Outline approach: Identification of wild and insectarium tsetse fly vectors of trypanosomes

The outline approach of geometric morphometry was used to distinguish tsetse species, vectors of the trypanosomes responsible for trypanosomosis in sub-Saharan Africa. Tsetse were captured and collected in Côte d'Ivoire (Tiessou and Sinématiali) and at the CIRDES insectarium (Bobo-Dioulasso, Burkina-Faso). At Tiessou, 61 individuals (40 males and 40 females) of Glossina tachinoides were collected, while at Sinématiali, 60 individuals (39 females and 21 males) of G. palpalis gambiensis were collected. Sampling or collection was carried out using ‘Vavoua’ traps. At the CIRDES insectarium, we collected 80 G. morsitans submorsitans aged 8 to 10 days, including 40 females and 40 males. The condition of the wings of the male and female tsetse flies from CIRDES was satisfactory. They were isolated, scan at the same resolution and then digitised by outline using CLIC 98 software. The three tsetse species were correctly discriminated based on of the size estimated by the perimeter of the contour. The known sexual dimorphism in tsetse flies was confirmed by this approach, with a significant difference (p<0.05). Discriminant analysis enabled three species to be distinguished on the basis of their shape. In addition, this method facilitated the precise reclassification of species in their original group with a high percentage or score (98.31% for females and 97.56% for males). Thus, the use of the contour approach to discriminate between species in the absence of homologous landmarks is efficient.