Lyme Disease worldwide

Borrelia Transmission System

The reason why Lyme Borrelia is such a successful emerging infectious disease, is because it uses a particularly successful system of reservoirs hosts in which Borrelia can survive – and vectors different types of ticks – capable of picking up and transmitting the Borrelia bacteria.

Different types of ixodus ticks that spread Lyme are common all over the world. There are 4 types of ticks that spread Lyme Borrelia and also infect people. These are called bridge vectors. However, these are not the only ticks that can spread Lyme Borrelia. There are still so-called ‘maintenance vectors’. In some areas, the maintenance vectors play a more important role than the bridge vectors and maintenance vectors might occasionally transmit the infection to a human.

Bridge Vectors:
Europa: i. ricinus
USA: i. pacificus, i. scapularis
Azië: i. ricinus, i. persulaticus

Maintenance vectors:
Europa: i. hexagonus, i. trianguliceps, i. uriae, h. concinna
USA: i. minor, i. affinis, i. dentatus, i. spinipalsis
Japan: i. turdus, i. ovatus, i. columnae, i. tanuki
Korea/Japan: i. nipponensis

 

Distribution of Ixodes ticks

Different vectors

All ticks tested in the laboratory had the capacity to transfer some Borrelia spirochetes. Only Ixodus ricinus and Ixodus scapularis could transfer all Borrelia spirochetes.

Different Lyme Borrelia strains

For a tick to get infected with Borrelia, large numbers of infected hosts must be present in the habitat of the tick. Birds, rodents, reptiles and various mammals prove to be competent reservoirs for the Borrelia spirochete. Since the discovery of Borrelia burgdorferi, around 20 other species of Lyme Borrelia have been discovered. It has taken some time for all discovered spirochetes to be named and classified. Currently there are 21 types of Lyme Borrelia known and every year new species are found. About 10 of these species are involved in Lyme disease in humans. 3 of these are well known: Borrelia afzelii, Borrelia garinii and Borrelia burgdorferii.

Adaptability of Borrelia

The ongoing transmission of Borrelia between cold-blooded vectors and warm-blooded hosts allows the Borrelia to lose genetic information. When there are multiple Borrelia present in the host, they can exchange genetic information. To survive in all the different circumstances in ticks and hosts, Borrelia changes its antigens. There are specific Borrelia antigens that are not expressed in the laboratory but only inside the host. In addition, Borrelia may lose genetic material from being cultured in the laboratory. The adaptability of  Borrelia can cause it to look completely different than what scientists would expect. Over time, this causes the ongoing emergence of new strains and genotypes of Borrelia.

Wordwide distribution of Borrelia

10 years ago, the picture we had of the distribution of Borrelia around the world was very clear with different strains on specific continents.

  • Borrelia afzelii, Borrelia garinii and Borrelia burgdorferii were present in Europa.
  • Borrelia lusitaniae was present in parts of Spain and North Africa.
  • Borrelia afzelii, Borrelia garinii and Borrelia valaisiana were present in Asia.
  • Borrelia japonica, Borrelia turdi and Borrelia tanuki were present in Japan.
  • Borrelia burgdorferii and Borrelia Bissettii were present in the United States.

With the discovery of new species and more research into the spread and distribution of these Lyme Borrelia species around the world a different picture was emerging. It wasn’t as simple as once thought. The picture was dynamic and rapidly changing.

  • In Canada and the United States, Borrelia kurtenbachii, Borrelia andersonii, Borrelia californiensis, Borrelia americana and Borrelia carolinensis have been discovered. Borrelia valaisiana, Borrelia afzelii, Borrelia garinii and Borrelia bavariensis also appear to be present in the United States.
  • In Europe, Borrelia valaisana, Borrelia spielmanii and Borrelia bavariensis have been discovered, of which bavariensis also occurs in Asia. The American species Borrelia bissetti also appears to be present in Europe.
  • In China, Borrelia Sinica and Borrelia Yangtze have been discovered.

The spread of the different ‘European’ and ‘American’ Borrelia species is no longer bound by continent. Migratory birds and continuously increasing air travel of people help spread these different species. The picture of distribution of 10-20 years ago seems to be no longer valid. This has medical implications because test kits struggle to pick up different types of Lyme-Borrelia.

Consequences

Nevertheless, based on tick studies and epidemiological data, it is often claimed that Lyme Borrelia isn’t present in a specific State or region. While patients report a Bull’s Eye Rash and / or clinical manifestations that resemble Lyme disease they are denied testing and/or treatment. The information on the spread and presence of co-infections is even worse. It is therefore my opinion that, on the basis of the absence of information, you can not conclude that no Borrelia is present in a specific geographical area.

The absence of proof is not the proof of absence.