Recently I was reading #WildMed topics on Twitter and saw @ExpeditionDocs tweet about an interesting article in NEJM: Human Borrelia miyamotoi Infection in the United States. I have previously written about Lyme Disease (Borrelia burgdorferi) in an article on this blog with my friend and amateur entomologist Scott Willis (The Low Down on Lyme Disease) as well as on the Family Medicine Reference blog (The Low down on Lyme Disease).

Krause et al. (NEJM Jan 27 2013) state:

Borrelia miyamotoi, a spirochete that is genetically related to the species of borrelia that cause relapsing fever, has been detected in all tick species that are vectors of Lyme disease.1,2 It was detected in Ixodes scapularis ticks from Connecticut in 2001 and subsequently has been detected in all areas of the United States where Lyme disease is endemic.

So this got me wondering about the prevalence of this spirochete in Canada given that we also have Ixodes scapularis. After a quick literature search I discovered an article titled, The prevalence of Borrelia miyamotoi infection, and co-infection with other Borrelia spp. in Ixodes scapularis ticks collected in Canada. Antonia Dibernardo et al. found that Borrelia miyamotoi infection (in ticks) was present in all provinces of Canad except Newfoundland. Thus Dibernardo et al. said,

Given the widespread distribution of B. miyamotoi, infection due to this agent should be considered in patients who have been exposed to blacklegged ticks in Canada.

What should be stressed is that there is a key methodological difference between these two studies. The first study in the US was looking at human serology tests to, “provide evidence of B. miyamotoi infection and the prevalence of this infection among people in the United States” (NEJM Jan 27 2013). While the latter study in Canada, was looking at specifically at infections in I. scapularis ticks (rather than humans).

Krause et al. conclude (NEJM Jan 27 2013) “The identification of B. miyamotoi antibody in 18 of our study patients, including seroconversion associated with symptoms in 3 patients, suggests that B. miyamotoi infection may [emphasis added] be prevalent in areas where Lyme disease is endemic in the United States”.

The Canadian study found on overall prevalence of less than 1 % for B. miyamotoi. They also noted:

Few ticks were co-infected, however a third of B. miyamotoi-infected ticks and a quarter of A. phagocytophilum-infected ticks were also infected with B. burgdorferi and co-infections of B. miyamotoi and B. burgdorferi occurred more frequently than would be expected by chance.

Overall these were two very interesting articles to read and further remind me of the importance of regular tick checks while working or playing in the outdoor environment. I particularly like the well summarized conclusion in the Canadian paper with the clinical so what statement:

The relatively limited (though expanding) distribution of blacklegged tick populations in Canada [22,28,29] and the lower prevalence of B. miyamotoi infection in these ticks means that at present the risk of infection of humans in Canada would be lower than in parts of the USA [6]. Nevertheless, our study indicated that B. miyamotoi is present across a wide geographic range in Canada, and clinicians should consider B. miyamotoi infection as a possible diagnosis, alongside Lyme disease, Anaplasmosis, Ehrlichiosis, Babesiosis and arboviral infections, in patients suffering from suspected infectious disease who have potentially been exposed to ticks in Canada.

Happy hiking! Comments or questions just drop me a line below.


1.  Krause PJ, Narasimhan S, Wormser GP, Rollend L, Fikrig E, Lepore T, Barbour A, Fish D. Human Borrelia miyamotoi infection in the United States. New Engl J Med. 2013;368(3):291–293. doi: 10.1056/NEJMc1215469.

2.  Dibernardo A, Cote T, Ogden NH, Lindsay LR. The prevalence of Borrelia miyamotoi infection, and co-infections with other Borrelia spp. in Ixodes scapularis ticks collected in Canada. Parasites & Vectors. 2014;7:183. doi:10.1186/1756-3305-7-183.