At least 3 species of the genus Borrelia (bacterium) are capable of triggering Lyme borreliosis. In the United States most cases of the disease are caused by Borrelia burgdorferi sensu stricto while in Europe Lyme disease develops due to either Borrelia afzelii or Borrelia garinii.
What is Lyme Disease?
Lyme borreliosis (Lyme disease) is an infectious disease caused by the aforementioned bacteria. Ticks are vectors i.e. carriers of the bacteria. Once bitten by an infected tick, patients contract the bacterium.
When it comes to risk factors for contracting Borrelia these are basically associated with any kind of outdoor activity especially if it takes place in areas where ticks are natural inhabitants. Tick bites may occur while gardening, hunting or hiking.
Furthermore, the risk increases if one has an animal that spends time outdoors. The dog, for instance, may easily contract ticks and allow these parasitic arachnids to be passed to the owner. The tick usually has between 24 and 36 hours to transmit the bacteria into the body. If removed sooner the risk of borreliosis significantly decreases.
Some ticks, especially blacklegged ones are very small and may sometimes be overlooked. So, it is no wonder that many people develop the disease without even being aware they have been bitten. Also, it is essential to mention that not all bitten individuals will contract the bacteria.
The disease has three staged. In the initial stage (localized form of borreliosis) the infection remains at the site of the tick bite. Left untreated the disease progresses entering the second stage when bacteria begin to spread throughout the body. And finally, the last, third stage of borreliosis is actually a late and disseminated form of the disease characterized by serious changes affecting multiple organs.
In the beginning of the infection symptoms mostly resemble the flu. There is wide body-itching, fever with chills, general ill-feeling, muscle ache and headache. Lightheadedness, fainting and stiff neck may occur as well. The hallmark of the initial stage of the infection is definitely a 'bull's eye' rash. This is a red and raised spot at the site of the tick bite with a clear center. The rash tends to increase in size and affect enormous portion of the skin.
Bacterial dissemination is a characteristic of the second stage. The bacteria spread to various organs, predominantly the brain, joints and the heart. Second stage of the disease is characterized by a range of symptoms and sign some of which are paralysis/weakness of facial muscles, muscle pain, joint swelling and palpitations.
In the end, late disseminated from of borreliosis develops later, months or even years after contracting the bacteria. Muscle pain and pain in joints are two most common features of this stage along with changes in sensorium (e.g. numbness, tingling etc.) and sometimes speech problems.
How is Lyme Disease Diagnosed?
There is a set of tests and exams which all need to be performed in order for Lyme disease to be confirmed or ruled out. Diagnosis lays on clinical findings, a history of tick bites or possible exposure to infected ticks and specific blood tests which confirm the presence of antibodies to Borrelia. Some problems doctors might face is the absence of characteristic bull's eye rash and the fact that many patients simply do not recall being bitten by a tick.
The bacterium per se is rather hard to be cultured in the laboratory settings so doctors usually stick to clinical findings and a history of exposure to endemic Lyme areas. Even serologic test which are basically the best option for confirming the infection might provide with false negative results. This is why serologic tests are considered only a support to clinical suspected cases and are never used as a diagnostic tool.
Nevertheless, serologic test do play certain role in the process of diagnosing the infection. Western blot and ELISA are two extensively used laboratory tests in cases of suspected Lyme disease. Initially doctors order ELISA test and if the results are positive, they opt for Western blot which is far more specific compared t ELISA. There is still controversy regarding these tests and Lyme disease. However, it is confirmed that Western blot may identify IgM antibodies in patients in the early stage with specificity of astonishing 94-96%. The sensitivity of ELISA is a bit lower. Namely, the overall sensitivity of ELISA is 64% but it may rise up to 100% in patients with disseminated form of the disease.
Erroneous test results are generally associated with cross-reactions with infections caused by certain viruses such as Epstein-Barr virus, cytomegalovirus or Herpes simplex virus. The major problem is the percentage of false negative results which reaches 36% compared to false positive results that only occur in 1% of all cases.
PCR or polymerase chain reaction is yet another test used in patients suffering from Lyme disease. Its role is to identify DNA of the bacteria but is not quite reliable because of poor laboratory technique. The higher efficacy of the test is reported in case of arthritis when synovial fluid is tested for the presence of bacteria.
Nowadays scientist are evaluating the efficacy of a new test called LTT-MELISA test, hoping that one day it will be far more reliable than the aforementioned ones.
All in all, Lyme disease is a severe infectious disease which needs to be diagnosed on time and treated aggressively. The diagnosis lies on clinical findings as well as a history of a tick bite but the role of serologic test should never be underestimated and these are supposed to be performed routinely.