A new study finds no evidence that mosquitoes can transmit Borrelia burgdorferi, the bacterium that causes Lyme disease. This study reinforces that ticks are the only proven source of infection.
What did the study show?
Many Lyme disease patients have questioned whether a mosquito bite could have been the source of their infection, especially as many do not remember finding a tick. This new study published just this June in the journal Parasites & Vectors offers strong reassurance that mosquitoes are not capable of carrying or transmitting the Lyme disease bacteria, Borrelia burgdorferi. Even when exposed under lab conditions, the bacteria could not survive inside mosquitoes or be passed to mice.
Graphical abstract from Pekľanská et al. (2025), “Experimental evidence rules out mosquitoes as vectors of Lyme disease,” Parasites & Vectors. Image reused under an open-access Creative Commons license (CC by 4.0).
Why does this matter?
It’s common for patients to be unsure of how or when they were infected, and that’s completely understandable. Many people don’t recall a tick bite because the deer tick nymphs responsible for most Lyme disease cases are very small (the size of a poppy seed!), and their bites often go unnoticed. With that in mind, knowing Lyme disease is only spread by ticks helps patients and families focus on the right prevention strategies and worry less about every mosquito or bug bite.
How was the study done?
To find out if mosquitoes can spread Lyme disease, scientists ran a detailed series of lab experiments. First, they let different species of mosquitoes feed on mice infected with Lyme-causing bacteria. In some cases, a few mosquitoes did pick up the bacteria, but the numbers were extremely low and the bacteria quickly died during digestion.
The researchers also tested whether the bacteria could survive long enough to be passed on to a new host, either naturally or through interrupted feeding. In every case, the answer was no. The bacteria couldn’t stay alive or infectious inside mosquitoes, and they never made it into the saliva, which is the only way a mosquito can transmit disease.
To make sure the experiment was working properly, the researchers also included infected deer ticks, which did successfully transmit the Lyme disease bacteria to mice. These findings confirm that mosquitoes cannot maintain or transmit the bacteria that cause Lyme disease.
What is the takeaway?
This research addresses a long-standing question within the Lyme disease community about the potential role of mosquitoes in transmission. By providing evidence that mosquitoes cannot serve as competent vectors for Borrelia burgdorferi, the findings help refine public health messaging and support prevention strategies that remain focused on tick exposure.
To learn how to protect yourself and your family from ticks, visit our guide on how to be Tick AWARE.
