الفهرس 
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Abstract
Strangles is one of the most important infectious respiratory diseases affecting equine causing high economic losses respresented in prolonged course, associated with serious complications which may be ended by death of affected animal. This work was designed to study the epidemiological, clinical aspects, post-mortem examinations of strangles. In addition, electrophoretic pattern of Streptococcus equi and experimental trial to use vaccination with M.protein and a whole cell culture vaccine. The results of this study revealed the following: Epidemiological pattern: The cumulative incidence of strangles during July, 2003 to June, 2004 was 37.53%. The seasonal occurance of strangles were 3.89%, 35.59%, 3.62% and 1.26% during winter, spring, summer and autumn, respectively. The highly significant rate of strangles affection was noticed during the spring. All ages of horses contract the disease; at the age of 6months to >1.5 years the incidence rate was 68.86%, at the age of 1 .5->3 years it was 8.33% and in foals less than 6 months it was 12.50% while in horses more than 3 year old, it was 11.83%. The highly significant rate of affection appeared in horses at 05- 1.5 years old. Clinically infected animals had sudden rise in body temperature (38-39.5°C) with variable degrees from respiratory distress, nasal discharge with or without abscessiated submaxillary lymph node. Postmortem lesion of dead control donkey showed enlarged, congested liver and enlagred, hemorrhagic lung while dead control animal showed enlarged and heamorrhagic submaxillary lymph node with diffuse necrotic areas at the lung.
The causative agent of strangles (Streptococcus equi) was isolated from the nasal discharge, pharyngeal swabs and submandibular lymph node abscesses. Streptococcus equi was characterized and identified by sugar fermentation test in which it does not ferment lactose, raffinose, sorbitol, inulin, mannitol and trehalose but ferment salicin and was found to be belonging to group C according to Lancefield classification. Molecular weight determination of the isolated Streptococcus equi was estimated by electrophoretic pattern SDS-PAGE. Streptococcus equi isolates were tested for their sensitivity to different antimicrobial agents which revealed that all S.equi isolates were highly sensitive to ampicillin, pencillin and gentamycin and were resistant to oxilinic acid and nalidixic acid. The immune response of vaccinated donkeys reached the maximum after three inoculations to 2.766 at 90 days post challenge as indicated with ELISA test in animal vaccinated with M.protein but in case of a whole cell culture the response reached to maximum level at 90 days post challenge(2.509). Vaccinated donkeys with M.protein was survived when challenged with Streptococcus equi culture. However, one donkey vaccinated with a whole cell culture vaccine was died postchallenge with S.equi culture.