OSMOTIC FRAGILITY OF ERYTHROCYTES IN CLINICALLY NORMAL DOGS AND DOGS INFECTED WITH PARASITES

The osmotic fragility of the erythrocytes was measured in blood sample s collected from randomly selected healthy and infected dogs at a dogs ' rescue shelter. The dogs were classified into six groups on the basi s of the final diagnoses from clinical, post mortem and laboratory fin dings. The minimum (less than 5 per cent) and maximum (more than 90 pe r cent) haemolysis of the erythrocytes of the clinically normal dogs ( group 1), occurred in 0.60 per cent and 0.30 per cent solutions of sod ium chloride (NaCl). For the non-anaemic hookworm-infected dogs (group 2a) the respective values were 0.8 per cent and 0.4 per cent NaCl, an d for the anaemic hookworm-infected dogs (group 2b) they were 0.85 per cent and 0.5 per cent NaCl, respectively. The erythrocytes from dogs with Babesia canis (group 3), concurrent hookworm and B canis (group 4 ) and EhrEichia canis infections (group 5) had minimum haemolysis in 0 .75 per cent NaCl and maximum haemolysis at between 0.20 per cent and 0.35 per cent NaCl solutions. The derivative fragiligrams for groups 2 a, 2b, 3 and 4 were shifted to the left, whereas the fragiligram for g roup 5 was similar to that for the clinically normal dogs (group 1). T he left shift for the hookworm-infected dogs was due to the increased osmotic fragility of a minor sub-population of the erythrocytes, but f or the dogs infected with B canis major sub-populations of the erythro cytes had an increased osmotic fragility.