Lyme Disease is an infectious disease that seems to be spreading. It has spread to over 30 countries and counting. In the US, it is most commonly caused by the bacterium Borrelia burgdorferi. Bacteria belonging to the same genus, Borrelia garini, and Borrelia afzeli are the common causes of the disease in Europe and Asia. Borrelia mayoni, a new species of the bacterium was discovered in 2015 by researchers from Mayo Clinic. The bacterium, Borrelia, is a spirochete. This means it is long, thin and spiral-shaped, it twists or spins to move around.
Lyme disease spreads to humans from animals. The bacteria spread by using natural reservoirs as hosts. The bacteria doesn’t cause much harm to the reservoir, an animal in which the bacteria lives. The reservoirs that can be infected by the bacteria are widely ranged from mice, lizards, birds, and a number of others. The bacteria can’t infect the human directly from the animal and requires a vector, an intermediate organism, to spread from animals to humans. Different regions are home to different vectors.
In the Northern US, its spread by the black-legged deer tick. Other types of lxodes ticks transmit Lyme Borrelia in western Northern America and Eurasia. These include the sheep tick, the taiga tick, and western black-legged tick. Ticks need blood to survive much like mosquitoes and hence they need a host to sustain their lives. Hence making these tiny bloodsuckers perfect for spreading a blood disease.
Ticks, like most arachnids, have three stages in their lives which are all crucial in the spread of Borrelia. The larval stage, the nymph stage, and the adult stage. The ticks get the bacteria while feeding off their host, the larva preferring small animals carries the disease along with it as it continues on its stages. The nymph having a broader spectrum of hosts spread the bacteria onto other reservoirs making the disease more prevalent. As an adult, the ticks prefer deer and that is how they spread the disease. Ticks while in the nymph and adult stage occasionally feed on humans and spread the disease to them.
Ticks are small and practically undetectable hence have a longer contact time with the humans feeding for a while off the host. The bacteria is transmitted within the saliva of the tick during feeding. It takes approximately 36-48 hours of attachment time for the bacterium to move from the tick’s gut into the saliva and into the bloodstream of the human. The Borrelia once in the human body affects the human in three stages.
The first stage lasts for a period of days and weeks after infection. In this stage, the first symptoms are noticeable, as it spreads a redness and inflammation expands across the infected area. Sometimes the space between the initial bite and the outer radius is clear of the bacteria and clears away of redness leaving behind a bull’s eye shaped rash. This marks the onset of the disease and is occasionally accompanied by flu-like symptoms.
The second stage is the early dissemination stage and occurs weeks to months after infection. The bacteria spread through the bloodstream or disseminate through the heart, brains, and joints. Generally, these areas are invaded by very few bacteria but the immune reaction being severe turns these tissues into warzones between the antigens and antibodies. They kill the bacteria but damage the tissue in the process. Rashes start popping up everywhere all over the body, then the other symptoms follow.
When the bacterium invades the heart tissue it is known as carditis. The tissue inflammation affects most heart functions. This is clinically presented as AV heart block, a condition whereby the channels conducting electrical signals from the higher chambers to the lower chambers of the heart are blocked leading to a change of the rhythm of the heartbeat to a slower tempo.
Lyme disease also causes swelling around nerves responsible for facial muscles at this stage as well, this causes facial nerve palsy, weakening or paralyzing facial muscles bilaterally (on both sides). When the bacterium affects the joints it can cause arthritis in the knee, wrist, and ankle. The bacterium in the brain affects the meninges, the outer lining of the brain, causing meningitis. Neck stiffness and headaches are also experienced. The final stage is the late dissemination stage which happens approximately a year after infection, this stage is marked by chronic arthritis of the joints.
Lyme disease can be treated by administering antibiotics depending on the stage and age of the patient, this would be most effective in the early stages. Patients should be monitored during medication as they may experience a reaction known as Jarisch-Herxheimer. This is an immunogenic reaction signalled by fevers, sweating, joint aches and muscle pain, it is caused by the reaction of the body to the antigens released by the Borelli upon breaking. Patients once treated heal well and the bacteria clears from their bloodstream.
People mainly affected by this are those exposed to the outdoors, woodlands, forests or natural habitats of wild animals. The attachment of ticks can be avoided by wearing long-sleeved clothes, hats, other protective gear and using bug spray while in the outdoors. When camping out it is advisable to constantly check for ticks to ensure none stay with you.