Cats spreading diseases costs the Australian economy billions each year

45 percent of Kiwi households have at least one cat.
45 percent of Kiwi households have at least one cat. Photo credit: Getty

By RNZ Sunday Morning

Diseases transmitted by cats cost the Australian economy more than A$6 billion annually through their impact on human health and livestock production, according to research conducted by Professor Sarah Legge and her colleagues at Australia National University in Canberra.

This news must be bad for New Zealand, too, with 45 percent of Kiwi households having at least one cat.

Professor Legge spoke to RNZ about the impact cats are having on things like medical care, insurance, social support and lost productivity.

While cats carry a lot of diseases and parasites that can affect humans, the most serious illnesses come from the Toxoplasma gondii parasite - which is passed on to humans mostly through contact with cat faeces.

"It's one of the most widespread pathogens in the world, so globally about 30 percent of people carry the parasite," she says.

When a cat is first infected with the parasite, the pathogen releases millions of eggs into the cat's faeces.

"These eggs are really resistant, so they can persist in the environment for many months and they're everywhere - they're in soil, bits of dust."

While humans can pick up these eggs from almost any surface they get onto, Legge says you're most likely to pick them up from gardens and children's sandpits.

"There have been cases where these eggs have been inhaled in dust, but more likely you get some contaminated material on your hands and then you touch your face, suck your thumb, and you ingest the egg," she says.

Humans can also be infected by toxoplasma by eating infected meat - as sheep and cattle can also pick up the eggs.

"If we eat that infected meat and it hasn't been cooked thoroughly enough to kill the parasite, we can get infected that way as well."

While 90 percent of people infected with toxoplasma didn't show any symptoms, Legge says the "unlucky ten percent" usually passed the illness off as something else, due to it's similarity to flu symptoms.

"But a proportion of them get very sick and end up in hospital and so they tend to be people who are immunocompromised, so cancer patients, transplant patients," she says. "Before people cottoned on to what was going on, toxoplasma was actually the biggest cause of death in AIDS patients."

The risk is also greater for pregnant women, if they are infected for the first time during their pregnancy - as the infection can cross the placenta and cause miscarriage or congenital defect.

"Now the incidence of that is quite low, but the impacts of course are terrible for the families, and they're lifelong," she says. "Affected babies can have impairments to their vision, to hearing, and have intellectual disabilities."

While serious illness from toxoplasma is fairly uncommon, the subtle effects it has on our mental health and behaviour can cost the economy a lot - in Australia, Legge and her colleagues estimate the pathogen costs the country more than A$6 billion annually.

Research shows that people infected with toxoplasma have signs of slower reaction times and slightly higher risk taking activities. Legge says people involved in workplace accidents and car accidents were more likely to carry the toxoplasma infection.

While the infection can be quite difficult to treat, some consequences of the illness can be suppressed if picked up early.

"In some countries, pregnant women are screened early in pregnancy to identify women that are vulnerable to a new infection," Legge says. "If they pick up a toxoplasma infection during pregnancy they can be given a cocktail of drugs to suppress the effects and reduce the risks of it crossing the placenta."

Those who are high risk or immunocompromised should also be tested for the pathogen - as action needs to be taken quickly if symptoms appear.

While the A$6 billion cost is certainly staggering, Legge says the cost is probably higher, as the study was only based on the known effects of toxoplasma. It has also been linked to bipolar disorder and other mental health conditions, while new research has also linked it to brain cancer.

"I think the consequences on your mental health is probably the thing that I find scariest about this parasite," Legge says.

"Although it's a difficult parasite to treat, there are definitely things we can do to limit transmission and reduce the risk of infection and that's probably the place to start."

She recommends wearing gloves and washing your hands after working in the garden, cooking meat properly and restricting the movements of cats.

"So don't let cats into children's sandpits, it's a terrible hotspot for toxoplasma eggs, and don't let cats into your garden. Don't have feral cats around farms, because if feral cats aren't pooing in the paddocks where livestock are, livestock are less likely to pick up the parasite."