Anaplasmosis: For health professionals

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• Key information
• Transmission
• Clinical manifestations
• Diagnosis
• Treatment
• Laboratory testing
• Surveillance
• Subscribe to the Zoonoses Bulletin

Key information

Anaplasmosis, also known as human granulocytic anaplasmosis, is a rickettsial tick-borne zoonotic disease caused by the bacterium Anaplasma phagocytophilum (A. phagocytophilum). A. phagocytophilum is an obligate gram-negative intracellular bacterium and is mainly transmitted by infected blacklegged ticks (Ixodes scapularis) and western blacklegged ticks (Ixodes pacificus). Consult with your provincial or territorial public health authorities to find out where ticks are most likely to be found.

Anaplasmosis, like most tick-borne disease infections, occurs during the warmer months, but infections can occur throughout the year. Ticks can be active whenever the temperature is consistently above freezing, and the ground isn't covered by snow.

It's critical to remove attached ticks promptly as the risk of transmission of A. phagocytophilum increases the longer the tick is attached. In most cases, infected blacklegged ticks and western blacklegged ticks transmit A. phagocytophilum between 24 to 48 hours of attachment. However, transmission can occur in less time.

Individuals may not be aware of or remember being bitten by a tick. Therefore, it's important that health professionals conduct a detailed patient history, including history of exposure to ticks, when assessing individuals with signs or symptoms suggestive of anaplasmosis.

Treatment shouldn't be delayed while waiting for confirmatory laboratory results. Most cases of anaplasmosis can be managed successfully with a timely diagnosis and appropriate treatment.

There's currently no vaccine available to prevent anaplasmosis. The best way to prevent tick-borne diseases is to prevent tick bites.

For individuals presenting with signs or symptoms of anaplasmosis, we encourage health professionals to consider the possibility of other tick-borne diseases, such as:

• babesiosis
• Lyme disease
• Powassan virus disease
• tick-borne relapsing fever

Learn more about:

• Ticks in Canada
• How to remove a tick
• How to prevent tick bites
• Provincial and territorial public health authorities

Transmission

Anaplasmosis is primarily acquired through the bite of an infected tick. The ticks known to transmit anaplasmosis are:

In Canada, there are 2 known strains of A. phagocytophilum that circulate:

1. Ap-ha, which infects people most often.
2. Ap-var1, which is considered non-pathogenic and does not infect humans.

Learn more about:

• Ticks in Canada

Other possible routes of transmission

A. phagocytophilum can survive for more than 1 week in refrigerated blood. Internationally, there have been limited cases of A. phagocytophilum being transmitted through blood transfusions and organ transplants. However, there have been no reports of cases transmitted this way in Canada.

Learn more about:

• Canadian Blood Services
• Héma-Québec

Clinical manifestations

The incubation period for anaplasmosis infection is 5 to 21 days.

Symptoms may be absent or range from mild to severe, and may progress over time, particularly in untreated individuals.

Individuals who develop symptoms days or weeks after a tick bite may not remember being bitten or associate symptoms with the bite.

Early symptoms of anaplasmosis are non-specific and may include:

• fever
• chills
• cough
• nausea
• malaise
• myalgia
• diarrhea
• vomiting
• headache
• arthralgias
• loss of appetite
• abdominal pain

Non-specific symptoms of anaplasmosis can be confused with those of other tick-borne diseases.

Complications due to anaplasmosis infection may occur and may include:

• seizures
• coma
• organ failure such as renal failure
• respiratory failure
• hemorrhagic manifestations
• cardiac complications such as heart failure, pericardial effusion, and cardiac tamponade
• neurological manifestations such as:
  • mental status changes
  • stiff neck
  • clonus
  • meningoencephalitis (not often reported)

Severe cases may lead to septic or toxic shock-like syndrome. Death from Anaplasmosis is rare with a case fatality rate less than 1% and usually due to organ failure.

Risk factors for a severe case of anaplasmosis may include:

• advanced age
• immunosuppression
• pre-existing health conditions

Rashes

While a cutaneous rash can occur at the site of infection, it's uncommon and doesn't have the appearance of an erythema migrans rash as seen in Lyme disease. The presence of an erythema migrans rash in a patient would be suggestive of an infection or co-infection with Borrelia burgdorferi (Lyme disease).

Hypersensitivity reaction to a tick bite

Individuals may develop a hypersensitivity reaction within 24 hours of a tick bite. A hypersensitivity reaction will produce an erythematous skin lesion less than 5 cm in diameter which doesn't expand and usually recedes within 48 hours.

Hypersensitivity skin reactions shouldn't be confused with erythema migrans as seen in Lyme disease. Individuals who develop erythematous skin lesions which haven't resolved within 48 hours should be reassessed to determine whether an erythema migrans rash has developed.

Diagnosis

Anaplasmosis should be considered in individuals presenting with:

• a history of tick exposure
• clinical signs and symptoms that are consistent with anaplasmosis

Laboratory testing can be conducted when appropriate.

In cases of unexplained exposure, health professionals should inquire about recent blood transfusions and organ transplants.

History of tick exposure

A history of tick exposure includes:

• a recent tick bite or
• living in or having recently visited a potential blacklegged or western blacklegged tick habitat

While a known history of tick exposure, particularly to blacklegged or western blacklegged ticks, helps with the diagnosis, absence of a history of exposure doesn't rule out anaplasmosis. Individuals may not recall a tick bite because ticks are tiny, and their bites are usually painless. Furthermore, blacklegged ticks and western blacklegged ticks can also be found outside currently identified risk areas.

A tick may carry multiple pathogens and transmit them to humans via a single bite. Therefore, while investigating anaplasmosis, health professionals should consider infection or co-infection with other tick-borne diseases, such as:

• babesiosis
• Lyme disease
• Powassan virus
• tick-borne relapsing fever

Consider consultation with an infectious disease specialist when suspecting co-infection.

Treatment

Most symptomatic cases of anaplasmosis can be managed successfully with a timely diagnosis and appropriate treatment.

While waiting for laboratory testing, initiate treatment with appropriate antibiotics for patients who present with clinical manifestations of anaplasmosis or other rickettsial disease.

Doxycycline is the most commonly recommended oral antibiotic for symptomatic adult and pediatric patients suspected of having anaplasmosis. Rifampin is another alternative.

Doxycycline is also the preferred treatment for other tick-borne diseases. However, doxycycline and other drugs used to treat anaplasmosis are not effective against babesiosis. If infection or co-infection with babesiosis is suspected or confirmed, a specific regimen is required.

Laboratory testing

Laboratories that employ conventional diagnostic assays and interpretive criteria should be the only laboratories conducting diagnostic testing. Health professionals should send samples to their provincial and territorial laboratories. They will coordinate with the National Microbiology Laboratory, when necessary.

Samples to collect for patients being investigated for anaplasmosis include:

• acute serum sample: collected as early as possible after symptom onset
• convalescent serum sample: collected 2 to 6 weeks after the acute sample

Laboratory tests for anaplasmosis include:

• detecting A. phagocytophilum DNA in whole blood, buffy coat or serum by polymerase chain reaction
• immunofluorescent assays detecting both immunoglobin G antibodies to prior infection
• identification of atypical morulae in the cytoplasm of granulocytes by microscopic examination of blood

Antibodies to A. phagocytophilum might remain elevated for many months to years after the disease has resolved. Comparison of paired, and appropriately timed, serologic assays provide the best evidence of recent infection.

Laboratory testing should be done through a licensed and accredited public health laboratory.

Surveillance

Anaplasmosis is a nationally notifiable disease. Nationally notifiable diseases are infectious diseases that have been identified collectively by the federal, provincial and territorial governments as priorities for surveillance and control efforts.

The national notification system receives cases reported through provincial and territorial public health authorities. Both confirmed and probable cases of anaplasmosis are reportable. The national case definition for anaplasmosis is used to classify cases reported to the Public Health Agency of Canada.

Provinces and territories have their own legislation for reporting of priority infectious diseases. Consult provincial or territorial public health authorities for reporting requirements in your jurisdiction.

Learn more about:

• Notifiable diseases online
• National case definition: Anaplasmosis

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The Zoonoses Bulletin is an email subscription list that will provide you with regular updates from the Public Health Agency of Canada regarding our work on zoonoses. Zoonoses are infectious diseases that can be spread between animals and people, including those that can be spread through the bite of a tick or mosquito.

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Related links

• National Collaborating Centre for Environmental Health: A review of ticks in Canada and health risk from exposure