Observations on Experimental Q Fever

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Abstract
Coxiella burnetii does not appear to be transmissible by Aedes aegypti, either mechanically by interrupted, but undelayed feedings, between donor and susceptible guinea pigs, or when refeeding was delayed for as long as 10 days to a mo. At temps. of 68-75[degree] the rickettsiae did not persist in the bodies of the insects for any considerable periods, even when the gut wall of freshly fed mosquitoes was punctured. In titration expts. with the tissues and feces of Dermacentor andersoni, it was found that minute dosages were infectious, the respective max. titers being 2 X 10-12 (1:500 billion) and 10-10, Saline suspensions of tick tissue, filtered through Berkefeld N and W candles, still titered to 10-8, the highest dilution tried. Feces from infected D. andersoni are very rich in rickettsiae, and the latter persisted in an infectious state in feces stored for as long as 586 days. Feces stored at room temp. and 70% humidity for nearly 6 yrs., still showed recognizable organisms on microscopic examination, antigenicity in serological tests, and immunized injected animals, but no strains were recovered in animals or embryonated hens'' eggs. Infection from tick feces, and from infected guinea pig spleen pulp and spleen emulsion penetrated the unbroken skin, as well as the abraded skin of test animals. Animals also became infected when powdered feces were dusted in the nostrils, eyes, and mouth in separate tests. The rickettsiae in adults of D. andersoni infected in the previous nymphal stage, and stored after molting for 65 and 127 days in a cold room at about 35 F, was highly virulent when single ticks were injected immediately on removal from chilling. Most of the test animals died after febrile courses and short incubation periods. Infection was recovered from houseflies, Musca domestica, caught at large in an animal room in which Q-fever-infected animals were kept. However, attempts failed to transfer infection from infected to normal guinea pigs kept separately, but in a common cage in which houseflies had free access to both. Houseflies allowed to feed on moistened, infectious tick feces, and on infected spleen pulp, were found to be contaminated with C. burnetii when injected into test animals.

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