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Anaplasmosis – Description, Causes, and Prevention.

Description

Anaplasmosis is a disease caused by the bacterium Anaplasma phagocytophilum. These bacteria are spread to people by tick bites primarily from the blacklegged tick (Ixodes scapularis) and the western blacklegged tick (Ixodes pacificus). People with anaplasmosis will often have fever, headache, chills, and muscle aches. Doxycycline is the drug of choice for adults and children of all ages with anaplasmosis.

Pathogenesis

Anaplasma phagocytophilum is an obligate intracellular bacterium which primarily attacks neutrophil granulocytes but also eosinophils of different species, including dog, cat, cattle, sheep, goat, horse, deer, rodents and birds. Monocytes and lymphocytes act as secondary host cells.

The elementary body is the infective stage and enters the host cell by phagocytosis. Elementary bodies are individual bacteriae about 1 µm in diameter and usually coccoid or ellipsoid in shape. Once they are captured inside the phagosomes, the pathogens replicate by binary fission, forming clusters of tightly packed elementary bodies termed initial bodies. Additional growth and replication lead to the formation of microcolonies, so called morulae, the configuration that typifies the genus. Apoptosis of the host cell causes a dissolving of the morulae so that the bacteria are released to the blood and are able to infect new cells. Furthermore bacteria can also be released by exocytosis too.

Anaplasma phagocytophilum infection is associated most commonly with the development of mild to moderate thrombocytopenia, also other cytopenias may occur, including neutropenia, lymphopenia, and mild anaemia.

Causes

Tick bites

Anaplasma phagocytophilum is the causative organism of anaplasmosis. The causative organism is carried by ticks, the bite of the carrier tick causes anaplasmosis. Anaplasma phagocytophilum has the following two carriers:

Blood transfusion

In rare cases, A. phagocytophilum has been spread by blood transfusion.

Risk factors

Ticks live near the ground in wooded or brushy areas. They do not fly or jump, so they can only reach a host who brushes up against them. Factors that increase your risk of a tick bite include:

Signs and symptoms

The signs and symptoms of anaplasmosis may include:

What are possible complications of anaplasmosis?

In rare cases, anaplasmosis can cause serious complications such as:

These complications are rare in the vast majority of otherwise healthy people. But they are more common in those who have weak immune systems. This includes people who have HIV/AIDS, cancer, or organ transplants. They may need additional treatments, such as fluids, breathing support, or kidney dialysis. In a small number of people, these complications can lead to death.

How is anaplasmosis diagnosed?

Your healthcare provider will perform a physical exam, and ask about your health history and your symptoms. Tell him or her if you know you had a recent tick bite or any outdoor exposure in areas of the country where these ticks are common.

Your healthcare provider will need results from certain tests to diagnose the condition. These may include the following blood tests:

Anaplasmosis is often hard to diagnose. You may have only very mild symptoms that could be caused by many other diseases. Some people with this disease may not know that a tick bit them. You may be referred to an infectious disease specialist for diagnosis.

How is Anaplasmosis Treated?

Treatment should be started even if the diagnosis of anaplasmosis is suspected clinically, as delay in treatment may aggravate the severity of the condition.  The following treatment approach is followed in treating anaplasmosis.

Antibiotic Therapy

Anaplasma phagocytophilum is resistant to antibiotics such as penicillins, cephalosporins, macrolides, aminoglycosides, and quinolones. However, patients with anaplasmosis respond well to tetracyclines (especially doxycycline). In patients treated with tetracycline antibiotics, relapse has never been reported.

The dosage of doxycycline:

If the patient cannot tolerate tetracycline antibiotics or if its use is contraindicated in the patient, then rifampin is prescribed. Chloramphenicol is no longer recommended for treating anaplasmosis.

Usually, doxycycline is not recommended during pregnancy, but it can be used if the anaplasmosis has become a life-threatening condition. Rifampin can also be used with little success.

The fever subsides within 24-72 hours if the patient is treated within the first five days of anaplasmosis. In severe cases, fever might take a long time to subside. Treatment must be continued for at least three days after the fever subsides and until clinical improvement is seen in patients. Even in the absence of a confirmatory report, if clinical response is observed within 48-72 hours, then the treatment must be continued for the recommended period. Standard duration of treatment is 7 to 14 days.

Prevention of anaplasmosis

There are several ways to help prevent anaplasmosis. The best prevention method is to take precautions against coming into contact with ticks.

If someone sustains a tick bite, they should immediately and completely remove it from their body. A tick needs to stay attached for 4–24 hours to transmit the bacteria responsible for anaplasmosis. Removing the tick can prevent transmission.

A person can help prevent tick bites by:

Ticks are active all year round, though more people are likely to come into contact with them during warmer months.

If possible, a person should also take a photo of any removed tick. Having access to a photo can help a doctor diagnose potential illness if symptoms start to occur.

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