Wellington Scoop

Is it serious? Cats, toxoplasmosis, and microchipping


One of the Wellington City Council’s justifications for its proposed anti-cat bylaw is the threat of toxoplasmosis. The council tells us it’s a disease “which can have serious health implications for humans, especially pregnant women and people with impaired immunity. New Zealand has high rates of toxoplasmosis, with more than 40% of the population infected.” Oh dear – so what’s it doing about this raging epidemic?

Given the widespread nature of the health risks and the imminent threat to the nation’s capital, I thought it best to consult the best medical mind on the planet – Google. Which took me to the US Centre for Disease Control in Atlanta, the hero of many a great pandemic movie. Here’s what they had to say about toxoplasmosis:

A single-celled parasite called Toxoplasma gondii causes a disease known as toxoplasmosis. While the parasite is found throughout the world, more than 60 million people in the United States may be infected with the Toxoplasma parasite. Of those who are infected, very few have symptoms because a healthy person’s immune system usually keeps the parasite from causing illness. However, pregnant women and individuals who have compromised immune systems should be cautious.

So the disease is very widespread throughout the world, and practically everyone who has it exhibits no symptoms as their immune system fights it off … that doesn’t exactly sound like the public health emergency being proclaimed by the Wellington City Council. But still, it’s reasonable to see what action can be taken … after all, who wants a disease, even if most people don’t even notice they’ve had it?

As it turns out, the cats that are the Council’s target aren’t even the top of the CDC’s list for sources of toxoplasmosis:

– Eating undercooked, contaminated meat (especially pork, lamb, and venison).

– Accidental ingestion of undercooked, contaminated meat after handling it and not washing hands thoroughly (Toxoplasma cannot be absorbed through intact skin).

– Eating food that was contaminated by knives, utensils, cutting boards and other foods that have had contact with raw, contaminated meat.

– Drinking water contaminated with Toxoplasma gondii.

– Accidentally swallowing the parasite through contact with cat feces that contain Toxoplasma.

Both the CDC and every reputable medical source that Google took me to agree – you’re far more likely to catch toxoplasmosis from contaminated meat than from your moggy. Some sources suggest that more than 80% of infections come from the food chain, for the simple reason that your cat – even if infected – will only shed the virus in its feces for a week or two in its entire life. And given New Zealand’s dire record of food safety – with more than 950 cases of salmonella resulting in 110 hospital admissions in 2014 alone – the odds from contaminated meat may well be higher for Kiwis. Even so, toxoplasmosis doesn’t even figure in the New Zealand Public Health Surveillance Report from the Ministry for Primary Industries, presumably because the consequences of the disease are so minor for the vast majority of people.

Still, it was worth investigating further, so I called the Ministry of Health, the people who genuinely care about the spread of disease in NZ. After being referred around a few times, I found a helpful chap who said that toxoplasmosis wasn’t an area of focus for the Ministry. When I asked whether microchipping cats would help reduce the disease, he just laughed.

As did Google. No amount of searching found a single study – reputable or otherwise – that showed a link between cat microchipping and reduced rates of toxoplasmosis in the population, a correlation that appears to exist only in the imaginings of Councillor Simon Woolf, who proposed compulsory microchipping.

Like so much of what the Wellington City Council gets up to these days, the imminent threat of toxoplasmosis seems to exist solely within the reality distortion field that glows over the council table. There’s no public health emergency and no research that backs their chosen solution – but there’s a very clear sense that the Council wants to push ahead with this pointless and expensive policy anyway. We can but shake our heads in wonder … and vote accordingly.


  1. syrahnose, 18. May 2016, 9:50

    Excellent research. Remember who drives this idiotic hysteria and vote them out.

  2. Andrew, 18. May 2016, 11:16

    The late Steve Jobs must have sold his reality distortion device to the WCC. I’d hate to imagine what they paid for it.

  3. Leonora Kolinsky, 18. May 2016, 11:38

    Thank you, PCGM. The birds for whose sake Wellington City Council and certain pressure groups wish to sacrifice the freedom of cats may pose more of a threat than cats, given that the aerial application of bird faeces can cover greater areas and infect more sensitive parts of buildings, such as air-conditioning, than the faeces of ground-based mammals. Not to mention the organisms in nesting materials and feathers. The more birds there are, native or not, the greater the health risks.

    The following from MBIE’s health and safety advice to employers and workers:
    “Bird droppings, especially in large concentrations, present a risk of disease to humans. Bird droppings are likely to be found during the following types of work which access nesting sites such as ledges, eaves and lofts:
    •Construction work, •Maintenance work, •Working in roof spaces, •Demolition work
    The most serious risks arise from organisms that thrive in droppings, nesting materials and feathers. These include:
    •Bacterial: e-coli, salmonella, listeriosis, campylobacter, psittacosi
    •Fungal: histoplasmosis, cryptococcosis, candidiasis
    •Viral: meningitis, Newcastle diseasse
    •Parasitic/Protozoal: toxoplasmosis, trichomoniasis.”

  4. Boris, 18. May 2016, 16:11

    There is a growing body of research into toxoplasmosis that suggests it alters our brains, or at least our thinking. It is known to alter the behaviour of rats and mice, to make them more reckless, and even attracted to cats. There is evidence that links toxoplasmosis infection in humans with a range of depressive disorders and schizophrenia. There is evidence to suggest that infected persons are greater risk takers, and more prone to sudden explosive rage episodes. There is evidence to suggest that infected persons are more than twice as likely to be involved in road accidents. There is evidence to suggest that infected humans are more attracted to cats. Research is ongoing.

    Either your Google search was lazy and inadequate, or perhaps you reported rather selectively on what you found. The parasite can only reproduce with cats as part of the cycle, under-cooked meat or no. So getting rid of cats in NZ would stop the cycle.

  5. PCGM, 18. May 2016, 16:28

    Boris – you mean the research that demonstrates there’s no statistically significant relationship between toxoplasmosis and cognitive function in humans? To quote:

    According to studies, latent Toxoplasma gondii infection may affect several functions of the human brain. Here we search for the association between latent toxoplasmosis and cognitive performance. We tested 70 individuals for latent T. gondii infection. There were 26 Toxoplasma-infected subjects and 44 Toxoplasma-free subjects. Within these two groups we assessed cognitive performance using a set of standardized, widely recognized neuropsychological tests: Trail Making Test, Stroop Test, Verbal Fluency Test, Digit Span Test and N-back test. The relationship between chronic toxoplasmosis and cognitive performance was assessed, with adjustment for age and sex. Patients with latent toxoplasmosis performed worse on one neuropsychological test, N-back Test–percentage of correct answers (beta -8.08; 95% CI – 15.64 to -0.53; p < 0.05) compared to seronegative patients. However, after adjustment for age and sex, no statistically significant associations between latent toxoplasmosis and the scores on any cognitive tests were noticed. As statistically significant relationship was not observed, this study does not confirm that chronic latent T. gondii infection affects cognition.

    The study is here. The effect you note is in rodent models, not in humans. But I guess taking a relatively speculative effect in an entirely different species and extrapolating that to “getting rid of cats in NZ” is pretty typical of the anti-cat zealots.

  6. Boris, 18. May 2016, 18:06

    Hmmm…not sure if you’d qualify me as a zealot. I was pointing out that toxoplasmosis cannot exist without cats, no matter how hard you try to blame it on poorly prepared food. So ridding NZ of cats would logically rid us of toxoplasmosis in time. Perhaps people who insist on a right to ‘own’ mammalian predators in a country with endangered fauna highly susceptible to them should be considered zealotry?

    One 4 year old study does not a scientific consensus make. As I said, studies are ongoing. This is not something that has been explored in depth previously. There is plenty of room to doubt that toxoplasmosis is harmless, despite it failing to figure in the New Zealand Public Health Surveillance Report. Smoking and tobacco once failed to register as health threats, and yet research continued, accumulating what eventually was accepted as a sufficient body of evidence.

  7. Boris, 18. May 2016, 19:47

    @PCGM – try these links to studies or articles about studies less ambivalent than the one you cited – here
    and here, and here, and here, and here, and here .

  8. gseattle, 18. May 2016, 19:53

    In New Zealand, there are now six sheep per person (down from 20) [stats.govt.nz].
    “Toxoplasmosis never goes away and is present on 100% of farms in New Zealand”. [msd-animal-health.co.nz]

    PCGM cites a study that didn’t find a toxo affect on human behavior. However there are many studies that report toxoplasmosis affects human behavior negatively, and dramatically, one only has to google it in good faith.
    One study found that rage is twice as likely in people with latent toxoplasmosis. [sciencedaily.com]

    While imprimis has a “treatment” for toxoplasma in humans, it can only kill the parasite when outside of its cysts (tachyzoite). As of 5-2016 there is no known way to penetrate the cysts walls, though the creature is able to exit and return to safety inside the cysts (bradyzoite). Once infected always infected right now.

    One massive misconception is that toxoplasma can’t really hurt you unless sick or pregnant, now known to be bogus. Instead, even in the “latent” form it is active when our defenses are down (not enough sleep etc) wreaking havoc around the amygdala in the brain, the fear center, for one. I’m convinced I have it and would like to find some sort of trick to penetrate those cyst walls in the brain. (Enzymes as simple as papaya enzyme-like enzymes dissolve the cyst walls in cat guts, releasing the parasites). Or maybe they can be lured out, to be killed, at least reducing their numbers greatly. [Abridged.]

  9. PCGM, 18. May 2016, 20:45

    Boris – So just to be clear, you’re unable to provide any academic research that backs up your statements, and you haven’t posted a single link to a peer-reviewed journal that substantiates your claims. But you’re still keen to ban cats on the basis that toxoplasmosis gives you an icky feeling in your waters. You’re right on one thing, however: a single study does not make the scientific consensus. And the scientific consensus is that toxoplasmosis is not a disease that causes serious health issues for the overwhelming majority of people who come into contact with it.

    And here’s where I have issues with anti-cat lobbyists. If you cared about human health in relation to animals, you’d be lobbying to ban the sale of fresh chicken (or salmonella-on-the-wing), and to get rid of all the cows in NZ due to the very real risks from bovine TB. You’re not doing those things – which ipso facto, demonstrates that your agenda is simply anti-cat rather than pro-health.

  10. PCGM, 18. May 2016, 21:00

    Boris – thanks for the links. I eventually found the one academic article amongst the press releases and pop-science articles, and it was quite interesting. It’s a nice hypothesis – but it’s only a hypothesis. More research is needed, clearly, because the hypothesis still mostly rests on the results from rodent trials. And to be clear, the one study you’ve quoted barely proves correlation, let alone causation.
    But – for the sake of argument – let’s assume that all of Wellington is in imminent danger from having more traffic accidents thanks to the pernicious effects of toxoplasmosis. The Wellington City Council’s preferred intervention is to microchip all the city’s moggies – so can you please post links to academic research that shows the reduction in infection rates that will result from microchipping, which therefore justifies the regulatory intervention and compliance costs.

  11. Boris, 18. May 2016, 21:03

    @PCGM: Please see my post above for a short list of articles including some direct links to peer reviewed studies. Note the research is ongoing, and it is not true that what we don’t know can’t hurt us.
    I am not an anti-cat lobbiest. But consider this: Ever since childhood I have had a fascination with snakes. I would dearly love to have one as a pet. But you know what? Wrong bloody country mate.

  12. Boris, 18. May 2016, 21:23

    @PCGM – oh jeez then – peer reviewed:
    Here and here and here
    and here and here.

    Micro chipping of cats (as for dogs) is a first step in establishing how many and where they are. I don’t know of any evidence that this will reduce toxoplasmosis infection in the short term, but I haven’t looked.

  13. gseattle, 19. May 2016, 6:01

    Toxo is high in sheep and affects human behavior and …
    Some Kiwis eat lamb and mutton.
    A U.N. report found NZ to have the highest rates of domestic violence in the world. Connect the dots.