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Associations between gastrointestinal parasites and Nidovirus infection in Western Australian Shingleback lizards (Tiliqua rugosa)

Martinez, Jazmin (2019) Associations between gastrointestinal parasites and Nidovirus infection in Western Australian Shingleback lizards (Tiliqua rugosa). Honours thesis, Murdoch University.

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Australia’s native reptile, the Shingleback lizard (Tiliqua rugosa) is under threat from a variety of causes including a newly discovered Nidovirus(1). This flu has caused an influx of Shinglebacks into rehabilitation centres, demonstrating upper respiratory tract infections (URTI). Therefore, understanding other factors that can impact on the progression of this infection is extremely important for the conservation of the Shingleback lizard population. Such factors include the effects of co-infections, which are composed of two or more pathogens working synergistically or antagonistically against each other. Interactions seen in co-infections tend to cause enhancement of pathogenesis(3). In this study we investigated the association between gastro-intestinal (GI) parasites and the Nidovirus within the Tiliqua rugosa population.

The main aims and hypothesis of this study is to investigate if any association exists between the abundance and diversity of individual parasitic loads, with the presence/absence of the novel Tiliqua rugosa Nidovirus. This will be completed by three objectives, (i) obtaining baseline data on the prevalence of infection, (ii) confirming the proportion of animals infected by coinfections and (iii) examine any possible relationship seen in co-infected Shingleback lizards.

Samples were collected from Shingleback lizards entering Native ARC Rehabilitation Centre and Kanyana Wildlife Rehabilitation Centre. Oral swabs were taken for virology analysis which was completed through polymerase chain reaction (PCR) technology. Faecal samples were collected when naturally produced and were analysed at Murdoch University laboratories, through malachite stained faecal smear(4) and zinc sulphate faecal flotation techniques(5).

There were three main findings from this study. First, prevalence of infection was relatively high, with 73 % of Shinglebacks infected with at least one species of gastro-intestinal parasite and 58.1% of Shinglebacks infected with the T. rugosa Nidovirus. Secondly, co-infections with gastro-intestinal parasites and Nidovirus were common; 48.4% of Shinglebacks carried both parasitic and viral infections, while 26% had only parasitic infections and 9% had only viral infections. Finally, evidence was found corroborating my initial hypothesis that the major clinical signs of viral infection, discharge from the eyes or nose, were enhanced in Shinglebacks which were co-infected with the virus and gastro-intestinal parasites.

This study suggests that the Nidovirus seen in the Tiliqua rugosa population is part of the multi dynamic route of disease seen in reptiles(6), in particular an emerging pattern between co infection with GI parasites suggest synergistic interaction may be a possible factor in the progression of pathogenesis in this viral infection. Therefore, possible immunological enhancement of the virus or/and the parasites may be seen within an individual host. It is not clear yet if this enhancement of infection is caused due to the immunosuppressive characteristics of the virus or due to high parasitic abundance causing immunological stress on the hosts.

This is the first comprehensive study of gastrointestinal parasitism in wild populations of Tiliqua rugosa and the first study of co-infections of gastro-intestinal parasites and Nidovirus. This paper will allow a clearer understanding of natural co-infections, synergistic and/or antagonistic relations between pathogens and the potential cause of pathogenesis.

Item Type: Thesis (Honours)
Murdoch Affiliation(s): School of Veterinary and Life Sciences
Supervisor(s): Ash, Amanda, Lymbery, Alan and O'Dea, Mark
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