Lyme disease is an infection caused by Borrelia burgdorferi transmitted to humans through tick bites. Understanding how people get infected with Lyme disease is essential for prevention and prompt treatment.
What causes Lyme disease?
- Lyme disease is caused by the bacteria Borrelia burgdorferi sensu lato. This bacteria naturally occurs in rodents, birds, and deer.
- In the United States, the bacteria is primarily transmitted by biting black-legged ticks, commonly known as deer. These ticks are found predominately in the US’s Northeastern, Mid-Atlantic, and Upper Midwestern regions.
- Other types of ticks, such as the Western black-legged and American dog ticks, have been known to transmit the disease in limited areas.
How do ticks get infected with Lyme bacteria?
Ticks get infected in the following ways:
Feeding on infected hosts
- In their early larval and nymph stages, ticks get infected by feeding on infected rodents, birds, and deer.
- The bacteria lives in the tick’s gut and salivary glands.
Passing through life stages
- The bacteria can stay with them after ticks molt into the next life stage. Infected larvae pass bacteria onto the next nymph stage, and infected nymphs pass it onto adult ticks.
This allows the passing of bacteria from one life stage to the next.
Passing from parent to offspring
- Adult female ticks infected with the bacteria can sometimes pass it on to their offspring. This further propagates the spread of Lyme bacteria through the tick population.
How does a tick transmit Lyme to a human?
For a human to get infected with Lyme disease, the following process needs to occur:
Get bitten by an infected tick.
- The tick must have already fed on an infected animal, acquiring the bacteria during its previous life stage.
Tick attached for ≥36-48 hours.
- Once the infected tick feeds, the bacteria migrate from its gut to its salivary glands. This process generally takes at least 36-48 hours from the attachment time.
Tick infected with bacteria.
- Certain ticks may be uninfected and, therefore, cannot pass on Lyme even if attached for >48 hours. The tick needs to carry an active infection.
Bacteria enter the tick’s saliva.
- As the tick feeds, the bacteria will enter the tick’s saliva and then get injected into the human host’s bloodstream with the saliva.
This allows the bacteria to be transmitted from the infected tick into a human and cause infection.
When are ticks active and looking for hosts?
Ticks quest for hosts primarily during the warmer months when people are more likely to be outdoors engaged in activities on grounds inhabited by ticks.
- Nymphs are most active during the spring and early summer months of May, June, and July.
- Their small size makes them easily overlooked until fully engorged after several days of feeding.
- Larvae are around the late summer months of July, August, and September when they quest for their first meal.
- Adult tick activity peaks in the more extraordinary fall and spring months but can be found any time temperatures are above freezing.
Where are ticks commonly found?
Ticks like wooded, brushy, humid environments. Some familiar places ticks are encountered include:
- Woods, forests, grassy marshes, and meadows.
- Brush and shrubs along trails, woods, and lawn edges.
- Low vegetation in lawns and parks.
- Around old stone walls and woodpiles.
- On animals like deer, dogs, horses, etc.
Performing tick checks after visiting tick-prone areas can help detect ticks before transmission occurs.
In summary, Lyme disease transmission requires being bitten by a specific type of infected tick that is attached for at least 36-48 hours. The bacteria reside in the tick’s gut and migrate to its saliva, which can enter a human host during feeding. Understanding tick behavior, peak activity times, and likely habitats can raise awareness of potential Lyme exposure so preventative measures can be taken. If a tick is found attached, prompt removal can prevent disease transmission. Being aware of Lyme disease risks provides the best opportunity for prevention.
Q: Can you get Lyme disease from a tick attached for less than 36 hours?
A: It is possible but considered unlikely. Studies show transmission generally occurs after 36-48 hours of attachment. Ticks removed within the first day or two are less likely to have transmitted the bacteria.
Q: Can Lyme disease be transmitted by fleas, mosquitoes, or other insects?
A: No. In the US, only black-legged ticks have been shown to transmit the bacteria that causes Lyme. Fleas, mosquitoes, and other insects do not carry or transmit the infection.
Q: Is there a vaccine available to prevent Lyme disease in humans?
A: No. Currently, there is no vaccine against Lyme disease approved for human use. Some vaccines for dogs are available. Research is underway for potential future vaccines.
Q: Can Lyme disease be transmitted through blood transfusions or organ transplants?
A: Very rarely. Documented cases of transmission through blood products or tissue transplants are exceptionally uncommon. Standard blood donor screening helps prevent this risk.
Q: Can Lyme disease be spread from person to person by touching, coughing, or sexual contact?
A: No. Lyme disease does not spread through casual contact with humans. Transmission requires a bite from an infected tick.