surveillance of vector-borne diseases in california: reasons, resources, and refinement
DESCRIPTION
Surveillance of Vector-Borne Diseases in California: Reasons, Resources, and Refinement. Anne Kjemtrup, D.V.M., M.P.V.M., Ph.D Research Scientist III California Department of Public Health Vector-Borne Disease Section. Assigned Objectives. - PowerPoint PPT PresentationTRANSCRIPT
Surveillance of Vector-Borne Diseases in California: Reasons, Resources, and Refinement
Anne Kjemtrup, D.V.M., M.P.V.M., Ph.DResearch Scientist III
California Department of Public HealthVector-Borne Disease Section
Assigned Objectives
1. What level of public health resource the area needs and whya) What vector-borne diseases merit
surveillance and investigation and why? 2. What information do we collect and why3. Demonstrate or illustrate how public health surveillance and/or
investigation and/or prevention impacts health of population (now and in the future)
4. What changes to current public health practice might be warranted – why and how would we implement them
5. How might we measure what we do and what impact we have with our efforts
6. What can we not do (What should we do to maximize resources? )
LEVEL OF PUBLIC HEALTH RESOURCE AREA NEEDS
Vector-Borne Diseases in CaliforniaPrimary Program Areas
• Rodent
• Flea
• Tick
• Mosquito
Public Health Surveillance
The ongoing systematic collection, analysis, interpretation, and dissemination of health data
SurveillanceCollectionAnalysisInterpretationDissemination
Public Health Action• Planning, implementing and
evaluating disease:– investigation– control– prevention
• Assess public health status• Define public health priorities• Evaluate programs• Stimulate research
Some vector-borne diseases require complex surveillance efforts to monitor, intervene, anticipate, detect, and study their epidemiology (just a few of surveillance functions)
Urban cycleRural cycles
??
??Bird/Mosquito Movement?Aedes, CulisetaAedes, Culiseta
Culex tarsalisCulex tarsalis
CulexCulexpipienspipiensstigmatstigmat..?? erythroerythro..
Dead end hosts
??
Rural cycles
??
??Bird/Mosquito Movement?
West Nile virus transmission cycles in California
Aedes, Culiseta
Culex tarsalisCulex tarsalis
CulexCulexpipienspipiensstigmatstigmat..?? erythroerythro..
Dead end hosts
??
Context* of Vector-Borne Diseases in CA
Context Endemic Disease**
Pathogen Vector Examples of diseases
1 West Nile virus, Lyme disease, plague
2 - Trypanosomiasis*** (Chagas disease)
3 - - Dengue, malaria
4 - - Leishmaniasis***
5 - - - Tick-borne encephalitis virus***
* Adapted from Braks et al, Parasites and Vectors 2011, 4: 192** Endemic infections with human cases*** Not specifically reportable in CA
Reportable Vector-Borne Diseases in CA(Context shown in parentheses)
Mosquito Tick Flea Rodent Other• Lyme disease
• West Nile virus (1)
• Relapsing fever (1)
• Plague (1)
• Hantavirus (1)
• Unusual disease (Chagas disease)
• Malaria (3,5) • Anaplasmosis/ehrlichiosis (1)
• Typhus (1,3)
• Dengue (3,5) • SFG Rickettsia, RMSF (1)
• Yellow fever (3,5)
• Tularemia* (1)
• Unusual disease (chickungunya)
• Babesiosis (1)
• Q fever* (1)* May also have non-vector source, e.g. animal, environment
9
Notifiable/reportable
Vector control
pathogen control
Vaccination, prophylaxis
Vector-surveillance
pathogen-surveillance
Dis
ease
bur
den
Intervention/Response Surveillance
Ris
k
Reservoir hosts: presence/absence/abundance/distribution
Vector: presence/absence/abundance/distribution
General population: exposure
General pop.: (A)symptomatic infected
General pop.:Symptomatic
Health care provider
hospital
Sero-surveillance, surveys
Public education
(Improved) diagnosis, treatment(s) recommendations
Adapted from Braks et al, Parasites and Vectors 2011, 4: 192
Current Prioritization of VBD*
* Subject to change with unexpected increase in disease burden, exotic vector introduction
Disease Risk Disease burden Action(s) Level of concern
West Nile virus (1)
Seasonal, geographically widespread
Death, morbidity, >100 cases/year
Vector-habitat control Education
+++
Lyme disease (1)
Seasonal, habitat specific Morbidity, ~100 cases per year
Education +++
Hanta virus (1)
Potential for geographically widespread
Death, morbidity. ~ 0 – 4 cases/year
Habitat modification/Education
+++
Plague (1) Seasonal, habitat specific Death, morbidity. ~ 0-1 case/year
Vector-habitat control/Education
++++
Tick-borne relapsing fever (1)
Seasonal, habitat specific Morbidity. ~0 – 4 cases/year
Habitat modification/Education
++
Imported mosquito-borne diseases Dengue, malaria, chickungunya (3,5)Associate with WNV surv. Infrast.
Various Tick-Borne Diseases (1)Rickettsia spp., Anaplasma, Babesia, etcAssociate with Lyme surv.infrast.
WHAT INFORMATION DO WE COLLECT AND WHY
Notifiable Disease Surveillance
Case definitions are established by the Council of State and Territorial Epidemiologists (nationally notifiable) or California Conference of Local Health Officers (state reportable) to standardize reporting across the country and state.– Need to be able to compare “apples to apples”– Comparable cases over time and space– Some “true” cases may not fit definition, while some non-
cases may fit definition– Case definitions are NOT diagnostic definitions!
Information Captured for VBD1. Demographics2. Laboratory
a) Some quite specialized for case definition purposes, e.g. Lyme disease, Dengue
3. Exposurea) Vector
i. Exposureii. Potential for on-going transmission
b) Environmenti. Elevation ii. Camping
c) Reservoir
DEMONSTRATE OR ILLUSTRATE HOW PUBLIC HEALTH SURVEILLANCE AND/OR INVESTIGATION AND/OR PREVENTION IMPACTS HEALTH OF POPULATION (NOW AND IN THE FUTURE)
Surveillance for West Nile Virus (context 1)
Surveillance translated into action
Environmental conditions
Mosquito species, abundance, infection prevalence
Seroconversions of sentinel chickens
Dead bird infection prevalence
# of human cases
Assessment Table
Response
EnvironmentalConditions
Rainfall
Runoff Temperature
Adult MosquitoVector Abundance
Virus Isolation
ChickenSeroconversions
Human Cases
Average
Overall Risk Level (Level 1=Normal; Level 2= Emergency Planning; Level 3=Epidemic Conditions)
Dead BirdInfections
Seasonality
Mosquito
Human
Lyme Disease (context 1)
• Human, vector, reservoir surveillance in CA• Surveillance information used at national level; defines
local risk as well• Risk communication:
– Provides prior probability information useful for diagnosis
– Specific populations at risk identified and targeted for information
• Continued surveillance still turns up surprises
Predictive Value of Laboratory Serology
Pred
ictiv
e va
lue
posi
tive
Prior probabiity
(n=806)
Targeted Public Health Education
Public
Occupational Health
Medical community
Kids
Surveillance work by VBDS and others identified new places of tick-encounter risk
Nymphal ticks:• In leaf litter and on
trees and logs in hardwood forests• Be aware that
nymphal ticks can be acquired from wood products such as logs, tree trunks, and wooden picnic tables
Courtesy Dr. Robert Lane, UC BerkeleyCourtesy Dr. Robert Lane, UCB
VBDS-CDPH
Dengue (context 3)Current Concerns for California
• Mosquito vector (Aedes albopictus) recently detected in southern California
• Capable of transmitting dengue, yellow fever, chikungunya, and several other encephalitis viruses
• Vicious day-biting mosquito; prefers mammals • Recent indigenous transmission of dengue virus in south Florida,
Texas, and Hawaii• Dengue incidence increasing world-wide
– Only a plane ride away? • Collecting information on imported cases, exposure, outcome
29
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Aedes albopictus• native distribution (blue)• established introductions (green)
Detected September 2, 2011El Monte trailer park, LA County
Oct. 27,2011: known infestation = 8 sq miles
Oct. 20: 18 / 66 larval samples positive adults found in 15 / 155 back yards inspected
Percent Foreign-Born
By MATTHEW BLOCH, SHAN CARTER and ALAN McLEAN | Source: 2005-9 American Community Survey, Census Bureau; socialexplorer.com
DengueNeed for Vigilance
Typhus (Context 1 or 2)
• Flea-borne typhus or “endemic” or “murine” typhus– Rickettsia typhi known agent– Urban wildlife (Opossum principally, rats historically)
serve as reservoir– “Cat flea” (Ctenocephalides felis) vector
• Historically known pockets in Los Angeles, Long Beach• Past few years detection expanded into Orange County• Public education primary response available
Typhus (Context 1 or 2)• New technologies, expanded surveillance identify new
challenges– Diagnostic/Surveillance
• Serology nonspecific, requires convalescent for confirmation
• Case definition – varies between states where reportable
– Ecology/Epidemiology• Role of Rickettsia felis? • Role of cats, particularly feral cats?• Can expanded surveillance better inform our
response?
Typhus: public concern
WHAT CHANGES TO CURRENT PUBLIC HEALTH PRACTICE MIGHT BE WARRANTED – WHY AND HOW WOULD WE IMPLEMENT THEM?
Healthy People 2020 goal: “to strengthen policies and improve practices that are driven by
the best available evidence and knowledge”
From: Jacobs et al, 2012. Prev Chronic Dis
Challenges/Opportunities• Technology transitions (e.g. CalREDIE)
– Impact workload – Eventual ability to better access data
• Changing disease landscapes can impact priorities (but sometimes brings resources)– Global level (H1N1)– National, state level (WNV)– Local level (typhus)
• Resources, resources, resources
Changes or Back to Basics?
• Training/information opportunities– CDC grand rounds
• Lyme disease (http://www.cdc.gov/about/grand-rounds/archives/2011/May2011.htm)
– CalREDIE trainings– Monthly Vector-Borne Disease PIO call provides general
updates throughout state.
Changes or Back to Basics?• Partnering with other agencies/organizations may improve
information gathering or identify resources
Changes or Back to Basics?• Establish standard criteria prioritization system diseases under
surveillance? • Proposal from Europe: (Balabnova, et al., 2011: PloS ONE 6(10) 1-7.)
CriteriaIncidenceWork and school absenteeismHealth care utilizationChronicity of illness or sequelaeCase fatality rateProportions of events requiring public health actionsTrendPublic attention (political agenda, public attention)Treatment possibilities and needs
Partnering with other agencies for VBD Surveillance: WNV example
Mosquito and Vector Control
Assoc. of California
Center for Vectorborne Diseases, UC
Davis
CA Animal Health and Food Safety
LabCA Dept Food and
Ag
California Department of Public Health
Results automatically sent to CDC
Local agencies enter field data
Central server
Historicaldatabase updated
Arbovirus bulletins
Field data retrieved and laboratory test results entered
Interactive maps automatically updated
Results reported to client automatically after entry
http://gateway.calsurv.org
Partnering with other agencies for VBD Surveillance: WNV example
Does Spot get Spots? Veterinary Survey for Canine Cases of Rocky Mountain Spotted Fever in California.
HOW MIGHT WE MEASURE WHAT WE DO AND WHAT IMPACT WE HAVE WITH OUR EFFORTS
Standard Surveillance Evaluation
1. Importance2. Usefulness3. Cost4. Quality
a. Simplicityb. Flexibilityc. Acceptablityd. Sensitivitye. Predictive value positivef. Representativenessg. Timeliness
Quick Ways to Assess Impact
• Website metrics If put out press release- hits to website or specific
provided links Many other assessible metrics (where are people coming
from to get to your website? Geographic location ? Etc)• Effort in completing report forms
% of forms that have complete info/not returned for more info?
Are there sections often not completed? Why?
Quick Ways to Assess Impact
http://www.cdph.ca.gov/programs/vbds/Pages/VBDSAnnualReports.aspx
WHAT CAN WE NOT DO? (WHAT SHOULD WE DO TO MAXIMIZE RESOURCES? )
Maximize resources• Evaluate program/effort• Prioritize ?
Still must send in info for reportable diseases, but worthwhile to invest effort for additional info for locally important diseases?
• Partner with other agencies or within agency Programs already in place that may be good place to
distribute PH info material (e.g. elder care services and West Nile virus)?
Vector control agencies/Environmental health to provide follow up information
Identify interns/students to participate in program• Other?
Acknowledgments
Questions?