936 RICKETTSIA 



Pathogenicity of R. nipponica tor Animals. — The viruses of tsutsugamushi fever, mite 

 fever, and scrub typhus appear to be closely related. They are not as a rule very infective 

 for guinea-pigs, though occasional strains may prove highly fatal, giving rise to ascites and 

 splenic enlargement after intraperitoneal inoculation. In white rats they produce an 

 inapparent infection. One of their most striking properties is their abiUty to give rise 

 to an acute reaction, characterized by circum-corneal injection, iritis, turbidity of the 

 aqueous humour, pannus, and the presence of rickettsial bodies in Descemet's membrane, 

 on inoculation into the anterior chamber of the eye of rabbits (Nagayo et al. 1931, Lewth- 

 waite and Savoor 1934, 1936). The serum of the animals often agglutinates Proteus OX K 

 10 days or so after inoculation. The viruses of this group are further distinguished by 

 the ulceration and bubo formation which they cause on intracutaneous injection of monkeys. 

 The virus of fievre boutonneusc appears to be the only other known Rickettsia that can 

 produce a marked local lesion in monkeys. After intraperitoneal inoculation with infective 

 material from the rabbit's eye, mice may die in a fortnight or so ; post mortem, there 

 is a sticky fluid in the peritoneum containing large numbers of rickettsia3. 



Pathogenicity of R. burneti for Animals. — This organism may cause a febrile reaction 

 in vionknjs inoculated intracutaneously or subcutaneously. No local lesion occurs in 

 the skin similar to that seen after intracutaneous inoculation with R. nipponica (Burnet 

 and Freeman 1937). Inoculated intraperitoneaUy into guinea-pigs, it gives rise, after 

 an incubation period of 2 to 18 days — depending on the dose — to a febrile non-fatal disease 

 of 4 to 6 days' duration. If the animal is killed during the height of the infection, the 

 spleen is found to be enlarged. The scrotal sac is seldom affected. Strains of American 

 origin are more virulent than those of Australian origin, frequently producing a fibrinous 

 exudate aroimd the spleen in which large numljers of rickettsise can be demonstrated 

 microscopically. The liver of guinea-pigs inoculated with either strain can be shown 

 by inoculation to lie highly infective (Derrick 1937, Dyer 1939, Burnet and Freeman 1939). 



Mice, rats and rabbits are all susceptible, but suffer from an inapparent infection. 

 In mice killed 7 to 10 days after a heavy intraperitoneal inoculation, the liver is enlarged 

 and pale, and the spleen is often greatly enlarged, tense, and of a uniform deep red colour. 

 Rickettsise are present in smears from both organs (Burnet and Freeman 1937, 1938). 

 Mice inoculated intranasally may develop pneumonitis, characterized by irregularly dis- 

 tributed nodules of consolidation, in which large numbers of rickettsise can be demonstrated 

 (Findlay 1942). 



Pathogenicity of R. quintana for Animals. — ^We have little exact knowledge of the 

 behaviour of the virus of trench fever in laboratory animals. Da Rocha-Lima (19206) 

 states that a small proportion of guinea-pigs may develop a low undulating fever after 

 inoculation with material containing this organism, but that infection cannot be trans- 

 mitted by passage to fresh animals. 



Notes on a lev; miscellaneous organisms. 



R. rocha-limse. — This organism was described by Weigl in 1921. It is appar- 

 ently a parasite of the body louse. It is distinguished from R. pediculi by morpho- 

 logical peculiarities and its variability (see also p. 1852). Introduced into a stock 

 of lice, it may spread with extraordinary rapidity (Weigl 1939). There is reason 

 to believe that it may give rise to a bactersemia in man. It has been regarded 

 })y some authors as the cause of trachoma, but the evidence in favour of this 

 is unconvincing (see Chapter 85). What relation R. rocha-limce has to similar 

 rickettsiae found in lice, such as R. weigli and others, is still doubtful (see Herzig 

 1939). 



R. conjunctivse. — Coles (1931, 1935, 1936) in South Africa described a rickettsia- 

 like organism in the conjunctival epithelium of sheep, goats, and cattle. Some- 

 times its presence was accompanied by inflammation. A similar organism was 



