This blog provides scientific facts, information and research regarding the growing spread of toxoplasmosis in our communities - and to our children, particularly in unprotected play areas. Over one third of the world's population is infected, and more than 60 million Americans, The US CDC states this "neglected parasite" is the second leading killer of food borne diseases.
PIP COURTNEY, PRESENTER: Australia's native wildlife is disappearing at an alarming rate and the feral cat is the chief culprit.
But they're now also affecting sheep farmers in Tasmania. The cats are carrying diseases which are being passed on to flocks, with disastrous consequences.
And as Ginny Stein reports, the Federal Government has announced a 10-year plan to effectively eradicate feral cats.
GINNY STEIN, REPORTER: Northern Tasmania - and Bruce Young has company. A trap was set last night and a deadly animal has been caught. This is it.
KEVIN KNOWLES: It's in good condition, no.
BRUCE YOUNG, SHEEP FARMER: Yes, looks like.
KEVIN KNOWLES: Healthy cat.
GINNY STEIN: This killer, one of an estimated 20 million currently roaming across Australia, is now on death row.
BRUCE YOUNG: I don't want to get bitten or scratched. While this caged feline may look like your average domestic cat, it's certainly not.
KEVIN KNOWLES, UPPER MEANDER LANDCARE GROUP: It's quiet now. It's just the aggression from the cat. Somebody's house cat will just sit in the trap quietly, wants to be let out. These things explode. READ Or Watch MORE
But for some animals, infection can be deadly. If an animal’s immune system isn't quite up to the task, either through illness or stress, the initial infection can lead to toxoplasmosis. The disease has a range of debilitating symptoms, including anorexia, lethargy, reduced coordination, apparent blindness, enlarged lymph nodes, disorientation, breathing difficulties, jaundice, fever, abortion, and death.
Feral cats are a huge threat to our native wildlife, hunting and killing an estimated 75 million animals across Australia each and every night. But the killing spree dodoesn'tnd there. There’s a parasite lurking in kitty’s litter that continues to kill wildlife long after the perpetrator has left the scene of the crime.
The killer is toxoplasmosis, a disease caused by the parasite Toxoplasma gondii. The parasite is spread by cats but it can infect any bird or mammal. Around one-third of humans worldwide are infected with the parasite. But the deadly effects on our wildlife are often overlooked.
What does toxoplasmosis do?
In many animals, Toxoplasma infection causes nothing more than a mild case of the sniffles. If the animal is healthy, the immune system usually produces antibodies that keep the parasite under control. The parasite then goes into a relatively dormant state, forming invisibly tiny cysts mainly in the heart, lungs, brain, eyes, and spinal cord. While the cysts stay with the animal for life, they rarely cause any direct harm.
Some of these side-effects may kill the host directly, while for others, they will make the host an easier target for predators. For example, blinded wildlife cannot see predators, while lethargic or badly coordinated animals might be too slow to escape.
But bandicoots are not the only victims. Toxoplasmosis is a confirmed killer of other Australian wildlife, including Tammar wallabies, koalas, wombats, and several small dasyurids.
In Tasmania, toxoplasmosis kills Bennett’s wallabies and pademelons, with infected animals found dead or stumbling around blindly during the day, vulnerable to predators or cars as they stumble onto busy roads.
A manipulative parasite with a motive
For animals lucky enough to survive the initial infection and its symptoms, the threat doesn't end there. While the parasite might appear to be dormant, it may be secretly manipulating its host’s behaviour.
Several studies have linked certain “risky behaviours” with latent Toxoplasma infection. For example, studies have shown that rats and mice infected with Toxoplasma not only lose their natural fear of cats, but are actually attracted to them.
Why? It all comes down to motive. The Toxoplasma parasite needs to pass through two different animal hosts to complete its life cycle. Some stages of the life cycle can occur in any warm-blooded animal (the intermediate host), but the sexual stages can only occur in a cat (the definitive host).
So when the parasite is in an intermediate host such as a mouse or a rat, it needs to pass back into a cat to complete its life cycle. To achieve this, the parasite manipulates the rodent’s behaviour, making it an easier meal for a cat.
But in wildlife, these risky behaviours will increase the risk of predation – not just by cats, but all predators including foxes, dogs, raptors, and reptiles.
And in a strange evolutionary twist, mothers infected withToxoplasma have been found to give birth to more sons in both mice and humans. While the reasons for this are unclear, infection with Toxoplasma may gradually skew the sex ratios of our threatened wildlife in favour of males. Over time, this would reduce the number of females in a population, further reducing the reproductive capacity of many declining species and exacerbating ongoing population declines.
Why are feral cats to blame?
Newly infected cats only shed the parasite for around two weeks. However, in that short time, a single cat can shed more than 20 million parasites in their faeces. Thousands of mammals and birds can then become infected by eating food, soil or water contaminated by a single cat. Under cool, humid conditions, these parasites can survive in the environment for at least 18 months, continuing to kill wildlife long after the cat has left the area.
While the parasite can also be transmitted by eating infected prey, studies have shown that marsupials in areas where cats may roam were 14 times more likely to be infected than those in areas without cats. Most responsible pet owners keep their domestic cats indoors and restrict their hunting activities, minimising the risk of infection. But feral cats need to hunt and kill to survive.
Therefore, feral cats are the most important player in theToxoplasma cycle. To break the cycle and eliminate the parasite, we need to eliminate feral cats.
A recent study found that 84% of feral and stray cats tested in Tasmania were infected with the parasite. Previous studies have found a similarly high prevalence in feral cats on both Christmas Island and Kangaroo Island.
These islands are currently refuges for a range of endemic and threatened species, many that have been driven to extinction on the Australian mainland. While Christmas Island has recently been earmarked for feral cat eradication, all three island refuges should be prioritised for targeted feral cat control programs.
Toxoplasmosis is yet another threat posed by feral cats against wildlife. The future of many of Australia’s threatened species increasingly hinges on our ability to control feral cats.
September 2012. A new study in the USA has found that free-roaming cats pose a threat from "serious public health diseases" to humans, domestic animals, and wildlife.
"This is a significant study that documents serious wildlife and public health issues associated with 125 million outdoor cats in the United States. Decision-making officials need to start looking at the unintended impacts these animals have on both the environment and human health when they consider arguments to sanction Trap, Neuter, and Return (TNR) cat colonies. These colonies are highly detrimental to cats, wildlife, and people, and only serve to exacerbate the cat overpopulation problem," said Darin Schroeder, Vice President for Conservation Advocacy at American Bird Conservancy.
Among the key findings of the paper are:
Free roaming cats are an important source of animal-transmitted, serious diseases such as rabies, toxoplasmosis, and plague.
Free roaming cats account for the most cases of human rabies exposure among domestic animals, and are the source for one-third of rabies post-exposure treatments in the United States. Because of inconsistent incident reporting, that number is likely an underestimate of the actual cases of rabies exposure.
Trap, neuter, and release (TNR) programs may lead to increased, un-inoculated populations of cats that can serve as a source of transmittable serious diseases.
The study found that since 1988, rabies has been detected more frequently in cats than in dogs; in 2008, the number of cats detected with rabies was four times higher than dogs. In 2010, rabies cases declined for all domestic animals except cats, which comprised 62 percent of all rabies cases for domestic animals.
According to the study, which cites numerous specific examples of rabies exposures from cats, ".......human exposure to rabies is largely associated with free-roaming cats because of people being more likely to come into contact with cats, [the existence of] large free-roaming cat populations and lack of stringent rabies vaccination programs."
TNR
Importantly, the study also seems to directly contradict notions that TNR programs lead to smaller sizes of cat colonies and that they pose no health risk. Those programs purport to capture all the cats in a colony, neuter and vaccinate them, and return them to a colony that is fed by volunteers.
"....neutered groups (colonies) increased significantly compared to [sexually] intact groups because of higher immigration and lower emigration. .........sexually intact adult cats immigrated into the neutered groups at a significantly higher rate than [they did to the] sexually intact group. .........immigrating sexually intact females had increased fertility along with increased survivorship of kittens as a population compensation response to neutered individuals."
The authors report that the data suggest that neutered cat groups act as an attractant of sexually intact free-roaming cats, thus negating the belief that TNR programs lead to decreases in free-roaming cat populations. This attraction and subsequent movement of unneutered and un-inoculated cats into cat colonies "...may severely limit the protection offered by vaccination of TNR processed cats and would not abate the [transmittable disease] threat of rabies in these groups."
The report also cited the dangers associated with TNR feeding stations in attracting raccoons, skunks, foxes, and other wild animals associated with rabies. The feeding stations not only increase the likelihood of contact between humans and rabies-exposed animals, they also increase the human and wildlife exposure to a potentially fatal parasite, raccoon roundworm, harboured by raccoons that is being seen in ever-increasing parts of the country. The danger to wildlife was illustrated in a 2008 study that found that five Florida panthers were killed as a result of a single such infected cat.
Acute toxoplasmosis
Another significant disease threat cited by the study concerns is a parasite frequently found in water or soil contaminated by cat faeces. This parasite is responsible for causing the disease toxoplasmosis. Consequences of contracting this parasitic infection are most serious if you are either pregnant, HIV positive, or are undergoing chemo-therapy treatment, and range from significant to severe to fatal. The report cited a 2011 study that found that 63 percent of the patients with acute toxoplasmosis had become infected through cat faeces.
The authors conclude by saying that their study "...highlights the serious public health diseases associated with free-roaming cats and underscores the need for increased public health attention directed towards free-roaming cats." The fact that rabies exposure in humans is disproportionately associated with free-roaming cats "...should be of paramount concern to health officials because of the high mortality rate of clinical rabies..."
The study was published in the peer-reviewed public health journal, Zoonoses and Public Health.
The paper was authored by R.W. Gerhold of the University of Tennessee's Center for Wildlife Health, Department of Forestry, Wildlife and Fisheries, and by D.A. Jessup, retired from the California Department of Fish and Game.
Your assistance is much appreciated, and "Please Tweet" - #ToxoTO - to register your support. Let's get make our sandlots and playgrounds safe for our children. Thanks.
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