He has also identified phenotypic markers that distinguish one from the other. The fish pathogenic strain is now classified as a separate species: Edwardsiella piscicida.

Picture: Electronic micrograph of E. Tarda (now E. piscicida) LTB4 strain after negative staining (Source: Courtesy of Lan et al. 2008)

Edwardsiella tarda is a bacterium that can infect a number of animal species and also humans. Edwardsiellosis is one of the most serious systemic bacterial diseases in fish, resulting in substantial losses in the fish farming industry all over the world.

Takele Abayneh Tefera has developed effective molecular tools for the identification and characterization of different strains of Edwardsiella. He developed a new TaqMan real-time and conventional PCR analysis for this purpose and then evaluated it in relation to the Loop Mediated Isothermal Amplification (LAMP) analysis. For the first time, he also used the Multi-locus Sequence Analysis (MLSA) for the typing and characterization of E. tarda, isolated from different sources. This is a useful tool for detecting sources of infection and for understanding the epidemiological relationship between isolates from the environment, fish, livestock and humans.

Prominent external pathological lesions observed in zebrafish callenged with Edwardsiella piscicida strains (Photo: T Abayneh)

The MLSA analysis showed that there exist geographic and host-specific genotypes of the species E. tarda. Bacterial strains from fish were found to be only distantly related to E. tarda type strain and other strains from humans. Furthermore, genetic and phenotypic analyses also confirmed a genetic divergence between these strains of bacteria.

The findings of this study indicate that the fish pathogenic strain has been wrongly classified as E. tarda. Phenotypic characterization by means of a number of biochemical tests and pathogenity studies on zebra fish identified phenotypic markers which also differentiate fish pathogenic strains from the reference bacterium.

Based on genetic and phenotypic differences, Tefera and his colleagues have proposed that fish pathogenic Edwardsiella strains previously classified as Edwardsiella tarda should now be classified as a new species: Edwardsiella piscicida. The new species has now been approved and incorporated into prokaryotic nomenclature.

Tefera's work also led to the introduction of a new Multi-locus Variable Number Tandem Repeat Analysis (MLVA) for the further typing of different isolates of the new species of bacteria Edwardsiella piscicida. Employing this method proved to be more sensitive than the MLSA-analysis when it came to investigating outbreaks of E. piscicida.

Takele Abayneh Tefera defended his doctoral research on 26th November 2013 at the Norwegian School of Veterinary Science with a thesis entitled: Fish pathogenic Edwardsiella tarda: Evaluation of molecular identification methods and characterization of a novel species.”

Main supervisor: Henning Sørum

Biography:
Takele Abayneh Tefera was born in Arsi, Ethiopia in 1970. He qualified as a veterinary surgeon at the Faculty of Veterinary Medicine, Addis Ababa University (AAU), Debre-zeit, Ethiopia in 1995 and took a master degree in Aquatic Medicine at the Norwegian School of Veterinary Science in 2007. He has worked as a District Veterinary Surgeon in Tigray, Ethiopia, and as a teacher and researcher at the School of Veterinary Medicine, Addis Ababa University (AAU), Debre-zeit, Ethiopia. He has also lectured in fish pathology at the Universities of Hawassa and Haromaya, Ethiopia.

Takele Abayneh TeferaTefera was formerly Head of School and Vice Dean at the Faculty of Veterinary Medicine, AAU, Ethiopia and a member of the National Technical Committee for standardization of Hides and Skin Quality in Ethiopia (2004-2005) and of the Regional Curriculum Committee for harmonizing the curricula of Southern and Eastern Africa Veterinary Schools (2004-2005).

Tefera has received support for his doctoral research from the Norwegian Ministry of Foreign Affairs under the quota scheme for research fellows. Prior to this, he received support from several international funds in England, Africa, Ethiopia and Sweden. During his PhD research period, he undertook a research residency at the Faculty of Veterinary Science in Vienna.

Contact information:
Takele Abayneh Tefera:
Mobile: +47 462 46 839
Email: TakeleAybaneh.Tefera@nvh.no or takeletefera99@gmail.com

Magnhild Jenssen, Information Officer at NVH
Tel.: +47 77 66 54 01
Mobile: +47 957 94 830
Email: magnhild.jenssen@nvh.no