Estimated read time: 3-4 minutes
This archived news story is available only for your personal, non-commercial use. Information in the story may be outdated or superseded by additional information. Reading or replaying the story in its archived form does not constitute a republication of the story.
SALT LAKE CITY -- Your pet may be making you crazy in more ways than one. New research has linked a common cat parasite which infects some 60 million humans to a neurotransmitter related to everything from depression to schizophrenia.
Toxoplasmosa gondii is carried by the common house cat - and many, many cats are carriers of the disease.
For years, doctors and scientists have known that Toxoplasmosa has some interesting effects on mice, for instance, making them paradoxically attracted to the smell of cat urine - essentially making them zombies that seek out their own destruction. This allows the infection to spread more readily when the cat eats the mouse and gets infected itself.
There has also been a lot of speculation on what kinds of effect this parasite, related to the common malaria bug, can have on humans. Things like depression, psychosis, or even something as simple as a tendency to be jealous.
A new study from the University of Leeds has shown that Toxoplasmosa directly affects dopamine production. In fact, it works on the same brain pathways as drugs used to treat schizophrenia, and may even cause an increased risk of the mysterious and frightening neurological disease.
- Blood transfusions or solid organ transplants
- Carelessly handling cat litter, which can lead to accidental consumption of infectious particles
- Eating contaminated soil (from vegetables)
- Eating raw or undercooked meat (lamb, pork, and beef)
The infection may also be passed from an infected mother to her baby through the placenta. Most primary infections produce no symptoms. The time between exposure to the parasite and symptom development is 1 - 2 weeks. The disease can affect the brain, lung, heart, eyes, or liver.
Symptoms in persons with otherwise healthy immune systems:
- Enlarged lymph nodes in the head and neck
- Headache
- Mild illness with fever, similar to mononucleosis
- Muscle pain
- Sore throat
- Confusion
- Fever
- Headache
- Retinal inflammation that causes blurred vision
- Seizures
"Based on these analyses, it was clear that T. gondii can orchestrate a significant increase in dopamine production in neural cells," said Dr. Glenn McConkey, lead investigator in the study.
Dopamine is a crucial neurotransmitter, and has all kinds of roles in different parts of the brain. It is related to pleasure, and therefore pleasure-seeking behavior, as well as risk-related decision making, sociability, attention span, and motivation. Lack of dopamine is one of the primary contributing factors in Parkinson's disease as well.
Changes in brain chemistry occur because the parasite actually carries the genetic code for dopamine production in its own genome. It forces host cells to produce tyrosine hydroxylase, which is needed for the production of dopamine, hence increasing dopamine levels in the infected part of the brain considerably.
"Humans are accidental hosts to T. gondii and the parasite could end up anywhere in the brain, so human symptoms of toxoplasmosis infection may depend on where parasite ends up," said McConkey.
This goes a long way to explaining lots of behavioral symptoms correlated to toxoplasmosis - decreased novelty seeking behavior, jealousy in men, increased warmth in women, schizophrenia and impulsiveness. In fact, toxoplasmosis is correlated to an increased risk of car accidents.
The upshot is that this research could actually help medical scientists figure out how to better treat diseases that are related to dopamine, and how it works in different parts of the brain.
Toxoplasmosis is a very common illness, especially in poverty-stricken areas, where upwards of 60 percent of humans can be infected. For healthy people, there's not a lot of immediate health risk and the disease is often left untreated. But for those who have weak immune systems, like the young or elderly, pregnant women or people with AIDS, the disease can be fatal.
But even those with strong immune systems that will suppress the infection can carry the illness latently, without any overt symptoms, and it's this kind of low-level infection that can make you subtly more likely to get into an accident or beat up that guy who is eyeing your girl.
Email: [dnewlin@ksl.com](<mailto: dnewlin@ksl.com>)
