Michelle Woodward’s research while affiliated with Louisiana State University and other places

In collaboration with the American College of Veterinary Pathologists.

An ∼12 yr old castrated mixed-breed dog was evaluated for a 7 wk progressive history of intermittent hyporexia, lethargy, and erosive dermatitis. Initial examination revealed disseminated papules and macules coalescing to irregularly shaped and serpiginous plaques with widespread erosion progressing to ulceration. Skin histopathology revealed transepidermal keratinocyte apoptosis with lymphocyte satellitosis and lymphocytic and histiocytic interface infiltrate. Histopathology combined with clinical signs and history were compatible with the diagnosis of erythema multiforme major. Treatment was initiated with multidrug immunosuppression. Following 36 hr with no improvement, intravenous human immunoglobulin (0.45 mg/kg IV) was administered resulting in notable improvement in the dog’s attitude and appetite within 2 hr and the dog’s skin lesions within 48 hr. Following discharge, the dog improved daily with near complete resolution of dermatologic disease achieved 1 mo postdischarge. All immunosuppressive medications were ultimately discontinued 5 mo following presentation. This is the first report of a dog with erythema multiforme major that has been successfully treated with a combination of intravenous immunoglobulin and immunosuppression.

A three-year-old male neutered Australian shepherd dog presented with a one-week history of diffuse ulcerative cutaneous nodules. On physical examination the dog had generalised lymphadenomegaly with multiple well-circumscribed subcutaneous to dermal nodules with central haemorrhagic ulceration affecting the face, dorsum, dorsal cervical area and abdomen. Histopathological findings revealed severe suppurative and pyogranulomatous dermatitis and panniculitis with acid-fast pleomorphic bacterium present. Mycobacterial culture of tissue was negative. Repeated PCR assays on formalin-fixed tissue followed by nucleic acid sequencing confirmed the presence of Mycobacterium avium complex. Treatment was initiated with clarithromycin (10.9 mg/kg orally every 12 hours) and rifampin (13.2 mg/kg orally every 24 hours) and resulted in clinical resolution of the lesions within two weeks. Treatment was continued for six months and then discontinued. Seventeen months following treatment discontinuation, the dog was clinically and systemically well with no relapse noted.

Background Topical therapy alone can be effective in the treatment of canine pyoderma. Topical products are commercially available as shampoos, sprays, wipes and mousses. To date, no studies have evaluated the efficacy of commercially available mousse products in the treatment of canine pyoderma. Objective To determine the residual antibacterial activity of canine hairs treated with mousse products containing different active ingredients. Animals Fifteen client‐owned dogs with no history of dermatological disease. Methods and materials Dogs were treated once with five mousse products [(i) 2% chlorhexidine and 1% ketoconazole, (ii) 2% chlorhexidine and 2% miconazole, (iii) 3% chlorhexidine and 0.5% climbazole, (iv) 2% salicylic acid 10% ethyl lactate and (v) phytosphingosine HCl 0.05%; control]. Hair samples were collected from each treatment area before application, one hour after application and on days 2, 4, 7, 10 and 14 post‐treatment. Collected hairs were weighed and plated on Mueller–Hinton agar plates streaked with a Staphylococcus pseudintermedius isolate showing no antimicrobial resistance. Plates were incubated for 24 h and bacterial growth inhibition zones around the hairs were measured. Results Mousses 1, 2 and 3 created significant inhibition zones up to Day 10 when compared to pre‐treatment samples. On Day 14, only mousse 3 produced a significant zone of inhibition when compared to the pre‐treatment sample. Mousses 4 and 5 showed no statistical difference between any of the samples. Conclusions and clinical importance These results suggest that three of the mousse products had residual activity in inhibiting S. pseudintermedius growth in vitro for at least 10 days.

This chapter provides guidelines for identifying ectoparasites by skin scraping of horses. Skin scraping is a diagnostic procedure that involves abrasion of skin lesions with a scalpel blade or curette. Its purpose is to detect the presence of microscopic ectoparasites, including mites such as Chorioptes spp., Psoroptes spp., Sarcoptes spp., and Demodex spp., as well as larval stages of the trombiculid mites. Scrapings may also be used to detect larvae of Pelodera spp., and Habronema spp. Ectoparasites tend to prefer certain areas of the body. The equipment required for skin scraping are clippers, sterile container, mineral oil, glass slides, coverslips and light microscope. Deep scrapings may also permit the detection of Pelodera spp, and occasionally Habronema spp. larvae. The blade is thoroughly cleaned between sites to prevent cross?-contamination of the samples, if multiple areas are to be sampled.

This chapter provides guidelines for performing brushing/grooming in pruritic horses. Brushing/grooming is a simple diagnostic procedure involving gross examination of hair and skin surface debris. It facilitates the detection of lice, other large ectoparasites, and surface feeding mites (such as Chorioptes equi) in pruritic horses. Ticks are not removed with brushing, but are detected by careful inspection, especially of the ears. The equipment required for performing brushing/grooming are stiff brush or denture-type toothbrush, flea comb, petri dish, dark surface and dissecting microscope. A flea comb to collect dander and other debris might improve recovery of ectoparasites such as mites. The dark surface increases the chances of seeing ectoparasites such as lice. Movement of ectoparasites may be the easiest thing to visualize.

Cellophane tape preparations are used to collect material from the surface of the horse's skin and coat. The purpose is to detect the presence of certain skin parasites, including Oxyuris equi, Chorioptes equi, and lice. Equipment required for this procedure is clear cellophane tape, mineral oil, glass slides, and microscope. If looking for Oxyuris equi eggs, the sample should be collected from several areas around the anal and perianal regions. If looking for other parasites, an area of scaling or alopecia is chosen. Cellophane tape preparation is particularly useful in obtaining Oxyuris equi eggs, and for trapping ectoparasites such as Chorioptes equi and lice, which otherwise move around during superficial skin sampling. The mineral oil helps to clear debris and facilitate visualization of ova, mites, and lice. The slide microscopically for evidence of ova or other parasites such as mites and lice are examined.

This chapter provides guidelines for performing fungal culture of superficial skin lesions in horses. The fungal culture of superficial skin lesions is performed for inoculation of fungal culture medium with material obtained from the skin, such as hair, crusts or scales. Types of samples used include plucked hairs within and surrounding the lesion, or skin crust removed from affected areas. Fungal culture of suspected subcutaneous and deep mycotic infections requires collection of tissue via biopsy. Fungal pathogens causing superficial mycosis in horses include dermatophytes and non-dermatophytes. The equipment required for performing fungal culture of superficial skin lesions are clippers, 70% isopropyl alcohol, cotton, mosquito forceps, scalpel blade, toothbrush, dermatophyte test medium (DTM) and Sabaroud's dextrose agar. DTM is the most commonly used test medium. DTM is the most commonly used test medium.

Onchocerca preparation is a diagnostic procedure for identifying Onchocerca cervicalis microfilariae in the skin of horses. The microfilariae of Onchocerca cervicalis tends to concentrate in the ventral midline, face, and neck, causing dermatitis and leukoderma, whereas the adult worms inhabit the funicular portion of the nuchal ligament. Characteristic dermatitis in conjunction with the presence of the microfilariae is supportive of cutaneous onchocerciasis. Cutaneous onchocerciasis may be accompanied by ocular onchocerciasis. Onchocerca microfilaria are approximately 220 µm in length and 8 µm in diameter. They have a characteristic "whiplash" movement. The tissue mincing step is important because it will facilitate the migration of the microfilariae out of the skin specimen. This longer incubation step may be useful when low numbers of microfilaria are suspected as it allows time for more microfilaria to migrate out of the tissue specimen.