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Ehrlichiosis Causes and Risks:
Ehrlichiosis is a recently-described disease caused by Ehrlichia organisms. It was first described in 1990. The two specific organisms which have been implicated are Ehrlichia chaffeensis and granulocytic
Ehrlichia. The Ehrlichia bacteria belong to the family Rickettsiaceae. Rickettsial organisms are responsible for a number of serious diseases with world-wide distribution such as Rocky Mountain Spotted Fever , Typhus , Murine Typhus , Scrub typhus, Queensland tick typhus, Boutonneuse fever , North Asian tick-borne
rickettsiosis, Rickettsialpox, and others. All of these diseases require an insect vector (tick, flea, mite) to transmit them to humans or other animals.
The infectious organism of Ehrlichiosis is transmitted to humans by the bite of ticks . Rickettsiae are often associated with a very specific ticks. Ehrlichia appears to inhabit the Lone Star tick
(Amblyomma americanum), the American dog tick (Dermacentor variabilis) and the deer ticks
(Ixodes damni and Ixodes scapularis). (NOTE: the deer tick is also the carrier of Lyme disease .)
The incubation period for Ehrlichiosis is approximately 9 days from the time of tick bite . Ehrlichiosis begins with fever, chills, headache, muscle pain
(myalgia), and nausea. A maculopapular or petechial rash appears in over half the cases and the disease may be mistaken for Rocky Mountain spotted fever. The symptoms are often quite general but the infected individual is usually sick enough to seek medical attention. Ehrlichiosis can be fatal. Recovery takes three weeks. The organism is sensitive to tetracycline and treatment results in improvement in 24 to 48 hours.
Prevention:
Ehrlichiosis is spread by tick bites. Preventing tick bites will prevent Ehrlichiosis and many other tick-borne diseases. Common measures include the use of insect repellent, appropriate clothing, sticking to trails and avoiding dense brush when hiking and not standing under overhanging foliage. After hiking or outings in the woods it is a good idea to examine yourself for ticks and remove any that may be found. Studies suggest that a tick must be attached for about 24 hours in order to cause disease, so early removal may prevent infection. The date and time of a tick bite should be recorded as the incubation period of some tick-borne diseases ( Lyme disease is up to 1 month) is long enough that the event could be forgotten.
Symptoms:
Signs and Tests:
- CBC shows decreased white blood cells (leukopenia), decreased platelets ( thrombocytopenia ).
- A granulocyte stain shows clumps of bacteria inside white blood cells.
- The platelet count shows decreased platelets (thrombocytopenia).
- Liver enzymes show elevated transaminase.
- A fluorescent antibody test is positive for E. chaffeensis or granulocytic Ehrlichia.
Treatment:
Rickettsial diseases, in general, are all responsive to a group of antibiotics belonging to the
tetracyclines. Treatment with tetracycline or doxycycline produces rapid improvement.
Note: Oral tetracycline is usually not prescribed for children until after all the permanent teeth have erupted; it can permanently discolor teeth that are still forming.
Prognosis:
With treatment full recovery is expected.
Complications:
Infection may damage many organ systems but typically the lungs and kidney are involved. Several cases have resulted in death.
Call Your Healthcare Provider:
Call your health care provider if you have had a recent tick bite or exposure to tick infested areas and have developed symptoms suggestive of
Ehrlichiosis. Be sure to mention the tick exposure to the health care provider.
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