Surveillance for Borrelia burgdorferi in Ixodes Ticks and Mice in British Columbia
Historically, Lyme disease prevalence has been low in the Pacific Northwest of North America. Because there have been many public misconceptions regarding the ability of laboratories to identify Lyme disease, we studied the prevalence of B. burgdorferi in the Ixodes pacificus tick (vector) and Peromyscus maniculatus mouse (host) in British Columbia (BC).
In this study, mice were trapped from 11 different jurisdictions in BC from May to September. IFA and Western blots were performed on mice serum to determine the presence of B. burgdorferi antibodies. Ticks were collected from trapped mice and with the flagging/dragging technique. A maximum of 5 ticks from each mouse were pooled for DNA extraction and subjected to real-time PCR which targeted the 23S rRNA gene of Borrelia spp. and ospA gene of B. burgdorferi at the BC Public Health Microbiology and Reference Laboratory. Two organs from each mouse were also subjected to the same molecular tests. A subset of tick DNA extracts (n=48) were also sent to CDC Fort Collins where multiplex PCR targeting fliD and gB31genes for B. burgdorferi was performed to check for concordance between the results.
No ticks were found by flagging during this study period; however a total of 467 ticks of different developmental stages were retrieved from 237 mice. For the serology results, 19 mice were confirmed to have antibodies against B. burgdorferi. For the molecular results, 3 tick pools were positive for B. burgdorferi but all mouse organs tested were negative. Of the positive tick pools, the corresponding mice were serologically positive. The subset of ticks tested by the two laboratories had identical results.
The positivity rate of B. burgdorferi in the B.C. Ixodes tick population was found to be 0.71%, suggesting very low incidence. The exposure rate in the mouse population to B. burgdorferi was determined to be 8.18%, suggesting that the infestation rate is also low in the host population. This observation may explain the continued low incidence of Lyme disease in BC.
M. G. Morshed,
S. Man, None
K. Fernando, None
Q. Wong, None
P. Tang, None
D. M. Patrick, None
S. Mak, None
B. Henry, None