Evaluation of the efficacy of combination therapy in T. b .brucei – infected mice using extracts of annona senegalensis and eucalyptus camaldulensis

Abstract

African trypanosomiasis is a parasitic disease affecting both humans and animals. Over 60 million people and 50 – 70 million animals are reported to be exposed to the disease. One of the major problems besetting the chemotherapy of the disease is parasite resistance to the available drugs. An attempt was made in this study to explore the potentials of combination therapy using methanol extracts of Annona senegalensis (leaf) and Eucalyptus camaldulensis (leaf) in different combinations to treat T. b. brucei - infected mice. One animal in the group treated with a combination of crude methanol extracts of A. senegalensis and E. camaldulensis (1:1) had parasites cleared from circulation two weeks into the treatment period and continued to survive for more than three months. The untreated control died 2 weeks post infection while the other groups did not survive beyond 20 days. The weight of the surviving animal increased tremendously over the period and infectivity tests using blood and cerebrospinal fluid from the animal were negative because parasites never appeared in the circulation of sub- inoculated animals. However, histopathological studies of the kidney and liver of the survived animal showed widespread intra renal tubular necrosis with thrombi formation and oedema of the hepatocytes. We conclude that in spite of the apparent long-term effects on the kidney and liver, the methanol extracts of the two plants, acting synergistically, possess appreciable potential for the development of drug combinations to overcome the problem of parasite resistance to conventional drugs.