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Characterization of Trypanosoma evansi type B.
Z K Njiru1, C C Constantine, D K Masiga
1Division of Health, School of Veterinary and Biomedical Sciences, Murdoch University, Murdoch, South Street, WA 6150, Australia. zknjiru@hotmail.com
Summary
This study identifies Trypanosoma evansi type B isolates in Kenyan camels, confirming their continued presence. New PCR tests were developed to differentiate Trypanosoma evansi variants and distinguish them from Trypanosoma brucei brucei.
Area of Science:
- Molecular Biology
- Parasitology
- Genetics
Background:
- Trypanosoma evansi possesses kinetoplast DNA with homogeneous minicircles but lacks maxicircles.
- Two major minicircle sequence variants (type A and type B) of Trypanosoma evansi have been previously described.
Purpose of the Study:
- To sequence the type B minicircle variant of Trypanosoma evansi.
- To develop specific PCR tests for distinguishing Trypanosoma evansi type A from type B.
- To develop and evaluate a maxicircle-based PCR test for differentiating Trypanosoma evansi from Trypanosoma brucei brucei.
Main Methods:
- Sequencing of the type B minicircle variant.
- Design and application of specific PCR assays targeting minicircle and maxicircle DNA.
- Phylogenetic analysis of minicircle sequences.
- Random Amplification of Polymorphic DNA (RAPD) analysis.
- Genotyping of the MORF2 locus.
Main Results:
- Three type B Trypanosoma evansi isolates were detected in camel blood samples from northern Kenya.
- Comparison of type B minicircle sequences showed >96% identity within the group and 50-60% identity to type A.
- Phylogenetic analysis confirmed distinct clusters for type A and type B isolates.
- Three camel isolates with type A minicircles lacked the RoTat 1.2 gene.
- Five isolates were identified as Trypanosoma brucei brucei based on minicircle heterogeneity and maxicircle presence.
Conclusions:
- The study confirms the existence of Trypanosoma evansi type B isolates in Kenya.
- Trypanosoma brucei brucei and Trypanosoma evansi type A lacking the RoTat 1.2 gene were also identified in Kenyan isolates.
- The developed PCR tests are effective for differentiating Trypanosoma species and variants.