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Population sub-structuring among Trypanosoma evansi stocks

Abstract

To investigate the population genetic structure of Trypanosoma evansi from domesticated animals, we have analysed 112 stocks from camels, buffaloes, cattle and horses using the tandemly repeated coding sequence (MORF2) and minisatellite markers 292 and cysteine-rich acidic integral membrane protein (CRAM). We recorded a total of six alleles at the MORF2 locus, seven at 292 and 12 at the CRAM loci. Nei’s genetic distance showed reduced allelic diversity between buffaloes and cattle stocks (1.2) as compared to the diversity between camels and buffaloes (3.75) and camels and cattle stock (1.69). The mean index of association (I A = 0.92) significantly deviated from zero, and the average number of multilocus genotypes (G/N ratio) was 0.21. Twenty-four multilocus genotypes were defined from the combination of alleles at the three loci. The Kenyan sub-populations showed F st = 0.28 and analysis of molecular variance showed significant divergence (22.7%) between the Laikipia, Kulal and Galana regions. The regional and host distribution of multi-locus genotypes significant population differentiation and high Nei’s genetic distances suggest existence of genetic sub-structuring within T. evansi stocks while the few multi-locus genotypes and deviation of association index from zero indicate the lack of recombination. In conclusion, this study reveals that some genetic sub-structuring does occur within T. evansi, which has a clonal population structure.

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Acknowledgements

We acknowledge the financial support from the International Foundation for Science (IFS grant number B3372 to ZK Njiru) for the initial collection and analysis of Kenyan samples. Genetic analysis funds were provided by Murdoch University and Western Australia Biomedical Research Institute (WABRI). We thank the Director of TRC-KARI Kenya for the provision of samples from Kenya, Sudan and Colombia, Prof. RCA Thompson for revising the manuscript and Dr. Simon Reid for providing Asian samples from Dr. Alan Dargantes from Central Mindanao University, Philippines, The Director of Balitvet, Dr. Abdul Adgid and Dr Sri Muharsini and Dr. Amir Husein from the Dept. of Parasitology, Balitvet. The reported work complies with the current laws of Kenya and Australia where the work was done.

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Correspondence to ZK Njiru.

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Njiru, Z., Constantine, C. Population sub-structuring among Trypanosoma evansi stocks. Parasitol Res 101, 1215–1224 (2007). https://doi.org/10.1007/s00436-007-0603-y

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Keywords

  • Polymerase Chain Reaction Reaction
  • Multilocus Genotype
  • Mixed Genotype
  • Minisatellite Locus
  • Polymerase Chain Reaction Band