An Experimentally Derived Method for Determining the Degree of Infection in Avian Malaria

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  • Department of Pharmacology, Marquette University School of Medicine, Milwaukee, Wisconsin


The 226 positive and 172 negative smears accruing during the daily (in some instances every second day) examination of the peripheral blood of fifty canaries mosquito-infected with Plasmodium cathemerium (Hartman) have been studied with the object of arranging them according to the time required to count a given number of asexual organisms. It was observed that the rate of progression and diminution in these infections occurred in such manner that a system of plus counting could be devised as follows.

  1. Negative—No organisms in 3 minutes
  2. 1+—Less than twenty organisms in 3 minutes
  3. 2+—Twenty organisms in 2 to 3 minutes
  4. 3+—Twenty organisms in 1 to 2 minutes
  5. 4+—Twenty organisms in 30 to 60 seconds
  6. 5+—Twenty organisms in 30 seconds or less
I believe this to be a simple, quick and reliable method of determining the degree of infection upon a comparative basis for all ordinary practical purposes.