Is the skin barrier abnormal in dogs with atopic dermatitis?

In mammalian skin, the stratum corneum exerts a barrier function that protects from transepidermal water loss and the penetration of exogenous molecules, such as allergens, from the environment. Recently, skin barrier defects have been shown to be of prime importance in the pathogenesis of human atopic dermatitis. In this review, we summarize the latest research data pertinent to the stratum corneum and barrier function of dogs with atopic dermatitis. At the time of this writing, there is increasing evidence that a skin barrier defect likely exists in dogs with atopic dermatitis. This barrier dysfunction is characterized by abnormal intercellular stratum corneum lipid lamellae, abnormal stratum corneum morphology, reduced and abnormal ceramide content and, in some but not all dogs, abnormal filaggrin expression. In association with these changes, there is higher transepidermal water loss in atopic than in normal canine skin. Furthermore, atopic inflammation appears to worsen transepidermal water loss and filaggrin expression. It remains unknown, however, if the changes observed are primary (i.e. of genetic origin) or secondary to atopic inflammation that also exists even in clinically normal skin. Finally, whether or not a therapeutic intervention aimed at restoring a dysfunctional skin barrier is of any clinical benefit to atopic dogs has not yet been proven unequivocally.     

Aspects of metabolism related to the occurrence of skin lesions in biotin‐deficient chicks

1. Chicks were fed on biotin‐deficient low‐ and high‐protein diets supplemented with increasing concentrations of biotin.

2. Biotin deficiency decreased hepatic activity of pyruvate carboxylase [EG 6.4.1.1] but activity of acetyl‐CoA carboxylase [EG 6.4.1.2] was comparatively unaffected.

3. Increasing dietary protein increased the severity of biotin deficiency as assessed by skin lesions and decreased plasma biotin concentrations.

4. The severity of the skin lesions over all the treatments was most closely related to plasma biotin concentration.     

Epithelial–immune crosstalk with the skin microbiota in homeostasis and atopic dermatitis – a mini review

The skin is a complex and dynamic ecosystem, wherein epithelial cells, immune cells and the skin microbiota actively interact and maintain barrier integrity and functional immunity. Skin microbes actively tune the functions of the resident immune cells. Dysbiosis – alterations in the resident microbiota – leads to the dysregulation of host immunity. Microbiome analyses in humans and dogs with atopic dermatitis (AD) have shown shifts in microbial diversity, and in particular, an increased proportion of staphylococci. Monogenic diseases that manifest AD-like symptoms provide insights into the pathogenesis of AD and the mechanisms of dysbiosis, from both the epithelial and immunological perspectives. The symbiotic relationships between the host and microbiota must be maintained constitutively. Detailed mechanisms of how host immunity regulates commensal bacteria in the steady state have been reported. The skin harbours multiple tissue-resident immune cells, including both innate and adaptive immune cells. Recent studies have highlighted the fundamental role of innate lymphoid cells (ILCs) in the maintenance of barrier functions and tissue homeostasis. ILCs directly respond to tissue-derived signals and are instrumental in barrier immunity. Epithelial cells produce alarmins such as thymic stromal lymphopoietin (TSLP) and interleukins (IL)-33 and IL-25, all of which activate group 2 ILCs (ILC2s), which produce type 2 cytokines, such as IL-5 and IL-13, boosting type 2 immune reactions. Dysregulation of the epithelial–ILC crosstalk results in allergic inflammation. This review highlights our understanding of the active interactions between the host epithelial and immune cells, and microbiota, providing a foundation for novel therapeutic strategies for inflammatory skin diseases.     

Some factors influencing the feather‐skin connection

1. The effects of anaesthesia, temperature, pH, scalding agents and bleeding on the connection of the feather to the skin were studied.

2. Anaesthetics and increasing the temperature tend to loosen the feather; low temperatures and scalding agents tighten the connection, and bleeding is without effect while the effect of pH is variable depending upon the substance used.

3. In all local applications of drugs, no significant changes were found between living and slaughtered birds.     

Marek’s disease virus and skin interactions

Marek’s disease virus (MDV) is a highly contagious herpesvirus which induces T-cell lymphoma in the chicken. This virus is still spreading in flocks despite forty years of vaccination, with important economical losses worldwide. The feather follicles, which anchor feathers into the skin and allow their morphogenesis, are considered as the unique source of MDV excretion, causing environmental contamination and disease transmission. Epithelial cells from the feather follicles are the only known cells in which high levels of infectious mature virions have been observed by transmission electron microscopy and from which cell-free infectious virions have been purified. Finally, feathers harvested on animals and dust are today considered excellent materials to monitor vaccination, spread of pathogenic viruses, and environmental contamination. This article reviews the current knowledge on MDV-skin interactions and discusses new approaches that could solve important issues in the future.     

The use of skin delayed‐type hypersensitivity as an adjunct test to diagnose brucellosis in cattle: A review

Summary

Brucellosis, caused by bacteria of the genus Brucella, is a contagious disease that causes economic loss to owners of domestic animals due to loss of progeny and milk yield. Because cattle, sheep, goats, and to a lesser extent pigs are considered to be the source of human brucellosis, serological tests have been used to screen domestic animals for antibodies against Brucella. Although the serological tests helped to eradicate brucellosis in many countries, serological tests are not always adequate to detect latent carriers of Brucella. Therefore, the use of the skin delayed‐type hypersensitivity (SDTH) test, which is independent of circulating antibodies, might improve the diagnosis of brucellosis. In the literature, however, there are conflicting reports as to the value of the SDTH test for the diagnosis of brucellosis. Some studies consider the test unreliable, whereas others advocate its use because it detects brucellosis earlier than serological tests. The objectives of this study were therefore to assess the characteristics of the SDTH test, to select a Brucella strain that will yield a suitable brucellin for use in the field, and to determine whether the use of serological tests in combination with the SDTH test improves the detection of brucellosis. The results of this study clearly show that the SDTH test detects latent carriers of Brucella and confirms brucellosis in cattle with ambiguous serological test results. Brucellins prepared from smooth or mucoid strains of Brucella are better suited for use in the field than brucellins prepared from rough strains because they detect brucellosis in cattle with acute as well as chronic infection. The SDTH test is highly specific (99.3% specificity), and repeated testing of naive cattle or cattle infected with microorganisms that serologically cross‐react with Brucella does not sensitize cattle to subsequent SDTH tests. However, it is possible that some naive cattle may serologically react to the injection of brucellin. The effect of these serological reactions on the sero‐diagnosis of brucellosis is limited, because cattle may only now and then react serologically either with the serum agglutination test (SAT) or the complement fixation test (CFT). Nevertheless, cattle infected with microorganisms that serologically cross‐react with Brucella may test seropositive for brucellosis 4 to 7 weeks after injection of brucellin, depending on the cross‐reacting microorganism. The value of the SDTH test for the diagnosis of brucellosis was demonstrated after an outbreak of brucellosis. When the SDTH test was used in combination with SAT and CFT at diagnostic threshold ≥2 mm or ≥1 mm (increase in skinfold thickness), respectively, 39/44 (88%) or 42/44 (95%) of the infected cattle were detected compared with only 27/44 (61%) when SAT and CFT were used. When cattle in areas of low prevalence or in areas free from brucellosis are tested with the SDTH test an increase ≥2 mm in skinfold thickness should be considered indicative of infection. When the control and eradication of brucellosis is based on test‐and‐slaughter, an increase of ≥1 mm in skinfold thickness should be considered indicative of infection. Repeated serological testing complemented with the SDTH test in this programme will shorten the quarantine (movement control) period of a suspect herd, limiting the financial loss incurred during outbreaks of the disease. Consequently, since the SDTH test usually does not interfere with the serological diagnosis and can safely be used to establish the infection status of cattle in a suspect herd, it is opportune to consider adding the SDTH test to the procedure currently used to diagnose brucellosis in individual animals.     

Epidermal dysplasia and Malassezia infection in two West Highland White Terrier siblings: an inherited skin disorder or reaction to severe Malassezia infection?

Two 9-month-old West Highland White Terrier siblings were referred to our clinic with pruritus, alopecia and lichenification. Cytological examination of Scotch tape strippings revealed Malassezia organisms and cocci. Skin biopsy specimens showed epidermal dysplasia. Treatment included bathing with a 2% miconazole/chlorhexidine-containing shampoo, orally administered ketoconazole (5 mg kg-1, every 12 h) and cloxacillin (25 mg kg-1 every 8 h). Six weeks later, the dermal infection had resolved and there was hair regrowth. However, the dogs were still moderately pruritic. Intradermal allergy testing was positive for house dust mites, storage mites and Malassezia. Immunotherapy was initiated, and treatment with ketoconazole and cloxacillin was stopped. Skin biopsies, which were performed in both dogs 4 months after the first presentation, revealed mild superficial perivascular dermatitis. The remaining mild facial pruritus was easily controlled with topical treatment. These two cases indicate that epidermal dysplasia might be an inflammatory or hypersensitivity reaction to the Malassezia infection or a result of excessive self-trauma, rather than a congenital keratinization disorder.     

A preliminary study on the effect of wounding on transforming growth factor-β1 and cartilage oligomeric matrix protein concentrations in the skin of horses

Objective: To evaluate whether wound type or site influence the production of cartilage oligomeric matrix protein (COMP) and transforming growth factor β1 (TGF‐β1), and determine if there is a correlation between TGF‐β1and COMP during healing. Study Design: Experimental. Animals: Standardbred horses (n=6), 4–8 years old. Methods: Six, standardized, full‐thickness skin wounds (open, straight, and elliptical) were surgically created on the neck (n=3) and metacarpus (3) on each horse. Wounds were randomly allocated to site and side. Tissue samples were collected before creating wounds and on days 7, 14, and 42. COMP concentration (μg/g dry weight of tissue) was determined using a standard competitive ELISA and TGF‐β1 (ng/g dry weight of tissue) was determined using a commercially available sandwich ELISA. Results: COMP concentrations were higher in intact skin on the neck compared with the metacarpus (P=.02). There was no difference in COMP and TGF‐β1 concentrations between the different wound types or sites during healing. There was no correlation between TGF‐β1 and COMP during healing. Conclusions: Within the limitations of the study design, production of COMP during healing of skin wounds does not appear to be influenced by wound type or anatomic site, nor does it appear to be correlated with TGF‐β1 concentrations.     

Mast cell distribution,epidermal thickness and hair follicle density in normal canine skin: possible explanations for the predilection sites of atopic dermatitis?

Mast cell counts, epidermal thickness and hair follicle density were quantified in toluidine blue stained sections of normal skin from 20 different body regions in 10 dogs and compared to the predilection sites of canine atopic dermatitis. Mast cell distribution varied significantly from site to site (P < 0.0001) and counts in the superficial dermis were significantly higher than the deeper dermis (P < 0.05). Mast cell counts were highest in the medial and lateral pinna (mean 10.4–11.3 per high power field, HPF) and in the ventral interdigital skin of the hind and fore feet (mean 9.2–9.5 per HPF). Counts in these regions were at least 150% higher than all the other sites (means ranging between 2.9 and 6.0 per HPF). Variations in mast cell counts, epidermal thickness or hair follicle density did not adequately explain the predilection sites of canine atopic dermatitis. However, the results provide some evidence that cutaneous mast cell distribution may be involved in the frequent occurrence of ear and foot pruritus in this disease.     

Parasitological diagnosis of canine visceral leishmaniasis: Is intact skin a good target?

The objective of this study was to evaluate intact skin of seroreactive dogs as a possible target for the parasitological confirmation of canine visceral leishmaniasis (CVL). For this purpose, 394 dogs identified in serological surveys carried out in the metropolitan region of Belo Horizonte were studied. Blood was collected from all animals for serology and a tissue sample was obtained from two sites for parasitological diagnosis. Skin obtained from the ear and scapular region was simultaneously analyzed in 247 animals and lesion samples and ear skin were analyzed in 147 dogs. Leishmania parasites were isolated from 310 (78.7%) animals, and all isolates were identified as Leishmania chagasi. Simultaneous isolation from two sites was possible in 240 of the 310 animals, including ear and scapular skin in 151/247 (61.1%) and ear skin and skin lesions in 89/147 (60.5%). Ours results suggest that intact skin is one of the main target sites for the parasitological confirmation of CVL in seroreactive dogs.     

What's in a name? Inflammatory airway disease in racehorses in training

The term 'inflammatory airway disease' (IAD) is often used to describe the syndrome of lower airway inflammation that frequently affects young racehorses in training around the world. In practice, this inflammation is generally diagnosed using a combination of endoscopic tracheal examination, including grading of amounts of mucus present and tracheal wash sampling. However, a recent consensus statement from the American College of Veterinary Internal Medicine concluded that bronchoalveolar lavage (BAL) sampling, rather than tracheal wash (TW) sampling, is required for cytological diagnosis of IAD and that tracheal mucus is not an essential criterion. However, as BAL is a relatively invasive procedure that is not commonly used on racing yards, this definition can only be applied routinely to a biased referral population. In contrast, many practitioners continue to diagnose IAD using endoscopic tracheal examination and sampling. We argue that, rather than restricting the use of the term IAD to phenotypes diagnosed by BAL, it is important to distinguish in the literature between airway inflammation diagnosed by BAL and that identified in the field using TW sampling. We suggest the use of the term brIAD for the former and trIAD for the latter. It is essential that we continue to endeavour to improve our understanding of the aetiology, pathogenesis and clinical relevance of airway inflammation identified in racehorses in training using tracheal examination and sampling. Future studies should focus on investigations of the component signs of airway inflammation.     

A survey of canine and feline skin disorders seen in a university practice: Small Animal Clinic, University of Montréal, Saint-Hyacinthe, Québec (1987-1988)

Dermatological disorders accounted for 18.8% and 15.2%, respectively, of all the dogs and cats examined at the Small Animal Clinic, University of Montreal, Saint-Hyacinthe, during a one-year period. In dogs, the most common groups of dermatological disorders encountered were bacterial folliculitis and furunculosis, allergic dermatitis, endocrinopathy, neoplasia, ectoparasitism, and immune-mediated dermatitis. The most common primary final diagnoses were bacterial folliculitis and furunculosis, atopy, food hypersensitivity, flea bite hypersensitivity, hyperadrenocorticism, and hypothyroidism. Breed predispositions were found for several canine dermatoses: bacterial folliculitis and furunculosis (collie, German shepherd, golden retriever, Newfoundland), atopy (boxer, golden retriever), food hypersensitivity (boxer, German shepherd), hyperadrenocorticism (miniature poodle), hypothyroidism (Doberman pinscher, Gordon setter), castration-responsive alopecia (chow chow), demodicosis (Old English sheepdog), and idiopathic pruritus (pit bull terrier).

In cats, the most common dermatoses were abscesses, otodectic mange, cheyletiellosis, flea bite hypersensitivity, atopy, flea infestation, neoplasia, and food hypersensitivity. Himalayan and Persian cats accounted for 50% of the cases of cheyletiellosis and 75% of the cases of dermatophytosis, respectively. Hereditary primary seborrhea oleosa was seen only in Persian cats.