Rolling Up Our Sleeves to Fight Rocky Mountain Spotted Fever

March 18, 2010 by Joanna Regan

CDC scientist Linda Cheng, collaring dogs in Arizona.

See: Tips for health care providers about RMSF.

I am a pediatrician by training, and people are often amused by that fact when I tell them what my job responsibilities sometimes include. Going door-to-door putting tick collars on dogs and treating yards with pesticide are not activities people typically associate with their children’s doctor. However, this is exactly what my team and I were doing last summer.

I am a medical officer at the CDC in the Rickettsial Zoonoses Branch, and my team consisted of public health specialists, including veterinarians and scientists. We traveled to eastern Arizona last summer to join with a group of concerned community members to tackle Rocky Mountain spotted fever (RMSF), a serious public health threat in this region.

In the Trenches

EIS Officer Barbara Knust, DVM, MPH, documenting treated areas.

RMSF has not historically been a problem in Arizona, but unfortunately this situation has changed dramatically in the last decade. In this community, and others, the common brown dog tick (Rhipicephalus sanguineus ) has become a vector for this deadly disease and has begun infecting people in and around their homes at an alarming rate. Our mission was to go door-to-door warning people about this risk, put a tick collar on every dog in the area, including strays, and treat every house with pesticide. As this work placed us at some risk for contact with ticks, we took the same precautions we recommended to community members, like treating our clothes with permethrin and applying DEET as a repellent. After a week of intense manual labor in the Arizona sun, it was time to return to the CDC.

It is personally satisfying to roll up my sleeves and work side by side with a community to tackle a dangerous problem like RMSF, but doing so also has great scientific value. By working to control a problem such as this one at the ground level, we develop a better understanding of the difficulties and challenges a community is facing.

Controlling the Pests

EIS Officer Kristina McElroy, DVM, MPH, DACVPM is treating houses and dogs for ticks

Although we know that the brown dog tick bites people, its primary food source consists of blood meals from dogs. This tick could not continue to infest this area without untreated dogs on which to feed. Thus, it seems logical that treating every dog in the community effectively for ticks would eliminate the problem. However, the reality is far more complex. Once these ticks have infested an area, they can persist in the environment without feeding for long periods of time, so houses and yards also need to be treated. Furthermore, the pesticide doesn’t kill tick eggs, so all environmental treatment needs to be repeated monthly, and tick collars need to be replaced every 3 months to continue to kill the newly hatching ticks. If everyone in the community is not completely compliant with this treatment regimen, the problem persists.

The overwhelming majority of community members with whom we talked had heard about RMSF and were familiar with the ongoing control efforts. Many people expressed to us, and we experienced firsthand, the difficulties that were arising while trying to achieve complete compliance with this regimen.

During our work, we occasionally came across vicious dogs. In these situations, we were unable to collar the dogs or treat the houses of the owners, so these yards remained safe havens for ticks. Stray dogs that were able to elude our team did not receive collars. These untreated dogs can also serve as safe harbors for ticks, moving freely between homes and re-infesting treated areas. Effective animal control programs serve a vital public health role in protecting people from these problems in many areas of the country, but are still underfunded or absent in some rural communities, such as this one.

Working with the Communities

Understanding the challenges this community is facing not only helps us better serve them, but also allows us to identify other communities at risk. It is clear from this experience that once this problem has emerged, it takes an enormous investment in time, resources, and community participation to control. We hope that through continued cooperation, we can help this community control, and one day, eradicate RMSF.

It is also clear from our field work that prevention of this problem is easier to achieve than control. You can help prevent this problem from developing in your community by supporting effective animal control programs and treating your pets appropriately for ticks before they begin bringing Rocky Mountain spotted fever home.

Tips for Health Care Providers

Rocky Mountain spotted fever (RMSF) is transmitted by ticks. The first symptoms of the disease are often fever and headache, followed in several days by a skin rash. Patients may also have signs of pneumonia or abdominal pain. If not treated properly, this disease can become severe, or even fatal, in the first week or two of symptoms, even in previously healthy people.
The first-line treatment for adults and children of any age is doxycycline. Most other antibiotics, including broad-spectrum antibiotics, do not work for treating this disease. It is very important to begin treatment with doxycycline as soon as the disease is suspected, because treatment started after the fifth day of symptoms is less likely to be helpful. For more information about treatment, visit http://www.cdc.gov/ticks/treatment.html
Eastern Arizona has an unusually high rate of RMSF. Since 2003, Arizona has reported over 80 cases, and 10% of the people diagnosed with the disease in this state have died. The vector for RMSF in Arizona is the brown dog tick, which lives on dogs and around people’s homes. Cases have occurred in this state year-round, including the colder months. For more information on cases in Arizona, visit http://www.azdhs.gov/phs/oids/vector/rmsf/rocky_mountain.htm
In Arizona and other areas, clusters of RMSF among family members and close contacts have been reported. Family members and other people who may have been exposed to the same environment should be informed of this higher risk when a new RMSF case is suspected.
Some people who have the disease do not remember being bitten by a tick, while others may not develop a rash. The wide variety of symptoms seen with this disease can make it difficult to diagnose. For information about symptoms, visit http://www.cdc.gov/ticks/symptoms.html
There is no way for doctors to be sure if a patient has the disease in the first 5 days of symptoms, because lab tests to confirm the disease take time to perform. Therefore, patients should always be started on doxycycline on the basis of clinical suspicion, and doctors should never wait for lab results to return before beginning treatment.
The gold standard test for confirming a diagnosis of RMSF is the IgG indirect immunofluorescence assay (IFA) performed on two serum samples taken 3 weeks apart. The first sample should be taken as early in the disease as possible, preferably in the first week of symptoms. In true cases of RMSF, the first IgG IFA titer is typically low, or “negative,” and the second shows a significant (fourfold) increase in IgG antibody levels. IgM antibodies usually rise at the same time as IgG but are less specific and more likely to represent a false positive. For a more in-depth explanation of testing, visit http://www.cdc.gov/ticks/diagnosis.html
RMSF is a nationally reportable disease. Proper laboratory testing and reporting can help us target aid to high-risk communities and limit the spread of RMSF. For information about how to report cases, contact your local health department. Physicians in Arizona may visit http://www.azdhs.gov/phs/oids/hcp_rpt.htm