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 bioRxiv.com 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.

SOME ARTICLES ON TOXOPLASMA GONDII:

Pallas’s cats at zoos infected with Toxoplasma gondii

Pallas's cat is sometimes referred to as 'Pallas cat'. The former name is the accurate one together with Manul. The ...
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Australian professor claims that toxoplasmosis from cats causes 200 fatal car accidents annually in Australia

Professor Sarah Legge, of the Australian National University and the University of Queensland is the lead scientist of a team ...
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In Korea an outbreak of human toxoplasmosis was caused by ingesting food contaminated with Toxoplasma gondii

This is a recently published study on how prevalent the disease called toxoplasmosis is in Korean cats and dogs. It ...
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Can cats be tested for toxoplasmosis?

Cats can be tested for toxoplasmosis. Serologic tests including ELISA (enzyme-linked immunosorbent assay) will show if a cat has been ...
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Can kitty litter cause birth defects?

The question hints at one of the great dilemmas of cat loving women who want to have a child. There ...
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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 ...
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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 ...
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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 ...
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Michael Broad

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

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