Lactic Acid Content of Blood of Trypanosome Infected Rats.

Experimental trypanosome infection in rats presents one of the simplest pictures of a protozoan blood infection. After an incubation period of about a week (depending upon the dose injected) there is a period of uncertainty when host and parasite become alternately dominant. Then the trypanosomes become definitely established in the peripheral circulation and increase in numbers progressively until death. Parallel with the increase in the number of trypanosomes there is a progressive decrease in the number of red cells. The significant features of the infection are: (1) An increase of the trypanosomes to a constant number which seems to be characteristic of the species; (2) Anemia, which is variable, ranging between 30% and 50% of the original cell count; (3) Sudden death with symptoms of dyspnea within 10 to 36 hours after the trypanosomes have reached the maximum concentration. There are no toxic symptoms and the injection of large numbers of trypanosomes or a large amount of serum taken from an animal shortly before death do not produce any symptoms of intoxication.

This picture raised 2 problems: (1) The reason for the cessation of the multiplication of trypanosomes; was it due to an inhibiting substance or to exhaustion of the substrate? (2) The actual cause of death. If the cause of death could be ascertained in this simple type of infection, the findings might throw light on the pathology of the disease in animals in which the course of infection is more complex and hence the cause of death more difficult to establish.

To elucidate these problems we decided to study the changes in the blood chemistry during the course of the infection. Kurt Schern 1 has shown that glucose has a protective effect on trypanosomes and that there was a reduction in the fermentable substances in the liver of trypanosome infected animals.