SUMMARY Sweet itch is an intensely pruritic dermatitis of horses recurring annually in Ireland from April to November. The tissue changes of sweet itch have similarities to immediate‐type hypersensitivity reactions which occur in skin sensitised to the saliva of bloodsucking insects. There was subepidermal oedema, and marked eosinophilia; the blood vessels were tortuous and enlarged. Microfilaria were not found in serial sections of lesions of 5 affected horses. The histopathology of the immediate dermal reaction to the intradermal injection of Culicoides extract shows dermal vasodilation and eosinophil diapedesis. Seven horses challenged intradermally with whole extract of Culicoides, Stomoxys calcitrans, Tabanidae and saline, gave immediate reactions to Culicoides, 3 gave immediate reactions to Stomoxys calcitrans. Immediate and delayed reactions only occurred at the sites of challenge with Culicoides extract. Three normal ponies when challenged intradermally with extracts of biting flies, showed minimal dermal reactions. RÉSUMÉ La dermite estivale récidivante est une maladie intensément prurigineuse des chevaux qui réapparait annuellement en Irelande du mois d'Avril au mois de Novembre. Les altérations tissulaires constatées alors présentent des similitudes avec celles constatées lors d'hypersensibilité cutanée à la salive d'insectes hematophages. On remarqua un oedàme sub épidermique et une éosinophilie nette. Les vaisseaux sanguins deviennent sinueux et dilatés. On ne put trouver de microfilaires dans des coupes sérées effectuées sur des biopsies prélevées sur 5 animaux. L'histopathologie de la réaction dermique immédiate à l'injection intradermique d'extraits de Culicoides montre une vaso dilatation dermique et une diapédàse éosinophilique. 7 chevaux ainsi soumis à l'injection intradermique d'extraits totaux de Culicoides, de Stomoxys calcitrans, de Tabanidés et d'eau salée montràrent une réaction immédiate à Culicoides et 3 d'entre eux à Stomoxys calcitrans. Les réactions immédiates et différées ne se produisirent seulement qu'aux endroits testés avec des extraits de Culicoides. Trois poneys normaux testés par voie intradermique avec des extraits de mouches piqueuses ne montràrent que des réactions dermiques minimes. ZUSAMMENFASSUNG “Sweet Itch” ist eine stark juckende Dermatitis des Pferdes, die in Irland alljährlich zwischen April und November aufzutreten pflegt. Die Gewebsveränderungen bei “Sweet Itch”ähneln denjenigen einer Allergie des Soforttyps, die an der auf Speichel blutsaugender Insekten sensibilisierten Haut zu beobachten sind. Es besteht ein subepidermales Oedem und deutliche Eosinophilie. Die Blutgefässe sind erweitert und gewunden. Mikrofilarien liessen sich in Serienschnitten der Laesionen von 5 Pferden nicht finden. Die Histopathologie der Sofort‐Hautreaktion auf intradermale Injektionen von Culicoides‐Extrakten zeigt Vasodilatation und eosinophile Diapedese. Sieben Pferde, die intradermal mit Ganzextrakten von Culicoides, Stomoxys calcitrans, Tabaniden und mit Kochsalzlösung geprüft wurde...
Surgery Instrumentation t o facilitate surgical repair of rectal tears in the horse: A preliminary report SPENSLEY, M. S., MEAGHER, D. M. and HUGHES, J. P. (1985) Proc. Am. Ass. equine Pruct. 31, 553-563.
Summary In a study of the skin reactivity of horses with lesions of sweet itch, six clinically normal horses and seven affected horses were challenged intradermally with extracts of Culicoides, Stomoxys, Tabanidae and Culex species. All the affected horses and three of the normal horses responded strongly to the culicoides extract. The skin reactions in the affected horses reached their maxima within 4 h in the majority of animals. Skin reactivity to culicoides was transferred to normal horses with serum from affected animals confirming that the reaction was an immediate hypersensitivity reaction. Three of the seven affected animals gave both immediate and delayed reactions when challenged with the culicoides extract. When the dermal reactions of 12 clinically normal and 10 affected horses were compared at 20 mins and 1 h after challenge, the reactions produced by the culicoides extract were significantly (P<0.025) greater in the affected than in the normal horses. Individual horses gave strong reactions to extracts of Stomoxys, Culex and Tabanidae species, but no consistent response was evident among the affected animals. Serum from horses with sweet itch sensitised the skin of normal horses to challenge with extracts of the biting flies and the transferred antibodies remained bound to the skin of the recipient horse for 72 h or longer. Although some variation among the affected horses occurred in passive transfer experiments, the response to Culicoides species extracts was consistently greater than for the other insect extracts tested. Résumé Pour étudier la réactivité cutanée des chevaux atteint de dermite estivale récidivante, six chevaux normaux et sept malades furent intradermo inoculés avec des extraits de Culicoîdes, de Stomoxys, de Tabanides et de Culex. Tous les chevaux malades et trois des chevaux normaux réagirent fortement à l'extrait de culicoïdes. Les réactions cutanées maximales furent atteints en moins de 4 heures chez la plupart des chevaux malades. La sensibilité cutanée aux culicoïdes fut conférée aux chevaux sains par l'administration de sérum de chevaux malades. Cela confirmait l'existence d'une réaction immédiate d'hypersensibilité. Trois des sept chevaux malades présentèrent deux réactions aux extraits de culicoïdes, l'une immédiate et l'autre différée. Lorsqu'on compara les reactions dermiques de 12 chevaux normaux et de 10 chevaux malades, 20 minutes, puis 1 heure après l'injection déclenchante, on observa que les réactions produites par l'extrait de culocoides étaient plus importantes de manière significative (P<0.025) chez les chevaux malades. Certains chevaux eurent des réactions individuelles marquées aux extraits de Stomoxys, Culex et Tabanides, sans qu'aucune réaction ne puisse être considérée comme interprétable. Le sérum prélevé sur des chevaux atteints de dermite estivale sensibilise — rait la peau des chevaux normaux à l'injection d'extraits de mouches piqueuses; les anticorps ainsi transférés restaient présents dans la peau des receveurs 72 heures et plus. A quelques variation...
Clinical, immunological and histopathological findings in 20 adult dogs of varying breeds with chronic (>or=6 months) inflammation confined to the pedal skin were compared over a 2-year period with those of a group of age-matched controls (n=20). All affected dogs were pruritic but systemically well. Lesions were present on all four feet in 18/20 cases. Affected feet were characteristically erythematous, swollen, painful and alopecic. Sinus tracts were evident in 4/20 dogs. Despite a methodical series of diagnostic tests, no underlying cause was identified. None of the dogs responded to antimicrobial therapy administered for 8 weeks, none had evidence of ectoparasitism and none satisfied the criteria for atopic dermatitis. There was no response to a dietary trial using a novel protein source. The condition was characterized histopathologically by epidermal hyperplasia, hyperkeratosis, spongiosis, dermal oedema and perivascular aggregates of lymphocytes and plasma cells. Clinical signs did not correlate with histopathological findings. Affected dogs had significantly elevated serum IgG and IgM concentrations. The results of lymphocyte proliferation assays and phenotypic studies to determine the relative percentage of CD3+, CD4+, CD8+ and CD21+ lymphocyte subsets, and the ratio of CD4+/CD8+ cells were not significantly different between groups. No age, sex or seasonal predilections were noted. All dogs subsequently responded to immunosuppressive doses of prednisolone or cyclosporin. The term immunomodulatory-responsive lymphocytic-plasmacytic pododermatitis is proposed to denote what may be a previously unrecognized condition in some dogs with pododermatitis of undetermined aetiology.
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