Rocky Mountain spotted fever

Rocky Mountain spotted fever (RMSF or tick-borne typhus fever) is a serious infectious disease that spreads through the bite of a tick infected with the organism Rickettsia rickettsii.


Causes/associated factors
Rocky Mountain spotted fever was first detected in the Rocky Mountain states, but it can occur in any part of the United States. RMSF has been reported in almost all 50 states, with the highest occurrence in North Carolina and Oklahoma. At least 50 percent of cases occur in the southern Atlantic states, from Maryland and Delaware to Florida. The western south-central states (Arkansas, Louisiana, Oklahoma and Texas) also have a higher incidence of the disease. In fact, only 3 percent of cases now occur in the Rocky Mountain states.
Rocky Mountain spotted fever occurs mainly from April through September, but it can develop during warm weather at any time of the year. Children and young adults are most likely to contract the disease, but it can affect people of any age. Each year, about 800 to 1,000 people are diagnosed with the infection.

Inside the human body, R. rickettsii invades cells that line the small and medium blood vessels. The damaged cells allow blood to leak through the vessel walls, resulting in a characteristic rash and damage to surrounding tissue and organs.


Transmission
Again, RMSF spreads mainly through the bite of an American dog tick or Rocky Mountain wood tick that is infected with the organism R. rickettsii. (Only about 1 to 3 percent of these ticks are infected with R. rickettsii.) Ticks are most often found in fields, wooded areas or other places that have tall grass, such as vacant lots or the edges of creeks, streams and wooded trails. The ticks crawl to the top of grass blades and may attach themselves to any animal or person who passes by. To contract RMSF, the infected tick must feed on your blood for six to 10 hours. Rarely, you can also catch the disease if a broken area in your skin is contaminated with infected tick feces or crushed tick tissue or fluids. The disease does not spread from person to person. Lifelong protection or immunity from the disease may develop after one infection.

Signs/symptoms
Symptoms of RMSF can vary greatly from person to person. Classic symptoms include fever and rash after a known or possible tick exposure. For some people, symptoms appear as early as 48 hours after exposure. For others, symptoms may not develop for up to 14 days. The average incubation period (time from exposure until symptoms appear) is about one week.
Early symptoms may include fever, chills, potentially severe headache, muscle pain, loss of appetite, nausea and vomiting. A red, flat rash often appears on the wrists and ankles about two to six days after the fever develops. The rash may spread up your arms, legs and trunk. It can also appear on the palms of the hands and soles of the feet. The rash may be confused with measles or other infectious, rash-producing illnesses. After a few days, the rash may develop pinpoint purplish areas of bleeding. Some people develop the rash later in the disease, and about 15 percent of infected people never develop a rash. Other symptoms may include abdominal pain, diarrhea, joint pain, sensitivity to light, red eyes, cough, confusion and lethargy.


Diagnosis
If you suspect an infection, seek medical attention right away. The doctor will ask questions about your medical history and do a physical exam. If necessary, a blood test or skin biopsy (taking a tissue sample for further examination) can help confirm the diagnosis. Blood tests may also be done to determine if the infection has affected your blood counts, electrolytes, or liver or kidney function. You may also need to have a lumbar puncture (placing a needle into the space between the vertebrae in the lower back to collect a sample of the fluid that surrounds the spinal cord and brain) to see if the infection has caused meningitis (inflammation of the membrane surrounding the brain and spinal cord). Treatment may begin before the test results arrive, however.

Treatment
When treated promptly, most people have a full recovery. Depending on your age and other individual factors, the doctor may prescribe an antibiotic such as doxycycline. Hospitalization is often necessary. Elderly adults or those with a chronic illness are more likely to have serious infections. During treatment, you may need blood tests to monitor your progress and response to treatment. If treatment begins within the first five days of illness, the fever usually subsides within one to three days. This may take longer if the illness is severe. Treatment is usually continued for one to two weeks depending on the severity of the illness.

Complications
Severe complications are possible if treatment is delayed, including:
damage to any organ in the body resulting from vasculitis (inflammation of the blood vessels)
disseminated intravascular coagulation (a blood clotting disorder that can lead to gangrene -- tissue death -- of the fingers, toes and limbs)
seizures (loss of consciousness accompanied by twitching or thrashing)
ataxia (difficulty controlling muscle movements)
spastic paralysis (the inability to move groups of muscles)
congestive heart failure (when the amount of blood pumped by the heart doesn't meet the body's requirements for oxygen and nutrients)
irregularities in heart rate
respiratory failure (when the amount of oxygen in the blood becomes dangerously low or the amount of carbon dioxide becomes dangerously high)
shock (when blood pressure is too low to provide adequate blood flow to organs or sustain life)
kidney failure
hearing loss
If left untreated, RMSF can be fatal for about 25 percent of people who contract the infection.


Pregnancy-specific information
If you're pregnant, avoid tall grass and wooded areas where ticks can be found. If you develop RMSF, chloramphenicol is the drug of choice. Doxycycline can affect the growth of teeth and bones in the fetus.

Senior-specific information
Older adults face a higher risk of developing more severe, even life-threatening cases of RMSF.

Prevention
A human vaccine for Rocky Mountain spotted fever is currently in development. There are some general preventive measures to keep in mind, however.
Reduce the number of ticks near your home by removing leaves and clearing any brush or tall grass around your home and gardens.

Avoid tick-infested areas, especially in the spring and summer months.

Don't forget your pets! Speak with your veterinarian about medications to help keep pets free of ticks.

If you must be outside in areas where ticks are found, walk on the center of trails to avoid grass and brush. Cover as much of your body as possible -- wear socks, shoes (preferably boots), a hat and a long-sleeved shirt with a tight-fitting collar. Tuck in your shirt and tuck your pant legs into your socks. Wear light-colored clothing so that ticks can be spotted more easily.

When you're outdoors, it's also a good idea to use an insect repellent. Brands containing diethyltoluamide (DEET) are most effective. They may be used on any exposed, intact areas of skin, but be cautious and follow the manufacturer's directions carefully. A 10 to 35 percent formula repellent is recommended for adults. Check with your doctor before using insect repellents if you're pregnant or breastfeeding.
The best approach is to use the lowest concentration of DEET effective for the amount of time spent outside:


30-percent DEET protects for six hours
24-percent protects for five hours
20-percent protects for four hours
6.65-percent protects for two hours
4.75-percent protects for an hour and a half

Even for children, products containing DEET are the most effective insect repellents. The safety of DEET does not appear to be related to the concentration in the repellent. There are no studies on skin absorption of DEET in children, but studies of similar substances suggest that absorption through the skin would not differ after age 2 months. Currently, 30-percent DEET is the maximum concentration recommended for infants and children over age 2 months. Again, the concentration of DEET used is based on the time the child is expected to be outside. Keep insect repellent out of the reach of children at all times.

You can also apply Permethrin, an EPA-approved insecticide that works to kill insects rather than repel them. Permethrin is not applied to your skin. Instead, it's applied to your clothing and shoes to kill ticks. The product retains its effectiveness for up to two weeks, despite as many as five launderings. The risk of adverse effects is low because Permethrin is not readily absorbed by the skin. Check with your doctor before using any insecticides if you're pregnant or breastfeeding.

Before going inside, check your hair and clothing for ticks. Once inside, do a full body exam, including the scalp. (It's important to do a daily full body exam whenever tick bites are a possibility, especially if you're camping outdoors or involved in prolonged outdoor activities.)

Shower promptly to get rid of ticks that may not have attached to your body yet, and put your outdoor clothing in the dryer for 30 minutes to kill any undetected ticks.
Tick removal
If you find a tick, remove it with a pair of tweezers, if available, or a finger protected with a rubber glove, tissue or paper towel. Grasp the tick as close to the skin as possible and pull it out with slow, steady pressure. This will loosen the tick's feeding parts and allow it to be removed intact. Avoid twisting, jerking, squeezing or crushing the tick, and make sure you remove the entire tick. (Older methods of tick removal, such as using oil, petroleum jelly, a hot match or alcohol, are not as effective and may actually make it impossible for the tick to release itself from your skin).

If there is any question regarding the type of tick involved, you may want to keep the tick in a container (such as a covered jar or sealed plastic bag) to show your doctor. Freeze the container if possible -- it may preserve the bacteria in the tick. The characteristics of the tick may influence treatment choices. If you don't need the tick for identification purposes, flush it down the toilet. After you've removed the tick, wash your hands and the affected area with soap and water and call your doctor for further instructions. Remove and dispose of all ticks found on pets in the same manner.