UC Merced research discovers increased dangers from parasite

New research at UC Merced has discovered that the toxoplasma parasite, an organism capable of infecting almost all warm-blooded animals, can be more dangerous than most believed.

The parasite is known to cause toxoplasmosis, a disease that can result in flu-like symptoms, but more serious cases also can cause lesions in the retina and the brain.

Researchers at UC Merced explained that the toxoplasma parasite is acquired orally, most commonly by eating undercooked meat. The parasite also can be acquired through interaction with cat feces, such as when people garden with soil that has been contaminated by infected stray cats.

According to the Centers for Disease Control and Prevention, toxoplasmosis is a leading cause of death attributed to food-borne illness in the United States. The CDC estimates that more than 60 million men, women and children in the U.S. carry the toxoplasma parasite, although very few will develop symptoms.

Kirk Jensen, an assistant professor in microbiology and immunology at UC Merced, has been one of the lead researchers and a co-author of a paper published Tuesday in “mBio,” an open-access journal presented by the American Society for Microbiology.

His interest in parasites and the immune system, Jensen said, started when he contracted malaria in his early 20s during a three-week trip to Suriname in South America.

After treating his disease and completing his undergraduate and graduate studies at the University of California, San Diego, Jensen began studying toxoplasma pathogens during his doctoral program at Stanford.

“What makes toxoplasma so amazing is that it doesn’t have any real host specificity; they can infect anything,” Jensen said. “They can evade and manipulate the immune system, then they enter into this cyst form, usually in our brain,” Jensen said.

Pregnant women and those with compromised immune systems, such as HIV/AIDS patients and those receiving chemotherapy, are more prone to toxoplasmosis, according to the CDC.

Jensen explained that there are some toxoplasma parasites found in North America and Europe, but that the organisms are more common in South America – especially in rural areas near the Amazon.

This new research project found that South American strains of the parasite are stronger and better at evading the immune system, resulting in disease in hosts that should have been immune.

“Normally you can vaccinate with certain strains, and that protects you from second infection of that same species,” Jensen said. “But we found that these South American strains go right through that.”

In a healthy immune system, replication of toxoplasma parasites is usually blocked by T-cells, a type of white blood cell, Jensen explained. The South American strains, however, are more virulent and can cause the immune system to shut down its response.

The ideal treatment would be a drug that activates the immune system during infection, Jensen said. “It won’t attack the parasite, but it will allow our immune system to better respond.”

Jensen started his research at the Massachusetts Institute of Technology, where he worked for six years before moving to UC Merced last summer. In Merced, Jensen plans to further explore this concept with the help of university research assistants.

This story was originally published February 24, 2015 at 8:07 PM with the headline "UC Merced research discovers increased dangers from parasite."