Abstract
The study on the Giardia canis (Hegner, 1922) of dog revealed the fact that there were at least 2 diverse strains, as has been found with Giardia in man, 1 These strains differed one from another with respect to the dimensions and shapes of their cysts and trophozoites. Differences were also noted in the ease of obtaining trophozoites and of producing excystation in vitro. Differences in size and shape of cysts remained constant as long as the diets were the same.
When infected animals (young puppies) were kept on a diet rich in carbohydrates, the mean dimensions of cysts were 11.47μ ± .03μ in one and 10.37μ ± .03μ in the other. However, when a carbohydrate diet was replaced by a high protein diet, the respective mean dimensions were found to be 12.05μ ± .03μ and 11.38μ ± .03μ. These changes were transitory in nature and were easily reversed by corresponding changes in the diet. In view of the fact that diets affected at the same time change in the bacterial flora from an acid-uric to a putrefactive type and vice versa, the question arises as to whether the variations in Giardia were due to the changes in diet directly or indirectly as result of changes in the bacterial flora.
With respect to the power to invade the tissues, the strains exhibited no differences—in no instance were there any trophozoites present within the tissues.
Incidentally, in the materials examined during the course of the experiments, there was observed a positive correlation between the lengths and breadths of cysts of the 2 strains, as has been found in the cysts of Giardia lamblia, 2 and paralleled the findings of Hegner in regard to Giardia agilis 3 and Trypanosoma diemyctyli. 4
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