FAMILY RICKETTSIACEAE 



1085 



The organisms are colored purplish 

 with the Giemsa stain, the two indi- 

 viduals of a pair being connected by a 

 zone of faintly blue stained material. 

 They are colored blue with Castaiieda 

 stain (Jour. Inf. Dis., 47, 1930, 416) and 

 bright red against a blue background with 

 Machiavello stain (Rev. Chilena de Hig. 

 y Med. Prev., 1, 1937, 101). Gram- 

 negative . 



Cultivation : In plasma tissue cultures 

 of mammalian cells, in the louse intestine, 

 in modified Maitland media with and 

 without agar, on chorioallantoic mem- 

 brane and yolk sac of chick embryo, the 

 latter being currently the medium of 

 choice. 



Optimum temperature 32°C in plasma 

 tissue culture, 35°C in chick embryo 

 cells. 



Immunology : Immunity prolonged but 

 may not be complete in man. Indis- 

 tinguishable from endemic (murine) 

 typhus in cross immunity tests in guinea 

 pigs, but distinguishable from Rocky 

 Mountain spotted fever and other rickett- 

 sial diseases in such tests. Neutraliz- 

 ing antibodies are found in the serum of 

 recovered guinea pigs and convalescent 

 humans up to 2 to 3 weeks after defer- 

 vescence. Killed vaccines produced 

 from infected lice and from infected yolk 

 sacs afford a high degree of protection 

 against the disease. Hyperimmune anti- 

 sera for therapeutic use have been pro- 

 duced in rabbits by injection with 

 infected yolk sac suspensions and in 

 horses and donkeys with infected mouse 

 lung suspensions. 



Serology : Strains from various parts 

 of the world are closely related as de- 

 termined by complement fixation; are 



distinguishable from other rickettsiae by 

 agglutination, complement fixation and 

 precipitin tests; have a common anti- 

 genic factor (alkali stable polysac- 

 charide) with Proteus 0X19; and have 

 a soluble antigen in yolk culture. 



Lethal effect : Heavily infected j^olk 

 sac cultures injected intravenously or 

 intraperitoneally are fatal to white mice 

 in a few hours. 



Resistance to chemical and physical 

 agents : Readily inactivated by heat and 

 chemical agents. A temperature of 50°C 

 kills the organism in 15 to 30 minutes, and 

 0.5 per cent phenol and 0.1 per cent 

 formalin kill the organism. 



Pathogenicity : Pathogenic for man, 

 apes, monkej's, guinea pigs, cotton rats, 

 gerbilles, the louse (Pediculus humanus). 

 Inapparent infections occur in white 

 mice, white rats and rabbits. A charac- 

 teristic febrile reaction with no mortality 

 and without testicular swelling occurs in 

 the guinea pig. Passage in guinea pigs 

 is accomplished by transfer of blood or 

 brain from infected animals. Causes a 

 febrile disease with e.xanthema and high 

 mortality in man. 



Source : Seen in the blood of tj'phus 

 patients and in smears of epithelial cells 

 of the intestinal tract of lice fed on 

 typhus patients. 



Habitat : The body louse (Pediculus 

 humanus var. corporis), head louse 

 {Pediculus humanus var. capitis) and 

 Pedicinus longiceps. The etiological 

 agent of epidemic typhus (European 

 typhus, classical typhus, typhus exan- 

 thematicus). 



2. *Rickettsia typhi (Wolbach and 

 Todd) Philip. {Dermacentroxenus 



* Some may regard the binomial Rickettsia typhi as invalid because of its previous 

 use by do Amaral and Monteiro for the organism causing eastern Rocky Mountain 

 spotted fever. However, because the binomial Dermacentroxenus typhi Wolbach 

 and Todd clearly has priority and because the binomial proposed by do Amaral and 

 Monteiro has never come into general use, Rickettsia typhi Philip has been accepted 

 for use in the Manual. If Philip's binomial had been rejected, then it would have 

 been necessary to accept Rickettsia nianchuriae Kodama et al. as this appears to have 

 priority over the more generally used Rickettsia mooseri Monteiro. — Editors. 



