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The approach to a pruritic canine patient begins with the history and clinical signs of the patient. From the age of onset, seasonality, acute/chronic itch, presence of alesional pruritus to response to previous treatment/s are important indispensable clues to aid identification of the aetiological pruritic agent. Puppies are more prone to develop contagious pruritic diseases such
as sarcoptic mange, dermatophytosis or demodicosis. Patients with onset of pruritus that begins less than
12 months of age is highly suspicious of cutaneous adverse food reaction (CAFR), whereas CAD patients
are typically presented between 12-36 months of age.5,6 Seasonal pruritus is often associated with flea allergic dermatitis or canine atopic dermatitis. A typical canine atopic patient is often presented with chronic alesional pruritus that respond previously to steroids.5 From clinical signs, sarcoptic mange infestation often manifests itself on the ear tip margins whereas it is the dorsal lumbar area for flea allergic dermatitis. The typical anatomical site that is involved in canine atopic dermatitis are the forepaws and also the concave ear pinnae.5 Needless
to say, patients are often pruritic, manifested clinically as either scratching, licking or having excoriation marks at these respective sites. If there is evidence of a parasitic infestation that could cause itching, they should be addressed accordingly and patient re-evaluated for persistence of pruritus on a later date. The new class of insecticides, isoxazolines such as fluralaner, sarolaner, afoxolaner and lotilaner offers a safe, efficacious
and even sustained efficacy for up to 90 days in one product.7-10 Understanding the pharmacokinetics
and pharmacodynamics of this or other classes of antiparasiticals would aid in its assimilation to the veterinarians’ approach to the pruritic patient potentially making it more flexible and robust.
For every pruritic patient, it is important for the attending veterinarian to evaluate the presence of superficial staphylococcal pyoderma and likewise important to determine to what portion of the overall itch is related to staphylococcal infection. This is the same of malassezia dermatitis. This can be done rather easily with routine cytology, collected from representative regions
with typical associated clinical signs. The attending veterinarian must remember that recurrent pyoderma
or recurrent malassezia dermatitis is often associated with an underlying allergic disease.11 Due to this high rate of recurrent pyoderma, it is often that patients are frequently exposed to antibiotics which adds selective pressure that culminates in antimicrobial resistance.12,13 Thus, a robust approach to a pruritic patient and antimicrobial stewardship is indispensable that goes hand-in-hand in modern day practice. Antibiotics are certainly not candies we should freely dispense. After the likelihood of an infestation and/or infection has been ruled out, the possibility of a CAFR must be investigated. Despite its clinical signs are virtually indistinguishable
from canine atopic dermatitis, CAFR does have its own particularities. CAFR is often thought to occur in younger patients, less than one year of age with non-seasonal pruritus, mostly widespread and generalized.5, 6 This pruritus is usually severe, constant with high variability
in its amelioration of pruritus with oral or parenteral glucocorticoids, with results ranging from poor to good.5,14 The only effective method to distinguish CAFR and CAD is to conduct a food trial either with a home- cooked elimination diet with novel sources of protein and carbohydrate or a commercial hydrolysed diet for 9-10 weeks. It is only with the lack of response from a food trial that we can finally arrive at the diagnosis of CAD.
If a systematic approach to a pruritic patient has been conducted and CAD confirmed, it not only allows
the attending veterinarian to appreciate the atopic patients’ itch clinical threshold and but also allows the identification flare factors associated with it. The itch clinical threshold is defined as the point where a pet begins to scratch due to a summation of events, where each contributes independently to the itch cascade. As pruritic thresholds are unique for each animal, a systematic approach allows attending veterinarians
to build a clinical pruritic impression for the patients under his/her care. Flare factors are biologic or environmental factors which induces the exacerbation of atopic dermatitis. Current recognized flare factors in CAD includes staphylococcal or yeast infections, flea infestation, dietary indiscretion and also environmental triggers.15
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