Date of Award
9-9-2024
Degree Type
Thesis
Degree Name
Master of Philosophy (MPHIL)
Discipline
Environmental Science
First Advisor
Prof. FONG Jonathan
Abstract
Blood parasites and ranaviruses are pathogens that impact freshwater turtles worldwide. Given that native turtle species in Hong Kong are already at a high risk of extinction, their survival becomes even more threatened in the event of a disease outbreak. However, prevalence of these pathogens among the native population in Hong Kong remains unstudied.
In this study, I aim to (1) obtain baseline prevalence data of blood parasites and ranaviruses in Hong Kong freshwater turtles, (2) compare different methods for detecting blood parasites and ranaviruses, (3) evaluate the applicability of using blood parasites as a wildlife forensic tool, assess and provide conservation insights regarding ranaviruses in Hong Kong freshwater turtle populations.
In Chapter 1, I present a literature review on blood parasites and ranaviruses, including their taxonomy, infections in reptiles and methods of detection. I also introduce the native turtle species in Hong Kong, as well as a loophole in the illegal trade of endangered turtles of claiming wild turtles to be captive bred.
In Chapter 2, I obtain prevalence data of blood parasites in Hong Kong turtles, and compare the methods (microscopy and real-time PCR) used in detecting blood parasite. For prevalence data, I collected samples from 185 individuals of 20 turtle species from the wild and captivity. I detected blood parasites in individuals of wild-sampled Big-headed Turtle (Platysternon megacephalum). In captive-sourced turtles, blood parasites were also found in confiscated P. megacephalum and an Indochinese Box Turtle (Cuora galbinifrons) that was likely to be wild caught. No blood parasites were found among captive-bred turtles. For method comparison, I find real-time PCR has a higher sensitivity than microscopy. When feasible, I recommend that a combination of both methods to minimise the chance of under-detection.
In Chapter 3, I obtain prevalence data of ranaviruses in wild-sampled and captive turtles of Hong Kong, and compare the three sampling methods (collecting blood, cloacal swabs and oral swabs). For prevalence data, a total of 222 individuals of 19 turtle species were screened for ranaviruses. Ranaviruses were detected in the wild-sampled turtles, including the endangered P. megacephalum and invasive Red-eared Slider (Trachemys scripta elegans). Ranaviruses were also present in five species of captive-sourced turtle, which includes a captive-bred colony of Golden Coin Turtle (C. trifasciata) from a conservation breeding project. For the different sampling methods, I suggest that a combination of the three methods be used in future studies due to the low agreement and difference insensitivity of results between the three sampling methods. Combining and analysing various sample types from the same individuals can help minimize the risk of misdiagnosis, that may occur when relying on a single sample type.
In Chapter 4, I discuss the feasibility of using blood parasites detection as a wildlife forensic tool to differentiate wild-caught and captive-bred animals. I also provide conservation insight on the importance of ranavirus screening and recommendations on disease risk analysis for future reintroduction projects of endangered turtles.
Language
English
Copyright
The copyright of this thesis is owned by its author. Any reproduction, adaptation, distribution or dissemination of this thesis without express authorization is strictly prohibited.
Recommended Citation
Leung, J. (2024). Assessing prevalence of blood parasites and ranaviruses in Hong Kong freshwater turtles (Master's thesis, Lingnan University, Hong Kong). Retrieved from https://commons.ln.edu.hk/otd/213/