Rocky Mountain spotted fever

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Rocky Mountain Spotted Fever

 

Definition

Rocky Mountain spotted fever (RMSF) is a tick-borne illness caused by a bacteria, resulting in a high fever and a characteristic rash.

Description

The bacteria causing RMSF is passed to humans through the bite of an infected tick. The illness begins within about two weeks of such a bite. RMSF is the most widespread tick-borne illness in the United States, occurring in every state except Alaska and Hawaii. The states in the mid-Atlantic region, the Carolinas, and the Virginias have a great deal of tick activity during the spring and summer months, and the largest number of RMSF cases come from those states. About 5% of all ticks carry the causative bacteria. Children under the age of 15 years have the majority of RMSF infections.

Causes and symptoms

The bacterial culprit in RMSF is called Rickettsia rickettsii. It causes no illness in the tick carrying it, and can be passed on to the tick's offspring. When a tick attaches to a human, the bacteria is passed. The tick must be attached to the human for about six hours for this passage to occur. Although prompt tick removal will cut down on the chance of contracting RMSF, removal requires great care. If the tick's head and body are squashed during the course of removal, the bacteria can be inadvertently rubbed into the tiny bite wound.
Symptoms of RMSF begin within two weeks of the bite of the infected tick. Symptoms usually begin suddenly, with high fever, chills, headache, severe weakness, and muscle pain. Pain in the large muscle of the calf is very common, and may be particularly severe. The patient may be somewhat confused and delirious. Without treatment, these symptoms may last two weeks or more.
The rash of RMSF is quite characteristic. It usually begins on the fourth day of the illness, and occurs in at least 90% of all patients with RMSF. It starts around the wrists and ankles, as flat pink marks (called macules). The rash spreads up the arms and legs, toward the chest, abdomen, and back. Unlike rashes which accompany various viral infections, the rash of RMSF does spread to the palms of the hands and the soles of the feet. Over a couple of days, the macules turn a reddishpurple color. They are now called petechiae, which are tiny areas of bleeding under the skin (pinpoint hemorrhages). This signifies a new phase of the illness. Over the next several days, the individual petechiae may spread into each other, resulting in larger patches of hemorrhage.
The most severe effects of RMSF occur due to damage to the blood vessels, which become leaky. This accounts for the production of petechiae. As blood and fluid leak out of the injured blood vessels, other tissues and organs may swell and become damaged, and:
  • breathing difficulties may arise as the lungs are affected.
  • heart rhythms may become abnormal
  • kidney failure occurs in very ill patients
  • liver function drops
  • the patient may experience nausea, vomiting, abdominal pain, and diarrhea
  • the brain may swell (encephalitis) in about 25% of all RMSF patients (brain injury can result in seizures, changes in consciousness, actual coma, loss of coordination, imbalance on walking, muscle spasms, loss of bladder control, and various degrees of paralysis)
  • the clotting system becomes impaired, and blood may be evident in the stools or vomit

Diagnosis

Diagnosis of RMSF is almost always made on the basis of the characteristic symptoms, coupled with either a known tick bite (noted by about 60-70% of patients) or exposure to an area known to harbor ticks. Complex tests exist to nail down a diagnosis of RMSF, but these are performed in only a few laboratories. Because the results of these tests take so long to obtain, they are seldom used. This is because delaying treatment is the main cause of death in patients with RMSF.

Treatment

It is essential to begin treatment absolutely as soon as RMSF is seriously suspected. Delaying treatment can result in death.
Antibiotics are used to treat RMSF. The first choice is a form of tetracycline; the second choice (used in young children and pregnant women) is chloramphenicol. If the patient is well enough, treatment by oral intake of medicine is perfectly effective. Sicker patients will need to be given the medication through a needle in the vein (intravenously). Penicillin and sulfa drugs are not suitable for treatment of RMSF, and their use may increase the death rate by delaying the use of truly effective medications.
Very ill patients will need to be hospitalized in an intensive care unit. Depending on the types of complications a particular patient experiences, a variety of treatments may be necessary, including intravenous fluids, blood transfusions, anti-seizure medications, kidney dialysis, and mechanical ventilation (a breathing machine).

Alternative treatment

Although alternative treatments should never be used in place of conventional treatment with antibiotics, they can be useful adjuncts to antibiotic therapy. The use of Lactobacillus acidophilus and L. bifidus supplementaion during and after antibiotic treatment can help rebalance the intestinal flora. Acupuncture, homeopathy, and botanical medicine can all be beneficial supportive therapies during recovery from this disease.

Prognosis

Prior to the regular use of antibiotics to treat RMSF, the death rate was about 25%. Although the death rate from RMSF has improved greatly with an understanding of the importance of early use of antibiotics, there is still a 5% death rate. This rate is believed to be due to delays in the administration of appropriate medications.
Certain risk factors suggest a worse outcome in RMSF. Death rates are higher in males and increase as people age. It is considered a bad prognostic sign to develop symptoms of RMSF within only two to five days of a tick bite.

Prevention

The mainstay of prevention involves avoiding areas known to harbor ticks. However, because many people enjoy recreational activities in just such areas, the following steps can be taken:
  • Wear light colored clothing (so that attached ticks are more easily noticed).
  • Wear long sleeved shirts and long pants; tuck the pants legs into socks.
  • Spray clothing with appropriate tick repellents.
  • Examine. Anybody who has been outside for any amount of time in an area known to have a population of ticks should examine his or her body carefully for ticks. Parents should examine their children at the end of the day.
  • Remove any ticks using tweezers, so that infection doesn't occur due to handling the tick. Grasp the tick's head with the tweezers, and pull gently but firmly so that the head and body are entirely removed.
  • Keep areas around homes clear of brush, which may serve to harbor ticks.

Resources

Organizations

Centers for Disease Control and Prevention. 1600 Clifton Rd., NE, Atlanta, GA 30333. (800) 311-3435, (404) 639-3311. http://www.cdc.gov.

Key terms

Encephalitis — Inflammation of the tissues of the brain.
Macule — A flat, discolored area on the skin.
Petechia — A small, round, reddish purple spot on the skin, representing a tiny area of bleeding under the skin.

Rocky Mountain spotted fever

 
an infectious tick fever originally seen in the Rocky Mountains of North America but now recognized in various other parts of North and South America. Characteristics include fever, headache, muscle pain, and rash. It was originally called “black measles” because of the appearance of the rash, and it is known by various other names in specific geographic areas.



Rocky Mountain spotted fever belongs to a group of insect-borne fevers caused by microscopic parasites known as rickettsiae, which attack the cells lining small blood vessels. The species Rickettsia rickettsii, responsible for Rocky Mountain spotted fever, is transmitted from rodent to humans by various ticks.
Symptoms. After the bite of the infected tick, there is an incubation period of 3 to 10 days before the major symptoms set in. Within a day or two after the bite, victims may feel somewhat ill and lose their appetite. The actual onset is marked by chills or chilly sensations, fever, headache, pain behind the eyes, joint and muscle pain, and photophobia. Other symptoms are nausea, vomiting, sore throat, and abdominal pain. Some patients become highly irritable and delirious, or so lethargic that they may lapse into a stupor or coma. Usually 3 to 5 days after the onset a rash appears on the wrists and ankles, then spreads to the trunk and limbs and occasionally to the face.



The appearance and progress of small red spots that eventually become larger sores distinguish Rocky Mountain spotted fever from the several diseases it resembles in its other symptoms (measles, typhoid fever, typhus).
Treatment and Prevention. Like other rickettsial diseases, Rocky Mountain spotted fever responds readily to treatment with tetracyclines and chloramphenicol. If untreated, it can be serious and often fatal. Preventive measures are directed mainly against the disease-carrying ticks and rodents.

Rock·y Moun·tain spot·ted fe·ver

an acute infectious disease of high mortality, characterized by frontal and occipital headache, intense lumbar pain, malaise, a moderately high continuous fever, and a rash on wrists, palms, ankles, and soles from the second to the fifth day, later spreading to all parts of the body; it occurs in the spring of the year primarily in the southeastern U.S. and the Rocky Mountain region, although it is also endemic elsewhere in the U.S., in parts of Canada, in Mexico, and in South America; the pathogenic organism is Rickettsia rickettsii, transmitted by two or more tick species of the genus Dermacentor; in the U.S. it is spread by D. andersoni in the western states and D. variabilis (a dog tick) in the eastern states.

Rocky Mountain spotted fever

n.
An acute infectious disease that is caused by the tick-borne bacterium Rickettsia rickettsii and is characterized by rash, muscle pains, and high fever. It is endemic throughout North America.

Rocky Mountain spotted fever (RMSF)

a serious tickborne infectious disease occurring throughout the temperate zones of North and South America, caused by Rickettsia rickettsii. It is characterized by chills, fever, severe headache, myalgia, mental confusion, and rash. Erythematous macules first appear on wrists and ankles, spreading rapidly over the extremities, trunk, and face and usually on the palms and soles. Hemorrhagic lesions, constipation, and abdominal distension are also common. The diagnosis is based on clinical examination and confirmed by laboratory analyses, including immunofluorescent antibody screens, complement fixation test, and Weil-Felix test. Early treatment with doxycycline or tetracycline is important because more than 20% of untreated patients die from shock and renal failure. A diet high in protein is important to avoid hypoproteinemia. Nursing care is especially important to avoid decubitus ulcers and hypostatic or aspiration pneumonia. Immunity follows recovery. Prevention includes the use of insect repellents, the wearing of protective clothing, frequent inspection of the body, and careful removal of wood or dog ticks. No vaccine is available. Care must be taken not to crush ticks, because infection may be acquired through skin abrasions. Also called Mexican spotted fever, mountain fever, mountain tick fever, spotted fever. Compare murine typhus, rickettsialpox. See also boutonneuse fever, scrub typhus, typhus.
enlarge picture
Rocky Mountain spotted fever: typical rash
An exanthematous disease common in the eastern US from April to October even in large cities—e.g., NYC
Agent Rickettsia rickettsii
Hosts Furry woodland creatures—rodents, et al
Vectors Wood—Dermacentor andersoni and D variabilis (dog) ticks
Lab Weil-Felix test is positive for antibodies to OX-19 and OX-2
Management Tetracycline, chloramphenicol
Mortality 3-10%; increased in blacks, increased > age 40

Rocky Mountain spotted fever

Spotted fever Infectious disease An exanthematous disease common in the eastern US from April to October even in large cities–eg, NYC Agent Rickettsia rickettsii Hosts Furry woodland creatures–rodents, et al Vectors Wood–Dermacentor andersoni and dog–D variabilis ticks Clinical 1 wk incubation, followed by a discrete pale, blanchable centrifugal maculopapular rash, which may be very dark, hence the alias, 'black measles', persistent headache, fever, ±coughs, rales, myalgia, malaise, splenomegaly; N&V, abdominal pain; CNS Sx–delirium, stupor, ataxia, meningismus; myocarditis, EKG changes, thrombocytopenia, multiple coagulopathies, renal failure, shock  Treatment Tetracycline, chloramphenicol Mortality 3-10%; ↑ in blacks, ↑ > age 40. See Rickettsial infection.

Rock·y Moun·tain spot·ted fe·ver

(rok'ē mown'tăn spot'ĕd fē'vĕr)
An acute infectious disease of high mortality, characterized by frontal and occipital headache, intense lumbar pain, malaise, a moderately high continuous fever, and a rash on wrists, palms, ankles, and soles from the second to the fifth day, later spreading to all parts of the body; it is typically contracted in the spring of the year primarily in the southeastern and the Rocky Mountain regions of the United States, although it is also endemic elsewhere in the United States, parts of Canada, Mexico, and South America. The pathogenic organism is Rickettsia rickettsii, transmitted by two or more tick species of the genus Dermacentor; in the United States it is spread by D. andersoni in the western states and D. variabilis (a dog tick) in the eastern states.
Synonym(s): tick fever (4) .

Rocky Mountain spotted fever

An acute infectious disease caused by the organism Rickettsia rickettsii and transmitted by the bite of an Ixodid hard tick from small rodents and dogs. The disease occurs mainly in south-eastern USA and South America. About a week after the bite there is fever, headache, nausea, muscle aches, loss of appetite and irritability and a rash of small round pink spots which spreads all over the body becoming darker. Most cases are mild, with fever for about 2 weeks, but some progress to an illness of great severity involving widespread haemorrhages and gangrene of the fingers, ears or genitalia and death within a week of onset. In these cases, prompt treatment with CHLORAMPHENICOL or a TETRACYCLINE antibiotic may be life-saving. Also known as tick typhus.

Rocky Mountains,

mountain range in the United States and Canada.
Rocky Mountain spotted fever - an acute infectious disease of high mortality, characterized by frontal and occipital headache, intense lumbar pain, malaise, a moderately high continuous fever, and a rash on wrists, palms, ankles, and soles from the second to the fifth day, later spreading to all parts of the body. Synonym(s): Rickettsia

Rocky Mountain spotted fever,

n.pr a severe bacterial disease caused by
Rickettsia rickettsii; characterized by the rapid onset of fever, headache, muscle pains, nausea, vomiting, and a characteristic rash. Without accurate diagnosis and antibiotic treatment, this condition can be fatal. The range for this disease is not limited to the Rocky Mountains but extends from Canada throughout the continental United States into Central and South America.
Enlarge picture
Rocky Mountain spotted fever (RMSP).

Rock·y Moun·tain spot·ted fe·ver

(rok'ē mown'tăn spot'ĕd fē'vĕr)
Acute infectious disease of high mortality, characterized by frontal and occipital headache, intense lumbar pain, malaise, moderately high continuous fever, and rash on wrists, palms, ankles, and soles from the second to the fifth day, later spreading to all parts of body; occurs in spring of the year primarily in the southeastern U.S. and the Rocky Mountain region, although it is also endemic elsewhere in the U.S., in parts of Canada, in Mexico, and in South America.

Rocky Mountain spotted fever (RMSF),

n a serious tick-borne infectious disease occurring throughout the temperate zones of North and South America, caused by
R. rickettsii, and characterized by chills, fever, severe headache, myalgia, mental confusion, and rash.

Rocky Mountain spotted fever

an infectious disease of small mammals, dogs and humans. It occurs mainly in certain areas within the USA. Called also tick fever, and it is also known by various names according to the geographic area.
Rocky Mountain spotted fever belongs to a group of insect-borne fevers caused by rickettsiae, which attack endothelium. The species, Rickettsia rickettsii, responsible for Rocky Mountain spotted fever is transmitted from rodent by various ticks. The clinical signs associated with infection in dogs are lethargy, anorexia, ocular and nasal discharge, lymphadenopathy and splenomegaly. A thrombocytopenia also occurs. Kennel epizootics have been recorded.