| Popis: |
Tropical theileriosis caused by the tick transmittedprotozoa parasite Theileria annulatais an economically important disease of cattle in many developing countries.The genetic and antigenic diversity within and between field parasitepopulations is an important epidemiological parameter that needs to beinvestigated and quantified for the development and deployment of novel controlstrategies. The effective role of recombination for generating genetic andantigenic diversity in natural parasite populations has been proposed. Theserecombined and genetically diverse parasite populations can give rise to newrisk factors, such as drug resistance, reduced vaccine protection, occurrenceof highly pathogenic isolates. Previous data indicated that genetic andantigenic diversity in T. annulatapopulations vary not only between different geographical regions but alsowithin a single host and this polymorphism is presumed to be due to the highlevel of genetic exchange occurring in parasite populations. The occurrence ofa sexual cycle has been confirmed in a closely related orthologue parasite, T. parva, however in T. annulata, an evidence for theoccurrence of mating has came from population genetic studies and noexperimental data is available yet regarding to the role of recombination aftertransmission of T. annulata to ticks.The completed genome sequence of T.annulata provided an opportunity to develop genetic markers for populationgenetic studies and also enabled the identification of new antigens. In thisstudy, a panel of 23 micro and minisatellite markers were used to identify,characterise and analyse two different clonal and nonclonal T.annulata isolates after recombination.We have measured the frequency of recombination in T. annulata isolates for each of four chromosomes. We have alsoinvestigated effect of recombination on antigenic diversity. The analysis usingpolymorphic markers demonstrated the existence of genetic exchange between T. annulata isolates and this evidentrecombination was experimentally shown for the first time. The highest level ofrecombination was found to be located on the forth chromosome. However, therewas no correlation between recombination rate and chromosomal length. It shouldbe pointed out that none of the recombined populations detected in the presentstudy showed a detectable level of antigenic diversity. This study wasfinancially supported by TUBITAK-111O718.KeyWords: PopulationGenetics, Sexual Recombination, Theileriaannulata |
