Viruses and Vectors: AJourney Through Zoonotic Disease Epidemiology in Australia and Beyond

Abstract

This thesis presents four projects addressing public health challenges related to zoonotic and vector-borne diseases in Victoria, Australia and Nigeria. The work presented here was completed during my field placement undertaken as part of the Australian National University Master of Philosophy (Applied Epidemiology), also known as the MAE. From March 2023 to December 2024, I undertook a joint field placement at CSIRO’s Australian Centre for Disease Preparedness (ACDP), and the Victorian Infectious Disease Reference Laboratory (VIDRL) at the Peter Doherty Institute for Infection and Immunity. The first study reports a Murray Valley encephalitis virus (MVEV) serosurvey. This was my epidemiology study; I had a key role in all aspects of this serosurvey, including study design, participant recruitment, data analysis and communication of findings. The serosurvey was conducted following Victoria's first outbreak of Murray Valley encephalitis since 1974. Between October 2023 and April 2024, 507 residents from 11 local government areas in northern Victoria were tested for MVEV antibodies. The seroprevalence was 2.0% (95% CI: 1.1%-3.6%), comparable to pre-outbreak background levels. No significant associations were identified between risk factors and seropositivity. These findings suggest that the region's population remains immunologically vulnerable to MVEV, underscoring the importance of ongoing vector control and mosquito bite prevention measures. This work was presented at the Communicable Diseases & Immunisation conference (CDIC) in Brisbane in June 2024 and a manuscript has been accepted for publication in the Communicable Diseases Intelligence (CDI) journal. The second study, my data analysis project, examines the molecular characteristics of rabies virus (RABV) in Nigeria, using whole-genome sequencing (WGS) to support the goal of eliminating human deaths from dog-mediated rabies by 2030. Between 2013 and 2021, brain samples from 60 RABV-infected dogs were sequenced and compared with 48 reference sequences. Phylogenetic analysis revealed that all sequences belonged to the Africa-2 clade, with evidence of human-mediated dog movement. Some study sequences were closely related to samples from Niger and Cameroon, while others were linked to distant Nigerian regions despite being collected within a short time period. These findings underscore the importance of WGS and phylogenetics in elucidating RABV transmission dynamics and guiding targeted One Health interventions for rabies control in Nigeria and the west African region. This work was presented at the 17th International Symposium on Veterinary Epidemiology and Economics in Sydney, November 2024. The third study evaluates the surveillance of Japanese encephalitis (JE) in Victoria following its emergence in 2022. Using a One Health approach, the evaluation assessed human, animal, and mosquito surveillance systems against the selected Centers for Disease Control and Prevention (CDC) surveillance attributes: timeliness, acceptability, representativeness, and flexibility. Stakeholders across the three sectors were interviewed or surveyed. The evaluation highlighted strengths in representativeness and f lexibility, such as the ability of mosquito surveillance to rapidly incorporate JEV testing into existing arbovirus surveillance programs, but also weaknesses such as poor timeliness and the absence of coordinated surveillance frameworks after the emergence of the virus. Recommendations included improving data sharing and governance to strengthen future One Health surveillance and response systems in Victoria. The final study investigates a cryptosporidiosis outbreak linked to an aquatic facility in northeastern Melbourne in early 2024. The outbreak, declared on 28 February and resolved by 11 April, consisted of 24 laboratory-confirmed cases. The median age of cases was 9 years [interquartile range: 2, 35], with equal proportions of males and females. All cases reported diarrhea and abdominal pain, with three hospitalisations and no deaths. The epidemiological investigations effectively identified swimming pools as a significant source of transmission. After the outbreak was declared, hyperchlorination and public health communication measures were implemented to mitigate further spread. This investigation demonstrated the importance of rapid public health response in controlling waterborne enteric outbreaks. In addition to these four major projects, this thesis describes teaching activities and additional public health experiences such as a measles outbreak investigation, that contributed to my field epidemiology training. Together, these projects and experiences fulfill the core competencies required by the MAE program. Show more