Categories: parasites

The reason why cats are definitive hosts for Toxoplasma gondii

Toxoplasma gondii lifecycle

In the life cycle of the Toxoplasma gondii protozoan, the only known definitive hosts are domestic cats and their relatives. This singular fact has worked against the cat because it opens the door to criticism by people who dislike seeing cats – domestic, stray and feral – outdoors. They say that the disease caused by this parasitic protozoan, toxoplasmosis, can make people mad. They say the oocysts from cat feces find their way to the oceans where they harm marine life such as Beluga whales and otters. It also means that in research to find a cure for toxoplasmosis the cat is used as a test subject. This happened over a long time at USDA laboratories which caused uproar in high political places because of its inherent cruelty (many cats were killed in this research).

That’s the background in brief. It is therefore interesting to read a research study which tells us for the first time why cats are the hosts.

The research is published on and is titled: Intestinal delta-6-desaturase activity determines host range for Toxoplasma sexual reproduction.

As usual the language used in the summary (the abstract) is very complicated. However, the key section is:

“Here, we defined the mechanism of species specificity for T. gondii sexual development and break the species barrier to allow the sexual cycle to occur in mice. We determined that T. gondii sexual development occurs when cultured feline intestinal epithelial cells are supplemented with linoleic acid. Felines are the only mammals that lack delta-6-desaturase activity in their intestines, which is required for linoleic acid metabolism, resulting in systemic excess of linoleic acid2, 3.”

In short, and as I understand it, cats lack an enzyme in their stomach (delta-6-desaturase) which would normally breakdown linoleic acid. As the enzyme is missing there is an excess of linoleic acid, which is a medium in which toxoplasma gondii thrives. That’s my interpretation of the text.

“We found that inhibition of murine delta-6-desaturase and supplementation of their diet with linoleic acid allowed T. gondii sexual development in mice.”

The discovery means that scientists can create the same state of affairs in mice which in turn means that they can test for toxoplasmosis using mice and not cats which should please cat lovers. It does beg the question as to why mice have less value than cats.


Does cat vomit contain toxoplasmosis?

This is a good question that had not occurred to me before I noticed that it is a Google search ...
Read More

Two cats use a human toilet at the same time

This is the first time I have seen a record of this sort of behaviour in a picture. Training cats ...
Read More

Benedict Cumberbatch to star in a cat movie!

Benedict Cumberbatch is playing the lead role in a film about Louis Wain, the eponymous and cat-loving English artist who ...
Read More

Fake news: New York Times’ article about house cats killing sea otters

The New York Times' article about sea otters becoming infected with Toxoplasma gondii is highly misleading to the point of ...
Read More

Inconclusive study does not find Toxoplasma gondii infection causes schizophrenia in people

An inconclusive study does not find Toxoplasma gondii infection causes schizophrenia as is reported on many websites this morning. The ...
Read More

Is it true that toxoplasmosis partially blinded two Turkish women?

A Turkish online newspaper, Hurriyet Daily News, reports that toxoplasmosis has caused partial blindness in two Turkish women. Both women ...
Read More

Toxoplasmosis is good for business

Toxoplasmosis, the 'litter tray parasite', is good for business which means that by most people's standards it is good for ...
Read More

USDA spends $650,000 of taxpayer’s money annually to toxoplasma-infect 100 kittens and kill them

I had no idea that it cost that much to carry out cruel and unnecessary animal experiments on kittens. There ...
Read More
Please comment here using either Facebook or WordPress (when available).
Michael Broad

Hi, I'm a 71-year-old retired solicitor (attorney in the US). Before qualifying I worked in a many jobs including professional photography. I have a girlfriend, Michelle. I love nature, cats and all animals. I am concerned about their welfare.

Leave a Comment

Recent Posts

Can a cheetah breed with a leopard?

There is some interest as to whether the cheetah can breed with any one of…

3 hours ago

Don’t ignore homeopathy as a possible treatment for your cat

Homeopathy is a controversial treatment for ailments in people. It can also be used as…

7 hours ago

The reason why cats feel pain when they eat ice cream

There was a craze on the Internet recently about cats eating ice cream and filming…

8 hours ago

Dog never barks and likes to be on elevated surfaces (he thinks he is a cat)

Mako acts like a cat and his human leader thinks it is because he was…

19 hours ago

“Stink and smell of cats” puts off a homebuyer

The Sun newspaper provides us with some insights, from the online lettings portal Mashroom, on…

1 day ago

During the pandemic lockdowns puppy farms and kitten mills are thriving

To varying degrees, governments have confined citizens to their homes or restricted their movements throughout…

1 day ago