Anaplasma and Ehrlichia are distinct bacterial infections that can affect both humans and animals, primarily transmitted through tick bites. These conditions are often discussed together due to their shared vector, similar flu-like symptoms, and the possibility of co-infection. Both belong to the Anaplasmataceae family of bacteria, which are obligate intracellular organisms, meaning they can only live inside the cells of a host.
Understanding How Anaplasma and Ehrlichia Spread
Anaplasmosis, caused by Anaplasma phagocytophilum, is primarily spread by the blacklegged tick (Ixodes scapularis) in the northeastern, mid-Atlantic, and upper Midwest United States, and by the western blacklegged tick (Ixodes pacificus) on the West Coast. This tick species is also known to transmit other pathogens like those causing Lyme disease and babesiosis, leading to potential co-infections.
Ehrlichiosis, caused by various Ehrlichia species, commonly involves Ehrlichia chaffeensis and Ehrlichia ewingii in the United States. E. chaffeensis and E. ewingii are primarily transmitted by the lone star tick (Amblyomma americanum), which is prevalent in the southeastern, south-central, and mid-Atlantic regions. Another species, Ehrlichia muris eauclairensis, is carried by the blacklegged tick and has been reported in Minnesota and Wisconsin. Transmission usually requires the tick to be attached for a specific duration, often ranging from 12 to 24 hours for Anaplasma and potentially longer for Ehrlichia, before the bacteria can be effectively transmitted.
Recognizing Symptoms in Humans
Symptoms of anaplasmosis and ehrlichiosis in humans typically manifest within 5 to 14 days after a tick bite, though many individuals may not recall being bitten. Patients frequently experience fever, chills, severe headache, and muscle aches.
Gastrointestinal symptoms such as nausea, vomiting, diarrhea, and loss of appetite can also occur in approximately 20% of anaplasmosis cases and are reported in ehrlichiosis. While a rash is uncommon in anaplasmosis, it is more frequently seen in ehrlichiosis. This rash typically develops around five days after fever onset, usually sparing the face but sometimes spreading to palms and soles.
Recognizing Symptoms in Animals
Anaplasmosis and ehrlichiosis can also affect animals, with dogs being frequently diagnosed. In dogs, Anaplasma phagocytophilum typically causes lameness, joint pain, fever, lethargy, and a reduced appetite. Most affected dogs exhibit these signs for about one to seven days. Less common signs include vomiting, diarrhea, coughing, and labored breathing.
Anaplasma platys, another species, primarily affects canine platelets, leading to a condition called cyclic thrombocytopenia, which can cause bruising or nosebleeds. For ehrlichiosis in dogs, symptoms often progress through acute, subclinical, and chronic phases. Stiff or swollen joints are a common symptom.
Diagnosis and Treatment Approaches
Diagnosing anaplasmosis and ehrlichiosis involves a combination of clinical assessment and specific laboratory tests. Healthcare providers often consider these infections if a patient presents with flu-like symptoms after potential tick exposure, especially in endemic areas. Blood tests such as a complete blood count (CBC) and a metabolic profile can reveal common abnormalities like low white blood cell counts (leukopenia), low platelet counts (thrombocytopenia), and elevated liver enzymes.
For definitive diagnosis, polymerase chain reaction (PCR) testing on a blood sample is highly sensitive and specific, particularly in the early stages of illness. Antibody tests, such as the indirect fluorescent antibody (IFA) test, can detect the body’s immune response, though antibodies may take several weeks to develop and persist for months or years after infection, making early diagnosis challenging. Microscopic examination of blood smears for bacterial inclusions within white blood cells (morulae) can also support a diagnosis, though their presence may be sparse.
Treatment for both anaplasmosis and ehrlichiosis typically involves the antibiotic doxycycline, which is effective for patients of all ages. Early intervention is important to prevent severe complications, and fever usually subsides within 24 to 48 hours of starting treatment. For humans, treatment generally lasts for 5 to 7 days, or until the patient has been without fever for at least three days. In animals, treatment duration can extend for at least 28 days.
Preventing Infection
Preventing anaplasmosis and ehrlichiosis involves reducing exposure to ticks for both humans and animals. When spending time outdoors, especially in wooded, brushy, or grassy areas where ticks reside, wearing protective clothing such as long pants tucked into socks can help create a barrier. Treating clothing and gear with permethrin, a tick repellent, or applying EPA-registered insect repellents containing ingredients like DEET or picaridin to exposed skin, offers additional protection.
After outdoor activities, thorough tick checks are important for both people and pets. For humans, this involves inspecting the entire body, including hidden areas like under the arms, in and around the ears, and behind the knees. Prompt removal of any attached ticks using fine-tipped tweezers can significantly reduce the risk of disease transmission, as ticks typically need to be attached for a certain duration to transmit bacteria. For pets, regular inspections and the consistent use of veterinarian-recommended tick prevention products, such as oral medications, topical treatments, or collars, are effective strategies to control tick infestations and minimize infection risk.