Laboratory diagnosis of psittacosis.

Date:
1937
Catalogue details

Licence: Public Domain Mark

Credit: Laboratory diagnosis of psittacosis. Source: Wellcome Collection.

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    the same manner as described for the organs of birds. Negative results, however, are almost the rule with human material obtained post mortem, probably because death usually occurs late in the course of the infection in man and the virus has largely disappeared. Blood obtained during the first four days of illness may contain the virus; it should be inoculated (defibrinated) in 0-5 to 1-0 ml. quantity intraperitoneally into mice. Later in the disease than the fourth day, blood practically always gives negative results on such inoculation. Microscopical examina- tion of blood films is extremely unlikely to give any useful information at any stage of the illness, though virus particles have been seen in them (Coles). Blood obtained from convalescent patients may be used to give a _ retrospective diagnosis by complement-fixation tests with the serum and an emulsion rich in virus (mouse-spleen). Such tests, however, laboratories and, for the present, blood to be tested in this way should be sent to Professor Bedson at the London Hospital, Whitechapel, E.1. Pleural fluid may be inoculated in similar amounts into mice with more hope of positive results. The deposit from larger quantities (when available), obtained by prolonged high speed centrifugation, can also be recommended. Sputum, particularly in the early stages of the disease, is the most likely material to give positive results. Unfortunately it is apt to be scanty or unobtainable but every effort should be made to get a specimen (not saliva), however small in amount. After making cultures on blood agar plates the sputum should be emulsified in about ten times its volume of broth by thorough shaking with glass beads in a stoppered bottle. The emulsion is then injected intraperitoneally into at least three mice in quantities of 0-25 to 0-5 ml. in the hope that at least one of the mice may escape the almost inevitable concomitant infection with pneumococci and survive long enough for the develop- ment of virus. Filtrates of the emulsion should be made, in addition, in the manner described for tissue emulsions; both the sand-and-pulp coarse filtrate and the filtrate obtained by passage through a Berkefeld V filter or gradocol membrane should be inoculated intraperitoneally in 1 to 2 ml. quantity into several mice. Such inoculation may be repeated on three successive days into the same mice and this procedure gives the best chance of detecting the often minute amounts of psittacosis virus. The mice are kept under observation, as described above; at least one further passage is advisable, using the spleen of one or more of the mice at the end of ten days and again at the end of a month for inoculation of fresh mice;