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Toxoplasma Gondii: The Brain Hitchhiker

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kitty3Toxoplasmosis is a widely known disease that results from infection with the Toxoplasma gondii parasite, one of the world’s most common parasites. Infection usually occurs by eating undercooked contaminated meat, exposure from infected cat feces, or mother-to-child transmission during pregnancy.  Estimates suggest that about 1/3 of the entire human population of the Western world is harboring the parasite in the form of “benign cysts” concentrated mostly in the brain.

The parasite can form cysts anywhere almost: hearts, lungs and eyeballs are common hiding places, but the brain is the preferred hangout for this organism.  If you are a cat lover, chances are high you are already infected, courtesy of your cat.  Cat brains are a natural repository for the adult protists, which reproduce inside our feline friends and spread from cat feces.  This is not to say that won’t infect any warm-blooded animal that they are capable of, but the only hosts truly necessary for their continued survival are felids, according to the CDC website.  Once infected, they usually infect you for your entire lifespan, mostly asymptomatically.toxo

The most interesting thing about the infection, though, is that the cysts hijack our brains, producing subtle but measurable and influences on behavior.  Scientists have suspected that the success of Toxoplasma is due in part to its’ ability to change rats and mice behavior, and causing them to stop fearing cats.

In a now famous study, it was demonstrated that mice, which have a morbid fear of cats and a strong fear reaction to cat odor, tend to lose that fear and unequivocally show a preference for cat odor after being infected with the parasite.

Mice aren’t the only ones whose brains can be hijacked, though: there’s a good chance that the parasite in your head may be at least partly responsible for the shots you call, too.  A growing body of research indicates that the manipulation theory, as it is called in medical and biological journals, extends to human in several ways.  Latent toxoplasmosis in humans has been associated with serious neurological disorders, including schizophrenia, intermittent explosive (rage) disorder and suicide.

In addition, research shows infection by Toxoplasma gondii, directly affects the production of dopamine, a key chemical messenger in the brain.  Dopamine is a natural chemical which relays messages in the brain controlling aspects of movement, cognition and behaviour. It helps control the brain’s reward and pleasure centres and regulates emotional responses such as fear. The presence of a certain kind of dopamine receptor is also associated with sensation-seeking, whereas dopamine deficiency in humans results in Parkinson’s disease.

Infection changes the way that your brain processes information, slowing reaction times (more traffic accidents) and changing your preferences for a great many things, from risk aversion to tidiness to extraversion.  The effects of Toxoplasma infection on an individual depend on genetics, with some genotypes immune to infection and less likely to experience effects, and gender.  To take one example, the effect on personality has been summed up after analyzing multiple studies, each with well over a hundred (and often several hundred) subjects.

According to Effects of Toxoplasma on Human Behavior, significant differences in personality factors were found between Toxoplasma-infected and -uninfected subjects in 9 of 11 studies, and these differences were not the same for men and women. After using the Bonferroni correction for multiple tests, the personality of infected men showed lower rule consciousness and higher vigilance. Thus, the men were more likely to disregard rules and were more expedient, suspicious, jealous, and dogmatic. The personality of infected women, by contrast, showed higher warmth, suggesting that they were more warm hearted, outgoing, conscientious, persistent, and moralistic.

Even sexual characteristics and preferences might be affected.  In one photograph study, men who harbor infections are consistently rated as being more dominant and masculine looking then men who don’t have infections – on the basis of photographs alone.  Toxoplasma increases expression of the genes coding for testosterone in men, and the effect is large enough to be seen by the naked eye and borne out by physical measurements, including a noticeable 3 cm boost in average height.

Although the mechanisms by which this parasite seems to influence its’ hosts are still being elucidated, its’ clear that it touches our lives in ways we never before imagined.  How much of “them” is really “us”?

Anti-Cancer Gut Bacteria

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The human microbiome is the subject of a burgeoning field of research.  The effect of gut microflora, and especially bacteria, has in the last few years been linked to anxiety, depression, gastrointestinal and autoimmune diseases, and numerous other disorders. Read More

Merck Backs Out of Vaccine Commitment to Africa

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Merck’s decision may leave more than 2 million children in West Africa unvaccinated and vulnerable to rotavirus in 2020.

At the same time Merck cut the vaccine supplies to West African countries, they began delivering RotaTeq to China.  Each vaccine will likely cost more than $40 per dose.  When asked if there was a connection between the launch in China and Merck not fulfilling their West African commitment, a Merck spokesperson wrote:

When faced with supply constraints, such as this, we evaluate all options to determine how we can fulfill the agreement we made with UNICEF and GAVI-eligible countries to the best of our ability, while at the same time meet the binding contract demands we have with other countries. The product we have allocated to China is what has been approved for use in that country to fulfill the terms of a binding agreement we signed with a local vaccine company in 2012. As I’m sure you can appreciate, the details of that contract is proprietary to Merck; as such, we cannot confirm the number of doses nor discuss price.

“Kids should not be denied vaccines just because they belong to a poor country.”-Dr. Mathuram Santosham at Johns Hopkins University

Where does that leave the kids in West Africa? UNICEF, which delivers vaccines to poor countries worldwide, says it’s trying to help the West African countries switch to another vaccine.  The World Health Organization prequalified two new rotavirus vaccines manufactured in India earlier this year:  Rotasil and Rotavac.  Both vaccines are available to Gavi at a cost of less than $2 per dose.

Unfortunately, the switch will not be quick-or easy.  Prequalification of a vaccine is the beginning of a long process, including a regulatory actions that must occur.   The process is daunting, with more than a few moving parts that require time and money.  New vaccines may be tested in small pilot programs, health care workers have to be retrained on vaccine administration, clinics need the ability to store and transport the new vaccine.  That will require possibly up to five years for the vaccine to be widely available in West Africa, says Frederick Cassels, at the nonprofit PATH, which helped develop Rotasil and Rotavac.  Even just a delay of a few years would put millions of babies at risk for rotavirus, says Johns Hopkins University’s Santosham. “We all as a community should come together and make sure these kids get this vaccine.”

According to Merck, their third quarter 2018 worldwide sales were $10.8 billion.  Good for Merck-really.  More profits mean more research, and more lives saved overall.  Most reasonable people realize that companies need to make a profit to stay in business, and that includes pharmaceutical companies.  But the pharmaceutical industry is not like other industries that sell tires or pizza.  Due to the nature of the business, pharmaceutical industry profits are made off of illness and disease–this requires a level of sensitivity and responsibility to the community that the local pizza joint does not need to make.

What level of responsibility do pharmaceutical companies owe to the people?  Has Merck denied their responsibility to the community and turned their back on the poor children of Africa?  Can a company be both profitable and ethical, or are those incompatible values?  These are questions that need consideration, since we live in a world with expanding need, and shrinking resources. 

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