Rocky Mountain Spotted Fever On Upswing - Tick-borne Infection Coming To A Back Yard Near You?

Main Category: Infectious Diseases / Bacteria / Viruses
Also Included In: Veterinary
Article Date: 08 Oct 2007 - 3:00 PDT

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Rocky Mountain spotted fever, a potentially deadly tick-borne infection, is increasing throughout the country, most notably in suburban areas, according to research being presented at the 45th Annual Meeting of the Infectious Diseases Society of America (IDSA).

In five years, reported incidence of the disease nearly tripled. Rocky Mountain spotted fever is caused by the Rickettsia rickettsii bacteria, which typically are spread through the bite of the dog tick or Rocky Mountain wood tick.

Within 14 days of being bitten by an infected tick, the victim typically gets a fever, headache, body aches, and upset stomach. After a few days, a light rash may appear on the ankles, wrist, and arms, and if the person is not treated with antibiotics, the rash often becomes extensive and organ failure may develop.

"The biggest problem is that people often don't remember being bitten by a tick, and by the time the classic rash appears, the disease has already progressed significantly, and it may be too late," said David Swerdlow, MD, who at the time of the study was the team leader for the Rickettsial Zoonoses Branch of the Centers for Disease Control and Prevention (CDC) Atlanta. "This disease is becoming more common in cities and suburbs, likely because people are going to rural areas and coming home to the cities, and possibly also because suburbia is encroaching on rural, tick-infested areas."

Before the discovery of appropriate antiobiotics in the late 1940s, Rocky Mountain spotted fever killed nearly a third of its victims, and although the death rate has declined to less than 2 percent, it remains a serious disease. The data show that nearly one in five of all people who had the disease - and more than one in three children - were hospitalized. It can cause pneumonia, kidney failure, acute respiratory disease, and clotting disorders. The disease is treated with antibiotics, typically doxycycline.

Rocky Mountain spotted fever was first recognized in the late 1800s in Idaho. Despite the name, today it actually is far more common in the eastern and central portions of the country, particularly in the mid-Atlantic states (Maryland to South Carolina) and west to Oklahoma.

The data were retrieved from the National Electronic Telecommunications System for Surveillance from 2001 to 2005 and included a total of 6,598 reported cases in 45 states. Twenty-two deaths were reported, although the actual number was likely higher, said Dr. Swerdlow. The reported incidence of the disease nearly tripled, from 695 cases in 2001, to 1,936 cases in 2005. The largest increase was in the South Atlantic states. Nationwide, 53 counties experienced a five-fold increase in the infection and 51 percent of counties were newly affected during those years. The incidence was greater in suburban than rural areas. The disease was reported in all but five states: Alaska, California, Hawaii, Maine, and Washington.

The disease typically occurs in spring and summer, and extremely wet years may result in increases in tick levels.

"With Rocky Mountain spotted fever on the rise, it is important that people realize that tick bites can be avoided," said John Openshaw, CDC Applied Epidemiology Fellow, who is presenting the data at IDSA. "It is particularly important for people to take precautions when they are in wooded or grassy areas. Wearing light-colored clothing can make ticks easier to see when hiking or working in the woods. In addition, it's important that people wear insect repellant and tuck pant legs into socks."

Physicians should consider treating patients who have symptoms and exposures consistent with Rocky Mountain spotted fever with antibiotics before laboratory testing is complete, because laboratory confirmation of the illness may take several weeks. Symptoms may include fever, headache, or body aches, especially when a rash is present (particularly on the ankles, wrist or arms), and the patient may have come in contact with ticks in grassy or wooded areas during the spring and summer months. Because other illnesses have similar symptoms, physicians may choose to treat for those conditions as well. Cases of Rocky Mountain spotted fever should be reported to the local or state health department.

Co-authors of the study in addition to Dr. Swerdlow and Openshaw are: J.W. Krebs, R.C. Holman, and E. Mandel.

IDSA is an organization of physicians, scientists, and other health care professionals dedicated to promoting human health through excellence in infectious diseases research, education, prevention, and patient care. Major programs of IDSA include publication of two journals, The Journal of Infectious Diseases and Clinical Infectious Diseases,, an Annual Meeting, awards and fellowships, public policy and advocacy, practice guidelines, and other membership services. The Society, which has about 8,000 members, was founded in 1963 and is headquartered in Arlington, Va.

http://www.idsociety.org.