Mei Zheng

The aim of my research project is to build transmission models to understand the underlying factors which drive the transmission of a bacterium called Coxiella burnetii (C. burnetii) in cattle herds. Infections in animals is thought to lead to abortions and animals can pass the bacterium to humans. When humans are infected, they can develop a disease called Q fever which can manifest through flu-like symptoms such as sudden fever, muscle pain and in some cases, pneumonia, hepatitis, and/or endocarditis.

In Europe, there is a vaccine for animals, but not for humans. In Australia, there is a vaccine for humans, but not for animals. I am interested in figuring out how C. burnetii persists within a cattle herd and whether there are ways we can control it in a cost-effective manner through vaccination or other interventions.

Since I mainly work on my laptop to build and run transmission models, I am not restricted to working in a specific building or space although you can usually find me in the JD Stewart Building, which is one of the Veterinary Science buildings on the main Camperdown campus. To test the possible parameter space of the model, I use the University of Sydney’s high performance computing cluster, Artemis, which is a powerful tool that I can sync up to through my own laptop via a secure file transfer protocol (SecureFTP) connection.

As a research team, we have travelled out to farms where we work with veterinarians to collect samples from dairy cows and then transport these back to special laboratories at the Camden campus to run different tests on them. For example, we can check whether the samples collected from cows have the bacterium (with PCR tests), or antibodies against the bacterium (with ELISA tests) in them.

So far, I have set up a model to capture the key transmission dynamics of C. burnetii in a cattle herd. I have mapped out a possible parameter space of the model from literature. I am currently testing this parameter space to find combinations of parameter values to match the observed herd prevalence. This will help us understand a bit more about how C. burnetii might possibly behave in a cattle herd.

The most challenging aspect about my work is that I am often working with a lot of unknowns and uncertainty with the parameters due to a lack of field data. Sometimes, this data is not available due to resource limitations with sampling frequency and size of the population to sample. Due to ethical and safety reasons, we cannot perform experimental studies to obtain key parameters to answer questions such as how long does an animal stay infected before they recover? In order to work around this, we map out a parameter space of possible values and dynamics and test this in our simulation models to see what is possible.