Epidemiology and control of communicable diseases in Western Australia, 2015-­2016

Abstract

The Communicable Disease Control Directorate (CDCD) within the Department of Health in Western Australia (WA) is responsible for protecting Western Australians from communicable diseases by monitoring, responding to, and, where possible, preventing infectious disease incidents in the community and hospital sector. The CDCD works closely with the government laboratory, PathWest, which is the main diagnostic laboratory in WA. During 2015­‐2016, I completed a dual field placement with the CDCD and PathWest. My experiences in these two placements fulfilled the requirements of a Master of Philosophy in Applied Epidemiology (MAE).

As part of my core MAE competencies I performed the first evaluation of the infectious syphilis surveillance system in WA. On the whole, the system adequately met its objectives, however, I was able to provide a number of recommendations for improvement. Recommendations included the collection of additional data to improve case management, the development of electronic notification forms to improve the timeliness of reporting, and implementing automatic upload of laboratory results to facilitate case follow‐up. The results of the evaluation were summarised and will be distributed to stakeholders.

I participated in two outbreak investigations associated with Salmonella Typhimurium PFGE1 (STM01). I was involved with the investigation of a community‐wide outbreak of STM01 and conducted a case‐control study to determine the risk factors for illness. I found that illness was associated with eating chicken cooked outside of the home, raw eggs, and particular brands of eggs. I reported the results back to the lead investigators to guide efforts in identifying the source. During interviews for the case­‐control study, a cluster of cases linked to a particular café was identified. I investigated the cluster with hypothesis‐generating questionnaires, developed a hypothesis for factors associated with illness, and designed a cohort study to test that hypothesis. We were unable to proceed with the analytical study, however, environmental investigations of the cafe added support to our hypothesis, and allowed us to provide recommendations to prevent future outbreaks.

During my time at PathWest, I investigated the relationship between inflammatory bowel disease (IBD), a chronic inflammatory condition of the gastrointestinal tract, and infection with Clostridium difficile, a spore forming anaerobic bacterium that can cause severe gastrointestinal disease. International studies showed that persons with IBD have both greater incidence of Clostridium difficile infection (CDI), and poorer outcomes following infection. To determine if the situation was similar in Australia, I conducted a large retrospective cohort study using linked hospital administrative data, statutory death notifications, and CDI surveillance data for WA. I found a high incidence of CDI in hospitalised patients with IBD, that was six fold higher than that previously reported for non‐IBD patients. In contrast with overseas studies, IBD patients in WA with CDI did not appear to be at increased risk of death, or experience longer hospital stays than IBD patients without CDI. The results are the first to report the current situation and outcomes of CDI in IBD patients in Australia.

In this thesis, I document the experiences and competencies I have gained during the MAE program.