Expert warns of spread of Rocky Mountain Spotted Fever

Aug 11 2005

An expert on infectious diseases at Johns Hopkins University School of Medicine, is warning that humans can inadvertently help spread infectious organisms beyond traditional state boundaries.

A recent outbreak in Arizona of Rocky Mountain Spotted Fever, has prompted Professor J. Stephen Dumler, a pathologist and microbiologist, to voice his concern that the first widespread outbreak of the tick-borne infection in Arizona is a growing and dangerous sign.

Dr. Dumler, who has spent nearly three decades studying the life-threatening, tick-borne infection known as Rocky Mountain Spotted Fever, highlights the importance of the recent outbreak in Arizona, as the first confirmed cases that could be traced back to ticks carried into to the state on feral dogs.

The population of this group of animals has markedly increased, along with the number of ticks.

The disease is apparently most often distinguished by a spotty rash that appears five to ten days after the first signs of infection.

It has been largely confined to the South Central and Southeastern United States, though a few cases have been reported in all 48 continental states.

According to Dumler, the number of people infected with Rocky Mountain spotted fever has peaked for the third known time this century, with more than 1,800 cases reported nationally in 2003 and 2004.

But scientists believe the number of unreported cases is much greater.

The fever is fatal in up to 10 percent of those who contract it.

Dumler believes that the best means of curbing the potentially deadly impact of the disease, is the growing awareness among physicians about the disease’s early signs and symptoms.

The fever can be effectively treated with specific antibiotics if caught early.

He says that unlike its more widespread cousin, Lyme disease, Rocky Mountain spotted fever is a dangerous and potentially fatal disease.

The U.S. Centers for Disease Control (CDC) report in their latest study, on 16 cases in which two children contracted the fever and died.

The first symptoms are apparently very hard to distinguish from many other illnesses.

Scientist say the first signs are body-wide aches and pains accompanied by headache and a sudden high fever, sometimes as high as 105 degrees Fahrenheit, and symptoms may include sore throat and nausea.

The spotty rash, which occurs in at least 85 percent of patients, does not appear until later in the infection and resembles a pinpoint pattern of pink-to-red spots sometimes over the entire body.

The rash is also noticeable on the soles of the feet and palms of the hands, where rashes do not usually appear.

Antibiotic therapy by this stage is less effective.

In the CDC study, government researchers took blood and skin tissue samples from 16 patients across southeastern Arizona, suspected of having the fever.

It was then confirmed by laboratory tests, including immunohistochemical staining, that 11 had the disease, while the remaining five were still probable cases.

The researchers then examined the patients’ home environments for possible clues to the source of infection, and they found fever-infected ticks in all the patients’yards.

The ticks were found in the cracks of stucco walls on patients’ homes, in crawl spaces under these homes, and on furniture placed outside for children and pets.

It seems that all patients owned and had come in contact with dogs with the infected ticks, and four of the patients had a recent history of tick bite.

Tests on the dogs’ blood confirmed they were infected with the spotted fever bacterium.

As a rule feral dogs and brown dog ticks are not a species found naturally in the Arizona region, but were introduced to the state as domesticated dogs that moved with their owners into the area.

Dumler says the study shows that Rocky Mountain spotted fever can show up in unexpected places, and physicians need to be on alert for the earliest signs and symptoms of the disease.

He says the next step is to develop faster and more reliable tests to detect the disease, so that physicians can more readily make a diagnosis, and begin treatment as early as possible.

Treatment for adults involves immediate, twice daily 100-milligram doses of the oral antibiotic doxycycline until the patient’s fever subsides.

Then patients need to continue the medication for an additional five days to prevent the disease from rebounding.

Rocky Mountain spotted fever is a bacterial disease caused by Rickettsia rickettsii, which can be spread by ticks that carry the bacteria and then bite humans.

Once inside the body, the infection spreads rapidly, causing inflammation of the blood vessels, shock, and the build-up of fluid inside the lungs and brain.

Though the precise origins of Rocky Mountain spotted fever are not known, the disease only occurs in North and South America.

The article will be published in The New England Journal of Medicine.