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Ehrlichiosis is bacterial illness transmitted by ticks that produces flu-like symptoms. Another tick-borne infection — anaplasmosis — is closely related to ehrlichiosis. But the two have distinct differences and are caused by different microorganisms.

The symptoms of ehrlichiosis range from mild body aches to severe fever and usually appear within a week or so of a tick bite. If treated quickly with antibiotics ehrlichiosis generally improves within a few days.

Ehrlichiosis and anaplasmosis are most common in spring and summer, when ticks are active and you're more likely to be outdoors enjoying activities such as gardening, hiking or camping.

The best way to prevent these infections is to avoid tick bites. Tick repellents, thorough body checks after being outside and proper removal of ticks give you the best chance of avoiding ehrlichiosis.

If a tick infected with ehrlichia or anaplasma bites you, the following flu-like symptoms may appear within five to 14 days of the bite:

• Mild fever
• Headache
• Muscle aches
• Nausea
• Vomiting
• Diarrhea
• Cough
• Joint pains
• Confusion
• Rash — rare in adults, but more frequent in children

Some people infected with ehrlichiosis or anaplasmosis may have symptoms so mild that they never seek medical attention, and the body fights off the illness on its own. But untreated ehrlichiosis or anaplasmosis with persistent symptoms can result in an illness serious enough for hospitalization. If you experience any of the above symptoms soon after you visit an area that you know has ticks, see your doctor.

Ehrlichiosis and anaplasmosis are two closely related infections, but the cause is two different microorganisms:

• Human monocytic ehrlichiosis (HME). This infection is caused by Ehrlichia chaffeensis bacteria, and is transmitted primarily by the Lone Star tick and the American dog tick.
• Human granulocytic anaplasmosis (HGA). This infection is caused by Anaplasma phagocytophilia bacteria, and is transmitted primarily by the deer tick.

Ticks may carry ehrlichia bacteria or anaplasma bacteria. A bite from an infected tick is the most common cause of transmission to humans.

The following tick populations — all of which may carry ehrlichia or anaplasma bacteria, or both — exist in the United States:

• The Lone Star tick (Amblyomma americanum) thrives in Midwestern and Southeastern states, especially Texas, Virginia, Oklahoma, North Carolina, Missouri, Georgia, Arkansas, Florida and Tennessee. This is the major tick transmitting ehrlichiosis.
• The deer tick (Ixodes scapularis) mainly infests Minnesota, Wisconsin and the New England states. The deer tick is the major tick transmitting anaplasmosis and is also the carrier for Lyme disease.
• The western blacklegged tick (Ixodes pacificus) lives in areas along the West Coast, from northwestern Washington to the southern tip of California. It also affects the west-central portion of Utah. This tick has been associated with both anaplasmosis and ehrlichiosis.
• The American dog tick (Dermacentor variabilis) is prevalent in states east of the Rocky Mountains and inhabits some Western states, including Idaho, California and Washington. This tick has been found to be naturally infected with the agent of ehrlichiosis.

The greatest risk for these infections is a bite from an infected tick. Tick-borne infections cannot spread directly from person to person. The following factors may increase your risk of contracting tick-borne infections:

• Being outdoors in warm weather. Most cases of ehrlichiosis occur from May to July when populations of the Lone Star tick are at their peak and people are outside for activities such as hiking, gardening and camping. Peak occurrence of anaplasmosis occurs in July and again in November, corresponding to the peak feeding behavior of the deer tick and the western blacklegged tick.
• Living in or visiting an area with a high tick population. Ticks are common in the southern, southeastern, northeastern, midwestern and extreme western United States. The central, inland western states have low populations of ticks.
• Age. Your risk of acquiring ehrlichiosis and anaplasmosis increases with age, though children and young people are still at risk. In contrast, Rocky Mountain spotted fever and Lyme disease generally affect children in greater numbers than adults.

It may take 14 days after a tick bite for you to begin showing signs and symptoms of ehrlichiosis or anaplasmosis. If you get symptoms within two weeks of a tick bite, see your doctor. Be sure to tell your doctor that you recently received a tick bite or visited an area with a high population of ticks.

Tick-borne infections are difficult to diagnose based solely on symptoms because the symptoms are similar to many other common causes of fever or body aches.

A pattern of blood test abnormalities may lead your doctor to a diagnosis. Your doctor may prescribe antibiotics after analyzing your symptoms and may have you undergo a specific diagnostic blood test. If the symptoms don't subside with your doctor's recommendations, see your doctor for a follow-up visit.

Ehrlichiosis and anaplasmosis can have serious effects on an otherwise healthy adult or child if you don't seek prompt treatment.

People with weakened immune systems are at an even higher risk for more serious and potentially life-threatening consequences, and people with anaplasmosis have developed other infections that take advantage of a weakened immune system. Serious complications of untreated infection include kidney failure, respiratory failure, prolonged fever, seizures, coma and others.

If your doctor suspects you have ehrlichiosis or anaplasmosis, he or she will likely give you a prescription for an antibiotic such as tetracycline or doxycycline. You'll generally take the antibiotics for seven to 10 days and should see the signs and symptoms subside in the meantime. Your doctor may have you take antibiotics for a longer period if you're at risk of contracting Lyme disease as well.

The best way to steer clear of ehrlichiosis and anaplasmosis is to avoid tick bites.

Most ticks attach themselves to your lower legs and feet as you walk or work in grassy, wooded areas or overgrown fields. After a tick attaches to your body, it usually crawls upwards to find a safer location to burrow into your skin for a blood supply. Common tick bite locations include the back of your knees, groin, underarms, ears, back of your neck and top of your head.

If you remove a tick in the first 24 hours after attachment, you greatly reduce your risk of infection. While you may not be able to avoid going into areas where ticks are present, the following tips can make it easier to discover and remove ticks before they attach to your skin:

• Wear light-colored clothing. Ticks are dark. Light clothing helps you and others notice ticks on your clothing before they can attach themselves to your skin.
• Avoid open-toed shoes or sandals. Ticks generally live in grassy areas or fields and can attach themselves to your feet and legs when you brush by. Wearing open-toed shoes or sandals increases the risk of a tick attaching to your bare skin and working its way under your clothes, out of sight from detection.
• Apply repellent. Products containing DEET (Off! Deep Woods, Repel) or permethrin (Repel Permanone) often repel ticks. DEET is very effective on your skin, but follow the concentration recommendations on the label and don't apply DEET to your face. A repellent with DEET may not be a good idea for children because they're more likely to get the repellent in their eyes.
• Wear long pants and a long-sleeved shirt. The less skin you expose, the less area a tick has to bite. For added resistance, wear shirts, pants and socks with permethrin impregnated into the fabric.
• Tuck your shirt into your pants and your pants into your socks. By doing this, ticks will be less able to crawl onto exposed skin.
• Stay on clear trails whenever possible. Ticks prefer grassy areas and are not fond of well-beaten paths.
• Pull back long hair. Ticks may attach to dangling hair and work their way to your neck or scalp. Pulling back long hair helps you see ticks better on your neck and limits the chance of them attaching in the first place.

• Inspect your body. Do a complete visual inspection of your body. Be sure to check your head and neck because ticks will continue to climb upward until they find a suitable burrowing site. Use your hands to feel through your hair and in areas you can't see when you return from your outing or garden.

  Ticks can be as small as a strawberry seed, and they usually attach to hidden skin. Be sure to check all the possibilities. A shower alone will rarely dislodge attached ticks from your head and body.

If you find a tick on your body, don't be alarmed. If you remove the tick within 24 hours of its attachment, chances of transmission of ehrlichiosis, anaplasmosis or other tick-borne illnesses are slim. Follow the steps below for safe removal of ticks:

• Use tweezers if possible. Use a pair of flat-tipped tweezers or cover your hand with a tissue or glove to remove a tick. A tick's saliva and bodily fluids can carry the same bacteria as their mouths and can enter your body through cuts or mucous membranes in your skin.

• Remove the tick slowly. Grab the tick by its mouthparts where it has attached to your skin. Pull it up and out of your skin steadily and slowly without jerking or twisting it. If you pull too quickly or grab the tick by its body, the tick will likely separate, leaving the mouthparts in your skin. If the tick's mouthparts do break off in your skin, remove them with tweezers.

  Petroleum jelly and hot matches are not effective treatments for removing ticks or tick parts from your skin. These methods may make matters worse by triggering the tick to release more of its bodily fluids that could cause further infection.

• Kill the tick. Once you have successfully removed the tick, kill it by placing it in an alcohol solution. Don't crush the tick in your hands or with your fingernails because the fluids it releases may contain infected bacteria. If you want to save the tick for testing in the event you become ill, put it in a plastic bag or a jar, date the container, and place it in the freezer.
• Clean the bite site. Wash thoroughly with hand antiseptic (povidone-iodine or benzalkonium chloride), soap and water.

• Monitor the bite site. In the following days and weeks, watch the bite site for a rash and keep a close eye on any unusual symptoms that develop such as fever, muscle aches or joint pain.

  While ehrlichiosis generally takes five to 10 days and anaplasmosis takes one to two weeks to develop noticeable symptoms, Lyme disease may take up to 30 days to cause a rash. If you notice anything out of the ordinary, see your doctor. If possible, bring the tick with you to your appointment.