The quantitation of trypanosoma congolense in calves. III. A quantitative comparison of trypanosomes in jugular vein and microvasculature and tests of dispersing agents.

Hemocytometer and cytofluorometric methods were used to count trypanosomes in the blood of neonatal and six-month-old calves infected with T. congolense. The correlation between these methods was highest in the six-month-old calves because their parasitemia was greater and the accuracy of cytofluorometric counting is reduced below 1,000 trypanosomes per microliter of blood. Fine needle aspiration biopsies showed many trypanosomes marginated in cerebral cortical capillaries, but few in muscle or liver. Quantitatively, the cerebral capillaries in the infected six-month-old calves were significantly wider than their controls with fewer endothelial nuclei suggesting capillary dilatation. There were fewer trypanosomes and no significant changes in capillary width in the neonatal calves. Several drugs were tried for activity in dispersing marginated trypanosomes into axial flow. Berenil and dexamethasone had a significant effect on trypanosome counts in blood and tissue whereas, epinephrine caused a fleeting increase in parasitemia. Hetastarch, dextran and cyclophosphamide had no specific effect. Fine needle aspiration bipsies of brain, thirty minutes after Berenil injection showed that the capillaries were cleared of trypanosomes.