Toxoplasmosis parasites moving between cells
Toxoplasmosis is a parasitic disease. It causes a mild illness in most people, but can be serious in pregnant women and people with weakened immune systems. Our research aims to develop new treatments for toxoplasmosis. It is also guiding our research into malaria, which is caused by a related parasite.
Three toxoplasmosis researchers
Toxoplasmosis researchers Associate Professor Chris Tonkin, Ms Mary-Louise Wilde and Dr Alex Uboldi
in the Institute's Centre for Dynamic Imaging

Toxoplasmosis research at WEHI

Our toxoplasmosis researchers are discovering how Toxoplasma parasites invade and survive within human cells. This is providing insights into the functioning of the related malaria parasite. Our goal is to use this knowledge to develop new treatments for toxoplasmosis and malaria.

What is toxoplasmosis?

Toxoplasmosis is caused by infection with Toxoplasma gondii, a parasite that infects up to 60% per cent of the population in some places. It is related to the parasites that cause malaria and cryptosporidiosis, two other globally significant illnesses.

Humans become infected with Toxoplasma through contact with parasites shed into the environment from infected cat faeces, or by eating raw infected meat. In most people, the initial infection causes mild, or no, symptoms.

In people with weakened immune systems, toxoplasmosis can lead to:

  • Brain damage, including encephalitis (inflammation), which can cause confusion and loss of coordination
  • Eye damage, impairing vision. Toxoplasmosis is a leading cause of blindness in some communities
  • Lung infections
  • Coma and death

Pregnant women with toxoplasmosis can transmit the parasite through the placenta to their foetus. This can cause problems including:

  • Premature birth
  • Brain damage, potentially causing abnormal brain size, seizures and intellectual disability
  • Eye damage, potentially causing blindness
  • Ear damage, causing hearing loss

Often these symptoms do not become apparent in the child until a decade or more after birth.


Chronic Toxoplasma infections

As well as causing an immediate ‘acute’ infection, Toxoplasma parasites can form cysts in the infected person’s muscles, heart, brain and eyes. These cysts are found in an estimate of 25 to 30 per cent of people world wide. The parasite can lie dormant in cysts for years. If a person’s immune system is later weakened, the parasite can emerge to cause severe toxoplasmosis.

Re-emergence of a dormant Toxoplasma infection is a significant cause of illness and death in people infected with HIV.

Chronic infection with Toxoplasma has been associated with mental disorders such as schizophrenia and bipolar disorder. It has recently been suggested that chronic infection of Toxoplasma in the brain might exacerbate symptoms in these conditions due to changes in neurotransmitter pathways.

How is toxoplasmosis treated?

Most people infected with Toxoplasma do not require any treatment. People with compromised immunity, and pregnant women, can be treated with anti-parasitic medications.

Toxoplasma infections can be reduced in people with HIV by treating with antiretroviral medications, which slow the loss of immune function.

Toxoplasma as a model organism

Toxoplasma is a parasite that is closely related to Plasmodium, which causes malaria. Many of the genes and proteins that are used by Toxoplasma to infect cells are similar to those used by Plasmodium.

Research into Toxoplasma can provide insights into processes that are also used by Plasmodium. Toxoplasma is easier to work with in the laboratory than Plasmodium because:

  • Toxoplasma is more easily grown in the laboratory.
  • It is easier to manipulate or disrupt genes in Toxoplasma than in Plasmodium.
Toxoplasma and Plasmodium parasites
Fluorescent microscopy reveals the internal structures of Toxoplasma and Plasmodium parasites



Associate Professor Chris Tonkin

Associate Professor Chris Tonkin in his office
Associate Professor
Acting Division Head, Laboratory Head
Super Content: 
Three researchers with monitor showing parasite

Institute researchers have discovered a way to halt the invasion of the Toxoplasma gondii parasite into cells.

Hands holding a laboratory dish

Research into malaria and toxoplasmosis, and the immune response to infection benefits from Australian Research Council (ARC) Future Fellowships program.

Dr Ethan Goddard-Borger recieves a 2013 veski fellowship by the Victorian Minister for Innovation Ms Louise Asher

Dr Goddard-Borger's research tackles a range of parasites including Toxoplasma, which can cause serious problems for people with compromised immune systems including expectant mothers.

Simona Seizova talking to camera

See PhD student Simona Seizova on Channel 11's science TV show Scope, explaining how she uses imaging techniques to study the parasite Toxoplasma gondii. 

(Watch from 16:50)