Good morning and welcome to the Saturday Lecture Series. I will be at the hospital today so below you will find most of the information you will need for the lecture.Feel free to post any question and I will do my best to answer them. This morning we have Tanzanian Peaberry coffee and bagels / toppings on the side table.
Is the Crazy Cat Lady born, or do the parasites MAKE her that way?
That may seem to be more of a joke than a question. However, given new evidence about Toxoplasma gondii and mental illness actually does beg that question. You see, I have a little theory. In X amount of cases, the parasite Toxoplasma gondii may actually cause an otherwise sane female to become a Crazy Cat Lady (I know of no Crazy Cat Men, so this will be a one sided discussion), and here is how. Female buys a cat, so she is already predisposed in her mental make up to like cats. Ok, so far, so good. No problems. Lets say that this person might have just a touch of mental illness, perhaps some schizophrenia or something. But just a small non-clinical aspect of her personality that does not need to be treated and is not that important in daily living. Let’s face it, everyone is a little goofy once in awhile; that doesn’t make you mentally ill. We all have our quirks. Perhaps the parasite brings out these quirks either by chance or by design. It would be in the best interest of the parasite to have many many cats in the same place living in close proximity. This would maximize the chance of reproduction of the parasite, would it not?
Humans may become infected by contact with cat feces or by eating undercooked meat. The importance of these modes of transmission may vary in different populations (3). Individual response to Toxoplasma infection is determined by immune status, timing of infection, and the genetic composition of the host and the organism (4).
Toxoplasma organisms have also been shown to impair learning and memory in mice (5) and to produce behavioral changes in both mice and rats. Of special interest are studies showing that Toxoplasma-infected rats become less neophobic, leading to the diminution of their natural aversion to the odor of cats (6). These behavioral changes increase the chances that the rat will be eaten by a cat, thus enabling Toxoplasma to complete its life cycle, an example of evolutionarily driven manipulation of host behavior by the parasite.
Lets move forward in time and infect this otherwise healthy cat-loving female with Toxoplasma gondii thusly:
The only known definitive hosts for Toxoplasma gondii are members of family Felidae (domestic cats and their relatives). Unsporulated oocysts are shed in the cat’s feces 
. Although oocysts are usually only shed for 1-2 weeks, large numbers may be shed. Oocysts take 1-5 days to sporulate in the environment and become infective. Intermediate hosts in nature (including birds and rodents) become infected after ingesting soil, water or plant material contaminated with oocysts 
. Oocysts transform into tachyzoites shortly after ingestion. These tachyzoites localize in neural and muscle tissue and develop into tissue cyst bradyzoites 
. Cats become infected after consuming intermediate hosts harboring tissue cysts 
. Cats may also become infected directly by ingestion of sporulated oocysts. Animals bred for human consumption and wild game may also become infected with tissue cysts after ingestion of sporulated oocysts in the environment 
. Humans can become infected by any of several routes:
- eating undercooked meat of animals harboring tissue cysts
. - consuming food or water contaminated with cat feces or by contaminated environmental samples (such as fecal-contaminated soil or changing the litter box of a pet cat)
. - blood transfusion or organ transplantation
. - transplacentally from mother to fetus
.
In the human host, the parasites form tissue cysts, most commonly in skeletal muscle, myocardium, brain, and eyes; these cysts may remain throughout the life of the host. Diagnosis is usually achieved by serology, although tissue cysts may be observed in stained biopsy specimens 
. Diagnosis of congenital infections can be achieved by detecting T. gondii DNA in amniotic fluid using molecular methods such as PCR 
.
In the following abstract we have a positive relationship between T. gondii and evolution of mental illness:
Abstract
Recent epidemiologic studies indicate that infectious agents may contribute to some cases of schizophrenia. In animals, infection with Toxoplasma gondii can alter behavior and neurotransmitter function. In humans, acute infection with T. gondii can produce psychotic symptoms similar to those displayed by persons with schizophrenia. Since 1953, a total of 19 studies of T. gondii antibodies in persons with schizophrenia and other severe psychiatric disorders and in controls have been reported; 18 reported a higher percentage of antibodies in the affected persons; in 11 studies the difference was statistically significant. Two other studies found that exposure to cats in childhood was a risk factor for the development of schizophrenia. Some medications used to treat schizophrenia inhibit the replication of T. gondii in cell culture. Establishing the role of T. gondii in the etiopathogenesis of schizophrenia might lead to new medications for its prevention and treatment…
From the article…Neuropathologically, studies of T. gondii in cell culture have shown that glial cells, especially astrocytes, are selectively affected (44,45). Postmortem studies of schizophrenic brains have also reported many glial abnormalities (46), including decreased numbers of astrocytes (47). Similarly, animal studies of Toxoplasma infections have demonstrated that this organism affects levels of dopamine, norepinephrine, and other neurotransmitters, which are well known to be affected in persons with schizophrenia.
What we have here is a parasite that can manipulate the brains of rats to become less neophobic so they get eaten by the cats. This completes the life cycle of the parasite. Why couldn’t the parasite from manipulate the neural structure and chemistry of the human brain to also continue the parasite’s life cycle? I will bet that near 100% of Crazy Cat Ladies are positive for T. gondii . How many of them are acting on free will and how many are truly ill? Just something to think about next time you see a news story about a Crazy Cat Lady, perhaps she is being driven by the parasite?
