This review article provides a comprehensive overview of the scientific understanding of bird–Borrelia interactions and their importance in the ecology of Lyme disease and other tick-borne infections. Drawing on more than a century of research, the authors trace the evolution of scientific knowledge from the earliest observations of Borrelia spirochetes to modern molecular and ecological studies.
Background
Lyme borreliosis is the most common tick-borne disease in many parts of the world. Traditionally, research has focused primarily on the relationship between ticks and small mammals, particularly rodents, which are widely recognized as important reservoirs of Borrelia bacteria. However, growing evidence suggests that birds also play a significant role in the maintenance and spread of these pathogens.
Birds frequently host ticks during migration and seasonal movements. Because many migratory species travel hundreds or even thousands of kilometers, they have the potential to transport infected ticks across regions, countries, and even continents. This makes birds important contributors to the geographic expansion of tick-borne pathogens.
Key Findings
The review highlights that birds are not merely passive carriers of ticks. Numerous studies have demonstrated that certain bird species may participate directly in the natural transmission cycles of Borrelia species. In some cases, birds can serve as reservoir hosts, supporting the survival and circulation of specific Borrelia strains within natural ecosystems.
Particular attention is given to Borrelia garinii, a species frequently associated with avian hosts. Research suggests that birds may play a crucial role in maintaining and disseminating this pathogen across broad geographic areas.
The authors also discuss how migratory routes influence the movement of infected ticks and pathogens. Through their seasonal migrations, birds may introduce Borrelia-infected ticks into new environments, contributing to the emergence of Lyme disease risk in previously unaffected regions.
Importance for Human Health
Understanding the ecology of Lyme disease requires more than studying ticks alone. The interactions among birds, ticks, mammals, and pathogens form a complex ecological network that directly influences disease transmission.
By transporting infected ticks and potentially acting as reservoirs for Borrelia species, birds may significantly affect human exposure risk. Their role becomes particularly important when assessing disease emergence, environmental changes, and the spread of tick-borne infections across different geographical regions.
Why Birds May Select for More Heat-Tolerant Borrelia Species
The role of birds in the ecology of Borrelia species may extend beyond their well-known function as carriers of infected ticks. Research suggests that certain Borrelia species, particularly Borrelia garinii, are better adapted to the higher body temperatures of avian hosts. As a result, birds may selectively support the survival and dissemination of strains with increased heat tolerance.
While other Borrelia species may be more sensitive to elevated temperatures, B. garinii appears to have evolved under selective pressure associated with warmer avian hosts. This adaptation may help explain why some Borrelia species persist under conditions that could be less favorable for others.
The observation is particularly interesting because it highlights important biological differences among Borrelia species. Understanding these differences may contribute to a more comprehensive view of Lyme disease ecology and emphasizes the importance of species-specific approaches when studying infection dynamics, host adaptation, and potential therapeutic strategies.
Scientific Significance
This review brings together decades of scientific evidence demonstrating that birds should be considered key ecological players in the epidemiology of Lyme borreliosis. The findings challenge the traditional view that focuses primarily on rodents and emphasize the need to incorporate avian hosts into future ecological and epidemiological studies.
The authors conclude that a comprehensive understanding of Lyme disease ecology must include the contribution of birds to pathogen maintenance, dispersal, and transmission dynamics.
Authors
- András P. Bózsik
- Dömötör M. László
- Borisz Egri
Affiliations
- Kázmér Albert Department, Széchenyi István University, Győr, Hungary
- Lyme Diagnostics Ltd., Budakalász, Hungary
Published In
Key Message
Birds, particularly migratory species, may play a far greater role in the maintenance and geographic spread of Borrelia bacteria than previously recognized, making them an essential component of Lyme disease ecology and future research efforts.
