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Ticks may be culprits for more diseases

April 20, 2001

NEW YORK (Reuters Health) -- Ticks may spread more diseases than previously

thought, California researchers have found.

Ticks carry bacteria that cause disease, including Lyme disease and Rocky

Mountain spotted fever. New evidence published in this month's Journal of

Clinical Microbiology implicates ticks in other maladies, including cat

scratch fever. This infection, as well as another illness known as " trench

fever, " are caused by members of a family of bacteria known as Bartonella.

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" We cannot say for certain that ticks are the vectors of these diseases, but

at the least we can say they carry Bartonella DNA and could be potential

(transmitters), " Dr. Bruno Chomel of the University of California at

and one of the study's authors, said in a prepared statement.

Chomel and his colleagues are beginning to suspect ticks in many diseases

where the pathways of transmittal seem fuzzy. One bacterium, Bartonella

quintana, caused the " trench fever " World War I troops caught on the

battlefield. In the trenches, lice spread the disease. But in a recent

outbreak in Seattle, Washington, lice were not a factor, the researchers

note.

Another infection, cat scratch disease, raises more questions about

transmission. While generally mild and self-limiting among people with

healthy immunity, the disease can lead to potentially fatal complications in

people with weak immune systems.

Scientists had thought that cat scratch fever, which is caused by Bartonella

henselae, was passed to humans from cat bites or scratches, as the name

would suggest. But past research has found that as many as 30% of human

patients infected may not have been bitten or scratched by a cat, and

another study linked the infection to tick bites.

For the current study, Chomel and colleagues set out to determine if ticks

might really be a possible channel of Bartonella-related disease. If

Bartonella organisms could be found in ticks before they fed on larger

animals, it would suggest that ticks played an important role in spreading

these illnesses.

To help answer this question, Chomel and colleagues collected hard ticks at

three sites in Santa Clara County and extracted DNA from their bodies,

hoping to match specific genes to those of Bartonella bacteria. Of the 151

ticks they examined, the researchers found nearly 20% carried a Bartonella

species, including those known to cause disease in humans.

" That's even higher than for known tick-borne diseases like Borrellia

burgdorferi (the cause of Lyme disease), " Chomel said in a press release.

The study doesn't provided positive proof that ticks are responsible for the

spread of these diseases in humans, he noted, but it does suggest that the

arthropods are worthy of more investigation.