Acute HME syndrome

Acute HME syndrome

Acute HME syndrome (Human Monocytic Ehrlichiosis) is a tick-borne disease caused by the bacterium Ehrlichia chaffeensis. This condition is characterized by the sudden onset of symptoms following the bite of an infected tick.

Etiology

The causative agent of Acute HME syndrome is Ehrlichia chaffeensis, an obligate intracellular bacterium that primarily infects monocytes and macrophages. The primary vector for this bacterium is the Lone Star tick (Amblyomma americanum).

Epidemiology

Acute HME syndrome is most commonly reported in the southeastern and south-central regions of the United States. The incidence of the disease peaks during the warmer months when tick activity is at its highest.

Pathophysiology

Upon transmission through a tick bite, Ehrlichia chaffeensis enters the bloodstream and infects monocytes. The infected cells then disseminate the bacteria throughout the body, leading to a systemic inflammatory response.

Clinical Presentation

The symptoms of Acute HME syndrome typically appear within 1-2 weeks after a tick bite. Common symptoms include:

• Fever
• Headache
• Myalgia
• Malaise
• Nausea
• Vomiting
• Diarrhea
• Rash (less common)

Diagnosis

Diagnosis of Acute HME syndrome is based on clinical presentation, history of tick exposure, and laboratory findings. Laboratory tests may include:

• PCR for Ehrlichia chaffeensis DNA
• Indirect immunofluorescence assay (IFA) for antibodies
• Complete blood count (CBC) showing leukopenia, thrombocytopenia
• Liver function tests showing elevated liver enzymes

Treatment

The treatment of choice for Acute HME syndrome is doxycycline, an antibiotic that is effective against Ehrlichia chaffeensis. Treatment should be initiated as soon as the disease is suspected to prevent complications.

Prognosis

With prompt treatment, the prognosis for Acute HME syndrome is generally good. However, delayed treatment can lead to severe complications, including respiratory failure, renal failure, and septic shock.

Prevention

Preventive measures include:

• Avoiding tick-infested areas
• Using tick repellents
• Wearing protective clothing
• Performing regular tick checks after outdoor activities

See Also

• Tick-borne diseases
• Ehrlichiosis
• Doxycycline
• Lone Star tick