No more cold-chain failures, using dehydrated reagents in ELISA antibody-detection against animal trypanosomes of African origin

Animal trypanosomoses due to trypanosomes of African origin (ATAO), mainly caused by Trypanosoma congolense type Savannah (TCS), T. brucei brucei (TBB), T. vivax (TV), and T. evansi, are widespread diseases that affect domestic and wild mammals and have a huge economic impact. ATAO clinical suspicions are usually confirmed by parasitological and molecular methods, while sero-epidemiological surveys are generally carried out using the OIE-recommended ELISA method based on whole cell lysate soluble antigens (WCLSA) from purified trypanosomes; this reagent is usually stored frozen. With a view to expanding this ELISA test, we assessed, standardized, and validated the use of dehydrated rather than frozen WCLSA and serum samples. For the three ELISA assays (TV, TCS & TBB), a repeatability study revealed no significant difference between repeats. The results obtained using frozen rather than freeze-dried antigen and serum strongly correlated for Pearson’s correlation values (>0.93) and Lin’s measure (“very good” to “excellent”). Reproducibility was robust, with Pearson’s correlation values >0.97 for inter technician effects, and 0.87 (TV) to 0.97 (TBB & TCS) for inter-laboratory tests; their combination was “very satisfactory” to “excellent” according to Lin’s measure and there was no impact on qualitative test results. Dehydrated reagents offer the advantage of shipment at room temperature, allowing the secured provision of reagents to regional laboratories. Together with a compendium of standard diagnostic protocols for ATAO (/OIE), dehydrated reagents will enable the serological diagnosis of ATAO at regional level in endemic countries. This very welcome improvement in the context of the Progressive Control Pathway for trypanosomes, recently launched by African countries, will possibly be extended to Latin America in the near future.