“Killer cat parasite” infects whales. Defending the cat

Beluga whale and toxoplasm oocyst

The newspaper headlines proclaiming “killer cat parasite” and “public health warning” are typically sensationalist. However, I expect it from online newspapers. Here are some examples of headlines:

  • Arctic Whales Infected With Domestic Cat Parasite
  • Public health warning as cat parasite spreads to Arctic beluga whales
  • Killer cat parasite spreads to Arctic: Toxoplasma found in beluga whales

However, they are unbalanced reports. They don’t present the entire story and in doing so the news media once again are a source of bad publicity for the domestic cat. I don’t like it because it is unfair. This article is in defence of the cat and adds information which helps to complete the story.

Most of us, by now know, about the microscopic parasitic protozoan called toxoplasma gondii. If you don’t please read these articles. In brief it is everywhere, from Alaska to Australia, in warm-blooded animals. A large percentage of people are infected with no symptoms. The domestic cat is said to be the only known animal to carry the adult parasite and to pass the durable eggs of this parasite (oocysts) in their faeces (ref: All Pets Veterinary Hospital). The oocysts can survive for many months but not indefinitely. The oocysts can be ingested and infect other animals.

Here is some important added detail:

How does the cat become infected?

The cat does not “create” the parasite from nothing (obvious but needs to be stated). The protozoan is not a product of the domestic cat. The cat is equally a victim as we are and as the whales are. Full-time indoor cats don’t hunt and don’t normally get infected. Cats become infected by eating infected wild animals who are themselves infected. The story is not just about cats.

How did the parasite get from someone’s garden to the Pacific Ocean or the Arctic Ocean?

The big question that is ignored by the newspapers is how the parasite gets from a cat’s feces to the beluga whale or any other sea creature. Sea otters have also been mentioned as being infected because they eat shellfish that are infected.

If an indoor cat uses cat litter and it ends up in a landfill site which is properly sited and maintained the parasite will eventually die at that site without infecting any other animal.

However, cat litter is sometimes flushed down the toilet. Discarding cat faeces this way can result in the parasite getting into the sea. This is a human created problem. Sewage treatment plants don’t kill the oocyts and the treated water is pumped into a freshwater source which flows to the ocean.

When cats go to the toilet outside, it is difficult to imagine how the oocysts in the feces can get to the Arctic from dry land in the middle of America. However, according to National Geographic, the main reason why this “killer cat parasite” gets from someone’s lawn or park to the ocean is because of what we do.

And what we do it create urban sprawl. We expand our activities and build roads and pavements. These smooth surfaces allow rainwater that contains the parasite to be carried into streams and rivers and thence to the ocean. The rainwater is called “surface runoff”.

Also human urban sprawl has destroyed wetlands. How many developments have we heard about which have destroyed wetlands or plans to destroy wetlands for housing? It is common in places such as California, USA and not uncommon in the UK, incidentally. Wetlands are described as “environmental kidneys”. They would capture some of these oocysts preventing them from getting to the ocean. Humankind has disturbed the balance of nature. The majority of California’s sea otters carry the parasite.

But for Humans

But for humans there would be no domestic cat. This is not a criticism of the cat, just a plain fact. But for humans there would be no toxoplasmosis problem, anywhere.

But for humans there would be no dying otters in Californian bays. We are in charge of the domestic cat, our environment and ourselves. We should take responsibility for the problem that the online newspapers describe as “Killer cat parasite spreads to Arctic….”

Presentation about preventing an infection in people


  1. Whale: Flickr – see original by Brian Gratwicke
  2. Oocysts: Spencer Greewood BSc.
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“Killer cat parasite” infects whales. Defending the cat — 5 Comments

  1. Just something else for cat haters to blacken cats names with.
    Human beings never take responsibility for being the ones causing everything that happens 🙁

  2. I think it’s pretty factual that humans are usually infected through contact with cat feces. But, it seems that cats take the full brunt when, in reality, the parasite is carried by other warm blooded animals (especially livestock) and birds. Ingestion of raw or undercooked meat poses a pretty good threat.
    Having visited ocean beaches all my life, I can say that birds heavily populate beaches.
    I think there could be more than one way that sea life could become infected.

  3. For goodness sakes it’s NOT a ‘cat parasite’ – it is a ‘parasite’ and it so happens that cats can have it. God I hate the media sometimes – they wallow in their ignorance. They would rather be ignorant I think. It makes for better stories.

    • I hate the media sometimes too. On this sort of subject (cats and science) they just make a story about it without ensuring it is balanced as they would if writing about the human.

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