Microsatellite genotyping supports the hypothesis that Teladorsagia davtiani and Teladorsagia trifurcata are morphotypes of Teladorsagia circumcincta.

Traditionally nematode species designations have been based on morphological criteria. However, it is has long been recognised that valid species designations are critical for basic biological and epidemiological studies. The ever increasing use of molecular and genetic techniques has allowed traditional classifications to be more closely examined. The sub-family Ostertagiinae is of particular interest as many of the species within this group are of economic importance worldwide, with unresolved classification complicating epidemiology, management, control and genetic studies. This study examines genetic differences between three morphological variants (morphotypes) within the genus Teladorsagia (sub-family: Ostertagiinae) using a multi-locus population genetic analysis approach. Five microsatellites were used to genotype a total of 31 T. davtiani (ScKiTD), 30 T. trifurcata (ScKiTT), and 31 T. circumcincta (ScKiTC). Population genetic analysis detected no genetic differentiation between T. davtiani, T. trifurcata, and T. circumcincta supporting the hypothesis that these are morphotypes of the same species.