What Are The Chances Of Getting Lyme Disease From A Tick Bite?

Lyme disease is caused by Borrelia, the bacteria responsible for infection. However, the transmission of this disease is complex and involves the reservoir and a vector. The chances of contracting Lyme disease depend upon various factors. According to researchers, the chances of getting Lyme disease even after a tick bite is quite low.

The Lyme disease is caused when the tick, carrying Borrelia burgdorferi, bites and transfers the bacteria from its gut region in to the blood of the person. The chances of getting the Lyme disease from the tick bites are low due to the following factors:

1. Type Of Tick Bite: Not all the ticks carry the bacteria. The bacteria have to reside in the mid gut region of the ticks for months and they require an optimum environment for residing. Thus, the most common carrier of Borrelia burgdorferi is deer tick. Thus, if there is tick bite from other species such as brown dog tick, the are chances of getting Lyme disease is very low.
2. Disease Carrying Tick Bite: Even if there is a bite by the deer tick, the prerequisite for Lyme disease is that particular tick should be already fed on the reservoir of the bacteria such as mice or deer. Thus, chances are low for the deer tick carrying the bacteria.
3. Transfer Of Bacteria In Blood: As soon as the tick fed on the human blood, the bacterium activates and starts replicating in the midgut. Then they move into the salivary glands and transfer into the human body. Thus, the tick should remain attached to the human body for sufficient time to transfer the bacteria.
4. Quantity Of Bacteria: The number of bacteria determines whether the infection will occur in the person or not. The small number of bacteria is killed by the immune system, but when in higher numbers, may cause symptoms of infection. Thus, for Lyme disease to develop, the bacteria should require a minimum concentration.

Lyme disease is of zoonotic origin as the responsible bacteria Borrelia is transmitted through the reservoir or hosts such as mice or deer to humans. Due to small size of tick in the nymphal stage, most of the infections are caused in this life phase of the tick. The ticks primarily acquire the bacteria from the mice and very rarely from the deer.

Once inside the tick, the bacteria stick themselves in the midgut of the tick through surface protein. When a tick feeds on the human blood, the tick down regulates one surface protein and up-regulates another surface protein while migrating from the gut to the salivary glands. The upregulated protein has an immunosuppressive effect and the chances of infection depend upon the bacterial expression of this protein. The transmission of the infection from the tick to human is rare.

The treatment strategy for Lyme disease is highly effective and completely eradicates the disease. But prevention is always better than cure. Thus, following are the preventive measures that can be used to reduce the chances of Lyme disease:

• Wear the light color clothes in the areas where the chances for getting the tick bite is high as the tick is dark in color and can be easily identified.
• Body should be fully covered.
• Maintain dry environment as ticks are found in humid areas.
• Insect repellent should be used.

For Lyme disease to occur, the causative agent i.e. bacteria have to pass from the host to the vector and then to the humans. Further, even after the tick bite, the chances of getting the disease depends upon the type of tick, whether the tick is vector or if the sufficient number of bacteria has transferred in human blood. It is interesting to note that even after the tick bite, the chances of developing the disease is low and is in the range of only 1%-5%.

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