Page 1242 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

Skin 1217

VetBooks.ir 12.5 12.6

Fig. 12.5 Onchocerca infection,
showing typical head lesion of
4 weeks’ duration with scaling,
crusts and alopecia. The horse
rubbed the affected areas
frequently.

Fig. 12.6 Ventral midline
dermatitis due to Onchocerca
infection. There is loss of hair
and scaling, with scattered
lesions either side of the midline,
and mild to severe pruritus
with biting and rubbing of the
thickened belly wall.

Diagnosis to see a resurgence of nematode-based cutaneous
The clinical picture is characteristic. Pruritus lesions.
regresses in winter and returns in summer. Biopsy
reveals the presence of larval worms in the skin of INSECT-INDUCED PRURITUS
clinically affected horses.
FLEAS
Management
Treatment is with ivermectin (0.2 mg/kg) or mox- Definition/overview
idectin (0.4 mg/kg) paste given orally and repeated Stickfast (or stick tight) fleas (Echidnophaga gallinacea),
in 4–6 months. Most cases resolve with a single found in warm climates, typically cause this problem.
treatment. A massive kill of larvae can exacerbate the Parasitised horses may be in contact with poultry or
eye and skin inflammation for 3–5 days after treat- current/former poultry sheds as well as areas fre-
ment. Consider using concurrent anti-inflammatory quented by pigeons.
glucocorticoid therapy to help minimise hypersensi-
tivity reactions to the dying larvae. MIDGES

Prognosis Definition/overview
The prognosis is very good. Culicoides spp. can cause irritation of the skin.
Variations in the target skin area of the horse
OXYURIS (PIN WORM) depend on the species involved. All horses are
attacked by Culicoides spp. and show signs of irrita-
Definition/overview tion, which leads to restlessness and even pruritus.
Female Oxyuris equi worms lay eggs on the perianal When climatic conditions are favourable for rapid
skin, causing irritation and self-induced trauma. generation of ‘wave’ attacks, many horses show this
Regular de-worming with routine anthelmintics has irritation, which rapidly abates with the passage
all but eliminated this disease, which is mainly seen of the ‘wave’ peak, leaving only those horses with
in stabled horses. With the introduction of more hypersensitivity reactions with a serious pruritic
judicial de-worming practices, clinicians may start problem.