A 3-year-old castrated male Labrador retriever with a history of atopic dermatitis presented with progressively more severe foot itching over the past two weeks. The main complaint was that the patient was taking oclacitinib maleate every day before treatment, and his condition was well controlled. The examination results showed that erythema and saliva were observed between the dog's four paws. Use clear acetate tape to take samples from between the affected toes to make impression smears and stain them with Romanovsky. The cytology results are shown in the figure below.

Try to answer the following three questions

What microorganisms were found during cytology examination?

What is the relationship between this pathogen and the animal’s current symptoms?

Why do animals with well-controlled atopic dermatitis experience increased itching?

1. What microorganisms are found in cytological examination?

The microorganism is Malassezia.

2. What is the relationship between this microorganism and the animal’s current symptoms?

Canine atopic dermatitis is the most common cause of Malassezia dermatitis in dogs. As a group, animals with atopic dermatitis have higher numbers of Malassezia in their skin than non-atopic animals. In addition, studies have shown that some dogs with atopic dermatitis develop immediate and delayed hypersensitivity reactions to Malassezia-derived allergens, suggesting that Malassezia plays a role in the pathogenesis of atopic dermatitis. plays an important role (Oldenhoff et al., 2014). Therefore, in addition to being an opportunistic pathogen, Malassezia may also be an amplifying factor in canine allergies. Finally, skin infections (bacterial and yeast) are common causes of itching and acute exacerbation of skin lesions in dogs with atopic dermatitis.

3. Why do animals with well-controlled atopic dermatitis experience increased itching?

Common reasons for aggravation of itching in atopic dermatitis include: improper medication or exposure to different allergens during the year or a certain season; the occurrence of pyoderma, Malassezia Secondary infections such as dermatitis or otitis media; infection with infectious ectoparasites (scabies or mites) or flea infestation; and simultaneous adverse skin reactions to food or contact allergies.