Ehrlichiosis With Difficulty In Breathing, Skin Rash And Muscle Pains - An Infection That Accompanies Lyme's Disease
Detection of Ehrlichiosis
A Word About The Lesser Known Organisms Ehrlichia
Ehrlichia species are small, gram-negative bacteria that grow in membrane-bound vacuoles within the host cells, in which they multiply to form intracytoplasmic colonies, the morulae (the Latin word for mulberry).
They have a special affinity for human white blood cells, both the granulocytes (neutrophils, eosinophils, and basophils) and the monocytes (macrophages). These cells form a line of defense of our body and provide protection against harmful microbes. Thus, this disease attacks and paralyzes our immune system.
Ehrlichiosis is a tick-borne zoonosis, with its main animal reservoirs being deer and dogs.
Clinically ehrlichiosis consists of two main variants:
- Human Monocytic Ehrlichiosis (HME) caused by Ehrlichia chaffeensis.
- Human Granulocytic Ehrlichiosis (HGE) caused by Ehrlichia phagocytophillia.
The peak incidence of the monocytic disease is from May through July. The disease is more common in men (75%) and is associated with increased outdoor exposure. Most individuals recall tick bites or exposure during 3 weeks before the onset of illness; usually these events take place during the season of greatest tick activity, that is from April to September. It is more common in rural areas. The median age of individuals affected is 44 years and the white-tailed rat is an important reservoir.
The bacteria causing granulocytic ehrlichiosis are transmitted along with Lyme's borrelia, both having a common vector Ixodes spp. of ticks. The infection peaks in July (summer months) and again in November, but cases occur throughout the year in warmer areas where the ticks remain viable. Its main animal reservoirs are the white-footed mouse, deer, horses, cattle, sheep and other mammals. This disease also predominantly affects males (79% of cases) and older persons (median age being 58 years).
Signs and Symptoms of Human Monocytic Ehrlichiosis
Human Monocytic Ehrlichiosis has an incubation period of 1-2 weeks (9 days) after the bite from an infected deer tick or a dog tick. Only one-third of the persons who seroconvert actually become ill. Its major vector is the Lone Star Tick (Amblyomma americanum).
The disease is seen primarily in the Southeast, mid-Atlantic and South Central states of the USA and also has a global endemicity (Isreal, Japan, and Mexico) also showing cases.
The disease begins to show with vague, non-specific symptoms consisting of fever, chills, headache, muscle ache, nausea, vomiting, pharyngitis, diarrhea, lymph node enlargement and feeling unwell.
Less common symptoms include gastric upsets, cough, difficulty in breathing and confusion.
A non-specific skin rash consisting of minute patches, small pimple-like lesions or hemorrhages develops on the trunk, especially, in the children.
Other signs include conjunctival injection, hemorrhages on the palate and swelling of hands and feet, along with desquamation or peeling of skin.
Severe complications consist of infection of the brain and its covering meninges (meningoencephalitis) leading to seizures and coma, kidney failure, acute respiratory distress, disseminated intravascular coagulation (clots forming in blood vessels throughout the body) and pericarditis (inflammation of the membrane covering the heart) and opportunistic fungal or viral infections.
Manifestations of Human Granulocytic Ehrlichiosis
Human Granulocytic Ehrlichiosis presents with symptoms similar to those of the monocytic disease, but the rash is conspicuous for its absence. After an incubation period of 8 days, the infected individual develops a flu-like illness with fever, chills, malaise, headache, nausea and vomiting in the decreasing order of frequency. Some individuals develop a cough or confusion later in the course. Seizures are rare.
Severe complications of this disease can include shock, kidney failure and respiratory distress.
Neurological manifestations consisting of meningoencephalitis, weakness of face and demyelination can develop.
Concurrent illness with Ehrlichiosis, Babesiosis and Lyme's disease can occur in the same individual as all the three are transmitted by the same common vector, Ixodes spp of ticks. It is possible that microbial infections in this situation lead to a more severe disease than infection with a single agent.
Individuals with granulocytic ehrlichiosis appear to be older and sicker than those with acute Lyme's disease.
Ehrlichia sennetsu causes an infectious mononucleosis-like illness, the sennutsu fever in the Far-East.
Ehrlichiosis - the disease
- Ehrlichia species are small Gram-negative bacteria that can only grow within host cells.
- Ehrlichiosis is a tick-borne zoonosis with its main animal reservoirs being dogs, deer, horses and cattle.
- In Human Monocytic Ehrlichiosis, the cells most commonly infected are monocytes and macrophages. The disease begins as a flu-like illness with skin rash, difficulty in breathing, and if untreated can complicate into acute respiratory failure and disseminated intravascular coagulation.
- Human Granulocytic Ehrlichiosis occurs concurrently with Babesiosis and Lyme's disease and runs a more aggressive course.
- Doxycycline is the treatment of choice for both variants.
- The disease can be prevented by wearing protective clothing and use of tick repellents.
Laboratory Findings and Detection of Ehrlichiosis
Blood test reports of a person suffering from Ehrlichiosis are something like -
- Reduced Platelet Counts (50,000-140,000/micro liter).
- Reduced White Cell Counts (up to 3500/micro liter).
- Elevation in Liver Enzymes (Aspartate and Alanine Amino Transferase).
- Elevation in serum creatinine levels).
Ehrlichiosis can be detected by the following methods:
- Microscopic examination of white blood cells for the presence of morulae.
- Indirect immunofluorescence assay of acute and convalescent samples.
- Polymerase chain reaction (PCR).
- Protein Immunoblotting.
- Direct Cultivation.
Variants of Ehrlichiosis
Human Monocytic Ehrilchiosis
Human Granulocytic Ehrlichiosis
Major cell target
April through September
Usually occurs alone
Occurs with Babesiosis and Lyme's disease
Areas endemic of Ehrlichiosis
Treatment and Prognosis of Ehrlichiosis
The usual treatment of choice is the antibiotic Doxycycline in a dose of 100 mg twice a day orally or as an intravenous injection. The same antibiotic is also administered to children suffering from this disease.
Defervescence occurs within 1 or 2 days. Therapy for 5-7 days is effective but should be continued for at least two weeks if Lyme's disease coinfection is suspected.
The median duration of disease is 1-2 weeks and clinical course ranges from symptomless seroconversion to multi-organ failure.
The disease runs a more aggressive course in the following situations:
- Immunosuppression (organ transplant recipients, HIV patients, those on steroid therapy).
- Individuals with a cough, diarrhea and enlarged lymph nodes.
The granulocytic form of the disease can be associated with opportunistic infections (disseminated candidiasis and aspergillosis) in immunosuppressed individuals.
Follow Precautions to prevent Ehrlichiosis
Ways to Prevent Ehrlichiosis
The best preventive measure is to avoid tick bites in endemic areas.
Valuable precautions include the following:
- Wearing of protective clothing.
- Use of tick repellents on the skin.
- Careful, frequent checking of the body with prompt removal of the ticks.
Ehrlichia infection is most likely controlled by a combination of cellular and antibody-mediated immune mechanisms.
Successful treatment is followed by an unusual rebound in lymphocyte counts.