Cats carry diseases that can be deadly to humans, and it’s costing Australia $6 billion every year

Rotiv Artic/Unsplash

Sarah Legge, Australian National University; Chris Dickman, University of Sydney; Jaana Dielenberg, The University of Queensland; John Read; John Woinarski, Charles Darwin University; Pat Taggart, and Tida Nou, The University of Queensland

Toxoplasmosis, cat roundworm and cat scratch disease are caused by pathogens that depend on cats — pets or feral — for part of their life cycle. But these diseases can be passed to humans, sometimes with severe health consequences.

In our study published today in the journal Wildlife Research, we looked at the rates of these diseases in Australia, their health effects, and the costs to our economy.

Professor Sarah Legge discusses the key findings of the study.

Based on findings from a large number of Australian and international studies, Australian hospital data and information from the Australian Bureau of Statistics, we estimate many thousands of people in Australia fall ill or sustain a minor injury as a result of cat-dependent diseases each year.

Our estimations suggest more than 8,500 Australians are hospitalised and about 550 die annually from causes linked to these diseases.

We calculated the economic cost of these pathogens in Australia at more than A$6 billion per year based on the costs of medical care for affected people, lost income from time off work, and other related expenses.

Toxoplasmosis

Toxoplasmosis is an illness caused by the parasite Toxoplasma gondii. It’s the most serious cat-dependent disease.

Newly infected cats shed millions of T. gondii oocysts (like tiny eggs) in their poo and these can survive many months in the environment.

Humans become infected when they ingest these oocysts, which are in the soil and dust in places where cats have defecated, especially sandpits, vegetable gardens or kitty litter.

Humans can also become infected from eating undercooked meat, if those farm animals have come into contact with cat-shed oocysts.

---

Read more:
Health Check: what bugs can you catch from your pets?

---

Up to one-third of people globally are infected with T. gondii, most without knowing it. Australian studies have reported infection rates between 22% and 66%.

Once infected, about 10% of people develop illness; the other 90% have no symptoms.

Based on overall infection rates and Australia’s population size, we estimate there are more than 125,000 new infections in Australia each year.

Of these, around 12,500 people get sick, mostly with non-specific, flu-like symptoms that resolve within a couple of weeks; 650 require hospitalisation, and 50 die, with these more serious cases often experiencing brain swelling and neurological symptoms.

People with compromised immune systems, such as those with cancer or HIV, are at highest risk.

Toxoplasmosis is caused by the parasite Toxoplasma gondii.
Yale Rosen/Flickr

Pregnant women who become infected for the first time can miscarry, or their babies may be born with congenital deformities.

Based on reported and estimated T. gondii infection rates in newborns, about 240 infected babies are born in Australia each year.

More than 20%, or about 50 of these babies, will have symptoms that require life-long care, including impaired vision or hearing, and intellectual disabilities. Another 90 babies will develop symptoms, usually related to vision or hearing, later in life.

Toxoplasmosis carries unique risks for pregnant women.
Freestocks/Unsplash

Long-term impacts of latent infection

Even if the initial infection causes little illness, the T. gondii parasite stays with us for life, encased in a cyst, often in the brain. These “latent” infections may affect our mental health and behaviour, such as delaying our reaction times.

Many studies have found people with T. gondii infection are more likely to have a car accident. A review of several studies found if there were no T. gondii infections, car accident rates would theoretically be 17% lower.

T. gondii infections also appear more common in people with mental health disorders such as schizophrenia, and in people who attempt suicide. Reviews across many studies suggest that without T. gondii infections, there could be 10% fewer suicides and 21% fewer schizophrenia diagnoses.

There’s still debate over whether the parasite causes car accidents and mental health disorders, or whether the association is explained by another shared factor. But it is possible T. gondii infection is a risk factor for these issues, in the same way smoking is a risk factor for heart attacks.

Scientists are still discovering how T. gondii influences the brain, but studies on rodents suggest it may involve changed brain chemistry or inflammation.

Putting it all together

If we accept T. gondii infections do increase the risk of car accidents, suicides and schizophrenia, then considering the incidence of these accidents and health issues in Australia, without T. gondii, we estimate we could potentially avoid:

• 200 deaths and 6,500 hospitalisations due to car accidents

• 300 suicides and 4,500 suicide attempts

• 800 schizophrenia diagnoses each year.

Combining deaths from car accidents and suicide with the 50 deaths from acute toxoplasmosis, we reach a total of 550 deaths related to T. gondii infection per year.

The hospitalisation total for T. gondii includes 650 for acute toxoplasmosis, 50 for congenitally infected babies, 6,500 for car accidents, and 800 for schizophrenia. We didn’t include hospitalisations for suicide attempts, as we didn’t have statistics on that. So this could be a conservative estimate, notwithstanding the fact there are other factors involved in car accidents and mental health issues.

Cat scratch and roundworm

Cat scratch disease is a bacterial infection (Bartonella henselae) that people can contract if bitten or scratched by an infected cat.

Typical symptoms include sores, fevers, aches and swollen glands. But more serious symptoms, such as inflammation of heart tissue, cysts in the organs and loss of vision, can also occur.

Prevalence figures are not available in Australia, but based on rates in the United States and Europe, where cat ownership patterns and cat infection rates are similar, we estimate at least 2,700 Australians get sick annually from cat scratch disease, and 270 are hospitalised.

---

Read more:
Your cat has toxoplasmosis and you’re worried? Join the club

---

Cat roundworm is a parasitic infection (Toxocara cati) that people and other animals can contract by accidentally consuming the parasite’s egg, which infected cats shed in their poo.

Most cat roundworm infections cause mild symptoms, but the migration of the larvae through the body can cause tissue damage, which can be serious if it occurs in a place like the eye or heart.

An adult cat round worm.
Beentree/Wikimedia commons, CC BY

What can we do?

Some 700,000 feral cats and another 2.7 million pet cats roam our towns and suburbs acting as reservoirs of these diseases.

There are no human vaccines for these diseases. Treatment for T. gondii infection in cats isn’t considered useful because cats usually shed the oocysts without the owner even realising the cat has the parasite. Cats can be treated to rid them of roundworm, but treatment for B. henselae (the bacteria that causes cat scratch) may not be effective.

But if you’re a cat owner, there are some things you can do. Keeping pet cats indoors or in a securely contained outdoor area could reduce the chance your pet will contract or pass on a disease-causing pathogen.

If cats are always kept indoors they have a low risk of catching and spreading the disease.
Jaana Dielenberg, Author provided

Cats should be kept out of veggie gardens and children’s sandpits. Washing hands after handling kitty litter and gardening, and washing vegetables thoroughly, can also reduce the risk of transmission.

As T. gondii can be contracted from infected meat, cooking meat well before eating, and not feeding raw meat to pets, can also help.

---

Read more:
One cat, one year, 110 native animals: lock up your pet, it’s a killing machine

---

The urban feral cat resevoir could be reduced by preventing access to food sources such as farm sites, rubbish bins and tips. We could do this with improved waste management and fencing.

People shouldn’t feed feral cats, as this can lead to cat colony formation, where infection rates are also higher.

Pet cats should also be desexed to prevent unwanted litters that end up as free-roaming ferals.

These steps would cost us and our pet cats little, but could prevent unnecessary impacts on our health and well-being.

Sarah Legge, Professor, Australian National University; Chris Dickman, Professor in Terrestrial Ecology, University of Sydney; Jaana Dielenberg, University Fellow, Charles Darwin University. Science Communication Manager, The University of Queensland; John Read, Associate Lecturer, Ecology and Environmental Sciences; John Woinarski, Professor (conservation biology), Charles Darwin University; Pat Taggart, Adjunct Fellow, and Tida Nou, Project officer, The University of Queensland

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Friday essay: crafting a link to deep time from ancient river red gum

Billy Griffiths, Deakin University

With a mischievous smile, Damien Wright gives the exhibit an unceremonious kick. The enormous, curved slab of river red gum rocks back and forth on the gallery floor, casting a wavering shadow over the “Do Not Touch” sign at its base.

A couple of anxious visitors shuffle over to investigate as Damien tells me how he made this wobbling wooden bowl, and why he chooses to work with the hardest, most challenging timbers.

Damien Wright, ‘Food Bowl’, 2017. Recovered Red Gum, 2800 x 1300 x 250mm.
Fred Kroh

The river red gum (Eucalyptus camaldulensis) once grew on the banks of the Murray River. Damien discovered the thick slab in a miller’s yard in Wodonga, where it had lain exposed to the elements for years, slowly warping in the heat. What others had dismissed as damaged wood, Damien saw as creative possibility: he relished the opportunity to work with wood that had been “cooked, cured and crazed by the sun”.

In his workshop in Northcote, Melbourne, he worked to accentuate the warp in the wood by curving the edges of the slab, creating a long, bowing channel, almost three metres in length and over a metre wide. Like all his work, this object is an argument he has made with his hands.

The rough, red, cracking grain of the wood runs lengthways across the piece, like gullies and rivulets spreading across a parched, burnt land. Damien encourages this comparison with his title, which is a pointed commentary on the mistreatment of the waterways on which the tree grew.

“It’s called Food Bowl”, he tells me. And then, gesturing to a knot in the centre, “It drains in the middle”.

Damien Wright, left, and miller Kelvin Barton with the slab that became Food Bowl, Wodonga, 2017.
Fred Kroh

For Damien, wood is a way of thinking about place and time — even deep time. A river red gum may grow for anywhere between 400 and 1,000 years before it falls. And as it decomposes over centuries it becomes a home for new life. Murray cod lay their eggs in drowned red gums.

To work with wood is to think beyond a human lifespan. When you look at something like the Murray-Darling system from the perspective of a grand old red gum, you see the fragility and inter-connectedness of the waterway, and how rapidly it has degraded with recent human interventions.

“And if you have that conversation about deep time in this country”, says Damien, “you have to talk about Indigenous people and this continent as an occupied and cultural space, not just a physical place”.

---

Read more:
Friday essay: when did Australia’s human history begin?

---

River red gums were a part of Australia’s environment long before people arrived here. They grew beside the Murray River when it was a wide, cold, fast-flowing stream; they witnessed its transformation in the late Pleistocene into a narrow, sinuous, seasonal river; and they have remained, over the past 13,000 years, as the water has slowed and warmed, forming swamps, low sand dunes and small lakes along the channel, and seasonal wetlands in the wider riverine plain.

These mighty trees have also been absorbed into the social and cultural worlds of Indigenous Australians. Their roots have been dug and hollowed out to create bowls, their bark cut to craft canoes, and their limbs burned to warm camps and cook food. In recent millennia, they presided over the most densely populated areas of the continent.

A red gum along the Wagirra Trail in Albury, 2017. Before European settlement, wooden canoes were cut from the trees and used by the Wiradjuri people on the Murray River.
Sarah McPhee/AAP

---

Read more:
The ring trees of Victoria’s Watti Watti people are an extraordinary part of our heritage

---

Damien tells me how he seeks to evoke this deep history through his craft as he shows me two of his other pieces: a striking lantern (Black Lighthouse) he made in collaboration with Yolngu craftsman Bonhula Yunupingu, which glows like a fire through thin, black wood; and an elegant reading chair and angular side table called Ned — a riff on Sidney Nolan’s Ned Kelly helmet, which it closely resembles.

Each piece of furniture has been made from red gum in a stage preliminary to fossilisation. The wood is black and almost as hard as stone. It is known as ancient red gum.

While other native timbers enable Damien to explore relationships with the Australian environment, the ancient red gum opens a conversation about deep time on this continent.

Geomorphologist Jim Bowler was the first to identify the material as red gum; he used radiocarbon dating to place its age at about 8,000 or perhaps 10,000 years old. Later I call him and, over the phone, he sketches out the wood’s journey from the banks of the Murray River to the workshops of inquisitive artisans like Damien.

The tree would have seeded after the end of the last ice age, at a time when sea levels were rising and the climate was warming.

The rapid snowmelt in the Victorian Alps caused the mountains to shed huge amounts of gravel, which was then swept into the Murray River. As red gums fell into an ancient channel they were covered by this new gravel, which sealed them in the riverbank.

Preserved from decay by the acidity of the water, the entombed wood slowly absorbed enormous amounts of iron and silica. This oxidising and ebonising process is what makes it black through to the centre and hard, much harder than other red gum.

Articulating a future

Jim first became aware of the red gum when he received some samples at the Melbourne Museum in 1990. The damp and fibrous wood had been unearthed in a quarry on Yorta Yorta land in Wodonga, where it was regarded as a nuisance by those more interested in the gravel around it.

Jim and his wife Joan Bowler recognised the significance of the timber and were eager to see it preserved and used. They helped arrange for the director of the museum to provide “authentications” for woodworkers to make it into furniture, and Joan and her friend Annetine Forell travelled the country over the following two decades, drawing the remarkable material to the attention of millers and craftspeople.

The late Kelvin Barton, a miller, woodworker and seventh-generation farmer, became a crucial intermediary. He collected the ancient red gum in Wodonga, reducing its water content in his ersatz kiln to turn it into workable timber. This was how Damien, a long-term friend and collaborator, came to encounter the ancient red gum — indeed it was in Kelvin’s yard that he found the much younger slab that became Food Bowl.

Ancient red gum, Wodonga, 2004.
Damien Wright

Damien uses the ancient red gum to articulate his vision for Australia. He sees craftsmanship as a language: a practice that is refined over time to communicate knowledge, beauty and ideas.

He considers his furniture — in its functionality as well as its elegance — as an embodiment of this philosophy. Objects tell stories. They become part of our everyday lives and express everyday futures:

My argument is that to take a material that is ten thousand years old and to articulate that in a beautiful and passionate way and to make that a relevant thing to our lives or to peoples’ lives is a way of articulating a future for this continent. It’s a way of understanding our place in time. It’s a way of dealing with people. It’s a way of projecting forward.

Damien Wright, Reading Chair and Ned, 2017. Ancient red gum and recovered black bean.
Fred Kroh

Joan Bowler shares this vision for the ancient timber. In 2008, her company Australian Ancient Redgum donated a six-metre “Fossil Tree” to the Children’s Garden at the Royal Botanic Gardens Victoria, so that “children can sit under this ancient tree and look up through the hollowed out centre and dream of what was and what might be”.

Trees that were seeded after the end of the last ice age, that survived the ruptures of invasion and industry, have reemerged to offer a deep-time perspective of the continent.

It is a scale that reveals the long-term costs of short-term exploitation, and renders processes like the degradation of the Murray-Darling river system into sudden events.

Ancient red gum also invites a longer view of Australian history. And in the hands of Joan and Damien, it calls for the acknowledgement of cultures and histories that for so long have gone unrecognised.

This is an extract from Living with the Anthropocene, Love, Loss and Hope in the Face of Environmental Crisis, edited by Cameron Muir, Kirsten Wehner & Jenny Newell (New South Books).

Billy Griffiths, Lecturer, Deakin University

This article is republished from The Conversation under a Creative Commons license. Read the original article.