Lyme disease is found all over the world, with the only exception being Antarctica, which means that it is possible to get the disease virtually anywhere in the world.
What Causes Lyme disease?
The main cause of Lyme disease is a spirochetal bacteria found under the Borrelia genus collectively known as Borrelia burgdorferi. This genus of bacteria has 18 species, but there are only three species that lead to Lyme disease: Borrelia burgdorferi and Borrelia mayonii, are found in North America, while Borrelia afzelii and Borrelia garinii are found in Europe and Asia.
How is it transmitted?
The spirochetal bacteria are not meant to be transmitted to humans by nature, instead, it was meant to infect wild animals. However, due to human-wildlife interaction, Lyme disease has eventually found its way into the human world.
The bacteria are usually found among small mammals and birds in the wild, which are the original hosts to the bacteria. Ticks feed on both of these sets of hosts, acquiring the bacteria and spreading it onto other wildlife. Ticks usually host onto deer, which is why they’re often referred to as deer ticks. However, Borrelia microbes are more often contracted by deer ticks from small mammals like mice and birds than from deer.
Besides, by the time ticks are old enough to be hosted by deer, they are usually large in size and easily detected. For this reason, transmission to humans is most common by ticks in the nymphal stage when they are still quite small. At that stage, they are small enough to attach to the human body and go undetected for more than 24 hours – the necessary time for the bacteria to be transferred. The ticks mainly feed on mice and birds, then transfer the bacteria to humans.
At adulthood, the ticks primarily use deer as hosts, but they are too big and can be spotted by humans, preventing the required period of attachment. At the nymphal stage, however, the ticks are small, and with help from secretions, the tick produces, the bite is painless. During the bite, the tick will produce secretions through its saliva to prevent pain, and this saliva is the one that contains the spirochetal bacteria.
Development of Lyme Disease
Once the bacteria are injected into the skin, it immediately begins to disrupt the immune system starting at the site of the bite. The bacteria’s does this in order to establish a protective environment where it can multiply in numbers before it spreads onto other areas. At this stage, you may notice a rash starting from the bit region and which tends to spread outwards in a circle.
It has been estimated that a deer tick must stay about 36 to 48 hours attached to the skin of a human in order to cause Lyme disease.
The bacteria are resistant to the natural immune system thanks to its double membrane envelope, which makes it very difficult to get deactivated. In addition, the spirochetes avoid detection by the immune system by decreasing its expression of surface proteins. It is these proteins that the immune system targets, but by decreasing the proteins, the bacteria can go undetected for longer, eventually spreading all over the body.