyloides westeri)
Description: Only a major problem in
foals – infected via pasture or mothers
milk. Horses develop immunity to
infection by six months of age.
Size/Appearance: Up to 1cm long,
slender hair-like worms.
Location: Small intestine
LARGE REDWORM (large strongyle)
Description: The most common species of large redworm
are Strongylus vulgaris and Strongylus edentatus. The use of
modern wormers has reduced the large redworm population so that
they are no longer as prevalent.2
Further information is available from: Zoetis UK Ltd, Walton Oaks, Dorking Road, Tadworth, Surrey KT20 7NS
EQUEST & EQUEST PRAMOX are registered trademarks of Pfizer Ltd.
EQUEST contains moxidectin. EQUEST PRAMOX contains moxidectin and praziquantel.
Size/Appearance: Up to 5cm long, dark-red in colour.
Advice on the use of these or alternative treatments must be sought from the medicine prescriber.
Use medicines responsibly: www.noah.co.uk/responsible/.
Location: Large intestine
EQUEST: 13 week dosing interval offers single dose control of all stages of encysted small redworm larvae,
other roundworm species and bots. EQUEST PRAMOX: 13 week dosing interval offers single dose control of
all stages of encysted small redworm larvae, other roundworm species, bots and all 3 species of tapeworm.
Symptoms: Can cause colic, sometimes fatal by blocking blood vessels.
1. Cogley & Cogley (1999) Veterinary Parasitology 86, 127-142
2. Love et al (1999) Veterinary Parasitology 85, 113-122
3. Proudman & Matthews (2000) In Practice 22, 90-97
4. Dowdall et al (2002) Veterinary Parasitology 106, 225-242
5. Proudman (2003) Journal of Equine Veterinary Science 23 (1), 6-9
manage
POM-VPS
AH 250/11
test
plan
dose
Symptoms: Diarrhoea, anorexia,
dullness, loss of weight, reduced
growth rate.