Tuberculosis and Seals: Sea Mammals as Harbingers of Disease

By Chris Healey

Seals introduced one of the deadliest illnesses in history to the Western Hemisphere centuries before Europeans carried it over. Researchers at the University of Tubingen in Germany published findings in the research journal Nature describing the role seals played in introducing tuberculosis to the Americas.

Before these findings, the presence of tuberculosis in North and South America prior to European exploration was unexplained. Tuberculosis spread across Africa, Europe, and Asia, but there was no evidence demonstrating tuberculosis concurrently existed in the Americas. The bacteria made its first appearance in Peruvian skeletal remains dating back to approximately A.D. 700 – centuries before the arrival of European explorers.

Research findings indicate approximately 2500 years ago, seals contracted a Mycobacterium strain from Africa and carried it across the ocean to the shores of Peru and Northern Chile. Possibly through seal predation, costal humans contracted a version of the seal Mycobacterium which had adapted to humans. Tuberculosis has been found in skeletal remains in North America dating back to approximately A.D. 900, indicating the seal-derived strain spread person-to-person from South America.

One limitation of this study was the inability to rule out humans passing the agent to seals. The researchers deemed that alternative a distant possibility; humans did not treat seals as livestock. A close relationship, such as between farmer and animal, is required to pass a pathogen from human to animal.

The seal-derived strain did not last long in the Western Hemisphere. Following European settlement, European tuberculosis strains outcompeted and eliminated those from seals. Today, viable seal-derived strains do not exist.

Tuberculosis is a condition caused by Mycobacterium tuberculosis, a slow-growing bacterium adept at evading host immune response. The illness is one of the greatest threats to public health worldwide. According to the World Health Organization, tuberculosis kills more people than any other infectious agent except HIV/AIDS.

Despite advancements in therapeutic techniques, there has been a resurgence of tuberculosis fueled by the emergence of HIV/AIDS in the late 20th century. As an opportunistic pathogen, tuberculosis kills more AIDS patients than any other illness.

Tuberculosis is not the first human illness associated with seals. They are susceptible to certain subtypes of influenza, including H7N7, H4N5, and H3N2. Influenza subtypes maintained in seal populations could be re-assorted in other animals, such as fowl or swine, to produce subtypes which are highly virulent in humans.


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Pandora Report 8.22.14

Did you see that the destruction of Syria’s most lethal chemicals is now complete? Well, it is! Its good news among so many biodefense stories covering Ebola. I have no interest in making the Pandora Report the “All Ebola, All the Time” newsletter. As such, we will look at one Ebola story as well as stories covering new discoveries in tuberculosis and influenza.

Have a fabulous weekend, and students, enjoy your last one before classes start on Monday!

Tuberculosis is Newer Than Thought, Study Says

A recent study published in Nature reports that tuberculosis originated less than 6,000 years ago and was carried to the new world by seals. Seals! This new research contradicts original timeline and species genesis and some scientists think this study provides more questions than answers.

The New York Times—“In the new paper, the team proposes that humans acquired tuberculosis in Africa around 5,000 years ago. The disease spread to people across the Old World along trade routes. Meanwhile, Africans also spread the disease to animals such as cows and goats. Seals that hauled out onto African beaches to raise their pups became infected. The bacteria then spread through seal populations until reaching South America. Ancient hunters there became infected when they handled contaminated meat.”

Enzyme Holds the Door for Influenza

As the fall season and semester approach, the flu season travels with it. I was delighted to read that Walgreens, in addition to CVS, will now offer seasonal flu shots in their stores. More interesting news about flu came out of Vanderbilt University, too. Researches have investigated enzyme phospholipase D (PLD) and it ability to help the influenza virus escape immune response. Blocking PLD could assist in preventing the flu.

Bioscience Technology Online—“Normally the virus slips into its host cell in the epithelial lining of the lungs through internalized membrane compartments called endosomes. By delaying this process, the researchers propose, PLD2 inhibitors may give the cell’s innate immune response more time to destroy it.”

Patient Checked for Ebola Virus in Sacramento

Internationally, the good news is that quarantines have been set up in Liberia, in attempt to contain the spread of Ebola. The bad news is that they have become fairly violent. Stateside, this week Dr. Kent Brantly and Nancy Writebol were released from Emory University Hospital after recovering from Ebola infections acquired in West Africa.

There was news of a possible case in Northern California. With few details provided as to the patient and transmission route, we learned that there is a patient being tested for Ebola in Sacramento. California Department of Health reported that the cases is low risk but that testing is being done out of “abundance of caution.”

San Francisco Chronicle—“‘In order to protect our patients, staff and physicians, even though infection with the virus is unconfirmed, we are taking the actions recommended by the CDC as a precaution, just as we do for other patients with a suspected infectious disease,” said Dr. Stephen Parodi, an infectious disease specialist at Kaiser Permanente North California. “This includes isolation of the patient in a specially equipped negative pressure room and the use of personal protective equipment by trained staff, coordinated with infectious disease specialists.’”


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