Veterinary Dermatology

Companion animal staphylococcal isolate antibiograms were screened retrospectively to determine the frequency of methicillin‐resistant (MR) infection byStaphylococcus aureus,Staphylococcus intermedius, andStaphylococcus schleiferi. Rates of MR were:S. aureus35%,S. intermedius17%, andS. schleiferi40%. Frequency of isolation of methicillin‐resistantS. aureus(MRSA) from dogs and cats was similar, whereas methicillin‐resistantS. intermedius(MRSI) and methicillin‐resistantS. schleiferi(MRSS) were significantly more common in dogs. MRSS was more commonly associated with superficial (skin and ear canal) infections, whereas MRSA was more commonly associated with deep infections. The MR strain resistance pattern to other classes of antibiotics was also investigated. MRSA was resistant to the most classes of antibiotics, followed by MRSI, while MRSS maintained the most favourable susceptibility profile. MR staphylococci may pose a significant risk to animal and public health. Therefore, to avoid selecting for resistant strains in cases of suspected staphylococcal infection, clinicians should consider culture and susceptibility testing early in the course of treatment.

In 66 dogs of various races consulting the veterinary clinic for skin problems suspicious of atopic dermatitis, parallel skin tests with two commercial brands of allergens and serological tests with the CMG IMMUNODOT system and with an ELISA assay using monoclonal anti‐IgE antibodies were performed. The most frequent sensitivities found were towards house dust (44%) and storage mites (50%). Depending upon the cut‐off point chosen, the CMG IMMUNODOT test was shown to have sensitivity, in respect to the skin test, varying from 54 to 100%, in an inverse relationship to specificity. The ELISA assay was found to be slightly less sensitive. These investigations also revealed some major discrepancies in skin test results among allergen extracts of different origins, confirming that skin test results should no longer be considered as the sole ‘gold standard’ in diagnosis of IgE‐mediated allergy. The experience gained confirms that modern serological tests using monoclonal anti‐IgE antibodies for detection of allergen‐specific IgEs in the dog are useful in the diagnosis of dog allergy.

A 10‐year‐old castrated male Shih Tzu presented with severe generalized pruritus. Skin scrapings revealed the presence of Sarcoptes scabiei var. canis. A Yorkshire terrier in the same household simultaneously developed pruritus due to scabies. Both dogs were treated with 300 μg/kg ivermectin, at first orally and then subcutaneously at 14 day intervals. However, live mites were still found on day 35, and the skin condition deteriorated in both dogs. These findings suggested that the S. scabiei in these dogs was clinically refractory to ivermectin. The pruritus in both dogs rapidly and completely disappeared following topical fipronil administration. This appears to be the first report of canine scabies refractory to ivermectin treatment.

Abstract  Although canine atopic dermatitis (cAD) is common, few models are available. The aim of this study was to evaluate high‐IgE beagles epicutaneously sensitized to house dust mite (HDM) as a possible model for cAD. Six high‐IgE beagles were environmentally challenged with HDM using various doses and protocols. Similar challenge protocols were used in positive and negative control dogs: three dogs with naturally occurring cAD and positive intradermal skin test (IDT) to HDM and three normal dogs without history of skin disease and negative IDT to HDM. All high‐IgE beagles and all atopic dogs developed severe cutaneous lesions and pruritus after challenge. Lesions were erythematous papules and macules in contact areas such as face, ears, ventral abdomen, groin, axillae and feet. They were first visible after 6 h and increased in severity over time. No normal dog developed pruritus or lesions. Biopsies of representative lesions in the high‐IgE beagles were taken for histopathology and immunohistochemistry. There was superficial perivascular dermatitis with mononuclear infiltrates and spongiosis. Lymphocytes and eosinophils accumulated in small epidermal micro‐abscesses with hyperplasia of epidermal IgE‐bearing dendritic cells. These findings suggest that this colony of high‐IgE beagles develops a dermatitis that clinically, histopathologically and immunologically resembles the naturally occurring canine disease. It is also concluded that this modality of challenge is not irritating to normal dogs but induces flare‐ups in hypersensitive atopic dogs.

The cutaneous barrier contains small, cationic antimicrobial peptides that participate in the innate immunity against a wide variety of pathogens. Despite their immune importance, knowledge of canine defensins and their expression is limited primarily to testicular tissue and their relation to coat colour. Studies have shown that the absence of these antimicrobial peptides contribute to increased secondary infections in humans. The goals of this study were to identify defensin and protease inhibitor peptide genes by performing a computer‐based iterative screen of the canine genome and to determine whether antimicrobial peptides are expressed in normal canine skin. Reverse transcription‐polymerase chain reaction (RT‐PCR) was used to test for the expression of several antimicrobial peptides in the skin of five normal dogs. RNA from testis was used for comparison. The iterative screen identified 65 putative antimicrobial peptide genes on nine chromosomes, the majority clustered on chromosomes 16 and 24. Amplification of normal canine skin cDNAs demonstrated expression of antimicrobial peptide genes in five different body sites. These findings will provide a tool for future studies examining the association between antimicrobial gene expression and cutaneous immunity in dogs.

Antimicrobial peptides (AMPs) are small proteins involved in defense against pathogenic organisms. Defensins and cathelicidin are the most frequently studied human AMPs. Our goals were to determine the distribution of AMPs and evaluate their mRNA expression in normal canine skin. Skin biopsies were taken from six healthy beagles. The relative transcript level of canine cathelicidin (cCath) and β‐defensin (cBD)‐1, cBD2 and cBD3 mRNA was quantified using quantitative real‐time polymerase chain reaction. Indirect immunofluorescence (IIF), using polyclonal antibodies against cBD2, cBD3 and cCath, was used to evaluate protein localization in the skin of healthy dogs. The Pfaffl method, using experimentally determined primer efficiencies of amplification, was used to determine the expression level of cCath, cBD1 and cDB3 relative to cDB2. The levels of cCath, cBD3 and cBD1 mRNA were 358, 296 and 177 times higher than those of cBD2, respectively. Using IIF, cBD2 and cBD3 protein fluorescence was detected in all layers of the epidermis, whereas cCath was detected predominantly in the stratum granulosum and corneum. In addition, antimicrobial peptide detection was limited to the infundibular portion of the pilosebaceous units. We have validated useful methods to evaluate AMPs in canine skin. Further studies are needed to compare AMP expression in healthy dogs with that of dogs with inflammatory skin conditions.

Acceleration of wound healing and improvement of scarring at skin graft donor sites and trauma or surgical lesions are important clinical goals in human and veterinary medicine. It has been discovered that wounds made on early mouse embryos heal quickly and perfectly, with no scars. The cellular and molecular differences between scar‐free embryonic healing and scar‐forming adult healing have been investigated. As a result, molecules have been identified which can be experimentally manipulated during adult healing, both to accelerate the process and to improve scarring. Some of these molecules represent pharmaceutical targets to which novel therapeutic agents have been developed. For example, embryonic wounds have high levels of TGFβ3 from endogenous keratinocytes and fibroblasts, but relatively low levels of TGFβ1 and TGFβ2 derived from degranulating platelets and inflammatory cells, by comparison to adult wounds. Therapeutically elevating the level of TGFβ3 allows adult rodent and porcine wounds to heal significantly faster and with improved scarring. These experimental findings have progressed into further studies in humans. A number of clinical trials with novel pharmaceuticals designed to accelerate healing and prevent scarring have been successfully completed, and further large patient‐based trials are ongoing. These studies indicate that pharmaceutical treatment of healing wounds to accelerate the process (e.g. accelerated re‐epithelialization of graft sites) or improve scarring may soon supplement the current surgical and device approaches to wound management.