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1. Lyme disease surveillance in Canada
Nick H. Ogden National Microbiology Laboratory @ Saint-Hyacinthe
For the visually or hearing impaired, this Government of Canada
presentation can be made available in an accessible format upon
request. Please contact the Lyme Disease Conference Secretariat
at maladie_lyme_disease@phac-aspc.gc.ca to request a copy.

2. Faculty/Presenter Disclosure
• Faculty: Dr N.H. Ogden has no commercial interests

3. Disclosure of Commercial Support
• This program has received no commercial financial or in-kind
support
• Potential for conflict(s) of interest:
– Dr Ogden has received no funding except from his employer

4. 4
Talk outline
• What is surveillance in a public health context?
• Environmental risk and how it has changed in Canada
• Surveillance objectives
• Surveillance methods
– Surveillance for environmental risk = “early warning”
– Human case surveillance

5. Surveillance – what is it?
WHO definition:
“the continuous, systematic collection, analysis and interpretation of health-
related data needed for the planning, implementation, and evaluation of public
health practice.” Such surveillance can:
1. serve as an early warning system for impending public health
emergencies;
2. document the impact of an intervention, or track progress towards
specified goals; and
3. monitor and clarify the epidemiology of health problems, to allow priorities
to be set and to inform public health policy and strategies.
5

6. LYME DISEASE RISK
6

7. 7
Lyme disease
• Bacterial infection caused by Borrelia burgdorferi
• Transmitted amongst wild animals hosts (rodents, squirrels, birds
etc) by ticks (Ixodes scapularis and I. pacificus), which also transmit
infection to humans
• Causes mild disease initially: flu-like with classic skin lesion
(erythema migrans)
• Then develops into more severe disease – Lyme arthritis,
neuroborreliosis and heart block

8. Photo by
N.H. Ogden
8
Host-seeking Larva
Engorged LarvaHost-seeking Nymph
Engorged Adult
Eggs
Borrelia burgdorferi s.s. transmission cycle depends on
the tick lifecycle
Engorged Nymph
Host-seeking adult
Engorged larva moults into nymph
Infection survives moult
Adults ticks feed on deer, but deer
don’t transmit B. burgdorferi
4 1
3500
2500
400250
50

9. Ticks that transmit B. burgdorferi: what they look like
Host-seeking nymph
Feeding nymph
Host-seeking adult female
Nymphs in various
stages of engorgement
Adult female ticks in various
stages of engorgement
Photo by
L.R. Lindsay
Photo by
L.R. Lindsay
Photo by
L.R. Lindsay
9

10. Where are ticks found – on a continental scale?
I. scapularis
I. pacificus
10

11. Where are ticks found – on a national scale?
I. scapularis
I. pacificus
11

12. Where are ticks found – on a landscape scale?
12
Photo: Dustin M. Ramsay

13. Where are ticks found – within a woodland?
13
Photo: Dustin M. Ramsay

14. Factors that determine where ticks and LD risk occur
• Climate: Has to be warm enough – too cold and they don’t complete
their life cycle before they die
• Habitat: Ticks spend most of their lives off their host in the surface
layers of the soil/litter – in unsuitable habitat they freeze in the winter
and desiccate in the summer. This essentially means woodland and
woodland edge.
• Host abundance: There have to be enough deer for the adult female
ticks, and there have to mice, squirrels, birds etc. Again this means
woodland and woodland edge.
14

15. How do we quantify Lyme disease risk in the
environment?
• Risk = density of ticks (D) x prevalence (P = proportion infected)
• Ixodes pacificus populations pose low risk – D is moderate, P is low
due to ecology of transmission
• Dermacentor variabilis populations pose no risk – D is moderate to
high, P= zero – B. burgdorferi is not transmitted by D. variabilis
• Ixodes scapularis populations pose high risk - D is moderate to high, P
is high due to ecology of transmission
• What about migratory bird-dispersed I. scapularis?
15

16. Low level but more widespread risk due to ticks spread by migratory birds
Photo by Bill Hilton Jr
(www.hiltonpond.org)
• In a resident population in one hectare:
– QAf 2,000 – 30% infected = 600
– QN 10,000 – 20% infected = 2,000
– QL 300,000 – 0% infected = 0
• Risk (D x P) = 2,600
• In a location with only bird-dispersed ticks
– QAf 20 – 30% infected = 6
– QN 1 – 20% infected = 0.2
– QL 0 – 0% infected = 0
• Risk (D x P) = 6.2
16

17. High risk Low risk
Risk of bird-
borne ticks
year 2000
Moderate risk
Risk assessment: risk maps combining temperature suitability and tick
dispersion ranges
Ogden et al Int J Health Geogr 2008
17

18. High risk Low risk
Risk of bird-
borne ticks
year 2020
Moderate risk
Risk assessment: risk maps combining temperature suitability and tick
dispersion ranges
Ogden et al Int J Health Geogr 2008
18

19. High risk Low risk
Risk of bird-
borne ticks
year 2050
Moderate risk
Risk assessment: risk maps combining temperature suitability and tick
dispersion ranges
Ogden et al Int J Health Geogr 2008
19

20. High risk Low risk
Risk of bird-
borne ticks
year 2080
Moderate risk
Risk assessment: risk maps combining temperature suitability and tick
dispersion ranges
Ogden et al Int J Health Geogr 2008
20

21. 2004 2014
21

22. Surveillance objectives
• What can we do to limit/prevent/control Lyme disease?
– Prevent cases:
• No vaccine
• Personal prevention
• Environmental control
– Make sure Lyme disease cases are diagnosed and treated early rather than
late
• Information on Lyme disease for the public
• Information for medical practitioners
• Surveillance aims to identify:
– The Canadian population at risk (where risk is occurring, which demographic
groups are getting Lyme) – to target information/action to prevent and inform
– The types of Lyme disease occurring – to help practitioners
– The efficacy of our preventive efforts
22

23. “EARLY WARNING” SURVEILLANCE
FOR ENVIRONMENTAL RISK 1:
ACTIVE TICK SURVEILLANCE
23

24. Active surveillance method 1. Rodent trapping
• Rodents are captured in baited live traps over one or more nights of
trapping
• Rodents are:
– Anaesthetised
– Examined for the presence of ticks
– Ticks collected
– Blood sample taken
– Blood tested serologically for infection
– Ticks tested for B. burgdorferi (etc.) by PCR
• Advantages:
– Combined with flagging it is the “gold standard” method
– Sensitive detection of ticks – rodents are good sentinels
– Sensitive detection of pathogens – testing engorged ticks is a good way of
detecting infected rodents and prevalence is often high in rodents
• Disadvantage:
– Not immediate result (a day later)
– Very resource intensive (people, traps, equipment)
– One site-visit takes 2 days
24

25. Active surveillance method 2. Drag sampling for ticks
• Dragging a 1m2 flannel across the woodland floor
using standardised time/distance/pattern
• Examine every 10m for presence of ticks
• Detects:
– Presence/absence of I. scapularis NOT I. pacificus
– The numbers of I. scapularis if present
– Presence and prevalence of infection with B. burgdorferi
(by PCR at NML)
• Advantages:
– Relatively easy to do – can visit several sites/day
– Immediate result
– Identifies risk to the public (what’s jumping on the drag =
what could jump on people)
– Detects ticks all through the season (adults, then
nymphs, then larvae, then adults)
• Disadvantages:
– Not as sensitive as rodent trapping for detecting ticks
– Less chance of detecting presence of B. burgdorferi than
testing rodents
25

26. Lyme disease risk in Canada by active field surveillance
26
Ogden et al. CCDR 2014 Bouchard et al. Can Vet J 2015
Gabriele-Rivet et al. Plos One 2015

27. “EARLY WARNING” SURVEILLANCE
FOR ENVIRONMENTAL RISK 2:
PASSIVE TICK SURVEILLANCE
27

28. The passive tick surveillance program
 Passive surveillance for I. scapularis has occurred in
Canada since 1990
 Ticks collected from patients at, submitted from,
medical and veterinary clinics
 Ticks collection and species identification by P/Ts
(NFL, NB, QC, ON, MB, SK, AB - PCR for Borrelia
burgdorferi at PHAC National Microbiology Lab
(NML)
 Passive surveillance data:
 Provide a long dataset (1990 to present)
 Have a wide geographic coverage
 Are sensitive……but non-specific due to detection of
bird-dispersed ticks (particularly by ticks from dogs)
 Increasingly variable participation PT public health due
to increasing costs
28

29. Obtaining early warning signals from passive tick
surveillance data
29
Alert maps: Koffi et al J Med Entomol 2012
Ogden et al Environ Health Perspect 2014
Leighton et al. 2012 J Appl Ecol
Cluster analysis: Ogden et al Environ Health Perspect 2010

30. NATIONAL LYME DISEASE CASE
SURVEILLANCE
30

31. Human case surveillance
• No practical, sensitive lab tests for early Lyme disease – requires
diagnosis on clinical grounds by a medical practitioner
• Main method of diagnosis of disseminated Lyme disease is serology
• But due to specificity issues, interpretation of serological tests needs to
be made with information that the patient has:
– appropriate clinical manifestations consistent with Lyme disease, and
– a credible history of exposure to Lyme disease vectors
• Early Lyme case report needs combination of clinical+exposure
• Disseminated Lyme case report needs combination of
clinical+lab+exposure
• Aims to capture new cases rather than post-treatment Lyme disease
syndrome
31

32. Lyme disease human case surveillance key findings
32
Coordinated national
surveillance starts
Ogden et al CCDR 2015
• Spatiotemporal trends in cases

33. Lyme disease human case surveillance key findings
• Incidence highest in adults 55-74 and males, and possibly a peak in
children 5-14
33

34. Lyme disease human case surveillance key findings
• Relatively low proportion of cases reported in early LD – awareness issues?
34

35. Lyme disease human case surveillance key findings
• Age variations in types of LD seen
EM (N = 206)
Neurological (N = 81)
Cardiac (N = 17)
Arthritis (N = 110)
35

36. Other emerging tick-borne diseases
• Diseases transmitted by I. scapularis (co-emerging
with Lyme) and/or I. pacificus:
– Anaplasmosis (Anaplasma phagocytophilum)
– Babesiosis (Babesia microti)
– Powassan virus
– Ehrlichia muris-like pathogen
– Borrelia mayonii
– Relapsing fever-like disease (Borrelia miyamotoi)
• Diseases/conditions transmitted by other ticks
– Monocytic ehrlichiosis (Ehrlichia chaffeensis)
– Rocky mountain spotted fever (Rickettsia reckettsii)
– Tick-bite paralysis