Transcript Toxocara canis

Climate change and zoonotic
diseases
OEMAC
Oct 5, 2010
Emily Jenkins, PhD, DVM, BSc
University of Saskatchewan
Learning objectives
• Have an understanding of the mechanisms by
which climate change may alter the ecology of
zoonotic diseases
• Identify zoonoses that may be influenced by
climate change in Canada
• Identify vulnerabilities and ways to predict
and mitigate the effects of climate change on
diseases of public health significance
Is the global climate really changing?
• 11 of the last 12 years are among the 12 warmest
since 1850
• Linear rate of warming in last 50 years is double the
centennial rate
• Present sedimentary levels of methane and carbon
dioxide are unprecedented in the last million years
“The present situation has no analogue.”
Delecluse 2008, OIE Revue Scientifique et Technique
Regional warming
1948-2008
2.0 C
1.5 C
2.1 C
1.6 C
1.7 C
1.4 C
http://www.msc-smc.ec.gc.ca/ccrm/bulletin/annual08/regional_e.cfm
Annual precipitation departures from normal
(Environment Canada, 1948-2009)
%
Year
Overall: warmer, wetter, and more extreme
http://www.cics.uvic.ca/scenarios/data/select.cgi#map
Western Arctic
Precipitation Change (%)
Each symbol represents a projection
from a Global Climate Model using a
given Emissions Scenario
2020’s
2050’s
Furgal and Prowse, 2007
2080’s
Mean Temperature Change (C)
Scenario storylines: socioeconomic
drivers of climate change
http://www.ccsn.ca/Help_and_Contact/Emissions_Information-e.html
2-4 C
4-6 C
6-8 C
Furgal & Prowse,2007
5-8%
5-15%
15-30%
Furgal and Prowse,
2007
Climate change in Canada
(Adapted from Rizzo, B. and E. Wiken.1992. Assessing the Sensitivity of
Canada's Ecosystems to Climate Change. Climate Change 21: 37-55.)
Effects of climate change on disease
• Development and survival of pathogens in
– the environment
– cold-blooded hosts and vectors
• Distribution and abundance of hosts
• Seasonal timing of life cycles and transmission
• Resistance, abundance, and behavior of hosts
NET EFFECTS!?
Plague
Avian influenza
Red Tides
Wildlife Conservation Society
Rift Valley
Fever
Babesia
Sleeping sickness
Cholera
Ebola
Tuberculosis
Parasites
Lyme Dz
Yellow fever
http://www.onehealthinitiative.com/index.php
Climate change will influence:
• Food, water, and environmentally transmitted
pathogens
– E.g. Toxocara, Giardia, Toxoplasma
• Rodent borne pathogens
– E.g. tularemia, Hanta virus, alveolar hydatid
disease
• Vector borne pathogens
– E.g. Lyme disease, West Nile Virus
Human health in a changing climate: a Canadian assessment of vulnerabilities and
adaptive capacity. Health Canada, 2008.
Food & environmentally transmitted
pathogens
FOOD WATER Sea Rivers Drinking Seafood
Meat Produce Processed Wildlife Pets Humans
Livestock ? ? ?
Hunter and Thompson 2005
Effects of climate change on food and
environmentally transmitted pathogens
• Altered development and survival of
pathogens in the environment
• Driven by changes in regional precipitation
and hydrology, and extreme weather events
• Altered frequency and severity of outbreaks
• Increase in existing health disparities for rural
and remote regions
Dog Roundworm
Toxocara canis
2 cm
Toxocara Eggs
Retinal Lesions of T. canis Ocular Larva Migrans
Zaman, Atlas of Medical Parasitology
USA Seroprevalence of Toxocara
• Estimate 14% of general public seropositive in
2008 national study
• Covert toxocariasis (childhood asthma?)
• Risk factors include: age, ethnicity,
socioeconomic status, education, pet
ownership, pica (blood lead levels) (Won et
al., 2008)
Toxocara in Canadians
L. Polley
Canadian
Database
For Animal
Parasites
Toxocara canis
absent in 1971
*
T. canis
present
in 1971
Unruh et al.,
1973
* T. canis
present in 2006
*
Salb et al., 2008
Toxoplasma
Life Cycle
From: Dubey, 1993
PPP 3-10 d
1-3 d
Patency ~ 2weeks
Toxoplasmosis in people
• NA Seroprevalence ~ 20% (9-40%), 33% globally
• Often asymptomatic – BUT…
• Acute toxoplasmosis
– Lymphadenopathy, flu-like symptoms
– Encephalitis (immunosuppressed)
• Congenital toxoplasmosis
– 140-1400 cases/year in Canada
– Retinochoroiditis (common)
– Hydrocephalus (rare)
In terms of prevalence and disease burden,
toxoplasmosis is probably the most important
parasitic infection in the North American
Arctic.
Peter Hotez, January 2010, PLOS NTD
Risk Factors
• General Risk Factors (US population)
– Consuming or working with raw ground beef, raw
shellfish, rare lamb, locally produced cured, dried,
or smoked meat, unpasteurized goat’s milk
– Age, education, living conditions, race/ethnicity
– Soil-related occupations
– Having 3 or more kittens
• Northern Risk Factors
– Preparing and consuming (raw) country foods
(caribou, seal and birds)
– Demographics (age, sex, education, income)
– Unfiltered surface water & natural water sources
Water-borne Human Toxoplasmosis
Victoria, BC, 1994-1995
Approximately 3,000 to 8,000 people infected
100 cases of acute toxoplasmosis (6-83 years old)
20 cases of ocular toxoplasmosis
8 cases with generalized toxoplasmosis
51 cases with lymphadenopathy
PLUS 12 congenitally infected children,
3 with unilateral and 3 with bilateral retinal lesions
Water-borne Toxoplasmosis Outbreak
Bowie et al 1997
Canadian Government survey in 2001
showed that two- thirds of First Nations
reserves had water supplies that were at
risk of contamination (King et al., 2009)
Future trends in northern water issues
• Climate-related impacts on the quantity,
quality and accessibility of drinking water
resources
• Overwhelm existing drinking water treatment
infrastructure
• Changes in permafrost affecting waste-water
treatment
Furgal, C., and Prowse, T.D. (2008): Northern Canada; in From Impacts to Adaptation:
Canada in a Changing Climate 2007, edited by D.S. Lemmen, F.J. Warren, J. Lacroix and E. Bush
Climate change and Toxoplasmosis in
Svalbard, Norway
• Prevalence in polar
bears has doubled in
last decade (now 46%)
• Detected in ring seals
for first time
• Warmer water
temperatures
– rapid development and
survival of oocysts
– influx of filter feeders
Jensen et al., 2010
PHAC Laboratory Surveillance
Data for Enteric Pathogens, 2006
Rodent borne zoonoses
Effects of climate change on
rodent borne disease
• Largely driven by changes in regional
precipitation and hydrology
• Increased amplitude of changes in reservoir
host abundance (boom bust scenarios)
• Increased severity of outbreaks
• Increased heterogeneity in spatial and
temporal patterns of outbreaks
• Changes in human behavior and land use
Tularemia in Deer Mice
Saskatchewan, Spring 2005
Wobeser et al., 2007
Affected Area (shaded) : 22,000 sq. km.
Hanta virus
http://www.mala.ca/cch/aded/adedrounds.asp H. Artsob, Feb 20 2007
Hanta virus outbreak in SW USA
• 6 yrs of drought 1987-1992
– Decreased predators of rodents
• Intense rains in 1993 (El Nino effect)
– Increased pinion nuts and grasshoppers
• >10 fold boom in mouse population
• Increased transmission to people
Rocque et al 2008 OIE
Occupational exposure to Hanta
•Sweeping out a barn and other ranch buildings
•Using compressed air and dry sweeping to clean up wood
waste in a sawmill
•Handling grain contaminated with mouse droppings and
urine
•Entering a barn infested with mice
•Planting or harvesting field crops
•Occupying previously vacant dwellings
•Disturbing rodent-infested areas while hiking or camping
•Living in dwellings with a sizable indoor rodent population
•Trapping and studying mice*
http://www.ccohs.ca/oshanswers/diseases/hantavir.html
Alveolar hydatid
disease
Lantis 1980
Global distribution E. multilocularis
Eckert et al., 2000
Effects of climate change on
Echinococcus in N. America
• Altered egg survival
• Altered distribution and abundance of
intermediate hosts
• Altered interfaces among wildlife, domestic
animals and people
• Differential effects on species/strains
• Concomitant with landscape change and
global translocation of hosts/pathogens
42
Drivers of emergence
Media hyperbole
Career making
Increased reporting
Increased awareness
Improved diagnosis
Newly recognized pathogen
Change in virulence of pathogen
Immunosuppression
Malnutrition
Change in feeding practices
Movement of hosts
Breakdown in water quality
Changes in slaughtering/rendering/waste
disposal
Poor vector control
J. Iversen
Misuse of antimicrobials
Breakdown in veterinary/public health infrastructure
Invasion of nidi
Increased urbanization
Clearing land
Allowing return of native vegetation/species
Dam building
Draining the swamp
Changing agriculture practices
Changing housing/shelter
Population fluctuations of reservoir species
Vaccine failures
Lack of quarantine
Reduced vigilance (diminishing returns)
Climate change
E. multilocularis in N. America
*71
Cases in
Alaska from
1951-1993
N1
A2
A4
*human
cases
E?
*
N2
*
MO
(Map from
Wilson et al., 1995)
STRAINS
From Nakao et al
2009
N= North American
A=Asian
E=European
(Peregrine et al.
in prep)
Global movement of pathogens
• Establishment of European strain in dogs
and/or wild canids in North America
• Implications for public health
– Owner seropositive?
– 53 cases in Europe
in 2008
• Implications for
wildlife translocations
Distribution and genotypes of red fox
Aubrey et al., 2009
Red fox and Arctic fox distribution
IUCN Redlist
Arthropod borne zoonoses
Vector for: Lyme Disease, Tularemia, Human Granulocytic Anaplasmosis, Human Babesiosis
Ogden et al., 2006 (In Health Canada, 2005: Health Policy Research Bulletin 11)
Lyme disease
(Borrelia burgdorferi)
Feeding
Larvae
Egg
Feeding
Randolph et al 2001
Nymph
Feeding
Adult
West Nile Virus life cycle
SK Health
51
West Nile virus in people,
Canada 2007
600
400
# reported
200
0
July
Aug
Sept
http://www.phac-aspc.gc.ca/wnv-vwn/pdf_nsr-rns_2007/wnvnr_2007final-eng.pdf
500
West Nile virus in people
Canada 2008
400
300
# reported
200
100
0
July
Aug
Sept
http://www.phac-aspc.gc.ca/wnv-vwn/pdf_nsr-rns_2008/wnvnr_200839-eng.pdf
Summer temperature departures from
normal in 2007, Environment Canada
Summer temperature departures from
normal in 2008, Environment Canada
Cumulative Degree Days
above 16°C
Jan Feb
Mar Apr
May
Jun Jul
Aug Sep
Oct
Nov Dec
0
0
0
1
23
84
189
284
302
303
303
303
Key Lake 0
0
0
0
6
37
96
143
145
145
145
145
S’toon
Degree Days: Measure of the amount of heat available for
development over a critical temperature threshold
(16°C for the prairie mosquito vector for West Nile virus).
Approximately 150 Degree Days are needed for one
generation of mosquitoes.
57
http://www.bccdc.ca/dis-cond/a-z/_w/WestNileVirus/Surveillance/WNv2009SurveillanceData.htm
http://www.bccdc.ca/dis-cond/a-z/_w/WestNileVirus/Surveillance/WNv2009SurveillanceData.htm
http://www.bccdc.ca/dis-cond/a-z/_w/WestNileVirus/Surveillance/WNv2009SurveillanceData.htm
Effects of climate change on WNv
• Increased development rate of vector and
pathogen
• Decreased survival of vector
• Increased heterogeneity in spatial and temporal
patterns of outbreaks
• Asynchrony of wildlife host and vector life cycles
• Altered human behavior
• Northward shift in distribution of vectors & virus
“Climatically speaking, we know
neither where we are coming from,
nor where we are headed, with
anything like the precision that is
required to predict spatially variable,
climatically sensitive diseases.”
Rogers and Randolph, 2003
Effects of climate change on zoonoses
• Increased severity, frequency, and spatial
heterogeneity of outbreaks of endemic
diseases
• Northward movement of vectors/pathogens
– Emergence of new pathogens
– Extinction at the top of the world?
• Emergence of disease at altered interfaces
among wildlife, domestic animal, and human
populations
Proactive management of risks of
climate change to public health
• Baseline knowledge of epidemiology and climate
susceptibility of diseases
• Predictive models for diseases with known
climate susceptibility
• Surveillance for emerging diseases [esp. wildlife]
• Mitigate through preparedness:
– identify vulnerable regions and populations
– triggers and delivery mechanisms for interventions
– establish mandates and communication channels
between animal and public health
Veterinarians?
Health Canada, 2005: Health
Policy Research Bulletin 11
Acknowledgements
• Jessica Hoopes, Prairie Diagnostic Services
• Ted Leighton and the Canadian Cooperative Wildlife
Health Centre
• Nick Ogden, Public Health Agency of Canada
• Harvey Artsob, and Animal Determinants of Emerging
Diseases rounds
• Tasha Epp and Chen-Chih Chen
• Janet Hill and the Hill Laboratory
• Ali White and Chris Somers (U Regina)
• Andrew Peregrine (U Guelph)
• Lydden Polley, Research Group for Arctic Parasitology