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Lyme disease, caused by the bacterium, Borrelia burgdorferi that normally lives in mice, squirrels and other small animals, is transmitted among these animals and to humans through the bites of certain species of ticks.
In the northeastern and north-central United States, the blacklegged tick (or deer tick, Ixodes scapularis) transmits Lyme disease and in the Pacific coastal United States, the disease is spread by the western blacklegged tick (Ixodes pacificus). About 1% of all deer ticks are infected with the bacteria. These ticks are called deer ticks as they usually feed and mate on deer. Ticks also feed on small rodents, birds, and other non-human animals. These animals may act as reservoirs for the Lyme disease bacteria (they carry the bacteria, but do not develop symptoms of the disease). If a tick feeds on an animal that carries the Lyme bacteria, the bacteria will enter the tick’s body, making it able to pass the bacteria on to other animals and humans. Although dogs and cats can get Lyme disease, there is no evidence that they spread the disease directly to their owners. However, pets can bring infected ticks into home or yard.
There is no credible evidence that Lyme disease can be transmitted through air, food, water, or from the bites of mosquitoes, flies, fleas, or lice. When a tick infected with Lyme disease bacterium bites a person, the bacteria can transfer to the person’s blood. The tick must stay attached to the person’s skin for 36-48 hours for infection to occur. Most people are infected through the bites of immature ticks called nymphs. Nymph ticks are very tiny (<2 mm) and very difficult to see. There is no evidence of person-to-person transmission of Lyme disease. For example, a person cannot get infected from touching, kissing or having sex with a person who has Lyme disease. Lyme disease acquired during pregnancy may lead to infection of the placenta and possible stillbirth, however, no negative effects on the fetus have been found when the mother receives appropriate antibiotic treatment. There are no reports of Lyme disease transmission from breast milk. Although no cases of blood transfusion related Lyme disease have been reported, scientists have found the evidence that the Lyme disease bacteria can live in blood stored for donation. So, as precaution, the American Red Cross and the USFDA recommned the persons with chronic illness due to Lyme disease not to donate blood. Lyme disease patients, treated with antibiotics and have recovered, can start blood donation beginning 12 months after the last dose of antibiotics was taken.
Most people are infected through the bites of immature ticks called nymphs. These ticks feed during the spring and summer months (between May and September). Tick activity increases greatly in the spring (starting in April or May) when eggs first hatch. Ticks are most active and often feed in late June or early July, and slowly become less active during the autumn months. Ticks are least active and least likely to feed during January and February. So one needs to take precautions against tick bites, and should continue these precautions through the fall. However, while unlikely to receive a tick bite during the winter, one should not rule out tick-borne disease if notice any symptoms of early Lyme or symptoms of any other tick-borne diseases and should still consult the physician about the possibility of these diseases.
Clinical Features (Symptoms & Signs):
Early Lyme disease is often marked by one or more of the following: A characteristic skin rash, called erythema migrans (red circular patch, often called a “bull’s eye” that appears at the site of the tick bite within 3 days to 1 month). About 70-80% of patients infected by B. burgdorderi develop this characteristic skin lesion. Other symptoms are fatigue, chills and fever (orten low grade), headache, muscle and joint pain, swollen lymph nodes etc.
Late Lyme disease – Some signs and symptoms of Lyme disease may not show until weeks, months, or years after a tick bite. Arthritis is most likely to appear as brief bouts of pain and swelling, usually in one or more large joints, especially the knees. Nervous system symptoms can include numbness, pain, nerve paralysis (often facial muscles, usually one side) and meningitis (fever, stiff neck, and severe headaches). Rarely, irregularities of the heart rhythm may occur. Problems with memory or cognition, fatigue, headache, and sleep disturbances sometimes persist after treatment.
Treatment: Most cases of Lyme disease can be cured with a few weeks of antibiotics taken by mouth. Antibiotics commonly used for oral treatment include doxycycline, amoxicillin, or cefuroxime axetil. Patients with certain neurological or cardiac forms of illness may require intravenous treatment with drugs such as ceftriaxone or penicillin. Patients treated with antibiotics in the early stages of the infection usually take antibiotics for several weeks (14-21 days) and recover rapidly and completely. A few patients, particularly those who are first diagnosed with later stages of the disease, may have persistent or recurrent symptoms. These patients may benefit from a second 4-week course of therapy. Longer courses of antibiotic treatment have not been shown to be beneficial and have been linked to serious complications, including death.
Prevention: There are several ways to prevent Lyme disease, including personal protection like wearing protective clothing, using insect repellents, tick control, post-exposure antibiotics, and early diagnosis and treatment. If a tick is attached to skin for less than 24 hours, the chance of getting Lyme disease is extremely small. But just to be safe, one should monitor health closely after a tick bite and be alert for any signs and symptoms of tick borne illness such as fever, nausea, severe headaches, muscle pain, rash, diarrhoea etc. And if there is so, one should consult with his family physician soon.