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Intradermal Test Results and Hyposensitization Efficacy in Horses with Different Disease Complexes

Retrospektive Studie der Pferde mit chronisch rekurrierender Blinddarmobstipation nach chirurgischer Versorgung mittels Erweiterungsplastik des Ostium caecocolicum

Marie Welters , Katja Shell

Abstract

In this retrospective study, intradermal test (IDT) results and the clinical efficacy of allergen-specific immunotherapy (ASIT) were evaluated in 84 horses diagnosed with equine asthma (EA), equine allergic skin disease (EASD), headshaking (HS), or combinations of these conditions. Inclusion was based on clinical diagnosis and suspicion of an IgE-mediated type I hypersensitivity component. IDT was performed using up to 23 selected allergen extracts based on clinical presentation. Insect allergens were the predominant sensitizers across all diagnostic groups. Mosquito allergens were positive in 77/84 horses, Culex in 72/84, Tabanus in 69/84, and Culicoides in 64/84. Environmental allergens such as dog epithelium (54/78 tested horses) and house dust mites (Dermatophagoides farinae 45/84; Tyrophagus putrescentiae 44/84) were also frequently identified. Relevant sensitization patterns were observed not only in EASD but also in EA and HS cases. ASIT was considered indicated in 55 horses based on clinical–allergological correlation; 52 horses were subsequently treated. Follow-up after at least eight months was available for 32 horses. Good to excellent clinical improvement was reported in 6/8 EA horses, 7/8 EASD horses, all 7 EA+EASD horses, and 2/3 HS horses. No serious adverse reactions were observed. The results support IDT-guided ASIT as a safe adjunctive therapy in horses with chronic allergic disease. Insect allergens appear to play a central role across different clinical presentations. IDT and ASIT may also represent useful diagnostic and therapeutic tools in selected horses with EA and HS.

Keywords: Horse; Intradermal Test; Allergen-Specific Immunotherapy; Equine Asthma; Equine Allergic Skin Disease; Headshaking; Insect Allergens

Pengliang Li, Xuyan Wu, Wei Wang, Cheng Zhang, Xiaochen Yang, Jixiang Li

Abstract

Impaction is one of the most common disease of the cecum in horses. It is important to distinguish between acute and chronic recurrent cases. Acute impaction occurs suddenly and resolves within a few days with medical and/or surgical treatment whereas in chronic cases the impaction within the base or the whole cecum occurs repeatedly at irregular intervals. The chronic recurrent cecal impaction (CRCI) is characterized by hypertrophy of muscle in the cecal base or entire cecum. The pathogenesis is not fully understood: hypothesis is that the cecal impaction induces a distension during the contraction of the circular muscle layer which is a stimulus of a hypertrophy of the circular and longitudinal muscle layer in the cecum. Furthermore, neuronal density in the plexus myentericus was found to be decreased significantly in the cecal wall of CRCI. Initially, in cases of CRCI the cecocolic orifice is not entirely blocked allowing partial transit of ingesta. Hypertrophy of the muscle layer (longitudinal and circular muscle) begins at the cecal base and as the disease progresses, the cecocolic opening becomes completely obstructed due to the automatic closure mechanism. The rectal and ultrasound exam are the most useful diagnostic steps while different degrees of cecal impaction and/or tympany, a marked thickening and cecal wall contractility due to palpation are found. The hypertrophy can be regarded as a pathognomonic sign. Treatment in our study was done by surgical enlargement of the cecocolic orifice (created by Huskamp 1990). Tissue samples of defined cecal regions were taken during surgery or necropsy: the circular and longitudinal muscle layer were significantly thicker, linear neuron densities were significantly lower each compared to clinically healthy horses. Based on smooth muscle thickening and neuron deficit, rectally palpable and ultrasound visible cecal wall thickening, horses suffering from CRI have a poor prognosis. Surgery by enlargement of the cecocolic orifice in horses with CRCI have a better prognosis if only the cecal base has a thickening and a normal cecal body wall.

Keywords: horses, chronic recurrent cecal impaction, surgical treatment enlargement cecocolic orifice, long-term survival

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Intradermal Test Results and Hyposensitization Efficacy in Horses with Different Disease Complexes

Retrospektive Studie der Pferde mit chronisch rekurrierender Blinddarmobstipation nach chirurgischer Versorgung mittels Erweiterungsplastik des Ostium caecocolicum

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