EQUINE STRANGLES MODELED IN MICE

Small animal models of Streptococcus equi infection have been confined to parenteral injection of mice which subsequently develop a septicae mia. To devise a model of infection more closely resembling strangles, 4.9 x 10(6) cfu of S. equi were placed on the nares of C3H and Balb/c mice (fifteen of each). Compared with ten uninfected controls, infect ed mice sneezed more often and their daily weight gain was significant ly reduced. Histopathological examination seven days after infection r evealed varying degrees of nasopharyngeal and regional lymphoid pathol ogy in twenty two mice. Eleven mice had an early or mild rhinitis in w hich the nasal epithelium presented microabscesses containing polymorp honuclear leucocytes. Another eleven mice had a suppurative rhinitis o r pharyngitis associated in most with regional lymphadenitis; in two m ice, abscessated lymph nodes had erupted into perinodal connective tis sues. Two mice had a vestibular abscess. The suppurative rhinitis was associated with extensive necrosis of nasal propria which occasionally extended to conchal bone, resulting in osteomyelitis. Multiple bacter ial abscesses were seen in the spleen of one mouse. Histological lesio ns were not detected in control mice or in eight infected mice. S. equ i was re-isolated from the nares of fourteen of the twenty two affecte d mice but not from the eight unaffected challenged mice or control mi ce. The close resemblance of this model to strangles in horses may jus tify its further use for the investigation of pathogenesis and protect ive immunity.