Trypanosoma congolense: the in vitro akinetoplastic induction sensitivity assay

The animal trypanosomiases and their chemotherapy: a review

Pathogenic animal trypanosomes affecting livestock have represented a major constraint to agricultural development in Africa for centuries, and their negative economic impact is increasing in South America and Asia. Chemotherapy and chemoprophylaxis represent the main means of control. However, research into new trypanocides has remained inadequate for decades, leading to a situation where the few compounds available are losing efficacy due to the emergence of drug-resistant parasites. In this review, we provide a comprehensive overview of the current options available for the treatment and prophylaxis of the animal trypanosomiases, with a special focus on the problem of resistance. The key issues surrounding the main economically important animal trypanosome species and the diseases they cause are also presented. As new investment becomes available to develop improved tools to control the animal trypanosomiases, we stress that efforts should be directed towards a better understanding of the biology of the relevant parasite species and strains, to identify new drug targets and interrogate resistance mechanisms.

In vitro assays to determine drug sensitivities of African trypanosomes: a review

In vitro test methods have been developed both for determining the sensitivity of isolates of pathogenic African trypanosomes and for evaluating new compounds for antitrypanosomal activity. The principles of the assays and their main advantages or drawbacks are presented and discussed. In vitro assays which do not require trypanosomes pre-adapted to culture conditions are the Drug Incubation Infectivity Test (DIIT) and the [3H]Hypoxanthine Incorporation Assay. Chemosensitivity tests which do require continuous growth of trypanosomes in vitro include photometric, fluorescence, growth inhibition, long-term viability and metacyclic incubation assays. Evidence is presented to use metacyclic or bloodstream forms in such assays but to avoid procyclic trypanosomes. The drug sensitivity of a homogeneous trypanosome population can be quantified by using photometric, fluorescence or growth inhibition assays lasting 1-3 days. Small numbers of resistant organisms hidden in a sensitive population can be detected employing long-term viability assays (7-10 days). Final selection of the assay to be employed will depend on the parameter to be investigated, and the equipment available.