Immunologic diseases

Selected equine cutaneous diseases for which there is strong evidence of an immunological aetiology are discussed in this section. The reactive disorders of urticaria, Culicoides hypersensitivity, erythema multiforme, drug eruptions and systemic granulomatous disease are included. The autoimmune diseases of the horse with cutaneous manifestations (pemphigus foliaceus, pemphigus vulgaris, bullous pemphigoid and cutaneous lupus erythematosus) are discussed. The clinical signs and diagnostic features of these immunologically induced equine dermatoses are defined, and the challenges in making a definitive diagnosis and managing the clinical signs are confirmed.     

Results of intradermal testing for the investigation of atopic dermatitis and recurrent urticaria in 50 horses in the south of England

Atopic dermatitis (AD) and recurrent urticaria (RU) are common immune‐mediated conditions of horses and ponies associated with high morbidity. Effective pharmacological treatment options are limited but identification of the causal allergens allows avoidance strategies and immunotherapy regimens to be employed. Intradermal testing (IDT) is the most widely accepted means of identifying the relevant allergens but there are no published reports of this technique being used in the UK for the investigation of dermatological disease. This study presents the results of testing with a varied panel of allergens in 50 horses with dermatological disease living in the south of England. Intradermal testing was performed in horses presented to The Liphook Equine Hospital for further investigation of AD or RU between June 2002 and March 2009. Allergen selection was based upon availability, results of previous studies, pollen charts and the likelihood of allergens being prevalent in the stable or pasture environment in the south of England. Injection sites were evaluated at 1 h (immediate phase), 4 h (late phase) and 24 h (delayed phase) and skin responses compared to the response generated by the positive control (histamine) at 1 h. Total numbers of positive reactions and numbers of positive reactions to specific allergens were similar in horses with atopic dermatitis and those with urticaria (P = 0.39). There was a statistically significant difference in the number of reactions observed at different time points, with more positive reactions occurring at 1 h than 24 h (P<0.001), and at 4 h than 24 h (P<0.001). Reading the test at 24 h rarely provides additional information. Reaction patterns were similar to those of previous studies performed in other countries with large numbers of positive reactions reported to mites, dusts and insects. Positive reactions were also common to allergens not previously identified as irritants or common allergens in equids; nettle, daisy, dandelion, horse chestnut, cat, cattle, sheep and pigeon. These allergens may be important causes of allergic dermatitis in equids in the UK; however, further studies should be performed in both normal horses and horses with allergic dermatitis to investigate irritant thresholds and validate these findings. Intradermal testing may be shortened from the conventional 24 h to 4 h without significantly affecting the results of the test.     

The Clinical and Serological Effect of a Gluten‐Free Diet in Border Terriers with Epileptoid Cramping Syndrome

Background

Canine epileptoid cramping syndrome (CECS) is a paroxysmal movement disorder of Border Terriers (BTs). These dogs might respond to a gluten‐free diet.

Objectives

The objective of this study was to examine the clinical and serological effect of a gluten‐free diet in BTs with CECS.

Animals

Six client‐owned BTs with clinically confirmed CECS.

Methods

Dogs were prospectively recruited that had at least a 6‐month history of CECS based on the observed phenomenology (using video) and had exhibited at least 2 separate episodes on different days. Dogs were tested for anti‐transglutaminase 2 (TG2 IgA) and anti‐gliadin (AGA IgG) antibodies in the serum at presentation, and 3, 6, and 9 months after the introduction of a gluten‐free diet. Duodenal biopsies were performed in 1 dog.

Results

Serum TG2 IgA titers were increased in 6/6 BTs (P = .006) and AGA IgG titers were increased in 5/6 BTs at presentation compared to those of controls (P = .018). After 9 months, there was clinical and serological improvement in all BTs with CECS strictly adhering to a gluten‐free diet (5/5). One dog had persistently increased antibody titers. This dog scavenged horse manure. On the strict introduction of a gluten‐free diet this dog also had an improved clinical and serological response. The diet‐associated improvement was reversible in 2 dogs on completion of the study, both of which suffered a relapse of CECS on the re‐introduction of gluten.

Conclusions

Canine epileptoid cramping syndrome in BTs is a gluten‐sensitive movement disorder triggered and perpetuated by gluten and thus responsive to a gluten‐free diet.     

Colostral transfer of antibodies specific for Hypoderma lineatum proteins

Antibodies to Hypoderma lineatum were transferred to calves via colostrum. The antibodies transferred in the colostrum demonstrated specificity to all the H. lineatum first-instar proteins which were resolved by non-denaturing polyacrylamide gel electrophoresis and were capable of mediating a Type I hypersensitivity reaction. The kinetic decline of colostrum-acquired antibodies, the effect upon development of an autologous humoral response to H. lineatum and the host or parasite protective role of these antibodies are discussed.     

Comparative studies on dialyzable leukocyte extracts containing transfer factor—A review

The current state of knowledge concerning dialyzable leukocyte extracts (DLE) containing transfer factor (TF) is reviewed. Recent studies indicate that antigen-specific TF is an RNA-peptide component(s) of DLE that promotes antigen-specific cell-mediated reactivity (CMR). DLE also has nonspecific (adjuvant) activities both in vivo and in vitro. The term TF is now restricted to antigen-specific activity related to the promotion of dermal delayed-type hypersensitivity reactions and production of mediators of cellular immunity (lymphokines). Comparative studies of DLE containing TF activity in humans, non-human primates, and non-primates (cows) are discussed. Other animal models, including guinea pigs, dogs, mice, rats, and rabbits, are reviewed.