Mosquito-borne Arbovirus Surveillance in West Virginia

Rachel Radcliffe, DVM, MPH

CDC Career Epidemiology Field Officer

Division of Infectious Disease Epidemiology

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Objectives

• Describe arbovirus surveillance in WV– Historical methods– Plans for 2011

• Describe 2010 arbovirus surveillance data

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Components of Mosquito-borne Arbovirus Surveillance

• Species– Humans– Mosquitoes– Dead birds– Horses

• Viruses– WNV– LAC– EEE– SLE

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Human Surveillance

• Local health departments receive reports from laboratories and healthcare providers– Conduct follow up to determine patient

case status– Environmental investigation to provide

education on mosquito-borne disease prevention

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Arbovirus Case Definition — Clinical Criteria

• Neuroinvasive disease – Fever (≥100.4°F or 38°C) AND – Meningitis, encephalitis, acute flaccid

paralysis, or other acute signs of central or peripheral neurologic dysfunction, as documented by a physician, AND

– Absence of a more likely clinical explanation. • Non-neuroinvasive disease – Fever (≥100.4°F or 38°C) AND – Absence of neuroinvasive disease AND – Absence of a more likely clinical explanation

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Arbovirus Case Definition — Laboratory Criteria

• Confirmatory Laboratory Criteria1. Isolation of virus or demonstration of specific viral antigen

or nucleic acid from tissue, blood, CSF, or other body fluid2. Four-fold or greater change in virus-specific quantitative

antibody titers in paired sera3. Virus-specific IgM antibodies in serum with confirmatory

virus-specific neutralizing antibodies in the same or a later specimen

4. Virus-specific IgM antibodies in CSF and a negative result for other IgM antibodies in CSF for arboviruses endemic to the region where exposure occurred

• Probable Laboratory Criteria1. Virus-specific IgM antibodies in CSF or serum

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Arbovirus Case Classification — Confirmed

• Neuroinvasive disease –Meets clinical criteria for neuroinvasive

disease – One or more of the 4 confirmatory

laboratory criteria• Non-neuroinvasive disease–Meets clinical criteria for non-

neuroinvasive disease – One or more of the 4 confirmatory

laboratory criteria

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Arbovirus Case Classification — Probable

• Neuroinvasive disease –Meets clinical criteria for neuroinvasive

disease – Only has virus specific IgM antibodies in

CSF or serum with no other testing• Non-neuroinvasive disease–Meets clinical criteria for non-

neuroinvasive disease – Only has virus-specific IgM antibodies in

CSF or serum with no other testing

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2010 Human Surveillance Data

• 8 cases of LAC reported from 5 counties– 4 confirmed and 4 probable– All neuroinvasive– Illness onsets occurred June–October–Median age of cases=7.5 years– 50% were female

• No cases of WNV, SLE, or EEE reported

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Travel-Associated Cases

• Dengue – 2 cases– Travel included Honduras and Phillipines– Both hospitalized

• Malaria– 3 cases– Travel included Nigeria and India– One hospitalization

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Mosquito Surveillance

• Routine mosquito trapping began in 2007• Trapping occurred May–October in most years• Trapping historically focused in Jackson and

Kanawha counties– Cabell and Ohio counties have also

participated• Mosquitoes tested for arboviruses depending on

species– Culex spp. tested for WNV and SLE– Non-Culex spp. tested for WNV, LAC, SLE,

and EEE

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2010 Mosquito Surveillance Data

• Trapping only occurred May–August in 3 counties

• 36,731 mosquitoes from 459 pools collected• 26 (5.7%) of 459 pools tested positive for

WNV – Positive pools found in all 3 counties

where trapping conducted• No pools positive for SLE, LAC, or EEE

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2011 Plans for Mosquito Surveillance

• New entomologist in DIDE• Regular mosquito trapping postponed– Assessing previous trapping methods and

locations–May do larval studies in a portion of the

state• Would like to see surveillance expanded to

more parts of state

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Dead Bird Surveillance

• Collection kits sent to local health departments each spring

• Freshly dead birds suitable specimens• Swab oral cavity of bird and send swab to

OLS– ID numbers obtained from DIDE prior to

OLS submission• Specimens tested for WNV, SLE, and EEE

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2010 Dead Bird Surveillance Data

• 9 dead bird samples tested• 0 were positive for WNV, SLE, and EEE• Specimens submitted from 8 counties

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2011 Dead Bird Surveillance

• Dead bird testing will continue• Specimen collection and suitable specimens

are the same• Specimens should be sent to OLS• OLS will send to Southeastern Cooperative

Wildlife Disease Study for testing

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Horse Surveillance

• Veterinarians submitted horse serum samples to OLS

• OLS sends specimens to National Veterinary Services Laboratory for WNV and EEE testing

• Free testing service

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2010 Horse Surveillance Data

• 3 horse specimens submitted and tested• 0 were positive for WNV and EEE• Specimens received from 2 counties

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2011 Horse Surveillance

• Testing service will continue• Specimen collection and submission to OLS

will remain the same• Advertising testing services through WV

Veterinary Medical Association

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Enhanced Passive Surveillance

• HAN sent at beginning of season to healthcare providers

• Letter sent to hospital laboratories• Communication with local health

departments• More outreach to veterinarians in 2011

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2011 Surveillance Activities

• May 2 — Email memo• May 9 — Hospital laboratory letter• May 16 — HAN to healthcare providers

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Arbovirus Surveillance Summary

• LAC continues to be the major arbovirus affecting humans in WV

• WNV continues to be detected in mosquitoes– Previous surveillance methods being

reviewed– Want to expand surveillance

• No arboviral cases detected in dead birds or horses– Submission numbers of both are declining– Assistance needed to increase submission

numbers

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