Sunday, May 5, 2013

Lyme Disease Co-Infection

A single tick bite can transmit more than Borrelia, the bacteria that causes Lyme disease. One tick bite can infect a person with one or several diseases. Many of these tick borne diseases share the same symptoms: fatigue, joint pain, fever, stiff neck, and muscle aches. It is not uncommon for a patient to experience the symptoms of Lyme disease, and test negative for Lyme.

The first antibody the body produces after exposure to Borrelia is immunoglobulin type M. It takes anywhere from two to four weeks for this antibody to be present in enough quantity to be detected by testing. If a patient is tested before this antibody is detectable, the test results will be negative. This antibody remains in circulation about six months after the patient is cured.

The second antibody the body produces following immunoglobulin type M, is immunoglobulin type G. This antibody circulates in the blood about four to six weeks after exposure, and disappears in less that a year. This antibody does cross the placenta, but does not necessarily infect the fetus.

A commonly used test to detect Lyme disease antibodies in patient serum is an enzyme linked assay (ELISA). It is quick, easy, and inexpensive. The problem with this test is that the Borrelia species changes its surface proteins during cell division. The body's response to this change renders it unable to produce the typical immune response. Even though the patient is infected with the Lyme bacteria, the test results are negative. Another issue with this test is the probability of different strains of Borrelia that cause Lyme disease. The ELISA does not detect these other strains.

To further complicate the disease, a single tick bite can transmit several bacteria at the same time. Co-infection with Borrelia and other pathogens make it more difficult to diagnose and treat. The immune response may be different after exposure to other microbes. Therefore, results of the ELISA test may be inaccurate.

The drug of choice for Lyme disease is doxycycline. This drug covers a broad spectrum of microbes transmitted by ticks, however, not all. Sometimes a combination of antibiotics must be used to cure a patient. In cases where a diagnosis of Lyme disease is made, but the infection is caused by a microbe not susceptible to doxycycline, the patient will remain ill.

Further studies are underway to better understand how co-infection progresses once the patient is infected. Results of this study will help with diagnosis and treatment of Lyme and other tick-borne infections.

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