Rock doc: Undulant fever in cattle and people
Normally, when a bacterium invades your body, it’s surrounded and engulfed by a white blood cell. At least that’s what we were taught in high school biology. If all goes well, the white blood cell kills the bacterium and the infection is over: case closed.
But a few bacteria have some tricks up their sleeves. One of them is the rod-shaped Brucella bacterium, the agent that causes brucellosis or what is sometimes known as “undulant fever” because it causes people to run debilitating fevers that wax and wane in intensity over long periods of time.
Brucellosis is nasty stuff. Untreated, it makes people sick for years. Over time the bacteria settle in the joints where they can do real damage. Both literally and figuratively, brucellosis is a crippling disease.
People don’t get the malady from people who already have it, but from farm animals like cattle and goats that are infected. Often it’s unpasteurized milk that transmits the disease. Diseases that are transmitted from animals to us are known as zoonotic maladies.
“Raw milk is quite risky in terms of spreading the infection from cattle to people,” Dr. Jean Celli told me recently. Celli is a new researcher at the Paul G. Allen School for Global Animal Health at Washington State University. He studies brucellosis, including how it behaves in the white blood cells of animals and people.
When the brucellosis bacterium is engulfed by a white blood cell, it hides inside a compartment of the cell called the endoplasmic reticulum (ER for short). Normally a white blood cell would kill a bacterium, but once one is inside the ER the white blood cell is hampered in any further response to the invader.
“The brucellosis bacterium multiplies in the ER,” Celli told me. “It can also be transported by the white blood cells and spread elsewhere in the body.”
On the good side, there aren’t any antibiotic resistant strains of Brucella. That helps make the malady treatable. In this country, people who are diagnosed with the disease take antibiotics for several weeks and are generally able to put the disease behind them.
But the situation is different in the developing world. In the first place, making the diagnosis is not simple. The symptoms — fever and fatigue — are the same as for some other diseases, including influenza and malaria. To make a rigorous diagnosis, doctors must culture samples of blood or bone marrow. That requires good laboratory work.
“And then there is the expense of several weeks worth of antibiotics,” Celli said.
Even in the U.S., some people who are given antibiotics may not stick with them for the whole period over which they are prescribed. That means that some patients relapse later on down the road.
“It really changes your life,” Celli said. “People who come down with the infection can be depressed for long periods as a side effect of the disease.”
In short, treating and recovering from brucellosis is nothing to sneeze at. But due to our good system for pasteurizing dairy products, brucellosis is rare in this country. Outside the U.S., however, about half a million people per year are infected. If researchers could better understand how brucellosis works within cells, disease processes could be interrupted via more effective treatment.
“If we knew how the brucellosis bacteria signal the white blood cells to reach the ER and what then leads the bacteria to exit infected cells and spread further, we might be able to develop medications that would stop the infection process,” Celli said.
Beyond that, if research leads to a better understanding of how brucellosis works in our bodies, we might be another step closer to better treatments of other diseases that hijack the immune system — diseases such as salmonella and tuberculosis.
Even setting aside the problems the disease causes people, it’s economically significant in farm animals, especially in the developing world.
Celli’s research into brucellosis is highly technical, and I’m sure it ain’t cheap. But combatting persistent diseases that affect livestock and people is the kind of investment we can make to create a better world for our children — and for the children of farmers living in the developing world.
Dr. E. Kirsten Peters, a native of the rural Northwest, was trained as a geologist at Princeton and Harvard. This column is a service of the College of Agricultural, Human and Natural Resource Sciences at Washington State University.