Eye scan showing ocular toxoplasmosis. Credit: João Furtado

In the first study of its kind to quantify the rate of ocular toxoplasmosis in Australian, a team from Flinders University has found that one in 149 Australians have retinal scars caused by the Toxoplasma gondii parasite, indicating it can be considered common.

Senior author Professor Justine Smith and her team analysed retina photographs of more than 5,000 people living in the Busselton area of Western Australia, with positive cases confirmed with antibody blood tests. “We found eight participants with blood-test-confirmed toxoplasmic retinal scars. Since about three-quarters of the retinal lesions would be in a position not visible in these particular photographs, we were able to estimate the prevalence of ocular toxoplasmosis to be one per 149 persons.”

Although associated with cats, many animals are infected with Toxoplasma gondii, generally contracting it in environments soiled by infected cats or by consuming other infected animals. For humans, while domestic cat faeces can be a vehicle, eating undercooked or raw meat from infected livestock is the most common risk factor. “Considering Australia’s substantial population of feral cats that are known to be infected, alongside high levels of farming and diets rich in meat, it’s imperative we understand the prevalence of the disease across the country,” said Prof Smith.

The full study was published in Ophthalmology Retina.