The focus of Stage 4 is the elimination of AAT transmission and the establishment of AAT-free areas. In Stage 4 the maintenance of some of the control measures deployed in Stage 3 is still required. In Stage 5 all control measures are lifted, and the free-status should be maintained in their absence.

A monitoring system including sentinel herds to assess AAT incidence is required, to ensure the absence of circulation of parasites and the absence of tsetse (when tsetse elimination was targeted in Stage 3). Serological tests for the detection of antibodies against trypanosomes [1] or tsetse saliva antigens [2] could be useful to demonstrate the absence of parasite circulation or the absence of tsetse.

1. OIE (2013) Trypanosomosis (Tsetse-transmitted). In Manual of Diagnostic Tests and Vaccines for Terrestrial Animals, World Organisation for Animal Health, OIE (2013)
2. Somda, M.B., et al., Identification of a Tsal152-75 salivary synthetic peptide to monitor cattle exposure to tsetse flies. Parasit. Vectors, 9 (2016), p. 149