Ehrlichiosis: Causes, Symptoms, Dangers, and Treatment

What is Ehrlichiosis?

Ehrlichiosis represents a group of infectious diseases affecting humans and various other mammals, caused by bacteria of the genera Ehrlichia and Anaplasma. These pathogens are transmitted primarily through the bite of infected ticks, making ehrlichiosis a classic example of a tick-borne zoonotic disease, i.e., an illness that can pass from animals to humans via an intermediary vector.

The most common clinical manifestations of ehrlichiosis include:

• Fever, often high and sudden in onset, is a common symptom
• Chills, which often accompany fever
• Headache, which can sometimes be severe
• Muscle pain (myalgia): widespread muscular aching
• Occasional gastrointestinal symptoms, like nausea or stomach discomfort, may occur

The primary treatment for ehrlichiosis is doxycycline, an antibiotic from the tetracycline class that is considered the gold standard for both adults and children when dealing with this infection. When diagnosed and treated promptly, ehrlichiosis generally responds well to therapy, with symptomatic improvement typically observed within just 24 to 48 hours of starting antibiotics.

However, the picture can change significantly when treatment is delayed or when the patient has pre-existing health conditions that compromise their immune system. In such cases, ehrlichiosis can progress to a severe, potentially life-threatening illness. This is why awareness, early recognition, and timely medical consultation are so critically important.

Understanding ehrlichiosis is not just a matter of academic curiosity. It is a practical health concern for anyone who hikes, camps, gardens, works outdoors, or lives in rural or semi-rural areas where ticks are present. The more you know about this disease, the better equipped you are to protect yourself and your loved ones.

---

Causes

The Bacteria Behind Ehrlichiosis

Ehrlichiosis is caused by obligate intracellular bacteria belonging to the genera Ehrlichia and Anaplasma, which are part of the family Anaplasmataceae. These are small, gram-negative bacteria that live and replicate only inside the cells of their host. Because of this, they cannot survive independently outside living cells.

The most medically significant species in human ehrlichiosis include:

• Ehrlichia chaffeensis, the primary causative agent of Human Monocytic Ehrlichiosis (HME), is predominantly found in the United States. This bacterium primarily infects monocytes and macrophages (types of white blood cells).
• Anaplasma phagocytophilum, the causative agent of Human Granulocytic Anaplasmosis (HGA), infects granulocytes, another type of white blood cell. Though technically now classified under a different species name, anaplasmosis shares so many characteristics with ehrlichiosis that it is often discussed together with it.
• Ehrlichia ewingii, which causes Human Granulocytic Ehrlichiosis, is particularly relevant in immunocompromised patients.
• Ehrlichia canis, primarily a pathogen in dogs, has had rare human cases documented.

How Is Ehrlichiosis Transmitted?

The bacteria responsible for ehrlichiosis are inoculated into the host’s bloodstream through the bite of an infected tick. The tick acts as both a reservoir and a vector for the pathogen, capable of replicating within the tick itself as well as within the vertebrate host.

In addition to humans, the vertebrate hosts susceptible to Ehrlichia and Anaplasma infection include:

• Dogs, particularly susceptible to Ehrlichia canis
• Cattle, sheep, and goats
• Rodents, important reservoir hosts
• Deer, particularly white-tailed deer, serve as a key reservoir for Ehrlichia chaffeensis in North America

The specific tick species responsible for transmission varies by geographic region:

• In North America, the Lone Star tick (Amblyomma americanum) is the primary vector for E. chaffeensis
• In Europe and Asia, the sheep tick (Ixodes ricinus) plays a significant role in transmitting Anaplasma phagocytophilum
• The black-legged tick (Ixodes scapularis), also known as the deer tick, transmits A. phagocytophilum in the northeastern and upper midwestern United States

Can Ehrlichiosis Spread from Person to Person?

Importantly, ehrlichiosis cannot spread from person to person. This means there is no risk of contracting the disease through ordinary social contact, respiratory droplets, or touch. Similarly, direct contact with an infected dog does not put humans at risk, as the bacteria cannot be transmitted directly from a dog to its owner.

However, in extremely rare circumstances, transmission has been documented through:

• Blood transfusions can pose a risk if blood from an infected donor is administered before the infection is detected
• Transplacental transmission, which occurs when an infected mother passes an infection to her fetus during pregnancy
• Direct contact with the blood or tissues of an infected, freshly slaughtered animal is considered a very rare route of exposure. This risk primarily affects hunters or slaughterhouse workers

These alternative routes of transmission are uncommon, but they underscore the importance of blood screening protocols and occupational safety measures in certain settings.

Why Are Ticks Such Effective Vectors?

Ticks are uniquely suited to transmit pathogens like Ehrlichia because of how they feed. Unlike mosquitoes, which feed quickly, ticks attach to their host and feed slowly. They often remain attached for 24 to 72 hours or more. During this prolonged feeding process, bacteria in the tick’s salivary glands are introduced into the host’s bloodstream. The longer the tick remains attached, the greater the likelihood of bacterial transmission.

This is why prompt tick removal is one of the most effective ways to reduce your risk of ehrlichiosis and other tick-borne diseases. Ticks should ideally be removed within the first 24 hours of attachment to minimize transmission risk.

---

Incubation Period

After a tick bite, symptoms do not appear immediately. This delay is known as the incubation period. For ehrlichiosis, symptoms typically begin to develop one to two weeks after the infected tick bite, with an average incubation period of approximately nine days.

This relatively short incubation period has important clinical implications. If you have recently spent time in a tick-endemic area and begin to feel unwell within two weeks, particularly with fever, headache, or muscle pain, it is essential to mention any possible tick exposure to your healthcare provider. This advice applies even if you do not recall being bitten.

It is worth emphasizing that tick bites are generally painless. Ticks produce compounds in their saliva that act as local anesthetics, making it easy to overlook a bite entirely. Many patients with ehrlichiosis do not remember being bitten at all. This is why awareness of endemic areas and activity patterns (hiking, camping, gardening) is just as important as remembering a specific tick encounter.

---

Symptoms

Typical Clinical Presentation

Ehrlichiosis typically presents as a non-specific febrile illness, which means its initial symptoms can resemble those of many other common infections, such as influenza. This non-specific nature is one of the reasons ehrlichiosis can be challenging to recognize and diagnose.

Patients infected with Ehrlichia bacteria typically experience the following symptoms:

• Fever often presents as high-grade (above 38.5°C / 101.3°F), appears abruptly, and tends to persist
• Chills often accompany fever
• General malaise and fatigue: a pervasive feeling of being unwell that is often severe
• Headache is often described as intense and generalized
• Muscle pain (myalgia): a widespread ache in the muscles, which can sometimes be quite intense

Less Common Symptoms

In addition to the typical presentation, some patients with ehrlichiosis develop less common symptoms, including:

• Gastrointestinal complaints, such as nausea and vomiting or diarrhea, are more frequently observed in some patient populations. These symptoms can contribute to dehydration if severe.
• Skin rash: The development of a rash, characterized by red spots or petechiae, is more commonly seen in children and typically appears after approximately five days of illness. It is less common in adults and when present can be an important diagnostic clue, though its absence does not rule out ehrlichiosis.
• Cough and mild respiratory symptoms: these tend to be more prevalent in adult patients.

How Symptoms Differ Between Children and Adults

One clinically interesting aspect of ehrlichiosis is that the disease can present somewhat differently depending on the patient’s age:

• In children: Skin rash is more commonly observed, and gastrointestinal symptoms (nausea, vomiting, abdominal pain) tend to be more prominent. Children may also appear more acutely ill at presentation.
• In adults: Respiratory symptoms, including mild cough and shortness of breath, are more frequently reported. Adults, especially those who are elderly or immunocompromised, are at higher risk for severe disease and complications.

The Importance of Recognizing Early Symptoms

Because ehrlichiosis often resembles influenza or other viral infections in its early stages, and because it occurs during spring and summer when respiratory viruses are less common, it is important to maintain a high index of suspicion in patients who:

1. Live in or have recently visited tick-endemic areas
2. Have a history of outdoor activities (hiking, camping, hunting, gardening)
3. Have had confirmed or possible tick exposure
4. Develop a febrile illness between April and September (peak tick season in the Northern Hemisphere)

Early recognition leads to earlier treatment, and earlier treatment significantly improves outcomes.

---

Complications

When Ehrlichiosis Becomes Severe

Most patients with ehrlichiosis who receive prompt and appropriate antibiotic therapy recover fully without significant complications. However, in a subset of patients, particularly those who experience delayed diagnosis and treatment or those with underlying health vulnerabilities, the disease can progress to serious and potentially life-threatening complications.

Neurological Complications

Similar to infections caused by Rickettsia species, Ehrlichia bacteria can in some cases affect the central nervous system (CNS). Neurological involvement occurs in a minority of patients but can be severe when it does occur. Manifestations include:

• Meningitis is the inflammation of the membranes surrounding the brain and spinal cord
• Meningoencephalitis, a more severe form, involves inflammation of both the meninges and the brain tissue itself
• Mental confusion refers to an altered mental status, disorientation, and difficulty concentrating
• Seizures are episodes of abnormal electrical activity in the brain
• Coma can occur in the most extreme cases

Cardiopulmonary Complications

In some patients, ehrlichiosis can progress to involve the cardiopulmonary system, leading to:

• Acute Respiratory Distress Syndrome (ARDS) is a life-threatening condition. In this syndrome, fluid accumulates in the lungs, which severely impairs oxygenation.
• Respiratory failure, which may require mechanical ventilation in severe cases.
• Cardiovascular involvement, which includes arrhythmias and heart failure in severe disease.

Sepsis-Like Syndrome

One of the most feared complications of ehrlichiosis is the development of a clinical picture resembling sepsis or septic shock. This involves:

• Systemic inflammatory response
• Coagulation disorders (disseminated intravascular coagulation, or DIC)
• Multi-organ failure
• Hemorrhage
• Cardiac arrest
• Renal failure
• Shock

Mortality and Risk Factors

The overall mortality rate associated with ehrlichiosis is significantly lower than that seen with some other tick-borne diseases, such as Rocky Mountain Spotted Fever (caused by Rickettsia rickettsii). According to the CDC, the case fatality rate for ehrlichiosis is estimated at approximately 1 to 3%. However, this figure may be an overestimate of the true mortality rate, given that many mild or subclinical cases likely go undiagnosed and resolve spontaneously without medical attention.

The following patient groups are at highest risk for developing severe disease and complications:

• Immunocompromised patients, including those with HIV/AIDS, cancer, or individuals receiving immunosuppressive therapy such as corticosteroids or chemotherapy, are at higher risk. Immunocompromised patients may develop an especially severe and prolonged course of illness.
• Elderly patients: Age-related decline in immune function increases their vulnerability to severe ehrlichiosis.
• Patients pre-treated with sulfonamide antibiotics, such as sulfa antibiotics like trimethoprim-sulfamethoxazole, not only fail to treat ehrlichiosis but may actually worsen the disease. This happens because the antibiotics suppress the immune response while allowing the bacteria to continue replicating. This is an important clinical caveat: sulfonamides should never be used to treat suspected ehrlichiosis.

The full spectrum of potential complications in high-risk patients includes:

• Neurological symptoms including confusion, seizures, and coma
• Hemorrhagic manifestations
• Cardiac arrest
• Respiratory failure
• Renal failure
• Septic shock

Understanding these risk factors can help both patients and clinicians maintain appropriate vigilance and ensure that high-risk individuals receive particularly prompt evaluation and treatment.

---

Diagnosis

Why Timely Diagnosis Matters

Because early recognition and treatment of ehrlichiosis can significantly improve the prognosis, it is critically important not to underestimate symptoms, especially when they appear after exposure to tick-endemic environments. This is especially true during the summer months (May through September in the Northern Hemisphere), when tick activity is at its peak and the likelihood of tick bites is greatest.

A key diagnostic challenge is that many patients do not recall being bitten by a tick, because tick bites are typically painless and unnoticed. Ticks are often very small (especially nymphs, which are the size of a poppy seed) and their saliva contains compounds that suppress both the sensation of the bite and the local immune response, allowing them to feed undisturbed.

Clinical Suspicion

Diagnosis begins with clinical suspicion. Healthcare providers should consider ehrlichiosis in any patient who presents with:

• Sudden-onset fever
• Headache and myalgia
• A history of possible tick exposure or residence/travel in a tick-endemic area
• Laboratory abnormalities consistent with tick-borne disease (see below)

This is particularly important because the typical laboratory results that support a diagnosis of ehrlichiosis, such as low white blood cell count and low platelet count, can also appear in other conditions. Waiting for definitive laboratory confirmation before starting treatment may result in dangerous delays.

Differential Diagnosis

Clinically, Ehrlichia infections share many symptoms with rickettsiosis (rickettsia infections). In many cases, they also overlap in geographic distribution. Both conditions present with fever, headache, myalgia, and potential rash, and both are transmitted by ticks. In endemic areas where both infections are present, careful differential diagnosis is essential.

Other conditions that may mimic ehrlichiosis include:

• Viral syndromes (influenza, infectious mononucleosis)
• Lyme disease (also tick-borne, but caused by Borrelia burgdorferi)
• Viral meningitis (if neurological symptoms are present)
• Bacterial sepsis from other causes
• Thrombocytopenic purpura
• Hepatitis (given the elevated liver enzymes sometimes seen in ehrlichiosis)

Laboratory Findings

Several characteristic laboratory abnormalities are commonly found in patients with ehrlichiosis:

• Leukopenia (low white blood cell count) occurs when there is a reduction in circulating white blood cells, particularly lymphocytes and granulocytes. This condition is a hallmark finding in many medical scenarios.
• Thrombocytopenia (low platelet count) occurs when platelet levels are reduced, which can increase the risk of bleeding.
• Elevated liver enzymes (transaminases), which can range from mild to moderate levels, reflect hepatic involvement.
• Elevated C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) are general markers of inflammation.
• Hyponatremia (low sodium) can occur in some patients.

It is important to note that none of these findings is specific to ehrlichiosis; they must be interpreted in the context of the clinical presentation and epidemiological history.

Specific Diagnostic Tests

At specialized centers, the definitive diagnosis of ehrlichiosis is typically made using Polymerase Chain Reaction (PCR) testing on blood samples. PCR detects the genetic material of the Ehrlichia bacteria directly and is highly sensitive and specific in the early stages of the disease.

It is critically important that blood samples for PCR be collected before starting antibiotic therapy, as antibiotics rapidly reduce bacterial load and can render PCR testing falsely negative. However, this should not mean delaying treatment significantly. If clinical suspicion is high, treatment should be initiated promptly. Samples should be collected as quickly as possible beforehand.

Other diagnostic methods include:

• Indirect immunofluorescence assay (IFA) measures antibodies against Ehrlichia. Antibody levels are often low or absent in the first week of illness, so this test is most useful for confirming a diagnosis retrospectively rather than guiding immediate treatment decisions.
• Blood smear microscopy: In some cases, intracellular clusters of Ehrlichia bacteria, called morulae, can be visualized within white blood cells on a peripheral blood smear. This finding is specific but not particularly sensitive.
• Culture: Ehrlichia bacteria can be grown in culture. However, this process is technically demanding and slow. It is primarily reserved for research settings.

Given the diagnostic limitations of each individual test, clinical judgment plays a crucial role in guiding the decision to start treatment. This judgment should be based on the overall picture: symptoms, epidemiological context, and initial laboratory results.

---

Treatment

Antibiotic Therapy: Doxycycline as First-Line Treatment

Ehrlichiosis is treated with antibiotic therapy, and doxycycline is universally recognized as the first-line treatment for both adults and children, regardless of age. This recommendation is consistent across all major medical authorities, including the CDC, the Infectious Diseases Society of America (IDSA), and the American Academy of Pediatrics (AAP).

Doxycycline is a broad-spectrum antibiotic belonging to the tetracycline class. One of its key advantages in the context of tick-borne diseases is that it is effective not only against Ehrlichia species but also against the closely related Rickettsia species. This is particularly valuable because distinguishing these two infections clinically can be difficult without laboratory confirmation.

Typical doxycycline dosing:

• Adults: 100 mg orally (or intravenously in severe cases) twice daily
• Children weighing less than 45 kg: 2.2 mg/kg per dose, twice daily (maximum 100 mg per dose)
• Duration: typically 5 to 7 days, extended to at least 3 days after fever resolves and clinical improvement is evident. More severe cases may require longer courses.

Clinical Response to Treatment

One of the reassuring aspects of ehrlichiosis therapy is that patients who are treated appropriately generally respond relatively quickly. Clinicians typically expect to see:

• Reduction in fever within 48 to 72 hours of starting doxycycline
• Gradual improvement in headache, myalgia, and general malaise
• Normalization of laboratory abnormalities (white blood cell count, platelet count, liver enzymes) over the following days to weeks

A failure to improve within 48 to 72 hours of starting doxycycline should prompt reconsideration of the diagnosis or evaluation for possible complications.

Treatment in Special Populations

Pregnant women represent a particularly challenging treatment scenario. Doxycycline is generally avoided during pregnancy due to potential adverse effects on fetal bone and tooth development. However, given that untreated ehrlichiosis can be life-threatening, the risks must be carefully weighed. Rifampin has been used as an alternative in mild cases during pregnancy, but this decision should always be made in close consultation with infectious disease specialists and obstetricians.

Patients with severe disease, including those with neurological involvement, respiratory failure, or septic shock**,** require hospitalization, intensive supportive care, and intravenous antibiotics. Management in an intensive care unit (ICU) may be necessary for the most critically ill patients.

What to Avoid: Sulfonamides

As previously mentioned, sulfonamide antibiotics (such as trimethoprim-sulfamethoxazole, commonly used for urinary tract infections and other bacterial infections) are contraindicated in ehrlichiosis. Not only do they lack efficacy against Ehrlichia bacteria, but there is evidence that they may actually worsen the clinical course of the disease. This is a critical point, as sulfonamides might otherwise be considered by clinicians unfamiliar with tick-borne diseases as a reasonable empiric treatment for a febrile illness.

No Vaccine Available

As of today, there is no approved vaccine for the prevention of ehrlichiosis in humans. Prevention therefore relies entirely on avoiding tick bites and practicing prompt tick removal, as discussed in the next section.

---

Prevention: How to Protect Yourself from Tick Bites

Since there is no vaccine for ehrlichiosis, prevention is built entirely around avoiding tick bites and minimizing the time ticks remain attached to the skin if a bite occurs. The following evidence-based strategies are recommended by leading public health organizations:

Personal Protective Measures

1. Wear appropriate clothing: When venturing into tick-prone areas (forests, grasslands, scrublands), wear long-sleeved shirts, long trousers tucked into socks, and closed-toe shoes. Light-colored clothing makes it easier to spot ticks before they attach.

2. Use EPA-registered insect repellents: Apply repellents containing DEET (20-30%), picaridin, IR3535, or oil of lemon eucalyptus to exposed skin and clothing. Products containing permethrin can be applied to clothing and gear (but not directly to skin) for added protection.

3. Stay on marked paths: Ticks are most abundant in tall grass, leaf litter, and dense vegetation. Walking in the center of trails reduces contact with vegetation where ticks wait to attach to passing hosts (a behavior called “questing”).

4. Perform thorough tick checks after outdoor activity: After spending time outdoors, carefully inspect your entire body for ticks, paying special attention to warm, hidden areas: behind the knees, in the groin, under the arms, in the navel, around the ears, in the hair, and at the nape of the neck. Check children and pets as well.

5. Shower promptly after being outdoors: Showering within two hours of coming indoors has been shown to reduce the risk of tick-borne disease, as it can wash off unattached ticks and provides an opportunity for a full-body tick check.

Tick Removal

If you find a tick attached to your skin, remove it promptly and correctly:

• Use fine-tipped tweezers to grasp the tick as close to the skin’s surface as possible.
• Pull upward with steady, even pressure. Do not twist or jerk the tick, as this can cause parts of the tick to break off and remain in the skin.
• After removing the tick, clean the bite area and your hands with rubbing alcohol or soap and water.
• Dispose of the tick by submerging it in alcohol, placing it in a sealed bag, or flushing it down the toilet. Do not crush it with your fingers.
• Do not use petroleum jelly, heat, or other folk remedies to remove ticks. These methods are ineffective and may increase the risk of disease transmission.

Environmental Control

• Modify your yard to create tick-hostile environments: keep grass mowed short, clear leaf litter and brush, and place a barrier of wood chips or gravel between wooded areas and lawn.
• Treat pets with veterinarian-recommended tick prevention products, and check pets for ticks after outdoor activity. Remember that while pets cannot directly transmit ehrlichiosis to humans, they can carry ticks into the home.
• Consider professional tick control treatments for yards in high-risk areas.

---

Ehrlichiosis in Dogs

While this article focuses primarily on ehrlichiosis in humans, it is worth briefly addressing the disease in dogs, both because it is commonly diagnosed in canines and because concerned pet owners often have questions about the potential risk to themselves.

Canine ehrlichiosis is caused primarily by Ehrlichia canis and is transmitted by the brown dog tick (Rhipicephalus sanguineus). In dogs, the disease can occur in acute, subclinical, and chronic phases and may present with:

• Fever and lethargy
• Loss of appetite
• Lymph node enlargement
• Abnormal bleeding (nosebleeds, bruising)
• Eye discharge
• Weight loss in chronic cases

Canine ehrlichiosis is treatable with doxycycline, similar to the human disease.

As noted by the CDC, canine ehrlichiosis is not directly transmissible from dogs to humans, since it requires a tick as an intermediary vector. However, dogs that spend time outdoors in tick-endemic areas may carry ticks into the home, creating an indirect risk to human household members. For this reason, effective tick prevention in pets is an important component of a household tick control strategy.

---

Ehrlichiosis vs. Rickettsiosis: Key Differences

Given that ehrlichiosis and rickettsiosis share many clinical features and geographic distribution patterns, it is useful to understand the key distinctions between these two tick-borne diseases:

The shared treatment with doxycycline means empiric therapy is appropriate for clinically suspected tick-borne disease, even before a definitive diagnosis is established. This fact underscores the importance of not delaying treatment while awaiting laboratory results.

---

Frequently Asked Questions

Can I get ehrlichiosis from my dog?

No. While dogs can become infected with Ehrlichia species, they cannot transmit the bacteria directly to humans. Transmission requires the bite of an infected tick. However, dogs can carry infected ticks into the home, so proper tick prevention for pets is still important for reducing household risk.

How long after a tick bite do symptoms appear?

Symptoms typically appear 1 to 2 weeks after an infected tick bite, with an average incubation period of about 9 days.

Is ehrlichiosis contagious?

No. Ehrlichiosis is not contagious between humans. It can only be transmitted through the bite of an infected tick, or in very rare cases through blood transfusion, transplacental transmission, or direct contact with infected animal blood.

Can children take doxycycline for ehrlichiosis?

Yes. Despite older concerns about doxycycline causing tooth discoloration in young children, major medical authorities including the CDC and the American Academy of Pediatrics now recommend doxycycline as the first-line treatment for ehrlichiosis in children of all ages, including those under 8 years old. The short treatment course used for ehrlichiosis (5-7 days) is associated with minimal risk of this side effect.

What happens if ehrlichiosis is not treated?

Untreated ehrlichiosis may lead to severe and life-threatening complications. These include neurological issues such as meningitis or encephalitis, respiratory failure, renal failure, and septic shock. In rare cases, it can even result in death. This is why prompt diagnosis and treatment are essential.

Is there a vaccine for ehrlichiosis?

No. As of today, there is no vaccine available for the prevention of ehrlichiosis in humans. Prevention relies on tick bite avoidance and prompt tick removal.

How is ehrlichiosis diagnosed?

Diagnosis is based on clinical suspicion (symptoms + epidemiological history) supported by laboratory findings (low white blood cell count, low platelets, elevated liver enzymes) and confirmed by PCR testing on blood samples. Serology (antibody testing) can confirm the diagnosis retrospectively but is not reliable in the first week of illness.

What is the difference between ehrlichiosis and Lyme disease?

Both are tick-borne diseases, but they are caused by different bacteria (Ehrlichia vs. Borrelia burgdorferi) and have different clinical presentations. Lyme disease characteristically produces a bull’s-eye rash (erythema migrans) and can cause chronic joint, cardiac, and neurological problems if untreated. Ehrlichiosis does not typically produce the bull’s-eye rash and more commonly presents as an acute febrile illness. Both can be transmitted by Ixodes ticks.

---

Sources and Bibliography

• CDC – Ehrlichiosis
• Ehrlichiosis – Jessica Snowden; Marc Bartman; Erwin L. Kong; Kari A. Simonsen. StatPearls, NCBI Bookshelf.
• ISS – Istituto Superiore di Sanità: Ehrlichiosi
• CDC MMWR – Canine Ehrlichiosis and Human Transmission
• Dumler JS, Madigan JE, Pusterla N, Bakken JS. Ehrlichioses in humans: epidemiology, clinical presentation, diagnosis, and treatment. Clin Infect Dis. 2007;45 Suppl 1:S45-51.
• Thomas RJ, Dumler JS, Carlyon JA. Current management of human granulocytic anaplasmosis, human monocytic ehrlichiosis, and Ehrlichia ewingii ehrlichiosis. Expert Rev Anti Infect Ther. 2009;7(6):709-22.
• Biggs HM, et al. Diagnosis and Management of Tickborne Rickettsial Diseases: Rocky Mountain Spotted Fever and Other Spotted Fever Group Rickettsioses, Ehrlichioses, and Anaplasmosis, United States. MMWR Recomm Rep. 2016;65(2):1-44.
• American Academy of Pediatrics. Red Book: 2021-2024 Report of the Committee on Infectious Diseases. Ehrlichia and Anaplasma Infections. Elk Grove Village, IL: AAP.