Rickettsial infections
There are a number of rickettsial infections. Rickettsialpox is a relativelymild disease caused by a member of the bacterial family called Rickettsia. Rickettsialpox causes rash, fever, chills, heavy sweating, headache, eye pain (especially when exposed to light), weakness, and achy muscles. Rocky Mountainspotted fever (RMSF), a tick-borne illness, Q fever, and Trench fever are also caused by bacteria and result in high fevers and characteristic rashes.
Like other members of the family of Rickettsia, the bacteria causing rickettsialpox live in mice. Tiny mites feed on these infected mice, thus acquiring the organism. When these mites feed on humans, the bacteria can be transmitted.
Rickettsialpox occurs mostly within cities. In the United States, the diseasehas cropped up in such places as New York City, Boston, Philadelphia, Pittsburgh, and Cleveland. It has also been identified in Russia, Korea, and Africa.
The bacteria causing RMSF is passed to humans through the bite of an infectedtick. The illness begins within about two weeks of such a bite. RMSF is themost 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.
C. burnetii, the bacteria that causes Q fever, lives in many differentkinds of animals, including cattle, sheep, goats, tick, cats, rabbits, birds, and dogs. In sheep and cattle, for example, the bacteria tends to accumulate in large numbers in the female's uterus (the organ where lambs and calves develop) and udder. Other animals have similar patterns of bacterial accumulation within the females. As a result, C. burnetii can cause infection through contaminated milk, or when humans come into contact with the fluids ortissues produced when a cow or sheep gives birth. Also, the bacteria can survive in dry dust for months; therefore, if the female's fluids contaminate the ground, humans may become infected when they come in contact with the contaminated dust.
Persons most at risk for Q fever include anybody who works with cattle or sheep, or products produced from them. These include farm workers, slaughterhouse workers, workers in meat-packing plants, veterinarians, and wool workers.
Q fever has been found all over the world, except in some areas of Scandinavia, Antarctica, and New Zealand.
The term trench fever refers to the crowded conditions in which troops foughtin during World War I and World War II. Because the causative bacteria is passed among humans through contact with body lice, overcrowding, and conditions which interfere with good hygiene (including regular washing of clothing) soldiers were predispose to this disease. Currently, homeless people in the United States are sometimes diagnosed with this illness. The bacteria is sometimes passed through the bite of an infected tick. This can cause the illness in people who participate in outdoor activity and encounter ticks in that particular area.
The specific bacteria responsible for rickettsialpox is called Rickettsiaakari. A person contracts this bacteria through the bite of an infected mite. After a person has been bitten by an infected mite, there is a delay ofabout 10 days to three weeks prior to the onset of symptoms.
The first symptom is a bump which appears at the site of the original bite. The bump (papule) develops a tiny, fluid-filled head (vesicle). The vesicle sloughs away, leaving a crusty black scab in its place (eschar). In about a week, the patient develops a fever, chills, heavy sweating, headache, eye pain (especially when exposed to light), weakness, and achy muscles. The fever rises and falls over the course of about a weak. A bumpy rash spreads across thebody. Each individual papule follows the same progression: papule, then vesicle, then eschar. The rash does not affect the palms of the hands or the solesof the feet.
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 dayof 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. Unlikerashes which accompany various viral infections, the rash of RMSF does spreadto the palms of the hands and the soles of the feet. Over a couple of days,the macules turn a reddish-purple color. They are now called petechiae, whichare 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 andfluid 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.
- Thepatient 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, lossof 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.
C. burnetii causes infection when a human breathes in tiny droplets, or drinks milk, containing the bacteria. After 3-30 days, symptoms of the illness appear.
The usual symptoms of Q fever include fever, chills, heavy sweating, headache, nausea and vomiting, diarrhea, fatigue, and cough. Also, a number of otherproblems may present themselves, including inflammation of the liver (hepatitis); inflammation of the sac containing the heart (pericarditis); inflammation of the heart muscle itself (myocarditis); inflammation of the coverings ofthe brain and spinal cord, or of the brain itself (meningoencephalitis); andpneumonia.
Chronic Q fever occurs most frequently in patients with other medical problems, including diseased heart valves, weakened immune systems, or kidney disease. Such patients usually have about a year's worth of vague symptoms, including a low fever, enlargement of the spleen and/or liver, and fatigue. Testingalmost always reveals that these patients have inflammation of the lining ofthe heart (endocarditis).
Two different bacteria can cause trench fever: Bartonella quintana andBartonella henselae. B. quintana is carried by body lice; B. henselae is carried by ticks.
Infection with B. quintana occurs when an infected louse defecates while feeding on a human. When the person scratches, the feces (which are full of bacteria) are rubbed into the tiny wound. Infection with B. henselaeoccurs when an infected tick bites a human, passing the bacteria along through the tiny bite wound.
Symptoms of trench fever begin about 2 weeks to a month after exposure to thebacteria. Sudden fever, loss of energy, dizziness, headache, weight loss, skin rash, severe muscle and bone pain can occur. Pain is particularly severe in the shins, leading to the nickname "shin bone fever." The fever can reach 105°F (40.5°C) and stays high for five to six days at a time. The temperature then drops, and stays down for several days, usually recurring in five to six day cycles. An individual may experience as many as eight cycles offever with the illness.
Most practitioners are able to diagnose rickettsial infections simply on thebasis of their symptoms, their rising and falling fevers, and characteristicrashes. Occasionally, blood will be drawn and tests performed to demonstratethe presence of antibodies (immune cells directed against specific bacterialagents), which would confirm a diagnosis.
Because rickettsialpox is such a mild illness, some practitioners choose to simply treat the symptoms (giving acetaminophen for fever and achiness, pushing fluids to avoid dehydration). Others will give their patients a course of the antibiotic tetracycline, which will shorten the course of the illness to about one to two days.
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 rateby 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).
Doxycycline and quinolone antibiotics are effective for treatment of Q fever.Treatment usually lasts for two weeks. Rifampin and doxycycline together aregiven for chronic Q fever. Chronic Q fever requires treatment for at least three years.
Erythromycin and azithromycin are both used to treat trench fever. Four weeksof treatment are usually necessary. Inadequate treatment often results in arelapse. In fact, relapses have been reported to occur as long as 10 years after the first episode.
Prognosis for full recovery from rickettsialpox is excellent. No deaths haveever been reported from this illness, and even the skin rash heals without scarring.
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 ofappropriate medications.
Certain risk factors suggest a worse outcome in RMSF. Death rates are higherin 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.
Death is rare from Q fever. Most people recover completely, although some patients with endocarditis will require surgery to replace their damaged heart valves.
Prognosis for patients with trench fever is excellent. Recovery may take a couple of months. Without treatment, there is always a risk of recurrence, evenyears after the original illness.
As with all mite- or tick-borne illnesses, prevention includes avoidance of areas known to harbor the insects, and/or careful application of insect repellents. Furthermore, because mice pass the bacteria on to the mites, it is important to keep mice from nesting in or around residences.
The mainstay of prevention involves avoiding areas known to harbor ticks. However, because many people enjoy recreational activities in just such areas, other steps can be taken:
- Wear light colored clothing (so that attachedticks are more easily noticed).
- Wear long sleeved shirts and long pants; tuck the pants legs into socks.
- Spray clothing with appropriatetick repellents.
- Examine. Anybody who has been outside for any amountof time in an area known to have a population of ticks should examine his orher 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.
Q fever can be prevented by the appropriate handling of potentially infectivesubstances. For example, milk should always be pasteurized, and people who work with animals giving birth should carefully dispose of the tissues and fluids associated with birth. Industries which process animal materials (meat, wool) should take care to prevent the contamination of dust within the plant.Vaccines are available for workers at risk for Q fever.
Prevention of trench fever involves good hygiene and decent living conditions. When this is impossible, insecticide dusting powders are available to applyto clothing. Avoidance of areas known to harbor ticks or the use of insect repellents is necessary to avoid the type of infection passed by ticks.
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