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?