Episode 93: Emma Wilson talks about Toxoplasma gondii infection and its consequences

// Aug 6, 2019

Our guest today is Dr. Emma Wilson, a researcher who has spent the past 15 years studying Toxoplasma gondii, a protozoan parasite that infects about a third of the world’s population.

She is a native of Scotland and a professor of biomedical science at the University of California, Riverside.

Toxoplasma gondii is a single-celled organism found in all mammals. The primary focus of Emma’s research is the immune response in the brain following Toxoplasma gondii infection. Her 2016 research paper in the online journal PLOS Pathogens connected the Toxoplasma gondii to brain dysfunction.

Show notes:

[00:03:05] Emma begins the interview taking about growing up was born in Glasgow with parents who were in the acting business.

[00:03:38] Emma shares how her father advised her to keep all of her doors open, which lead her as a youth to pursue everything she found interesting.

[00:04:30] Dawn asks if Emma decided to major in ecology in an effort to help save the rainforests.

[00:05:28] Ken asks about Emma’s experience with a “proverbial crazy professor” who showed her a room full of rattlesnakes and how that experience led to Emma’s curiosity in immunology.

[00:06:54] Ken asks whether if it’s that she was paid to stand out in the bush so that mosquitos could feast upon her during a research trip to Tanzania.

[00:08:16] Ken asks if Emma’s experience in Africa was limited to mosquitos or if she was able to see some of the impressive wildlife there.

[00:09:26] Emma discusses her experiences after her research trip to Africa and her decision to pursue work in immunology at Dr. William Harnett’s lab at the University of Strathclyde.

[00:10:32] Dawn asks about the research Emma did in Harnett’s lab.

[00:11:46] Dawn mentions that Emma had the opportunity to attend a conference in Philadelphia where she met many interesting people. She goes on to ask about the conference and how she ended up spending the next five and a half years at the University of Pennsylvania.

[00:13:52] Dawn mentions another conference Emma was able to attend, this one in California, where she stood out for asking so many questions. Dawn asks about how this led her to go to work at University of California, Riverside.

[00:16:50] Ken mentions that the primary focus of Emma’s research at Riverside is the immune response in the brain following Toxoplasma gondii infection, further mentioning that in an episode of the podcast “This Week in Parasitism” Dr. Dickson Despommier referred to Toxoplasma gondii as the most successful parasite on Earth. Ken asks Emma to give an overview of what Toxoplasma gondii is and does.

[00:18:58] Dawn asks why Toxoplasma gondii has such a high infection rate in countries such as France and Brazil, where close to 80 percent of people are infected. In the U.S., only 15 to 30 percent of people are infected.

[00:20:49] Ken mentions that Eskimos, who’s traditional diet is rich in raw meat, have an almost 100 percent infection rate.

[00:21:19] Ken asks how the Toxoplasma parasite prevents digestion in the stomach.

[00:23:12] Emma discusses how most cases of Toxoplasma in healthy adults present little to no consequences of infection, but that congenitally infected children or people who are immunocompromised can have serious consequences.

[00:25:33] Ken asks how an immunocompetent individual keeps the infection at bay and if there is any risk associated with that constantly active immune response in the brain to this infection.

[00:27:32] Ken explains that cats are the only definitive host of the toxoplasmosis parasite because it can only complete its sexual reproduction cycle in the gut of a cat. He goes on to explain that cats eat rats, and sometimes rats eat cat feces, which infects the rats with Toxoplasma gondii, When the cats eat these rats the cats perpetuate the cycle. Ken asks Emma to explain how the infection changes the fundamental fear response in rodents that they naturally have to cats.

[30:48] Ken mentions amazing videos on the web showing infected mice approaching cats and rubbing up against them affectionately.

[00:31:50] Dawn asks if vegetarians are safe from Toxoplasma gondii infection, given that humans typically contract the parasite via uncooked meat from intermediate hosts such as sheep, cows, goats, and pigs.

[00:33:03] Dawn asks if the relationship between the toxoplasmosis parasite and their host can be mutually beneficial.

[00:34:24] Dawn asks if seafood can lead to infection.

[00:35:33] Ken mentions that there is presently no vaccine for Toxoplasma gondii; however, there are commonsense preventative measures such as pregnant women avoiding cat litter and wearing gloves while gardening. Ken goes on to ask if there are any other ways to reduce chances of infection.

[00:37:42] Dawn mentions that Emma and her colleagues at Riverside had a 2016 paper in the journal PLOA Pathogensthat described how Toxoplasma infection leads to a disruption of neurotransmitters in the brain. Dawn goes on to mention that Emma postulated that the infection triggers neurological disease in those who are already predisposed to such diseases.

[00:41:45] Dawn asks if the sex of an animal changes the effect of toxoplasmosis.

[00:42:36] Ken asks if Emma thinks there would be different effects on animals in the wild, in terms of toxoplasmosis infections, or if the laboratory experiments provide a good model for infection.

[00:43:21] Ken mentions that in terms of neurological disease, Toxoplasma’s strongest correlation is with schizophrenia, but Ken mentions that Emma believes the parasite’s presence is a precipitating factor.

[00:44:45] Emma explains the arguments for and against the belief that toxoplasmosis infections are asymptomatic in most humans and acts as a silent partner that serves no role.

[00:47:01] Dawn asks if we should be looking into the effects of eradicating toxoplasma in asymptomatic humans, and, if so, how would this be accomplished.

[00:48:04] Dawn mentions that there are some reports that humans who display risk-taking behavior are more likely to be infected with Toxoplasma gondii, including a higher likelihood in individuals who die in motorcycle accidents as well as entrepreneurs. Dawn asks if there is sufficient evidence to suggest that Toxoplasma gondii might alter risk taking behaviors in humans.

[00:49:42] Dawn brings up that after the aforementioned 2016 paper  was published, Emma was quoted as saying that for the first time it has been shown that the direct disruption of a major neurotransmitter in the brain resulted from the infection.  Dawn asks Emma if her research has since then been focused more on the mechanisms of the parasite.

[00:53:07] Ken mentions that in 2016, Sugden et al published results of a study looking at a cohort of early middle-aged individuals that suggested Toxoplasma gondii infection does not result in increased susceptibility to neuropsychiatric disorders, poor impulse control or impaired neurocognitive ability. In addition, they found no association between infection and aberrant personality types. He asks why these findings do not reflect other contemporary research on Toxoplasma gondii.

[00:56:12] Dawn asks about Emma’s collaboration with Michael White, with whom she is looking at Toxoplasma gondii cyst formation.

[00:57:49] Emma discusses the findings of her2017 paper “Brains and Brawn: Toxoplasma Infections of the Central Nervous System and Skeletal Muscle” in which she discussed how Toxoplasma infection can affect skeletal muscle.

[00:59:04] Dawn asks if these effects related to skeletal muscle also occur in people who are asymptomatic.

[01:00:47] Ken asks if there might be a way to mitigate the impact of acute and chronic Toxoplasma gondii infection via dietary manipulation or supplementation.  Ken referenced a 2016 paper published in PLOS One, in which a Chinese research team reported that T. gondii seems to hijack the host’s PPAR signaling pathway to downregulate the metabolism of fatty acids, lipids and energy in the liver.  Ken said that he wonders if a ketogenic diet or supplementation with exogenous ketones might be beneficial?

[01:02:37] Dawn asks what the future of Toxoplasma research should look like given that the broad impact of Toxoplasma gondii on international society and economics is poorly understood.

[01:04:22] Ken mentions that in reference to Toxoplasma gondii, there were a whole spat of papers that sensationalized the nature of the infection. He goes on to ask what responsibility should university press offices and the researchers themselves have in preventing clickbait and communicating science effectively.

[01:06:58] Dawn mentions that when Emma moved to Riverside she decided to focus on work and not getting into a relationship, but despite this ended up getting married and now has a busy household.

[01:07:57] Dawn mentions that when Emma became pregnant her husband took care of the cat litter. Dawn asks if he still changes the cat litter today.

[01:08:19] Dawn asks if Emma has any other final words of advice for people trying to avoid Toxoplasma gondii infection.




Emma Wilson UC Riverside faculty page

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