Discovery of a novel dsRNA virus in Trichomonas gallinae

Ardan, Dalal (2022) Discovery of a novel dsRNA virus in Trichomonas gallinae. Doctoral thesis, University of East Anglia.

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Trichomonas gallinae is a single-celled protozoan parasite and causative agent of avian trichomonosis, canker or frounce. While a majority of infected birds are asymptomatic, it can be deadly and is the cause of huge die-offs and population declines representing an existential threat to some avian species. Thus understanding the difference between virulent and avirulent strains of this parasite is of considerable interest and importance for its management. Viruses that infect protozoan parasites can modulate virulence, and in the related parasite Trichomonas vaginalis, Trichomonas viruses are known to affect the pathological outcomes of infection. I set out to determine whether the variation in virulence observed from T.gallinae subtypes might be similarly correlated with the presence of viruses. Specifically I undertook to screen an archive of genetically diverse T. gallinae isolates from the UK which was hosted from the Tyler laboratory for the presence of viruses. It appeared based on preliminary, standard analyses that the ostensibly avirulent C10 lineage might be host to an active viral infection. I then went on to use Transmission Electron Microscopy and negative staining of supernatants to validate the presence of virus in the isolates identified in the screen. I then evaluated the phenotypic differences between infected and closely related uninfected isolates using Scanning Electron Microscopy and Transmission Electron Microscopy and finally determined the genomic sequence of the novel virus identified from the transcriptome of this isolate. Infected cells were smaller and grew less well than uninfected controls consistent with a fitness deficit from infection. They had a peripheral punctate distribution of virus that was confirmed by Electron Microscopy where the virus could be visualized in the cell periphery and where the infections appeared to affect cellular morphology, topology and ultrastructure, particularly of the Golgi apparatus. Finally, the identity of the virus was confirmed as a member of the Totiviridae a dsRNA virus with a close affinity to the TVV1 family of viruses from T. vaginalis. The sequence providing support for the idea that contemporary T. vaginalis may not have arisen monophyletically but could contain components from more than one T. gallinae. In summary, I present evidence for a virus infection in an avirulent T gallinae isolate which has considerable implication for the understanding and management of this important avian disease and more broadly for the evolution of the T. gallinae/T.vaginalis group of parasites.

Item Type: Thesis (Doctoral)
Faculty \ School: Faculty of Science > School of Biological Sciences
Depositing User: Chris White
Date Deposited: 23 Aug 2023 07:02
Last Modified: 23 Aug 2023 07:02

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