Re: Lyme disease in BC

Issue: BCMJ, vol. 53 , No. 8 , October 2011 , Pages 394 Letters

This is in response to “Lyme disease in British Columbia: Are we really missing an epidemic?” [BCMJ 2011;53:224-229]. I can only assume that the title is an implied rebuttal of Ending Denial: The Lyme Disease Epidemic: A Canadian Public Health Disaster, edited by Helke Ferrie. 

Within the covers of this book are the true-life stories of Canadians who suffer from a disease that shares symptoms of Borrelia infection, test positive at US specialty labs for Borrelia, respond to Borrelia treatment, and yet test negative here in Canada. The book is also packed with science that debunks the IDSA’s strict diagnostic and inadequate treatment guidelines. It is interesting to see such a rebuttal from employees of the BCCDC who are, ultimately, responsible for Lyme testing and the education of our doctors.

I would like to address a number of inconsistencies and oversights in the Henry and Morshed article. 

Strain diversity is a complicating factor in the diagnosis of Lyme disease. Scotland found that they were missing many local cases and, so, changed testing protocols in order to test for local strains. Many more cases were identified that would have been missed if changes to testing had not occurred.[1,2] Even current Canadian studies are finding novel strains and warn that current testing may not be picking up these local strains.[3,4

Henry and Morshed completely rely on the precarious idea that serological Lyme testing is picking up all cases of Borrelia infection, both in humans and in rodent surveillance. The fact that the 2008 survey found that 221 cases of Lyme disease were clinically diagnosed and only 13 were officially reported is a clear indication that something is amiss.[5

Another issue of importance is surveillance. Henry and Morshed point to Jack Teng’s study of southern Okanagan tick populations as an indication that neither the vector nor the pathogen (Bb) is present in the area. 

It is important to point out that the flagging of ticks in this study was conducted only in arid areas of the Okanagan and, as Henry and Morshed point out in their article in regard to ecological niche modeling, “The habitat [of Ixodes ticks] in these areas is characterized by low-lying vegetation such as high grass and brush, with abundant leaf litter and a nearby water source.” 

Dr Teng found Dermacentor ticks because he only looked in areas that are not conducive to Ixodes ticks. He had less than 2% of the ticks he did find tested. Considering that Dermacentor ticks are not known to vector Lyme disease, it is misleading to include the number of Dermacentor ticks in the statistics for ticks that test negative for Lyme disease.  

In other areas where Ixodes ticks were collected, Henry and Morshed state that less than 1% of those ticks tested positive for Bb. In their own words, “there is no validated direct test for the B. burgdorferi bacterium in blood or other samples and the organism cannot be easily cultured.” And yet, ticks are tested by culturing then only polymerase chain reaction testing culture-positive samples. 

Henry and Morshed would not pick up strains of Borrelia that are not cultured, and it is unknown how many ticks would have tested positive had the ticks been directly tested by PCR, the standard used by the National Microbiology Lab. I would be interested to know if economics is involved with the decision to culture before PCR.

The bottom line is that Dr Henry and Dr Morshed cannot make claims of the prevalence of Lyme disease because testing, both in humans and surveillance, is not accurate. Because of this, Lyme disease should be a clinical diagnosis (beyond the bull’s-eye rash). 

It is more than unfortunate that the BCCDC tells doctors to rely on insensitive serological testing and does not trust doctors enough to allow them to make a clinical diagnosis in the absence of the bull’s eye. Based on Dr Henry’s survey of BC doctors,[5] erythema migrans rashes are not even recognized as reportable to the BCCDC by the majority of BC doctors who responded to the survey, so the statistics surrounding Lyme disease are further confused. 

Epidemic or not, true cases of Lyme are being missed in BC and those “cases” are people: people who are suffering from an entirely preventable and treatable condition. It is time for these employees of the BCCDC to stop defending their position and get down to the business of helping the citizens of this province. 
—Sheri Souch
Kaleden


References

1. Evans R, Mavin S, Ho-Yen DO. Audit of the laboratory diagnosis of Lyme disease in Scotland. J Med Microbiol 2005;54:1139-1141.
2. Ho-Yen DO, Mavin S, Evans R, et al. Local Borrelia burgdorferi sensu stricto and afzelii strains in a single mixed antigen improves Western blot sensitivity J Clin Pathol 2009;62:552-554.
3. Ogden NH, Margos G, Aanensen DM, et al. Investigation of genotypes of Borrelia burgdorferi in Ixodes scapularis ticks collected in surveillance in Canada Appl Environ Microbiol 2011;77:3244-3254.
4. Scott JD, Lee MK, Fernando K, et al. Detection of Lyme disease spirochete, Borrelia burgdorferi sensu lato, including three novel genotypes in ticks (Acari: Ixodidae) collected from songbirds (Passeriformes) across Canada. J Vector Ecol 2010;35:124-139.
5. Henry B, Crabtree A, Morshed M. Physician awareness of Lyme disease in British Columbia. BCMJ 2011:53:73.

Sheri Souch,. Re: Lyme disease in BC. BCMJ, Vol. 53, No. 8, October, 2011, Page(s) 394 - Letters.



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