Surveillance and spatial analysis of vectorborne diseases

1
Surveillance and spatial analysis of vector-borne
diseases

• FioCruz, Rio, Brazil
• 19 Março 2007

Uriel Kitron Dept. of Pathobiology and Center
for Zoonoses Research University of Illinois
2
Elements of disease surveillance and control

• Data sources
• Data layers
• Data storage
• management
• Data integration

• Data analysis
• Data visualization
• Application
• dissemination

3
Sources existing tools for spatial data

• Field data
• Surveillance data
• Environmental data
• Data Analysis
• Approaches

• GPS
• GIS
• Remote sensing
• Spatial statistics, time series, dynamic models
• Landscape ecology epidemiology
  Metapopulation biology Ecological risk assessment

SCALE
4
Geographic Information Systems (GIS)
A system to capture, manage, manipulate,
analyze, model, display spatially referenced
data for research, management and planning
Human cases
Human settlements
Water bodies
Soil type
Vegetation data
Adult mosquitoes
5
Spatial Statistics Geostatistics

• Global clustering
• (spatial autocorrelation, K
  function, join counts)
• Local clustering (hot spots)
• interpolation smoothing and kriging
• Spatial filtering
• (screening of spatial components)
• Spatial - temporal processes

6
First Law of Geography (Tobler 1979)

• Everything is related to everything else, but
  
• near things are more related
• than distant things.

Calculation of Spatial Statistics
Based on giving weight to the distances between
items of interest
7
Role of GIS, remote sensing spatial analysis
in VBD research

• Analysis of transmission dynamics on multiple
  scales
• Consideration of complex role of landscape
  climate
• Development of predictive spatial models and
  risk maps

SCALE
8
Temporal and Spatial Scale and Resolution

• Geographic - ranging from the village/town to the
  continental level
• Temporal - ranging from the duration of an
  outbreak, through the seasonal to multi-year
  models
• Multiple scales can be considered simultaneously
  or in succession, but with caution

9
Some examples Vector borne zoonoses

• 1. Chagas disease distribution,
  habitat modification and role of various
  zoonotic hosts
• 2. West Nile virus - introduction and
  distribution in an urban area
• (3. Malaria space-time association of
  cases in Trinidad)

10
Zoonotic Vector-borne diseases (VBD) transmission
system
Humans (domestic
animals)
Vector
Pathogen
Reservoir Host(wildlife)
Environment
11
2. Eco-Epidemiology of Chagas Disease in
northwest Argentina

• Univ. of Buenos Aires, Argentina
• National Vector Control Program, Argentina
• Instituto Fatala Chabén, Argentina
• CNRS-IRD, France
• Rockefeller University, NY. USA
• CDC, USA
• Univ. of IllinoisSupported by NIH/NSF EID
  Program through FIC

12
CHAGAS DISEASE

• ZOONOSIS CAUSED BY PROTOZOAN
• TRYPANOSOMA CRUZI.
• ONLY IN THE AMERICAS.
• ONLY INFECTS MAMMALS.
• 10-18 MILLION PEOPLE INFECTED,
• 30 AFFECTED BY HEART DISEASE.
• MOST INFECTIONS INITIALLY
• ASYMPTOMATIC, PROGRESS TO CHRONIC.
• MAIN ROUTES OF INFECTION
• VECTOR-BORNE
• FROM MOTHER TO NEWBORN
• BLOOD TRANSFUSION
• NO VACCINE.
• NO EFFECTIVE DRUGS FOR CHRONICS.

SWOLLEN EYE IN 5 OF CASES
13
Life cycle of Trypanosoma cruzi
14
COMPLEXITY OF TRANSMISSION CYCLES OF T. cruzi
Zeledón R. CIBA Foundation Symposium, 1974.
15
Chagas study - Specific Aims

• Analyze spatial temporal pattern of
  reinfestation by triatomine bugs and T. cruzi
  infection in bugs, dogs and people
• Identify mechanisms underlying these patterns
• Determine source of colonizing vectors and of T.
  cruzi infection using morphometrics and molecular
  analyses
• Develop empirically based, spatially structured
  mathematical models of reinfestation and
  transmission
• Develop risk maps at village, Department and
  Province-wide levels

16
Eco-Epidemiology of Chagas Disease In Northwest
Argentina study area

Departamento Moreno
Landsat Thematic Mapper
Santiago del Estero Province
Amama
17
STUDY AREA, 2002
18
Typical Compound with home and multiple
peridomestic structures
19
Peridomestic Structures refuge for bugs and
sources for reinfestation
Pig corral
Storeroom
Goat corral
20
Mapping and geostatistical tools
Sketch maps made in the field during 1993-2002
Ikonos Satellite imagery (1-4m2)
Digital map for each village
Joining of attribute data to a GIS file
Clusters of high infestation and potential
sources of community reinfestation
SPATIAL STATISTICS
21
Georeferencing - relating infestation data to
locations
22
Reinfestation by T. infestans (5 years
post-spraying)
23
Gi(d) local spatial statistic

• Gi(d) ?j Wij(d) xj
• ?j xj
• Wij(d) is a spatial weights matrix with
• values of one for all links within
• distance d of a given I
• Concern about multiple comparisons
• (need to adjust significant z value)

We used Gi(d) to detect local and focal
clustering of infestations (number of bugs per
structure)
24
FOCAL ANALYSIS OF REINFESTATION IN AMAMÁ
Primary source of T. infestans 1993
Subsequent infestations were clustered around an
initial focus at a distance of 450 mts.
Potential secondary sources fell within the range
of the clustering around the primary source.
Cecere et al. 2005. Am. J. Trop. Med. Hyg.,
71(6) 803810.
25
Moving upscale - Including other
villages. Internal and external sources of
reinfestation.
Trinidad
Mercedes
External sources Villages not sprayed and
located within 1,500 m of the treated villages.
Cecere et al. EID, 2006
26
RECOMENDATION
An effective control program on the community
level would entail residual spraying with
insecticides of the colonized site and all sites
within a radius of 450 m, and all communities
within 1,500 m of the target community in order
to prevent the subsequent propagation of T.
infestans
27
Reinfestation by a sylvatic bug T. guasayana
Abundance of T. guasayana by site was
significantly clustered.
High density of free-ranging goats and natural
ecotopes determined the clustering of T.
guasayana.
Vazquez-Prokopec et al. 2005. J. Med. Entomol.
42 571-581.
28
Abundance and spatial distribution of T.
guasayana were positively associated with the
local density and spatial distribution of goats.
29
No association with abundance and spatial
distribution of pigs or chickens.
30

• Are dogs and cats reservoir hosts of T. cruzi?
• What is the relative role of dogs and cats as
  sources of T. cruzi to domestic T. infestans
  bugs?
• What variables do we need to measure for this
  purpose?
• What is the natural course of infection and
  infectiousness in domestic dogs and cats?

31
SEROPREVALENCE SURVEYS OF DOGS USING ELISA, IHA
AND IFAT ? INFECTION
Marcela Orozco, Francisco G. Petrocco y Cruz
Pino, 2003.
32
XENODIAGNOSIS OF DOGS BY USING INSECTARY-REARED,
NON-INFECTED BUGS THAT BLOOD-FEED TO REPLETION ON
EACH DOG ? INFECTIOUSNESS
TWO WOODEN BOXES WITH 10 NON-INFECTED BUGS EACH,
INDIVIDUALLY EXAMINED FOR INFECTION 30 AND 60
DAYS LATER
Francisco G. Petrocco, 2003.
33
BEFORE ANY CONTROL INTERVENTIONS AGE-SPECIFIC
PREVALENCE OF T. CRUZI IN DOGS IN TWO VILLAGES
FORCE OF INFECTION (?) 43-73 PER YEAR
BASED ON A S ? I MODEL, ASSUMING AGE- AND
TIME-INDEPENDENT TRANSMISSION, NO SERORECOVERY
AND NO DIFFERENTIAL SURVIVAL DUE TO T. CRUZI.
Gürtler et al. Am. J. Trop. Med. Hyg. 73 95-103,
2005.
34
HETEROGENEOUS DISTRIBUTION OF INFECTIOUSNESS TO
BUGS OF DOGS SEROPOSITIVE FOR T. CRUZI
Superspreaders
Gürtler et al. Parasitology 134 1-14, 2006.
35
INFECTIOUSNESS OF SEROPOSITIVE DOGS ASSOCIATED
INVERSELY WITH NUTRITIONAL AND APPARENT CLINICAL
STATUS
Petersen et al., Parasitol. Res. 87208-14, 2001.
36
AGE-RELATED DECLINE IN THE PREVALENCE OF
INFECTIOUS DOGS AND IN THE INFECTIOUSNESS TO BUGS
OF SEROPOSITIVE DOGS
37
HOST-VECTOR CONTACT IN DOMESTIC SITESDOGS AND
CHICKENS PREFERRED TO HUMANS RELATIVE TO HOST
AVAILABILITY
38
VERANDA WHERE PEOPLE, DOGS AND CATS SLEEP AT
NIGHT FOR 5-7 MONTHS A YEAR
Amamá, 1983
39
RELATIVE CONTRIBUTION TO TRANSMISSION OF DOGS
TO CATS TO HUMANS14 5 1? Dogs are the
most IMPORTANT RESERVOIR HOSTS, but cats also
play a role

• INDEX BASED ON MULTIPLYING
• HOST-SPECIFIC BLOOD MEAL INDICES,
• HOST PREVALENCE OF INFECTIOUSNESS,
• HOST INFECTIOUSNESS TO BUGS.

40
SOME CONCLUSIONS

• DOGS ARE A KEY FACTOR FOR DOMESTIC TRANSMISSION.
• REMOVING INFECTED DOGS SHOULD DECREASE THE
  INTENSITY OF HOUSEHOLD TRANSMISSION OF T. cruzi.
• EFFECTIVE VECTOR SURVEILLANCE LEADS TO THE
  NATURAL ELIMINATION OF INFECTED DOGS
• ? CULLING OF INFECTED DOGS NOT NEEDED.
• DOMESTIC DOGS COMPLY WITH ALL THE IDEAL
  CHARACTERISTICS OF AN ANIMAL SPECIES AS SENTINEL
  OF T. CRUZI TRANSMISSION.

41
STUDY AREAS OVER TWO DECADES AMAMA (RED), CORE
(BLUE), PERIPHERAL (GREEN) 2500 SQ. KM.
2002--
1985--
40 houses
1992--
130 houses
300 houses
1988--
600 houses
42
Moreno Department
5,439 houses, 2,911 rural houses, 275 villages,
25,000 habitants.
Vazquez-Prokopec et al
43
Department level clustering of infestation
5,439 houses, 2,911 rural houses, 275
villages, 25,000 habitants
Vazquez-Prokopec et al
Significantly associated with human population
density, density of rural houses, density of
houses with dirt floors
44
HETEROGENEITY AT VARIOUS LEVELS

• BUG ABUNDANCE AT DOMESTIC AND PERIDOMESTIC SITE
  LEVELS
• HOST INFECTION 'INFECTED HOUSEHOLDS'
• HOST INFECTIVITY TO BUGS 'SUPERSPREADERS'
• SPATIAL DISTRIBUTION OF INFECTED DOGS WITHIN AND
  AMONG VILLAGES gt 'HOTSPOTS OF TRANSMISSION'
• gt VERY FOCAL TRANSMISSION

45
Prerequisites for an active zoonotic VBD focus

• Vector survival
• Presence of reservoir hosts
• Pathogen transmission
• Opportunities for human/animal exposure

46
1. West Nile virus Eco-epidemiology of disease
emergence in urban areas

• Develop a spatial model and risk maps based
  on
• demographic and environmental risk factors for
  WNV and SLE in birds, mosquitoes and humans
• reservoir capacity and differential effects of
  WNV on various bird species
• anthropogenic features of the urban environment
  that support Culex mosquito production,
  mosquito-bird transmission and virus
  amplification.
• Dynamics of viral transmission over space and
  time using molecular evolutionary and
  phylogeographic techniques

funded by NSF/NIH Ecology of Infectious Disease
Program
47
Research Team

• Co-Investigators
• University of Illinois
• Uriel Kitron
• Marilyn Ruiz
• Tony Goldberg
• Jeff Brawn
• Scott Loss
• Michigan State University
• Edward Walker
• Gabe Hammer

• Collaborators
• Audubon Chicago Region
• Karen Glennemeier
• Judy Pollack
• Illinois Department of Public Health
• Constance Austin
• Linn Haramis
• Illinois State Water Survey
• Kenneth Kunkel

funded by NSF/NIH Ecology of Infectious Disease
Program
48
Chicago
49
(No Transcript)
50
West Nile Virus in Illinois

• 2001 - 123 positive bird specimens, 0 human cases
• 2002 - 884 human cases, 66 deaths, more than any
  other state that year
  (U.S. - 4,156/284)
• Over 680 cases occurred in Chicago and
  surroundings
• 2003 - 54 human cases, 1 death (U.S 9,862/264)
• 2004 - 60 human cases, 4 deaths (U.S.
  2,539/100)
• 2005 - 252 human cases, 12 deaths (U.S.
  3000/119)
• 2006 210 human cases, 9 deaths (U.S. 4180/149)

2002, 2005, 2006 hot and dry
2002
2003
51
2002
2005
2006
2004
2003
52
Locations of human WNV cases in 2002 with land
cover
Human WNV case rate per 10,000 people
53
Smoothed Map of Disease Cases summarized by
1196 1.8 km hexagons
Local Spatial Autocorrelation of Cases - LISA
statistic (Anselin)
Range 0-15 cases/cell
54
WNV Human Cases with Housing Density
1

• Human cases tend to be outside of the more
  densely populated urban core.
• 3 areas with most cases (circled on map)
• in the south, near Oak Lawn
• 2) in north, around Skokie
• 3) southwest of Skokie

3
2
55
Vegetation
PhysiographicRegion
56
Dominant patterns in the Chicago urban landscape

• Each different colored area represents a place
  with a common set of factors related to housing,
  vegetation, socio-economics, and land use

Ruiz et al, Int'l J Health Geog 2005
57
Urban Type 5, dominated by 40s, 50s, and 60s
housing. Mostly white, moderate vegetation and
moderate population density. 435 cases (64) were
in this group, 2.27 cases per 10,000 people
(RRgt3.5). (All other types lt0.65
cases per 10,000)
58
2005 Field Sites
59
Site 3 Oak Lawn North
Green site Saint Casimirs Cemetery
Residential site
60
Avian Host Community

• Bird Surveys
• Line transect bird surveys during May and June
• Bird Mist-netting
• 6-8 nets/morning from sunrise to noon during May
  to October
• Seropositivity of Captured Birds
• ELISA
• Virus Detection in Captured Birds - RT-PCR

61
Overall Prevalence 19.9 (n 1062)
62
Vector Community

• Adult Mosquito Trapping - MIR
• Light trap, gravid trap, aspirator
• Quantification of Mosquito Productivity
• Catch basins, containers
• Index of Culex Density
• Ovitraps
• Mosquito Bloodmeal Analysis

63
(No Transcript)
64
Ultimately, our goal is to be able to explain and
predict
2005 outbreak
Mosquito pool WNV test results
Human WNV cases, 10/3/2005 185/197 in greater
Chicago
65
Weekly 2005 mosquito infection rate by watershed
and cases of human illness in Cook and DuPage
County, Illinois. Human illness cases are
preliminary data and should not be considered
authoritative.
66
Weekly 2005 mosquito infection rate by watershed
and cases of human illness in Cook and DuPage
County, Illinois. Human illness cases are
preliminary data and should not be considered
authoritative.
67
Important Processes Behind the Cluster Patterns

• Ecological
• Mosquito and bird habitat suitability
• Housing, landscape and catch basins
• Socioeconomic
• Lifestyle
• Access to healthcare, biased reporting
• Race, income
• Mosquito Abatement Districts
• Control methods
• Geographic location

68
Pattern and Process

• For P. vivax in Icacos - tight clustering in
  space and time suggests a common source and
  direct contact between cases - the Icacos
  outbreak
• For P. malariae in Nariva-Mayaro - loose
  clustering in space and time suggests several
  independent epicenters
• For P. falciparum, lack of association in
  clustering in space with clustering in time,
  suggests independent imported cases

69
Some general Questions 1 Research

• Spatial determinants of disease transmission
• Spatial associations of risk factors with disease
  and interaction with temporal processes
• Origins of diseases and outbreaks

70
Some general Questions 2 Surveillance/Control

• How do we most effectively plan and conduct
  surveillance/control programs based on
  disease/risk patterns
• How do we evaluate control programs based on
  changes in disease patterns
• How do we integrate spatial epidemiology
  research with surveillance/control programs?

71
microscope. Levins, 1968
Upscale vs. Downscale
Spatial heterogeneity and processes that
operate on the micro- and meso- scale may not
be detected using high temporal but low spatial
resolution

• The detailed analysis
• of a model for purposes
• other than that which it
• was constructed may be
• as meaningless as
• studying a map under a

Spatial
Generality
Resolution
Model
Temporal
Spectral
Precision
Realism