The myth that other insects could possibly spread Lyme disease stems from a study from Germany that evaluated the presence of Lyme spirochetes in mosquitoes. From this study came the patient-culture myth that you could get Lyme disease from mosquito bites.
Mosquitoes, lice and other insects have a different way of digesting their blood meal compared to ticks. When an insect ingests the spirochetes that cause Lyme disease they will be killed in the midgut because insects other than ticks have a different acidity and use proteases, certain digestive enzymes, to digest their meal. The midgut of other insects is hostile to the Lyme spirochete.
Relapsing fever spirochetes can be transmitted by lice. In contrast with Lyme spirochetes they are able to survive the harsh environment of the midgut of lice but relapsing fever is a different disease.
A fair amount of studies report the presence of Lyme spirochetes in mosquitoes and most studies found that between 1-3% of the mosquitoes indeed carried the Lyme spirochete. However, the presence of a spirochete in a mosquito doesn’t mean they are able to transmit it to humans. It is not so simple.
When Lyme spirochetes are ingested by ticks they adapt to the new environment by changing their outer surface proteins (osp-A) and remain immobile while the tick molds into the next developmental stage. When the tick feeds in the next stage the dormant spirochetes reactivate. The spirochetes start changing their outer surface proteins again to adapt to a vertebrate host, leave the midgut and disseminate into the saliva glands. From the saliva glands they are inoculated into the skin of the host. These developmental changes in the spirochete take approximately 2 days to complete. Far longer than a mosquito feeds.
Because of this low attachment and feeding time of the mosquito they are unlikely to ingest many Lyme spirochetes and they cannot be transmitted from the mosquito to the host because the mosquito is attached for only 90 seconds which is not long enough to transmit Lyme spirochetes. This is confirmed in studies that also failed to show the ability of mosquitoes to transmit Lyme spirochetes to vertebrate hosts.
Mosquitoes also feed from vessels and cannulate dermal capilaries and rarely draw blood from the interstitial tissue. The destruction of skin by tick feeding facilitates the uptake of Lyme spirochetes whereas the cannulation of capilaries by mosquitoes does not.
Besides that mosquitoes do not meet the complex transmission requirements of Lyme spirochetes, ticks secrete saliva into the host. The components of this saliva assists the spirochetes within the new host. Other insects don’t need this protein in their saliva because they feed in a much shorter time and thus don’t have to temporarily shut down the inflammation response around the bite site. Without the assistance of these components of the tick saliva, Lyme spirochetes would be unable to infect a host.
No case reports
There are no case reports of patients that develop an erythema migrans after a mosquito bite in the literature.
It seems unlikely that mosquitoes can transmit Lyme disease.
Some mosquitoes transmit viruses and parasites like Malaria. If you are visiting endemic area for these diseases protect yourself and get the required travel vaccinations. If you develop an erythema migrans, visit a doctor. It might mean that you have overlooked a tick bite.
Source of the myth
- Occurrence of Borrelia burgdorferi s.l. in different genera of mosquitoes (Culicidae) in Central Europe. Ticks Tick Borne Dis. 2016 Mar;7(2):256-63. Melaun C, Zotzmann S, Santaella VG, Werblow A, Zumkowski-Xylander H, Kraiczy P, Klimpel S.
- Mosquitoes and soft ticks cannot transmit Lyme disease spirochetes. Parasitol Res (2002) 88: 283–284. Matuschka FR, Richter D.
Surviving the midgut
- Blood digestion in ticks, p. 197-212. In F. D. Obenchain and R. Galun (ed.), Physiology of ticks. (1982) Akov, S.
- Clonal polymorphism of surface antigens in a relapsing fever Borrelia sp., p. 235-245. In G. G. Jackson
and H. Thomas (ed.), Bayer symposium VII: the pathogenesis of bacterial infections. Springer-Verlag, Heidelberg, Federal Republic of Germany. (1985) Barbour, A. G.
- Variation in a major surface protein of Lyme disease spirochetes. Infect. Immun. 45:94-100. (1984) Barbour, A. G., S. L. Tessier, and S. F. Hayes.
Borrelia burgdorferi sensu lato in mosquitoes
- Isolation of the spirochaete Borrelia afzelii from the mosquito Aedes vexans in the Czech Republic. Med Vet Entomol (1998) 12:103–105. Halouzka J, Postic D, Hubalek Z.
- Investigation of haematophagous arthropods for borreliae–summarized data, 1988-1996. Folia Parasitol (Praha). 1998;45(1):67-72. Hubálek Z, Halouzka J, Juricová Z.
- Ticks and biting insects infected with the etiologic agent of Lyme disease, Borrelia burgdorferi. J Clin Microbiol. 1988 Aug;26(8):1482-6. Magnarelli LA, Anderson JF.
- The etiologic agent of Lyme disease in deer flies, horse flies, and mosquitoes. JInfect Dis 154:355–358 (1986) Magnarelli LA, Anderson JF, Barbour AG.
- Experimental infections of mosquitoes with Borrelia burgdorferi, the etiologic agent of Lyme disease. JInfect Dis 156:694–695 (1987) Magnarelli LA, Freier JE, Anderson JF.
Borrelia transmission requirements
- Dynamics of Borrelia burgdorferi transmission by nymphal Ixodes dammini ticks. JInfect Dis 167:1082–1085 (1993) Piesman J.
- Induction of an outer surface protein on Borrelia burgdorferi during tick feeding. Proc Natl Acad Sci USA 92:2909–2913 (1995). Schwan TG, Piesman J, Golde WT, Dolan MC, Rosa PA.
- Role of saliva in tick/host interactions. Exp Appl Acarol 7:15–20 (1989) Ribeiro JM.