Is latent Toxoplasmosis worth doing something about?

by jsalvatier 8y17th Nov 201129 comments


Toxoplasmodi gondii is a parasitic protozoa who's primary host is cats but also infects other mammals, primarily mice and rats but including humans, as part of its life cycle. Infection by Toxoplasmodi gondii is called Toxoplasmosis and may be acute (flu like symptoms) or latent. 

Toxoplasmosis is extremely common. Worldwide, about 30% (US 11%; France 88%!) of people about of people have Toxoplasmosis.

Toxoplasmosis is known to cause behavioral changes in rats:

It has been found that the parasite has the ability to change the behaviour of its host: infected rats and mice are less fearful of cats—in fact, some of the infected rats seek out cat-urine-marked areas. This effect is advantageous to the parasite, which is able proliferate if a cat eats the infected rat and thereby becomes a carrier.

Observational studies suggest that latent Toxoplasmosis may also cause behavioral changes in humans (source paper). The observed differences between infected people and non-infected people include:

  • Decreased novelty seeking behavior
  • Slower reactions
  • Lower rule-consciousness and greater jealousy (in men)
  • Greater warmth, conscientiousness and moralistic behavior (in women)
It's also suspected by some of being a cause of Schizophrenia.
Obviously some or all these may be due to unobserved 3rd causes.
There haven't been any randomized studies yet, as far as I know. It seems like such studies would be easy to conduct rigorously since a high fraction of the population is already infected. For example, by finding people who are already infected and randomly cure some of them. This kind of experiment is even pretty close to how you would expect the information to be used. 
I've been around cats a fair amount and the base rate is high in the US, so my chances of having latent Toxoplasmosis seem fairly high. Thus I am curious whether this is worth doing something about. Diagnosis sounds like it is fairly simple (PCR on blood samples). It's easy enough so that it can be done in large scale studies at least. Treatment is done with atovaquone and clindamycin, which appear to be relatively inexpensive.
I'd expect the effects to be net negatives (most random changes are detrimental) and even if the behavioral effects are smallish, the effects over a lifetime will add up. Has anyone else gotten tested and/or treated for latent Toxoplasmosis? Is it worth it?