Abstract
A mass outbreak by strangles was occurred in a horse pasture land of our area during June to August in 1995. Almost all foals and mares (77.1%) were infected with Streptococcus equi subspecies equi and a mare died of a sickness. Horses with strangles showed a characteristic swelling of the mandibular and medial retropharyngeal lymph nodes, in addition to the general symptoms. Pathological swelling of lymph nodes were reduced or ruptured after treatment with antibiotics and horses recovered from a sickness several weeks later. From the results of the bacterial examination, it was identified the separated bactria with Streptococcus equi subspecies equi by the biochemical properties. Although the fertility rate was more than 70% before the occurrence of strangles, it was lower to be 63% in this year. As the mass outbreak in horses with similar symptoms to strangles were reported in some areas, it seemed that strangles would be spread in Iwate prefecture.
