Tierdermatologie Deisenhofen
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Pruritus
Clinical clues for pruritus:
Pruritus is frequently used interchangeably with "itch". If it itches, then
scratch it…. However "itch" is not just scratching. In dogs, cats and
horses, pruritus can cause the following behaviour: rubbing (with front and
back paws / hooves) at the nose and eyes; rubbing the sides of the face
along the furniture or ground or grass; scratching at the ears with the hind
paws/hooves; rolling on the back, licking and biting of the dorsal / ventral
paws, claws and/or clawbeds; biting or licking at the flanks, ventrum
(especially cats); tugging at the hairs individually (trichotillomania is seen
in cats); nibbling or "cobcorning" or licking at the forelegs (antebrachael
area); rubbing the tail base on furniture, fences, ground (also referred to
as "scooting"); biting and licking at the perianal skin; some special
additional behaviors include: dragging of the belly / ventral abdomen over
the floor (especially in some breeds of dogs such as pugs, bull terriers);
head shaking (in horses).
Cause of pruritus:
Determining the exact cause of pruritus is one of the more difficult
challenges in veterinary dermatology. A careful clinical examination is
essential to help formulate the differential diagnosis list and microscopy is
frequently required to help work through this. Unfortunately allergies are
not the only cause of pruritus, infections as well as ectoparasite
infestations may occur alone or concurrent to allergies.
Clinical examination and differential diagnoses list:
Pruritus without lesions and without a cytologically evident superficial
infection should suggest atopic dermatitis or scabies incognito as the two
major differential diagnoses.
Pruritus with lesions may result from self trauma and/or from secondary
infection / ectoparasite infestation. Lesions need to be carefully examined
for clues such as folliculitis (seen with demodicosis, dermatophytosis and
staphylococcal infections), papules and pustules (seen with insect bites,
staphylococcal infections and uncommonly with pemphigus). The
distribution of both the pruritus and the lesions must also be carefully
assessed. For example, involvement of the caudal half of the dog or cat
suggests a flea bite hypersensitivity, of the pinnae, elbows and hocks
suggests scabies, of the sparsely-haired areas such as axillae and ventrum
of either contact allergy or atopy, of the head of atopic dermatitis,
recurrent otitis externa is frequently associated with both hypothyroidism
and hyperadrenocorticism and with atopic dermatitis as well as food
hypersensitivity.
Labrador with demodecosis
Labrador with atopy