Boost for tick disease research

Dec 10 2007

Roman Ganta, a professor of diagnostic medicine and pathobiology at Kansas State University, has been awarded a grant of $1,825,000 by the National Institutes of Health to figure out how to stop the tick-borne bacteria, Ehrlichia chaffeensis, from making animals and people sick.

This is the second grant of roughly the same size Ganta has received for this research.

Ehrlichia chaffeensis affects people and animals primarily in the southeastern and south central regions of the U.S. It is transmitted by the lone star tick. The resulting sickness, termed Ehrlichiosis, is hard to diagnose because its symptoms' similarities with other, more minor infections. Symptoms include headache, fever, malaise and muscle aches. For those with compromised immune systems, the bacterial infection could be fatal.

Though very few cases are reported -- around 1,500 since the Centers for Disease Control deemed it a disease of concern in the late 1980s -- Ganta estimates that as many as 50,000 people have actually contracted ehrlichia chaffeensis. Though relative to the nation's population that doesn't seem significant, the ensuing infection and symptoms can be serious, especially if untreated. As many as half of the patients diagnosed with ehrlichiosis require hospitalization.

This particular tick-borne pathogen is also unique because it circumvents the initial defenses of the immune system of the animal or human the tick bites, according to Ganta.

When bacteria enters the mammalian body the response is typically the same: the bacteria multiply and the immune system gears up, sending out its own organisms -- cells derived from white blood cells called macrophages -- to seek out and destroy the offender.

The average, healthy immune system can clear the body of most bacterial infections. But ehrlichia chaffeensis gets past that first line of defense, making the infection persist and the subsequent illness difficult to get rid of.

"It's like the enemy entering into a battlefield and knowing exactly where the landmines are and diffusing them all," Ganta said.

Over the last five years, Ganta's research team has been working under a prior federal grant, also from the National Institutes of Health, to uncover exactly how the bacteria works. They recreated the bacteria using cells from mice and from ticks. The current study revealed that the tick cells are what made the difference, and that the tick's ecology changes the bacteria by adding proteins, enabling bacteria to slip by the immune system.

"Understanding the molecular basis for persistence by these bacteria has been critical in developing effective methods to control this and other tick-borne pathogens," Ganta said. "Our research is focused on understanding the pathogen evasion mechanisms, and then using those to defeat it."

The trick now is to learn how to turn those proteins off, leaving the bacteria vulnerable, Ganta said. That's the research his new grant will fund.

Ganta said that tick-borne pathogens like ehrlichia chaffeensis have long been recognized as a persistent concern for the health of several companion animals and livestock. The number of cases in humans has also risen in recent years, increasing the threat to public health.

The hope is that once Ganta comes up with a way to fight off the bacteria, that will pave the way for solutions to other forms of ehrlichia, some of which are devastating for cattle and other food animals.

The $1,825,000 grant is for five years of study at $365,000 a year.