A new study by Flinders University has found that one in 150 Australian’s have retinal scars caused by Toxoplasma; a parasite which causes the infectious disease known as toxoplasmosis. Toxoplasmosis can progressively damage the retina and lead to vision loss.
While the parasite is closely associated with animals, with cat faeces being a common carrier, the most common route of infection for humans is by eating undercooked or raw meat sourced from infected livestock.
We need people to be aware this disease exists, so they can make informed decisions about how they prepare and eat their meet
Many animals around the world are infected, generally contracting the disease in environments soiled by infected cats or by consuming other infected animals.
In the study, published in the journal, Ophthalmology Retina, Professor Justine Smith, Strategic Professor in Eye & Vision Health at Flinders University, and her team, analysed retina photographs of over 5000 people living in the Busselton area in Western Australia.
Three specialised ophthalmologists, including Professor Smith, assessed the scans for toxoplasmic retinochoroiditis, with positive cases confirmed with antibody blood tests.
“Among the 5000 people, we found eight participants with blood test-confirmed toxoplasmic retinal scars. Add to that that 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,” said Professor Smith.
Professor Smith says that, considering Australia’s substantial population of infected feral cats, understanding the prevalence of the disease is imperative. Her work represents the first effort to quantify the rate of ocular toxoplasmosis in the country, with the findings indicating the condition can be considered common.
With this knowledge, experts say it is important for people to understand the risk factors of toxoplasmosis and ways to avoid it.
“While people are often familiar with pregnant women needing to avoid cat litter trays, we also need everyone to know that preparation of meat is an important risk factor,” says Professor Smith.
“We need people to be aware this disease exists, so they can make informed decisions about how they prepare and eat their meet. The parasite can be killed easily by cooking the meat to an internal temperature of 66ºC (or medium) or by freezing it prior to cooking.”
There is no cure or vaccine for toxoplasmosis, and symptoms vary depending on the age, health and genetic of the infected individual. While the most common disease seen in a clinical setting is retinal inflammation and scarring, known as ocular toxoplasmosis, Professor Smith says many people are asymptomatic.
‘Prevalence of Toxoplasmic Retinochoroiditis in an Australian Adult Population: a Community-Based Study’ by Lisia B. Ferreira, João M. Furtado, Jason Charng, Maria Franchina, Janet M. Matthews, Aus A.L. Molan, Michael Hunter, David A. Mackey and Justine R. Smith will be published in the journal Ophthalmology Retina. DOI to come.