FAMILY RICKETTSIACEAE 



1097 



alimentary tract of the goat louse (Lino- 

 gnathus stenopsis). Resembles Rickett- 

 sia trichodectae morphologically and oc- 

 curs only extracellularly in the lumen of 

 the gut. 



Rickettsia melophagi Noller. (Arch. 

 Schiffs- u. Tropenhyg., 21, 1917, 53.) 

 Found upon and in the cuticular layer 

 covering the epithelium of the midin- 

 testine of the sheep tick (Melophagus 

 ovinus). Occurs characteristically in 

 pairs of fairly uniform size, coccoid and 

 sometimes rod-shaped. Gram-negative 

 but stains fairly well with carbol-fuchsin 

 and gentian violet. Stains deep purple 

 with Giemsa's method and bright red 

 with Machia Velio's method. Has been 

 cultivated on non-living culture media, 

 a glucose-blood-bouillon agar medium. 

 The ability of Rickettsia melophagi to 

 infect sheep has been the subject of 

 contradictory claims. Small laboratory 

 animals seem not to be susceptible. 



Rickettsia ovina Lestoquard and Dona- 

 tien. (Lestoquard and Donatien, Bull. 

 Soc. Path. Exot., 29, 1936, 108; Ehrlichia 

 ovina Moshkovsky, Usphekhi Soure- 

 mennoi Biologii (Russian) (Advances in 

 Modern Biology), 19, 1945, 18.) Found 

 in the blood of diseased sheep from 

 Turkey and Algeria. The organisms oc- 

 cur as minute coccoid granules, grouped 

 in masses and present only in the mono- 

 cytes and never in endothelial cells. 

 They stain uniformly dark red with the 

 Giemsa stain but did not stain with the 

 Castaiieda technic. Infected ticks {Rhi- 

 picephalus bursa) are thought to be the 

 vectors. 



Rickettsia pisces Mohamed. (Ministry 

 Agr., Egypt., Tech. Sci. Serv. Bull. 214, 

 1939, 6 pp.) In the monocytes and 

 plasma of the blood of a fish {Tetraodon 

 fahaka) showing necrotic ulcers on its 

 head and both sides of the body. The 

 heart, liver and intestines showed le- 

 sions. The organisms were minute coc- 

 coid forms varying from 0.2 to 0.4 micron 

 in diameter and frequently occurring in 

 pairs. 



Rickettsia rocha-liynae Weigh (Prz- 

 glad. Epidemj., 1, 1921, 375.) Occurs 

 in lice (Pediculus humanus) but is ap- 

 parently non-pathogenic either to lice or 

 to vertebrates. Larger and more pleo- 

 morphic than Rickettsia prowazekii. In 

 smears or sections of the gut of lice, 

 Rickettsia rocha-limae occurs in agglomer- 

 ated masses, grouped like staphylococci. 

 They occur both extracellularly and in- 

 tracellularly and stain more deeply than 

 Rickettsia prowazekii. Weigl claims to 

 have cultivated this species on artificial 

 culture media under anaerobic condi- 

 tions. Not pathogenic for laboratory 

 animals or man. 



Rickettsia suis Donatien and Gayot. 

 (Bull. Soc. Path. Exot., 35, 1942, 324.) 

 Causes a disease in swine, the pathology 

 of which resembles heartwater of rumi- 

 nants. See Genus III, Coivdria, Family 

 Rickettsiaceae. 



Rickettsia trichodectae Hindle. (Par- 

 asitology, 13, 1921, 152.) In the species 

 of biting lice {Trichodectas pilosus) 

 which may be found on horses. This 

 insect does not suck blood. The or- 

 ganisms occur extracellularly in the ali- 

 mentary tract of the louse. The aver- 

 age size is 0.3 to 0.5 by 0.5 to 0.9 micron 

 and occasionally longer forms occur. 



Rickettsia weigli Mosing. (Arch. Inst. 

 Pasteur, Tunis, 25, 1936, 373.) Con- 

 cerned in an epidemic disease which 

 broke out in 1934 among employees of 

 the Institute of Biology in Lwow who 

 were engaged in feeding supposedly un- 

 infected lice on their persons. Mosing 

 and others have suggested the possibility 

 that this rickettsia may be an extreme 

 mutant of Rickettsia pediculi. Small 

 coccoid to rod-shaped organisms staining 

 well with the Giemsa stain, usually 

 slightly longer than Rickettsia prowa- 

 zekii. In the louse {Pediculus hu- 

 manus), the rickettsiae occur extracellu- 

 larly in the intestinal lumen forming a 

 layer covering the surface of the epithe- 

 lial lining. Not pathogenic for the louse 

 as is Rickettsia prowazekii and Rickettsia 



