204 PYOGENIC BACTERIA IN DOMESTIC ANIMALS 



STREPTOCOCCUS EQUI. 



Occurrence and Pathogenesis. The Streptococcus equi was first seen 

 by Rivolta in 1873, and identified as the cause of strangles in the 

 horse by Schiitz in 1888, and also by Sand and Jensen, independently, 

 at about the same period. The specific disease which it causes is 

 also known as Coryza contagiosa equorum, distemper; "Druse der 

 Pferde," in German; and "Gourme," in French. Strangles is a febrile, 

 infectious, mucopurulent affection of the nasal and buccal mucosa, 

 with abscess formation in the laryngeal and retropharyngeal lymph 

 glands. The Streptococcus equi is found in the nasal discharge and 

 in the abscesses in the affected lymph glands; in the latter often in 

 pure culture, in the former, of course, mixed with other bacteria. 

 It sometimes causes a simple nasal catarrh without suppurative 

 processes in the glands, and at other times suppurative pleuritis and 

 exanthematous affections, with vesicle and pustule formation. It may 

 also cause septicemia and pyemia. Metastases have been found in 

 the brain, liver, spleen, kidneys, mesenteric gland's, and intestines, etc. 



Morphology and Staining Properties. The Streptococcus equi is 

 composed of cocci which may be spherical or oval or perfectly cylin- 

 drical short disks. The latter arrangement is often seen in tissues, 

 and the disks may be so crowded that the dividing lines of the indi- 

 vidual cocci are invisible, causing the organism to appear like a curved 

 filament rather than a true streptococcus. The chains are usually 

 very long, and may contain from fifty to one hundred cocci; they are 

 rarely straight, but, as a rule, curved and twisted. Short chains also 

 occur, and sometimes even diplococci and single cocci. The organism 

 stains with the ordinary watery anilin stains, and is Gram positive. 

 The washing in alcohol, however, must not be continued for too 

 long a period, as it may cause decolorization of the organism. Some 

 observers claim that the Streptococcus equi does not stain by Gram's 

 method. 



Cultural and Biologic Properties. The Streptococcus equi grows in 

 the presence or absence of free oxygen, and at room or incubator 

 temperature. In bouillon the growth forms fine flocculi, which fall to 

 the bottom of the tube and later develop a sediment, leaving the 

 upper strata of the medium clear. In gelatin stick cultures very small 

 punctiform white colonies are formed along the stab. On agar slants 

 or plates the colonies reach the size of a pinhead. They are grayish, 

 not transparent, do not become confluent, and adhere firmly to the 

 medium. On solidified blood serum the colonies are glassy and 

 translucent, and become confluent at a later stage. In the condensed 

 water of blood-serum tubes a fine precipitate composed of very long 

 chains is found. Some authors claim that there is no growth on 

 potatoes, others state that a grayish, slimy growth is present after 

 eight days. The organism does not ferment sugar; on artificial media 



