Abstract: Sixteen healthy horses with no history of skin or respiratory disease were used for an intradermal testing (IDT) threshold study, in order to determine the concentrations of 13 commercial allergenic insect extracts most appropriate for IDT. Five dilutions of each extract were used, which included the manufacturer's recommended concentrations for equine IDT, plus one dilution higher and three lower than these standard concentrations. Allergens tested included caddisfly (Trichoptera spp.), mayfly (Ephemeroptera spp.), horsefly (Tabanus spp.), deerfly (Chrysops spp.), fire ant (Solenopsis invicta), black ant (Camponotus pennsylvanicus), cockroach mix (Periplaneta americana and Blattella germanica), mosquito (Aedes aegypti), house fly (Musca domestica), moth (Heterocera spp.), flea (Ctenocephalides canis/C. felis), Culicoides variipennis and Culicoides nubeculosis. Two separate methods were used to calculate the allergen concentration for each insect extract where the normal horses, as a group, ceased to show false-positive ('irritant') reactions. 'Irritant' threshold concentrations were determined for 9/13 of these allergens, whereas the other 4 were undetermined due to either insufficient reactivity (flea, C. variipennis) or excessive reactivity (black ant, moth) to the concentrations tested. Recommended concentrations for future use in equine patients with suspected insect hypersensitivity include: 125 pnu mL(-1) (mayfly); 250 pnu mL(-1) (caddisfly, horsefly, deerfly, fire ant, house fly); 500 pnu mL(-1) (cockroach); 1000 pnu mL(-1) (mosquito); and 1:10 000 w/v (C. nubeculosis). Résumé Seize chevaux sains, sans historique de maladie cutanée ou respiratoire ont été inclus dans une étude sur le seuil de concentration des extraits pour intradermoréactions (IDT), afin de determiner les concentrations optimales de 13 extraits commerciaux d’insectes. Cinq dilutions de chaque extrait ont été utilisées: la concentration recommandée par le fabricant pour tester les chevaux, 1 dilution plus forte et 3 dilutions plus faibles que les concentrations standard. Les allergènes testés étaient: Trichoptera spp., Ephemeroptera spp., Tabanus spp., Chrysops spp., Solenopsis invicta, Camponotus pennsylvanicus, Periplaneta Americana, Blattella germanica, Aedes aegypti, Musca domestica, Heterocera spp., Ctenocephalides canis/C. felis, Culicoides variipennis, et Culicoides nubeculosis. Deux méthodes différentes ont été utilisées pour calculer la concentration allergénique de chaque extrait pour laquelle aucune réaction faussement positive (‘irritante’) n’est observée. Des concentrations ‘irritantes’ ont été déterminées pour 9/13 allergènes, mais pas pour les 4 autres allergènes à cause d’une réactivité insuffisante (puce, C. variipennis) ou d’une réactivité excessive (black ant, moth) aux concentrations testées. Les concentrations recommandées pour l’utilisation chez les chevaux suspects d’hypersensibilité aux insectes sont: 125 pnu/ml (mayfly); 250 pnu/ml (caddisfly, horsefly, deerfly, fire ant, house fly); 500 pnu/ml (cockroach); 1000 pnu/ml (moustique); et 1:10 000 w/v (C. nubeculosis). Resumen Dieciséis caballos sanos, sin historia de enfermedades de piel o respiratorias, fueron utilizados para un estudio de umbral en un test intradérmico (TID) con el fin de determinar las concentraciones más adecuadas de 13 extractos de insectos comerciales alergénicos para el TID. Se utilizaron cinco diluciones de cada extracto, en las cuales se incluyeron las concentraciones recomendadas por el fabricante para el TID equino, más una dilución más alta y tres diluciones inferiores a estas diluciones estándar. Los alergenos incluidos fueron: tricóptero (Trichoptera spp.), mosca de mayo (Ephemeroptera spp.), tábano (Tabanus spp.), mosca del ciervo (Chrysops spp.), hormiga roja (Solenopsis invicta), hormiga negra (Camponotus pennsylvanicus), mezcla de cucarachas (Periplaneta americana y Blattella germanica), mosquito (Aedes aegypti), mosca doméstica (Musca domestica), polilla (Heterocera spp.), pulga (Ctenocephalides canis/C. felis), Culicoides variipennis, y Culicoides nubeculosis. Se utilizaron dos métodos separados para calcular la concentración de alergeno necesario para cada extracto de insecto, donde los caballos normales, como grupo, no mostraron una reacción positiva (‘irritante’) falsa. La concentración umbral ‘irritante’ fue determinada para 9/13 de estos alergenos, mientras que en los cuatro restantes no pudo determinarse debido a una reactividad insuficiente (pulga, C. variipennis) o excesiva (hormiga negra, polilla) en las concentraciones utilizadas. Las concentraciones recomendadas para su uso futuro en pacientes equinos con una hipersensibilidad a insectos son: 125 pnu/ml (mosca de mayo); 250 pnu/ml (tricópteros, tábano, mosca del ciervo, hormiga roja, mosca doméstica); 500 pnu/ml (cucaracha); 1000 pnu/ml (mosquito); y 1:10 000 w/v (C. nubeculosis). Zusammenfassung Sechzehn gesunde Pferde, die bisher keine Anzeichen von Hautkrankheiten oder Erkrankungen des Respirationstraktes gezeigft hatten, wurden fuer eine Studie zur Bestimmung des Schwellenwerts beim Intradermaltest (IDT) verwendet, um die fuer IDT geeignetste Konzentration von 13 kommerziellen Insektextraktallergenen zu bestimmen. Fuenf Verduennungen von jedem Extrakt, die vom Hersteller empfohlene Konzentration, eine hoehere und drei kleinere Verduennungen mit eingeschlossen, kamen zum Einsatz. Koecherfliege (Trichoptera spp.), Eintagsfliege (Ephemeroptera spp.), zwei Bremsenarten (Tabanus spp. Und Chrysops spp.), zwei Ameisenarten (Solenopsis invicta und Camponotus pennsylvanicus), eine Kuechenschabenmischung (Periplaneta americana and Blattella germanica), Stechmuecke (Aedes aegypti), Stubenfliege (Musca domestica), Motte (Heterocera spp.), Floh (Ctenocephalides canis/C. felis), Culicoides variipennis, und Culicoides nubeculosis Allergene wurden verwendet. Zwei unterschiedliche Methoden wurden verwendet, um die Allergenkonzentration fuer jeden Insektenextrakt zu bestimmen, bei der die Gruppe von normalen Pferden keine falsch-positiven (‘irritierenden’) Reaktionen mehr zeigte. ‘Irritierende’ Schwellenwertkonzentrationen wurden fuer 9/13 dieser Allergene bestimmt, in den anderen vier Extrakten war das auf Grund von mangelnder Reaktivitaet (Floh, C. variipennis) oder ueberschiessender Reaktivitaet (Camponotus pennsylvanicus, Motte) der getesteten Konzentrationen nicht moeglich. Die empfohlenen Konzentrationen fuer zukuenftige Verwendung beim Pferd mit Vcerdacht auf Insektallergie sind 125 pnu/ml (Eintagsfliege); 250 pnu/ml (Koecherfliege, Bremsen, Solenopsis invicta, Stubenfliege); 500 pnu/ml (Kuechenschabe); 1000 pnu/ml (Stechmuecke) und 1:10 000 w/v (C. nubeculosis).
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This study aims to ascertain the most appropriate concentrations for intradermal testing (IDT) of 13 commercial allergenic insect extracts on healthy horses. Findings from this research will provide guidance for future investigations of suspected insect hypersensitivity in equine patients.
Understanding Irritant Threshold Concentrations
The study involved 16 healthy horses that had no history of skin or respiratory diseases. They were subjected to an IDT that used different concentrations of 13 commercial allergenic insect extracts. The goal was to find the ‘irritant’ threshold concentrations of these extracts suitable for IDT on horses.
The insect allergens tested included extracts from various species such as caddisfly, mayfly, horsefly, deerfly, fire ant, black ant, a mix of cockroach species, mosquito, house fly, moth, flea, and two types of biting midges known as Culicoides variipennis and Culicoides nubeculosis.
Five dilutions of each allergenic extract were used for the IDTs. The dilutions included the manufacturer’s suggested concentrations for equine testing, one dilution higher than the suggested concentration, and three dilutions lower than it.
Key Findings and Recommendations
The ‘irritant’ threshold concentrations were determined for 9 out of the 13 allergens. For the remaining four allergens, the findings were inconclusive due to either insufficient reactivity (flea and C. Variipennis) or excessive reactivity (black ant and moth). The threshold concentration is the level at which the horses, on average, ceased to show false-positive (‘irritant’) reactions to the allergens.
The recommended concentrations for future use in diagnosing insect hypersensitivity in horses were determined to be 125 pnu/mL for mayfly, 250 pnu/mL for caddisfly, horsefly, deerfly, fire ant, and house fly, 500 pnu/mL for cockroach, 1000 pnu/mL for mosquito, and 1:10,000 w/v for C. nubeculosis.
These findings are significant as they provide a reference point for future studies. Being aware of these ‘irritant’ concentrations will help in predicting false-positive test results, subsequently improving the reliability of IDT in diagnosing insect hypersensitivity among horses.
Cite This Article
APA
O Morris D, Lindborg S.
(2003).
Determination of ‘irritant’ threshold concentrations for intradermal testing with allergenic insect extracts in normal horses.
Vet Dermatol, 14(1), 31-36.
https://doi.org/10.1046/j.1365-3164.2003.00322.x
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