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Ehrlichioses - Causes, Symptoms and Treatment

Definition

Ehrlichioses are tick-borne infections which are cause an abrupt onset of fever, chills, headache, and a general feeling of illness (malaise). Different species of ehrlichiae inhabit different types of white blood cells. In general, however, ehrlichioses are very similar in the symptoms they produce and in the way they are diagnosed and treated.

This disease occurs primarily in the southeastern and south central regions of the country and is primarily transmitted by the lone star tick, Amblyomma americanum.

Causes

Ehrlichiosis is caused by several bacterial species in the genus Ehrlichia (pronounced err-lick-ee-uh) which have been recognized since 1935. Over several decades, veterinary pathogens that caused disease in dogs, cattle, sheep, goats, and horses were identified. Currently, three species of Ehrlichia in the United States and one in Japan are known to cause disease in humans; others could be recognized in the future as methods of detection improve.

Symptoms

The symptoms of HME and HGE are the same and usually occur within 5 to 10 days following a bite from an infected tick.
The common symptoms are :-

Fever
Muscle aches
Weakness
Joint pain
Headaches
Nausea
Vomiting, and
Joint pain
A rash

Illness is usually mild, but occasionally may be life-threatening, especially if untreated Antibiotics are the treatment of choice.

Treatment

The initiation of treatment in patients in whom ehrlichiosis is suspected should not be delayed until confirmation of the diagnosis. For any patient with a history of tick exposure/bite who presents with fever, malaise, and other constitutional symptoms and signs with no apparent and reasonable explanation, antibiotic therapy specific for ehrlichiosis should be started. Some physicians advocate a "watch and wait" period of 24 hours when a mild case of ehrlichiosis is suspected. If no improvement is seen, treatment is started. The specimens that will be used for confirmatory PCR assay and culture should be obtained before antibiotic treatment is started. At this time, a serum sample should also be obtained for serologic testing.

Treatment is usually started based on the person's symptoms-
1. Tetracycline
2. Doxycycline
3. chloramphenicol

Diagnosis is made based upon clinical grounds, symptoms and/or serology and history of tick exposure. Mortality is dependent on cardiac and central nervous system involvement or delay in treatment.