Hypersensitivity reactions (HR) are immune responses that are exaggerated or inappropriate against an antigen or allergen. Coombs and Gell classified hypersensitivity reactions into four forms. Type I, type II, and type III hypersensitivity reactions are known as immediate hypersensitivity reactions
An 8-day-old newborn female twin Holstein calves with a history of weakness, anorexia, emaciation and convulsion were presented to Tabriz University Veterinary Teaching Hospital. On admission, the calves were febrile and recumbent. Physical examination revealed many ticks from the external body