Lyme disease

Lyme disease, sometimes referred to as Lyme infection, is a bacterial illness, transmitted to humans by the bite of deer ticks (Ixodes ticks) carrying a bacterium known as Borrelia burgdorferi. The disease has been reported in the Northeast, Mid-Atlantic, North Central, and Pacific coastal regions of the United States and in Europe, where it was first described almost 100 years ago. Lyme disease can affect the skin, joints, heart and the nervous system. It occurs in phases - the early phase beginning at the site of the tick bite with an expanding ring of redness, being diagnosed on the patient's clinical signs of illness and the detection of Lyme antibodies in the blood.

Lyme disease can affect multiple body systems and produce a range of symptoms. Not all patients with Lyme disease will have all symptoms and many of the symptoms are not specific to Lyme disease, but can occur with other diseases as well. The incubation period from infection to the onset of symptoms is usually one to two weeks, but can be much shorter (days), or much longer (months to years). Symptoms most often occur from May through September, because the nymphal stage of the tick is responsible for most cases.

Lyme disease is diagnosed clinically based on symptoms, objective physical findings (such as erythema migrans, facial palsy or arthritis) or a history of possible exposure to infected ticks, as well as serological blood tests. The EM rash is not always a bullseye, i.e., it can be red all the way across. When making a diagnosis of Lyme disease, health care providers should consider other diseases that may cause similar illness. Not all patients infected with Lyme disease will develop the characteristic bullseye rash and many may not recall a tick bite.

Lyme disease is classified as a zoonosis, as it is transmitted to humans from a natural reservoir among rodents by ticks that feed on both sets of hosts. Hard-bodied ticks of the genus Ixodes are the main vectors of Lyme disease. Most infections are caused by ticks in the nymphal stage, as they are very small and may feed for long periods of time undetected. Larval ticks are very rarely infected. Tick bites often go unnoticed because of the small size of the tick in its nymphal stage, as well as tick secretions that prevent the host from feeling any itch or pain from the bite. However, transmission is quite rare, with only about 1% of recognized tick bites resulting in Lyme disease; this may be because an infected tick must be attached for at least a day for transmission to occur.

Folk remedies for tick removal tend to be ineffective, offer no advantages in preventing the transfer of disease, and may increase the risks of transmission or infection. The best method is simply to pull the tick out with tweezers as close to the skin as possible, without twisting, and avoiding crushing the body of the tick or removing the head from the body. The risk of infection increases with the time the tick is attached and if a tick is attached for less than 24 hours, infection is unlikely. However, since these ticks are very small, especially in the nymph stage, prompt detection is quite difficult.

Antibiotics are the primary treatment for Lyme disease; the most appropriate antibiotic treatment depends upon the patient and the stage of the disease. According to the Infectious Diseases Society of America guidelines, the antibiotics of choice are doxycycline (in adults), amoxicillin (in children), erythromycin (for pregnant women) and ceftriaxone, with treatment lasting 10 to 28 days. Alternative choices are cefuroxime and cefotaxime. Treatment of pregnant women is similar, but doxycycline should not be used.

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