Anaplasmosis

What anaplasmosis is

Anaplasma phagocytophilum infects neutrophils, a type of white blood cell. It is transmitted by the blacklegged tick (Ixodes scapularis) in the eastern US and the western blacklegged tick (Ixodes pacificus) on the Pacific coast. Cases peak in late spring and summer, when nymph ticks, which are tiny and easily missed, are active. Most people do not remember a tick bite. Rarely, it spreads through blood transfusion.

Because the same tick carries Lyme disease, babesiosis and Powassan virus, co-infection is possible.

Symptoms

Symptoms begin 5 to 14 days after a bite, often abruptly:

• fever and chills
• severe headache
• muscle aches
• marked tiredness and malaise
• nausea, vomiting, loss of appetite or diarrhea
• cough in some people
• confusion, especially in older adults

A rash occurs in fewer than 1 in 10 people. If a bull's-eye rash appears, it suggests Lyme disease as well.

Severe illness

Severe disease is more likely in older adults, people with weakened immune systems and those whose treatment is delayed. Complications include:

• breathing failure and acute respiratory distress
• bleeding problems
• kidney failure
• septic shock-like illness
• secondary infections
• rarely, nerve problems

Most deaths are in people with weakened immunity or delayed diagnosis, but the overall death rate in treated patients is low.

Anaplasmosis vs Lyme disease and other tick-borne illness

Diagnosis

Doctors make an initial diagnosis from symptoms and possible tick exposure, and start treatment without waiting for test results. Supporting tests include:

• complete blood count: low white blood cells (leukopenia) and low platelets (thrombocytopenia)
• liver function tests: raised ALT and AST
• PCR blood test: detects Anaplasma DNA; most useful in the first week
• blood smear: may show clusters of bacteria (morulae) inside neutrophils
• antibody tests: a rise between two samples 2 to 4 weeks apart confirms infection afterwards

Testing for Lyme disease and babesiosis may be done at the same time.

Treatment

Doxycycline is the treatment of choice for adults and children of all ages, usually for 10 to 14 days, so it also covers possible early Lyme disease. Short courses of doxycycline do not cause the tooth staining seen with older tetracyclines. Most people feel better within 24 to 48 hours. Failure to improve suggests another diagnosis or co-infection.

For people who cannot take doxycycline, rifampin is an alternative in some cases, such as pregnancy or severe allergy, but it does not treat Lyme disease.

Severe illness needs hospital care with supportive treatment.

Antibiotics are not recommended for a tick bite without symptoms to prevent anaplasmosis.

Prevention

• Use EPA-registered repellents such as DEET, picaridin or oil of lemon eucalyptus on skin, and permethrin on clothing and gear.
• Wear long sleeves and trousers tucked into socks in wooded and grassy areas, and walk in the center of trails.
• Check your body, children and pets for ticks daily after being outdoors, including the scalp, armpits, groin and behind the knees.
• Shower within 2 hours of coming indoors.
• Remove ticks promptly with fine-tipped tweezers, grasping close to the skin and pulling straight up steadily.

Outlook

With prompt doxycycline, most people recover fully within days to a couple of weeks, though tiredness can linger. There is no chronic form of anaplasmosis, and infection does not reliably protect against future infections.

Frequently asked questions

What are the symptoms of anaplasmosis?

Symptoms usually start 5 to 14 days after a tick bite and include sudden fever, chills, severe headache, muscle aches and tiredness. Nausea, vomiting and confusion can occur. A rash is uncommon, which helps distinguish it from Lyme disease and Rocky Mountain spotted fever.

How is anaplasmosis treated?

Doxycycline is the recommended antibiotic for adults and children, usually for 10 to 14 days. It should be started as soon as anaplasmosis is suspected, without waiting for test results. Most people improve within 1 to 2 days.

Is anaplasmosis the same as Lyme disease?

No. Both are spread by the blacklegged tick, but they are caused by different bacteria. Anaplasmosis typically causes fever and abnormal blood counts without a rash, while Lyme disease often causes an expanding rash. Doxycycline treats both, and co-infection can occur.

Can anaplasmosis be fatal?

It can be, but deaths are rare, especially with prompt treatment. Severe illness is more likely in older adults, people with weakened immune systems and those whose treatment is delayed. Seeking care early for fever after tick exposure is the best protection.

How long after a tick bite do anaplasmosis symptoms start?

Symptoms usually start 5 to 14 days after the bite. Many people never notice the tick because nymph ticks are as small as a poppy seed. Fever after time in tick areas during spring and summer should prompt a medical visit.