The effect of endogenously produced carbon monoxide on the oxygen status of dogs infected with Babesia canis.

Carboxyhaemoglobin fractions were found to be significantly higher (P less than 0.05) in dogs (n = 5) with severe babesiosis than in control subjects (n = 5). The enzymatic conversion of haem to biliverdin by haem oxygenase is the only known source of endogenous carbon monoxide. We propose that the increased production of endogenous carbon monoxide following the haemolysis associated with babesiosis, results in the carboxyhaemoglobinaemia observed in this study. The superimposition of carboxyhaemoglobinaemia on severe anaemia results in further compromise of the oxygen status of dogs with severe babesiosis, and probably plays a role in the pathogenesis of the hypoxic tissue damage associated with this condition.