Evaluation of the value of staining hair samples with a modified Wright-Giemsa stain and/or showing illustrated guidelines for the microscopic diagnosis of dermatophytosis in cats.

BACKGROUND: Direct examination of the hair is a simple diagnostic test for the diagnosis of dermatophytosis; training is needed to use this test. HYPOTHESIS/OBJECTIVES: To evaluate whether use of modified Wright-Giemsa blue stain and/or photographic images of infected and uninfected hairs improved the user's ability to identify infected or uninfected hairs. ANIMALS: Ten cats with, and 10 cats without, dermatophytosis due to Microsporum canis (n = 20). MATERIALS AND METHODS: Twenty unstained and 20 stained hair samples from each group (n = 40) were anonymized and examined by veterinarians using a light microscope. Participants recorded samples as "infected" or "uninfected". Participants were then shown and allowed to use photographic images while examining the same 40 samples. RESULTS: Without staining, investigators correctly identified 12.7 ± 4 of the 20 samples (mean ± SD) and with staining 13.6 (±3). After illustrative guidelines were shown, they correctly identified a mean of 16.9 (±2.5) unstained slides and 15.8 (±2.3) stained slides. "Illustrated guidelines" and "hair infection" significantly increased the probability of a correct answer, whereas "staining" did not. Logistic regression determined that "study participant", "illustrated guidelines" (OR = 2.6) and "hair infection" (OR = 2.1) had a significant influence on the results, whereas "staining" did not. Sensitivity and specificity of direct examination were 70.5% and 56%, respectively, compared with culture status. CONCLUSIONS AND CLINICAL IMPORTANCE: When examining hairs for the presence or absence of infected dermatophyte hairs, diagnostic accuracy was improved when observers used illustrated guides compared with just examining stained slides.

Trichoscopic diagnosis of cutaneous Pelodera strongyloides infestation in a dog.

BACKGROUND: Pelodera strongyloides infestation has rarely been reported in dogs. It is a saprophytic free-living nematode, found in moist decaying organic matter, whose L3 larval stages occasionally can invade the skin of dogs and humans. Larvae penetrate the follicular infundibula causing an erythematous and pruritic dermatitis. The disease is usually diagnosed by deep skin scraping or histopathology, with large numbers of parasites readily identified in hair follicles. CASE REPORT: Pelodera strongyloides dermatitis was diagnosed in a six-year-old mixed breed dog presenting with alopecia, erythema and severe pruritus on the ventrum and limbs. The infestation was diagnosed by microscopic examination of plucked hair shafts and confirmed on microscopic examination of skin biopsies collected for histopathology. Only two of 10 deep skin scrapings gave positive findings. The nematode infestation was eradicated following two applications, 2 weeks apart, of a moxidectin/imidacloprid spot-on product. CONCLUSION AND CLINICAL IMPORTANCE: Skin scrapings are considered the diagnostic test of choice for P. strongyloides infestations. In this case, parasites were identified by hair trichograms more readily than by skin scrapings.