Studies on immuno-conglutinin levels in animals infected with T. brucei have shown that immuno-conglutinin appears in rabbits infected with T. brucei ‘M’ variant within 7 days after infection and reaches its peak titre within 30 days. In rabbits infected with the more virulent ‘R’ variant immuno-conglutinin levels rose more rapidly and reached peak titres within 10–14 days after infection.

High levels of immuno-conglutinin are detectable in the sera of rabbits and cats infected with trypanosomes before a significant amount of neutralizing antibody is produced. This difference is most marked in animals infected with the antibody-resistant variant ‘R’ which is more virulent for rabbits.

In animals treated effectively the immuno-conglutinin level dropped to its pre-infection level, while the titre of neutralizing antibody only decreased to a slightly lower level.

No change in the titres of immuno-conglutinin and neutralizing antibody was observed after treatment of animals infected with a drug-resistant strain.

These results are very promising for further field trials and introduce a new approach and method for testing the efficiency of chemotherapy in trypanosomiasis.