FAMILY EICKETTSIACEAE 



1093 



Small bacterium-like, pleomorphic or- 

 ganisms varying in size from coccoid 

 forms to well marked rods. Occur as 

 cytoplasmic micro-colonies with diffuse 

 or compact distribution of the organisms 

 through the cytoplasm. Also seen ex- 

 tracellularly, where they appear as small 

 lanceolate rods, diplobacilli and occa- 

 sionally segmented filamentous forms. 

 Chains of 3 to 6 elements often seen. 

 Quite uniform in size and morphology in 

 infected yolk sacs and in mouse spleen 

 with exceedingly minute forms in heavily 

 infected material. Small lanceolate rods, 

 0.25 by 0.4 to 0.5 micron, bipolar forms 

 0.25 by 1.0 micron, diplobacilli 0.25 by 

 1.5 microns. Non-motile. 



With Giemsa's stain they appear red- 

 dish-purple, with Machiavello's stain 

 bright red against a blue background. 

 Gram-negative. 



Cultivation : May be cultivated in 

 plasma tissue cultures, in modified Mait- 

 land media and in the yolk sac of chick 

 embryos. 



Immunology: There is complete cross 

 immunity between Australian and 

 American strains of Q fever in guinea 

 pigs. Strains from other parts of the 

 world also ci'oss immunize. 



Serology : American and Australian 

 strains are identical by agglutination and 

 agglutinin absorption. Strains from 

 various countries are serologically related 

 as shown by complement fixation. Q 

 fever is distinguishable from other 

 rickettsial diseases by complement fixa- 

 tion tests. No common antigenic factor 

 with any Proteus strain has been demon- 

 strated. 



Filterability : The infectious agent of 

 Q fever readily passes Berkefeld N filters 

 which are impermeable to ordinary bac- 

 teria and W filters which are impermeable 

 to typhus and spotted fever rickettsiae. 



Resistance to chemical and physical 

 agents: Comparatively resistant to heat, 

 drying and chemical agents. Survives 

 at least 109 days in cell -free media with- 



out loss of titer, resistant to 60°C for 1 

 hour and to 0.5 per cent formalin and 1 

 per cent phenol when tested in fertile 

 eggs. 



Pathogenicity : Pathogenic for man, 

 guinea pig and the white mouse. The 

 monkey, dog, white rat and rabbit are 

 mildly susceptible. Certain bush ani- 

 mals in Australia, particularly the bandi- 

 coot, are susceptible and these animals 

 have been found naturally infected. 

 Other rodents and marsupials are mildly 

 susceptible. Calves have been experi- 

 mentally infected and cows have been 

 found recovered from naturally acquired 

 infections. 



A febrile reaction occurs in guinea pigs 

 but mortality is low except with heavily 

 infected yolk sac which causes a high 

 mortality. On subcutaneous or intra- 

 dermal inoculation a marked inflamma- 

 tory thickening of the skin occurs at the 

 site of inoculation. On autopsy the 

 spleen is enlarged from 2 to 12 times by 

 weight and is engorged with blood. 

 Transfer in guinea pigs and mice is ac- 

 complished by transfer of infected liver 

 and spleen. A febrile reaction often ac- 

 companied by pneumonitis occurs in 

 man, but mortality is low. 



Source : First seen in smears from mice 

 inoculated intraperitoneally with infec- 

 tious material by Burnet and Freeman 

 (Med. Jour. Australia, 2, 1937 (2), 281). 



Habitat : The wood tick {Dermacentor 

 andersoni) and the ticks, Dermacentor 

 occidentalis, Amblyomma americanum, 

 Haemaphysalis leporis-palustris , Ixodes 

 dentatus and Haemaphysalis humerosa. 

 Several other species of ticks have been 

 shown to transmit experimentally the 

 virus of Q fever. It has been found to 

 survive in the ova of the female ticks 

 (Dermacentor andersoni and Haemaphy- 

 salis humerosa) . The bandicoot {Isodon 

 macrurus) is probably the natural reser- 

 voir of the disease in Australia. The 

 etiological agent of Q (Queensland) fever 



